Portia africana
Encyclopedia
Portia africana is a jumping spider
(family
Salticidae) found in Angola
, Cameroon
, the Central African Republic
, Gabon
, Ghana
, the Ivory Coast, Sierra Leone
, Zaire
and Zambia
. Its conspicuous main eyes provide vision more acute than a cat
's during the day and 10 times more acute than a dragonfly's
, and this is essential in P. africana′s navigation, hunting and mating.
Like other species
of the genus
Portia, P. africana prefers to hunt web-based spiders, jumping spiders and other types in that order. When hunting web-based spiders, Portias use trial and error
to find a way to mislead the prey until the Portia is in a position to bite the victim. While other Portias live and hunt as individuals, P. africana forms large populations both in savanna
areas and in the dense "cities" which social jumping spiders build in vegetation near the shoreline of lakes. In the savanna, groups of P. africana, generally consisting of small juveniles, delay the prey until one juvenile bites the victim, and sometimes the juvenile shares the food with other. In vegetation near shorelines, P. africana hunts in the social jumping spiders' cities. There, two species of assassin bug prey on P. africana, and one also preys on the other.
Before courtship
, males spin a small web between boughs or twigs, that they hang under, ejaculate into, and then soak the semen into reservoirs on their pedipalp
s. If a female smells a male of the same species, the female stimulates the males to court. While hunting, mature females of P. africana emit olfactory signals that reduce the risk that any other females, males or juveniles of the same species may contend for the same prey.
s in that the usual body segment
s are fused into only two tagmata
, the cephalothorax
and abdomen
. These are joined by a small, flexible pedicel
, which allows the abdomen to move while spinning silk. The top of the cephalothorax is covered by a carapace
. In the genus
Portia
, the carapace slopes gently upward almost to the back, then steeply down, and either side has a steep slope with a slight "devil's horn" ridge along the top.
In spiders and other chelicerates, there is only one pair of appendages before the mouth, the chelicerae
, and in spiders these house fangs that inject poison into the prey. Behind the mouth is a pair of pedipalp
s ("palps" for short), and those of male spiders are quite large and are used for displaying and mating.
In 1978 in Sierra Leone
, Wanless found adult females 4.8 to 9.6 millimetres in body length and adult males 5.2 to 7.2 millimetres. Both sexes have orange-brown carapaces with light orange round the eyes. The female's carapace has faint sooty markings, and short fine white and light brownish hairs lying over the surface, with a scanty tuft behind the fovea. Males have sparse white tufts on their thorax and irregular white bands above the bases of all but the first pair of legs. Female's chelicerae are orange with blackish markings, decorated with dense white hairs at the top and long light brown hairs near the bottom; while male's chelicerae are orange-brown, with darker markings and a layer of thin fine light brown hair. The abdomen of both sexes is mottled yellow-brown and black, but the female's has tufts of orange-brown to dark brown hairs while the male's is mottled yellow-brown and black, clothed in white, orange-brown and black hairs, with conspicuous orange and cream white tufts. The legs of both sexes have many strong spines, and are yellow-brown to orange-brown with black stripes at the top part, and brown with darker brown and yellow-brown markings in the lower part.
Spiders groom themselves regularly, and more often if wet or dirty. They moisten their fangs, draw the legs one at a time through the fangs, and "comb" the legs with the fangs and palps. The first and fourth pairs of legs are then used to groom other parts of the body, and the only place they appear not to reach is the dorsal surface of the carapace.
Like many species of spider, a P. africana lays a continuous dragline of silk as it moves, and from time to time anchors the dragline to a surface with a spot of sticky silk. This allows the spider to return to the surface if the animal is dislodged. A spider about to jump first lays a sticky silk anchor, and then lays out a dragline as it flies.
When disturbed, P. africana and some other Portias leap upwards about 100 to 150 millimetres, often from the cryptic rest pose, and often over a wide trajectory. Usually the Portia then either freezes or runs about 100 millimetres and then freezes.
's and 10 times more acute than a dragonfly
's. Jumping spiders have eight eyes, of which the two large ones in the center-and-front position (the anterior-median eyes, also called "principal eyes") are housed in tubes in the head and provide acute vision. The other six are secondary eyes, positioned along the sides of the carapace and acting mainly as motion detectors. In most jumping spiders, the middle pair of secondary eyes are very small and have no known function, but those of Portias are relatively large, and function as well as those of the other secondary eyes. The main eyes focus accurately on an object at distances from approximately 2 centimetres to infinity, and in practice can see up to about 75 centimetres. Like all jumping spiders, Portias can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimetres wide at 20 centimetres away, or up to 18 millimetres wide at 30 centimetres away. Jumping spider's main eyes can see from red to ultraviolet
.
Generally the jumping spider
subfamily Spartaeinae
, which includes the genus
Portia
, cannot discriminate objects at such long distances as the members of subfamilies Salticinae or Lyssomaninae
can. However, members of Portia have vision about as acute as the best of the jumping spiders, for example: the salticine Mogrus neglectus can distinguish prey and conspecifics up to 320 millimetres away (42 times its own body length), while P. fimbriata can distinguish these up to 280 millimetres (47 times its own body length). The main eyes of a Portia can also identify features of the scenery up to 85 times its own body length, which helps the spider to find detours.
However, a Portia takes a relatively long time to see objects, possibly because getting a good image out of such small eyes is a complex process and requires a lot of scanning. This makes a Portia vulnerable to much larger predators such as bird
s, frog
s and mantis
es, which a Portia often cannot identify because of the predator's size.
Spiders, like other arthropod
s, have sensors, often modified setae (bristles), for smell, taste, touch and vibration protruding through their cuticle
("skin"). Unlike insects, spiders and other chelicerates do not have antennae
.
(adapted to run), allowing them to hunt insects without using webs. However, species of the genus
Portia prefer to hunt other spiders, often invading their victims' webs. Some Portia species including P. africana, also efficiently hunt other jumping spiders.
's Kimumu region, a savanna
area which is dry and hot throughout the year, P. africana forms large numbers in the webs of other spiders, in the nest complexes of other jumping spiders, around solitary nests of other jumping spiders, and around the nests of oecobiid
spiders. While most aggregations of P. africana there include adult and also juvenile of all stages, most groups consist only of small juveniles. A group of small juveniles can prevent jumping spiders and oecobiids from entering or leaving its nest. One of the juveniles will lunge and bite the victim, and sometimes others of the group join in feeding.
In vegetation near the shoreline of Lake Victoria
, social jumping spiders build nest complexes, in which P. africana hunts, apparently without building capture-webs. The assassin bugs Nagusta sp. indet. ("not identified") and Scipinnia repax prey on P. africana and on social jumping spiders and other types of prey in the complexes. Nagusta usually hunts in groups of two to three, apparently catches P. africana when the latter is busy invading a jumping nest complex, and often shares the prey. Scipinnia repax preys on P. africana in a similar way but alone, and also preys on Nagusta.
, as of 2011 researchers do not know how long a Portia can retain such memories nor whether a Portia may use different trial and error starts for some prey species.
Such tactics enable Portia species to take web-based spiders from 10% to 200% of their size, and Portia species hunt in all types of webs. In contrast, other cursorial spiders generally have difficulty moving on webs, and web-building spiders find it difficult to move in webs unlike those they build. When hunting in another spider's web, the slow, choppy movements and the flaps on its legs make Portia species resemble leaf detritus caught in the web and blown in a breeze. P. africana and some other Portia species use breezes and other disturbances as "smokescreens" in which these predators can approach web-based spiders more quickly, and revert to a more cautious approach when the disturbance disappears. A few web spiders run away when they sense the un-rhythmical gait of a Portia entering the web – a reaction Wilcox and Jackson termed "Portia panic".
Females of Portia also build webs to catch prey directly, and those of P. africana are usually attached to rigid surfaces such as rocks and tree trunks. These "capture webs" are funnel-shaped and widest at the top and are about 4,000 cubic centimetres in volume. The web is initially built in about 2 hours, and then gradually made stronger. A Portia often joins her own web on to one of a web-based non-salticid spider.
Portia species can make detours to find the best attack angle against dangerous prey, even when the best detour takes a Portia out of visual contact with the prey, and sometimes the planned route leads to abseiling
down a silk thread and biting the prey from behind. Such detours may take up to an hour, and a Portia usually picks the best route even if it needs to walk past an incorrect route. If a Portia makes a mistake while hunting another spider, it may itself be killed.
When hunting, mature females of P. africana, P. fimbriata, P. labiata, and P. schultzi emit olfactory signals that reduce the risk that any other females, males or juveniles of the same species may contend for the same prey. The effect inhibits aggressive mimicry against a prey spider even if the prey spider is visible, and also if the prey is inhabiting any part of a web. If a female of one of these species smells a male of the same species, the female stimulates the males to court. These Portia species do not show this behaviour when they receive olfactory signals from members of other Portia species.
All Portia species eat eggs of other spiders, including eggs of their own species and of other cursorial spiders, and can extract eggs from cases ranging from the flimsy ones of Pholcus
to the tough papery ones of Philoponella
. While only P. fimbriata (in Queensland) captures cursorial spiders in their nests, all Portia species steal eggs from empty nests of cursorial spiders.
The venom of Portia is unusually powerful against spiders. When a Portia stabs a small to medium spider (up to its own weight), including another Portia, the prey usually rans away for about 100 to 200 millimetres, enters convulsions, becomes paralysed after 10 to 30 seconds, and continues convulsing for 10 seconds to 4 minutes. Portia slowly approaches the prey and and takes it. Portia usually needs to inflict up to 15 stabbings to completely immobilise a larger spider (1.5 to 2 times its own weight), and then the Portia may wait about 20 to 200 millimetres away for 15 to 30 minutes from seizing the prey. Insects are usually not immobilised so quickly but continue to struggle, sometimes for several minutes.
In laboratory tests, P. africana appeared to be a poor hunter. These tests, like those for other Portia species, were individual contests between one hunter and one prey.
Before courtship
, a male Portia spins a small web between boughs or twigs, which he hangs under and ejaculates on to. He then soaks the semen
into reservoirs on his pedipalp
s, which are larger than those of females.
A female P. africana prefers to lay her eggs on a silken platform free from detritus.
In a laboratory, male P. africana copulated with female P. labiata but not eggs were laid. During all cases the female P. labiata twisted and lunged in an attempt to bite.
As in other Portia species, if a mature male meets a sub-mature female, he will try to cohabit with her.
When moult
ing, all Portias spin a horizontal web of a diameter about twice their body length and suspended 1 to 4 mm (0.0393700787401575 to 0.15748031496063 in) below a leaf. The spider lies head down, and often slides down 20 to 30 mm (0.78740157480315 to 1.2 in) during moulting. They spin a similar temporary web when resting.
, Cameroon
, the Central African Republic
, Gabon
, Ghana
, the Ivory Coast, Sierra Leone
, Zaire
and Zambia
.
Around Kenya
's Kisumi at the Equator
, P. africana lives on level ground about 1,400 metres above sea level where there is no dry season, and inhabits open savanna
containing clumps sisal
and euphorbia.. There, P. africana appears in large, dense but localised populations of three species of jumping spider, all with bodies less than 5.0 millimetres long.
In vegetation near the shoreline of Lake Victoria
, social jumping spiders build dense nest complexes, in which P. africana hunts. The assassin bugs Nagusta sp. indet. and Scipinnia repax prey on P. africana, and S. repax also preys on Nagusta.
Portia africana is one of 17 species in the genus Portia
as of May 2011. Wanless divided the genus Portia into two species group
s: the schultzi group, in which males' palps have a fixed tibia
l apophysis
; and the kenti group, in which the apophysis of each palp in the males has a joint separated by a membrane. The schultzi group includes P. schultzi, P. africana, P. fimbriata, and P. labiata
.
Portia africana is closely relation to P. alboguttata, of which only females have been found, in Malawi and South Africa.
The genus Portia is in the subfamily Spartaeinae
, which is thought to be primitive. Molecular phylogeny
, a technique that compares the DNA
of organisms to construct the tree of life, indicates that Portia is a member of the clade
Spartaeinae
, that Spartaeinae is basal (quite similar to the ancestors of all jumping spiders), and that the Spartaeus
, Phaeacius
, and Holcolaetis
genera are its closest relatives.
Jumping spider
The jumping spider family contains more than 500 described genera and about 5,000 described species, making it the largest family of spiders with about 13% of all species. Jumping spiders have some of the best vision among invertebrates and use it in courtship, hunting and navigation...
(family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Salticidae) found in Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
, the Central African Republic
Central African Republic
The Central African Republic , is a landlocked country in Central Africa. It borders Chad in the north, Sudan in the north east, South Sudan in the east, the Democratic Republic of the Congo and the Republic of the Congo in the south, and Cameroon in the west. The CAR covers a land area of about ,...
, Gabon
Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
, Ghana
Ghana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
, the Ivory Coast, Sierra Leone
Sierra Leone
Sierra Leone , officially the Republic of Sierra Leone, is a country in West Africa. It is bordered by Guinea to the north and east, Liberia to the southeast, and the Atlantic Ocean to the west and southwest. Sierra Leone covers a total area of and has an estimated population between 5.4 and 6.4...
, Zaire
Zaire
The Republic of Zaire was the name of the present Democratic Republic of the Congo between 27 October 1971 and 17 May 1997. The name of Zaire derives from the , itself an adaptation of the Kongo word nzere or nzadi, or "the river that swallows all rivers".-Self-proclaimed Father of the Nation:In...
and Zambia
Zambia
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
. Its conspicuous main eyes provide vision more acute than a cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
's during the day and 10 times more acute than a dragonfly's
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
, and this is essential in P. africana′s navigation, hunting and mating.
Like other species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Portia, P. africana prefers to hunt web-based spiders, jumping spiders and other types in that order. When hunting web-based spiders, Portias use trial and error
Trial and error
Trial and error, or trial by error, is a general method of problem solving, fixing things, or for obtaining knowledge."Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again."...
to find a way to mislead the prey until the Portia is in a position to bite the victim. While other Portias live and hunt as individuals, P. africana forms large populations both in savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
areas and in the dense "cities" which social jumping spiders build in vegetation near the shoreline of lakes. In the savanna, groups of P. africana, generally consisting of small juveniles, delay the prey until one juvenile bites the victim, and sometimes the juvenile shares the food with other. In vegetation near shorelines, P. africana hunts in the social jumping spiders' cities. There, two species of assassin bug prey on P. africana, and one also preys on the other.
Before courtship
Courtship
Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. In courtship, a couple get to know each other and decide if there will be an engagement or other such agreement...
, males spin a small web between boughs or twigs, that they hang under, ejaculate into, and then soak the semen into reservoirs on their pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
s. If a female smells a male of the same species, the female stimulates the males to court. While hunting, mature females of P. africana emit olfactory signals that reduce the risk that any other females, males or juveniles of the same species may contend for the same prey.
Body structure and appearance
Spiders are chelicerates, which differ from other arthropodArthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s in that the usual body segment
Segmentation (biology)
Segmentation in biology refers to either a type of gastrointestinal motility or the division of some animal and plant body plans into a series of repetitive segments. This article will focus on the segmentation of animal body plans, specifically using the examples of the phyla Arthropoda,...
s are fused into only two tagmata
Tagma (biology)
In invertebrate biology, a tagma is a specialized grouping of arthropod segments, such as the head, the thorax, and the abdomen with a common function. The segments of a tagma may be either fused or moveable.-Tagmata:...
, the cephalothorax
Cephalothorax
The cephalothorax is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax...
and abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
. These are joined by a small, flexible pedicel
Pedicel (spider)
The pedicel of a spider is a small, flexible cylinder that joins the cephalothorax and abdomen. This helps the spider to spin silk without moving the cephalothorax....
, which allows the abdomen to move while spinning silk. The top of the cephalothorax is covered by a carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. In the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Portia
Portia (genus)
Portia is a genus of jumping spider which feeds on other spiders . They are remarkable for their hunting behaviour which suggests they are capable of learning and problem solving, traits normally attributed to much larger animals....
, the carapace slopes gently upward almost to the back, then steeply down, and either side has a steep slope with a slight "devil's horn" ridge along the top.
In spiders and other chelicerates, there is only one pair of appendages before the mouth, the chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, and in spiders these house fangs that inject poison into the prey. Behind the mouth is a pair of pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
s ("palps" for short), and those of male spiders are quite large and are used for displaying and mating.
In 1978 in Sierra Leone
Sierra Leone
Sierra Leone , officially the Republic of Sierra Leone, is a country in West Africa. It is bordered by Guinea to the north and east, Liberia to the southeast, and the Atlantic Ocean to the west and southwest. Sierra Leone covers a total area of and has an estimated population between 5.4 and 6.4...
, Wanless found adult females 4.8 to 9.6 millimetres in body length and adult males 5.2 to 7.2 millimetres. Both sexes have orange-brown carapaces with light orange round the eyes. The female's carapace has faint sooty markings, and short fine white and light brownish hairs lying over the surface, with a scanty tuft behind the fovea. Males have sparse white tufts on their thorax and irregular white bands above the bases of all but the first pair of legs. Female's chelicerae are orange with blackish markings, decorated with dense white hairs at the top and long light brown hairs near the bottom; while male's chelicerae are orange-brown, with darker markings and a layer of thin fine light brown hair. The abdomen of both sexes is mottled yellow-brown and black, but the female's has tufts of orange-brown to dark brown hairs while the male's is mottled yellow-brown and black, clothed in white, orange-brown and black hairs, with conspicuous orange and cream white tufts. The legs of both sexes have many strong spines, and are yellow-brown to orange-brown with black stripes at the top part, and brown with darker brown and yellow-brown markings in the lower part.
Spiders groom themselves regularly, and more often if wet or dirty. They moisten their fangs, draw the legs one at a time through the fangs, and "comb" the legs with the fangs and palps. The first and fourth pairs of legs are then used to groom other parts of the body, and the only place they appear not to reach is the dorsal surface of the carapace.
Movement
When not hunting for prey or a mate, Portia species adopt a special posture, called the "cryptic rest posture", pulling their legs in close to the body and their palps back beside the chelicerae ("jaws"), which obscures the outlines of these appendages. When walking, most Portia species have a slow, "choppy" gait that preserves their concealment: pausing often and at irregular intervals; waving their legs continuously and their palps jerkily up and down; and moving each appendage out of time with the others and continuously varying the speed and timing.Like many species of spider, a P. africana lays a continuous dragline of silk as it moves, and from time to time anchors the dragline to a surface with a spot of sticky silk. This allows the spider to return to the surface if the animal is dislodged. A spider about to jump first lays a sticky silk anchor, and then lays out a dragline as it flies.
When disturbed, P. africana and some other Portias leap upwards about 100 to 150 millimetres, often from the cryptic rest pose, and often over a wide trajectory. Usually the Portia then either freezes or runs about 100 millimetres and then freezes.
Senses
Jumping spiders have significantly better vision than other spiders, much more acute than that of other animals of similar size, and clearer in daylight than a catCat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
's and 10 times more acute than a dragonfly
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
's. Jumping spiders have eight eyes, of which the two large ones in the center-and-front position (the anterior-median eyes, also called "principal eyes") are housed in tubes in the head and provide acute vision. The other six are secondary eyes, positioned along the sides of the carapace and acting mainly as motion detectors. In most jumping spiders, the middle pair of secondary eyes are very small and have no known function, but those of Portias are relatively large, and function as well as those of the other secondary eyes. The main eyes focus accurately on an object at distances from approximately 2 centimetres to infinity, and in practice can see up to about 75 centimetres. Like all jumping spiders, Portias can take in only a small visual field at one time, as the most acute part of a main eye can see all of a circle up to 12 millimetres wide at 20 centimetres away, or up to 18 millimetres wide at 30 centimetres away. Jumping spider's main eyes can see from red to ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
.
Generally the jumping spider
Jumping spider
The jumping spider family contains more than 500 described genera and about 5,000 described species, making it the largest family of spiders with about 13% of all species. Jumping spiders have some of the best vision among invertebrates and use it in courtship, hunting and navigation...
subfamily Spartaeinae
Spartaeinae
The Spartaeinae are a subfamily of the spider family Salticidae . It was established by Fred R. Wanless in 1984 to include the groups Boetheae, Cocaleae, Lineae, Codeteae and Cyrbeae, which in turn were defined by Eugène Simon....
, which includes the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Portia
Portia (genus)
Portia is a genus of jumping spider which feeds on other spiders . They are remarkable for their hunting behaviour which suggests they are capable of learning and problem solving, traits normally attributed to much larger animals....
, cannot discriminate objects at such long distances as the members of subfamilies Salticinae or Lyssomaninae
Lyssomaninae
The Lyssomaninae are a subfamily of jumping spiders, with eight described genera.The Lyssomaninae are not part of the Salticoida, to which over 90% of all salticid species belong.Six of these genera occur only in the Old World:* Asemonea O...
can. However, members of Portia have vision about as acute as the best of the jumping spiders, for example: the salticine Mogrus neglectus can distinguish prey and conspecifics up to 320 millimetres away (42 times its own body length), while P. fimbriata can distinguish these up to 280 millimetres (47 times its own body length). The main eyes of a Portia can also identify features of the scenery up to 85 times its own body length, which helps the spider to find detours.
However, a Portia takes a relatively long time to see objects, possibly because getting a good image out of such small eyes is a complex process and requires a lot of scanning. This makes a Portia vulnerable to much larger predators such as bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s and mantis
Mantis
Mantis is the common name of any insect in the order Mantodea, also commonly known as praying mantises. The word itself means "prophet" in Latin and Greek...
es, which a Portia often cannot identify because of the predator's size.
Spiders, like other arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s, have sensors, often modified setae (bristles), for smell, taste, touch and vibration protruding through their cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
("skin"). Unlike insects, spiders and other chelicerates do not have antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
.
Hunting and feeding
Most species of jumping spiders appear to be cursorialCursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
(adapted to run), allowing them to hunt insects without using webs. However, species of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Portia prefer to hunt other spiders, often invading their victims' webs. Some Portia species including P. africana, also efficiently hunt other jumping spiders.
Tactics specific to Portia africana
In KenyaKenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
's Kimumu region, a savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
area which is dry and hot throughout the year, P. africana forms large numbers in the webs of other spiders, in the nest complexes of other jumping spiders, around solitary nests of other jumping spiders, and around the nests of oecobiid
Oecobiidae
The spider family Oecobiidae consists of about 100 species.They are rather small ; some of them build tiny webs close to the ceiling in people's homes...
spiders. While most aggregations of P. africana there include adult and also juvenile of all stages, most groups consist only of small juveniles. A group of small juveniles can prevent jumping spiders and oecobiids from entering or leaving its nest. One of the juveniles will lunge and bite the victim, and sometimes others of the group join in feeding.
In vegetation near the shoreline of Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
, social jumping spiders build nest complexes, in which P. africana hunts, apparently without building capture-webs. The assassin bugs Nagusta sp. indet. ("not identified") and Scipinnia repax prey on P. africana and on social jumping spiders and other types of prey in the complexes. Nagusta usually hunts in groups of two to three, apparently catches P. africana when the latter is busy invading a jumping nest complex, and often shares the prey. Scipinnia repax preys on P. africana in a similar way but alone, and also preys on Nagusta.
Tactics used by most of Portia
Web-based spiders have poor spatial appreciation and get much of their information from reading tensions and movement in their web. P. africana, P. fimbraba and P. labiata can use their eight legs and two palps to pluck another spider's web with a virtually unlimited range of movements, using a trial and error method, until it finds and repeats a set of movements that either lures the prey out into the open or calms the prey while the Portia walks slowly close enough to bite the victim. If the prey stops being controlled by the sequence, the Portia tries new combinations until one works, and then repeats the new sequence. While such hunting shows use of least short-term memoryShort-term memory
Short-term memory is the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory is believed to be in the order of seconds. A commonly cited capacity is 7 ± 2 elements...
, as of 2011 researchers do not know how long a Portia can retain such memories nor whether a Portia may use different trial and error starts for some prey species.
Such tactics enable Portia species to take web-based spiders from 10% to 200% of their size, and Portia species hunt in all types of webs. In contrast, other cursorial spiders generally have difficulty moving on webs, and web-building spiders find it difficult to move in webs unlike those they build. When hunting in another spider's web, the slow, choppy movements and the flaps on its legs make Portia species resemble leaf detritus caught in the web and blown in a breeze. P. africana and some other Portia species use breezes and other disturbances as "smokescreens" in which these predators can approach web-based spiders more quickly, and revert to a more cautious approach when the disturbance disappears. A few web spiders run away when they sense the un-rhythmical gait of a Portia entering the web – a reaction Wilcox and Jackson termed "Portia panic".
Portia species can make detours to find the best attack angle against dangerous prey, even when the best detour takes a Portia out of visual contact with the prey, and sometimes the planned route leads to abseiling
Abseiling
Abseiling , rappelling in American English, is the controlled descent down a rock face using a rope; climbers use this technique when a cliff or slope is too steep and/or dangerous to descend without protection.- Slang terms :...
down a silk thread and biting the prey from behind. Such detours may take up to an hour, and a Portia usually picks the best route even if it needs to walk past an incorrect route. If a Portia makes a mistake while hunting another spider, it may itself be killed.
When hunting, mature females of P. africana, P. fimbriata, P. labiata, and P. schultzi emit olfactory signals that reduce the risk that any other females, males or juveniles of the same species may contend for the same prey. The effect inhibits aggressive mimicry against a prey spider even if the prey spider is visible, and also if the prey is inhabiting any part of a web. If a female of one of these species smells a male of the same species, the female stimulates the males to court. These Portia species do not show this behaviour when they receive olfactory signals from members of other Portia species.
All Portia species eat eggs of other spiders, including eggs of their own species and of other cursorial spiders, and can extract eggs from cases ranging from the flimsy ones of Pholcus
Pholcus
The spider genus Pholcus contains the Daddy long-legs spider P. phalangioides.Confusion often arises because the name "Daddy longlegs" is also applied to two other unrelated arthropods: the Harvestman and the Crane Fly....
to the tough papery ones of Philoponella
Philoponella
Philoponella is a genus of uloborid spiders. Like all Uloboridae, these species have no venom.The species P. vicinus uses its silk to crush its victims to death.-Cooperation:...
. While only P. fimbriata (in Queensland) captures cursorial spiders in their nests, all Portia species steal eggs from empty nests of cursorial spiders.
The venom of Portia is unusually powerful against spiders. When a Portia stabs a small to medium spider (up to its own weight), including another Portia, the prey usually rans away for about 100 to 200 millimetres, enters convulsions, becomes paralysed after 10 to 30 seconds, and continues convulsing for 10 seconds to 4 minutes. Portia slowly approaches the prey and and takes it. Portia usually needs to inflict up to 15 stabbings to completely immobilise a larger spider (1.5 to 2 times its own weight), and then the Portia may wait about 20 to 200 millimetres away for 15 to 30 minutes from seizing the prey. Insects are usually not immobilised so quickly but continue to struggle, sometimes for several minutes.
In laboratory tests, P. africana appeared to be a poor hunter. These tests, like those for other Portia species, were individual contests between one hunter and one prey.
| Prey | | Performance | P. africana | P. labiata | P. schultzi | P. fimbriata (Q) | P. fimbriata (NT) | P. fimbriata (SL) |
|---|---|---|---|---|---|---|---|
| Salticid | Tendency to pursue prey | 77% | 63% | 58% | 87% | 50% | 94% |
| Efficiency in capturing prey | 29% | 40% | 36% | 93% | 10% | 45% | |
| Web-building spider |
Tendency to pursue prey | 74% | 83% | 84% | 91% | 94% | 64% |
| Efficiency in capturing prey | 65% | 79% | 72% | 92% | 81% | 83% | |
| Insect | Tendency to pursue prey | 48% | 35% | 52% | 27% | 30% | 43% |
| Efficiency in capturing prey | 67% | 71% | 69% | 41% | 83% | 78% |
Reproduction and lifecycle
While many jumping spiders rest in approximately circular nests, female Portia species place a leaf or similar object near the top of her capture web as a rest. A submature male also makes a similar nest in a capture web, but mature males do not make capture webs.Before courtship
Courtship
Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. In courtship, a couple get to know each other and decide if there will be an engagement or other such agreement...
, a male Portia spins a small web between boughs or twigs, which he hangs under and ejaculates on to. He then soaks the semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...
into reservoirs on his pedipalp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
s, which are larger than those of females.
A female P. africana prefers to lay her eggs on a silken platform free from detritus.
In a laboratory, male P. africana copulated with female P. labiata but not eggs were laid. During all cases the female P. labiata twisted and lunged in an attempt to bite.
As in other Portia species, if a mature male meets a sub-mature female, he will try to cohabit with her.
When moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
ing, all Portias spin a horizontal web of a diameter about twice their body length and suspended 1 to 4 mm (0.0393700787401575 to 0.15748031496063 in) below a leaf. The spider lies head down, and often slides down 20 to 30 mm (0.78740157480315 to 1.2 in) during moulting. They spin a similar temporary web when resting.
Ecology
P. africana has been found in AngolaAngola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
, the Central African Republic
Central African Republic
The Central African Republic , is a landlocked country in Central Africa. It borders Chad in the north, Sudan in the north east, South Sudan in the east, the Democratic Republic of the Congo and the Republic of the Congo in the south, and Cameroon in the west. The CAR covers a land area of about ,...
, Gabon
Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...
, Ghana
Ghana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
, the Ivory Coast, Sierra Leone
Sierra Leone
Sierra Leone , officially the Republic of Sierra Leone, is a country in West Africa. It is bordered by Guinea to the north and east, Liberia to the southeast, and the Atlantic Ocean to the west and southwest. Sierra Leone covers a total area of and has an estimated population between 5.4 and 6.4...
, Zaire
Zaire
The Republic of Zaire was the name of the present Democratic Republic of the Congo between 27 October 1971 and 17 May 1997. The name of Zaire derives from the , itself an adaptation of the Kongo word nzere or nzadi, or "the river that swallows all rivers".-Self-proclaimed Father of the Nation:In...
and Zambia
Zambia
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
.
Around Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
's Kisumi at the Equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
, P. africana lives on level ground about 1,400 metres above sea level where there is no dry season, and inhabits open savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
containing clumps sisal
Sisal
Sisal is an agave that yields a stiff fibre traditionally used in making twine, rope and also dartboards. The term may refer either to the plant or the fibre, depending on context...
and euphorbia.. There, P. africana appears in large, dense but localised populations of three species of jumping spider, all with bodies less than 5.0 millimetres long.
In vegetation near the shoreline of Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
, social jumping spiders build dense nest complexes, in which P. africana hunts. The assassin bugs Nagusta sp. indet. and Scipinnia repax prey on P. africana, and S. repax also preys on Nagusta.
Taxonomy
Portia africana was originally described by Simon in 1886 as Linus africana. The species has also been named Cocalus africana (Thorell, 1893) and Neccocalus africana (Roewer, 1964), and finally P. africana since 1978.Portia africana is one of 17 species in the genus Portia
Portia (genus)
Portia is a genus of jumping spider which feeds on other spiders . They are remarkable for their hunting behaviour which suggests they are capable of learning and problem solving, traits normally attributed to much larger animals....
as of May 2011. Wanless divided the genus Portia into two species group
Species group
A species group is an informal taxonomic rank into which an assemblage of closely related species within a genus are grouped because of their morphological similarities and their identity as a biological unit with a single monophyletic origin.-Use:...
s: the schultzi group, in which males' palps have a fixed tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
l apophysis
Tubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
; and the kenti group, in which the apophysis of each palp in the males has a joint separated by a membrane. The schultzi group includes P. schultzi, P. africana, P. fimbriata, and P. labiata
Portia labiata
Portia labiata is a jumping spider found in Sri Lanka, India, Burma , Malaysia, Singapore, Java, Sumatra and the Philippines. In this medium-sized jumping spider, the front part is orange-brown and the back part is brownish...
.
Portia africana is closely relation to P. alboguttata, of which only females have been found, in Malawi and South Africa.
The genus Portia is in the subfamily Spartaeinae
Spartaeinae
The Spartaeinae are a subfamily of the spider family Salticidae . It was established by Fred R. Wanless in 1984 to include the groups Boetheae, Cocaleae, Lineae, Codeteae and Cyrbeae, which in turn were defined by Eugène Simon....
, which is thought to be primitive. Molecular phylogeny
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
, a technique that compares the DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
of organisms to construct the tree of life, indicates that Portia is a member of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Spartaeinae
Spartaeinae
The Spartaeinae are a subfamily of the spider family Salticidae . It was established by Fred R. Wanless in 1984 to include the groups Boetheae, Cocaleae, Lineae, Codeteae and Cyrbeae, which in turn were defined by Eugène Simon....
, that Spartaeinae is basal (quite similar to the ancestors of all jumping spiders), and that the Spartaeus
Spartaeus
Spartaeus is a spider genus of the Salticidae family .The genus was renamed from Boethus in 1984 because the name was found to be preoccupied.-Species:* Spartaeus abramovi Logunov & Azarkina, 2008 — Vietnam...
, Phaeacius
Phaeacius
Phaeacius is a spider genus of the family Salticidae , found in sub-tropical China and between India and the Malay Peninsula, including Sri Lanka, Sumatra and the Philippines...
, and Holcolaetis
Holcolaetis
Holcolaetis is a genus of the spider family Salticidae .Like Euryattus and Thiania bhamoensis, these spiders build a flat, densely woven egg sac that is not contiguous with the silk of the nest...
genera are its closest relatives.