Symphurus thermophilus
Encyclopedia
Symphurus thermophilus is a species
of tonguefish
, family
Cynoglossidae, notable for being the only flatfish
known to be an obligate
inhabitant of hydrothermal vent
s. It is known from several widely dispersed locations in the western Pacific Ocean
and occurs in great numbers. They are tolerant of harsh conditions and are often found in close association with elemental
sulfur
, including molten sulfur pools that exceed 180°C in temperature. As they are not significantly different in appearance and feeding habits from other tonguefishes, they are thought to be relatively recent colonizers of vent ecosystem
s.
These fish were first observed in nature in 1988, and were provisionally assigned to the species Symphurus orientalis before being recognized as a new species. The species name thermophilus is from the Greek
thermos meaning "heat" and philos meaning "lover", referring to its association with hydrothermal vents.
, to the Rumble 3 and Macauley Submarine Volcanoes on the Kermadec Ridge off northern New Zealand
, including the Nikko Seamount near Minami-Iohjima Island
, the Minami-Ensei Knoll in the Mid-Okinawa Trough, the Kasuga-2 and Daikoku Seamounts in the Marianas Islands arc, and the Volcano-1 and Volcano-2 Seamounts in the Tonga arc. It is likely that S. thermophilus also occurs at yet-unexplored vent sites between these locations.
S. thermophilus occurs only within relatively shallow active hydrothermal vent sites at a depth of 239-733 m, with most found between 300-400 m. Both adult
s and juveniles
are found in the same habitat
s. Unusually for a vent fish, S. thermophilus favors environments that are rich in sulfur; they have been observed oriented vertically on solid sulfur walls, resting on beds of newly congealed sulfur adjacent to a rivulet of molten sulfur, and even on a thin crust of consolidated sulfur pebble
s overlaying a molten sulfur bed with a temperature of 187°C (though the crust is considerably cooler).
While many flatfish species prefer a fine substrate
to burrow in, S. thermophilus frequent coarse substrates and are sometimes found over solid surfaces. At the Kaikata Seamount, S. thermophilus was observed on coarse sand
bottoms where water
of 19-22°C was percolating
through the sediment
. At the Minami-Ensei Knoll, this species was found on white metachromatic sediments in water 5-10°C warmer than the ambient seawater
. At the Kasuga-2 Seamount, it occurred on a variety of dark and light-colored gravel
sediments and on bacterial mats.
Where it occurs, S. thermophilus is often extremely abundant; it is the most numerous obligate
vent vertebrate
known to date. At the Kaikata Seamount, they are found in such numbers that the fish overlap one another on the bottom. Point densities at the Daikoku Seamount have been recorded as high as 392 individuals per square meter; these densities are an order of magnitude
higher than flatfish densities reported anywhere else.
Like other tonguefishes, S. thermophilus has a laterally flattened body with united dorsal
, caudal, and anal fins. Both eye
s, which are fairly large and rounded in this species, are located on the left side of the head in adults. The pectoral fins and lateral line
are absent, and there is only a single, right-side pelvic fin. The head
is moderately long, with a blunt snout
and long, broadly arched jaw
s. There are 4-5 rows of teeth on the upper and lower jaws of the blind side, and 2-3 and 1 rows on upper and lower jaws respectively of the eyed side. The teeth are sharp and recurved, and better developed on the blind-side jaws.
The body is notably deep compared to other Symphurus species. The origin of the dorsal fin is located above the eyes and contains 88-94 rays. The dorsal fin pterygiophores and neural spines have a 1-2-2-2-2 interdigitation pattern. The pelvic fin is moderately long, contains 4 rays, and is connected to the body by a delicate membrane
. The anal fin contains 74-80 fin rays. The caudal fin is relatively long and contains 14 rays. The scale
s are small and strongly ctenoid in shape, numbering 47-56 rows transversely and 100-112 rows longitudinally.
The eyed side of the body is medium to dark chocolate brown in color, mottled with numerous dark, irregularly shaped blotches and white speckles. There are also five to eight darker, complete or incomplete crossbands. Some individuals have a white patch over two-thirds of the abdominal cavity
, sometimes with bluish-green tints and bordered posteriorly by a black blotch. The abdominal area posterior to the gill opening
is blackish brown and much darker than the rest of the body. Occasionally there are one or two irregular to nearly circular white spots along the body midline. The fin rays are dark at the base and lighter towards the tips, and there is an irregular dark spot at the base of the caudal fin. The blind side of the body is white, with scattered dark melanophores.
The maximum known length is 8.7 cm for a male
and 11.2 cm for a female
. The fish from the Nikko Seamount are nearly twice as large as those from the Kasuga-2 and Daikoku Seamounts. This may be because of the higher biological productivity at Nikko, or because Kasuga-2 and Daikoku were recently colonized.
S. thermophilus spend most of their time on the sea floor, moving forwards or backwards by undulating their bodies and sometimes burying themselves completely in the substrate. They seem to be attracted to loose sediments, probably related to the uncovering of food, and often congregate in pits. The fish frequently rest atop one another without reaction.
The vent communities that co-occur with S. thermophilus differs greatly between seamounts. They co-occur with large numbers of the snail
Oenopota ogasawaarna at the Daikoku Seamount, and with the abundant shrimp
Opaepele loihi at the Nikko Seamount. They also frequently occur with the crab
Austinograea yunohana, which are found at Nikko, Daikoku, and Kasuga-2. Large bythograeid
crabs have been observed attempting attacks on the fish, though not successfully. S. thermophilus likely experiences little to no predation pressure, which coupled with the high food biomass
available allows their high densities.
The affinity of this species for native sulfur has yet to be explained. The morphology
of S. thermophilus does not show any differences from other deepwater Symphurus species that would suggest adaptation
s to its unique habitat. However, S. thermophilus likely possesses extensive physiological
and biochemical
adaptations for coping with the harsh conditions around hydrothermal vents, such as temperature
and pH
fluctuations, and exposure to heavy metals. In particular, they must have high hemoglobin
oxygen
affinities and efficient respiratory system
s to deal with the toxic hydrogen sulfide
in venting fluid. S. thermophilus is also capable of tolerating pH as low as 2, akin to sulfuric acid
, and can rest over pools of molten sulfur without harm. Individuals of S. thermophilus often show skeletal abnormalities such as undeveloped fin rays or fused bone
s, likely attributable to the vent environment.
of S. thermophilus varies significantly from seamount to seamount, with the only constant being polychaete worms, which are most important for individuals on Daikoku and Volcano-1 Seamounts. Other population
s feed predominantly on crustacean
s; the main prey item of S. thermophilus on the Nikko Seamount is the alvinocaridid shrimp
Opaepele loihi, and on the Kasuga-2 Seamount they eat mostly palaemonid shrimp
. The fish at these sites appear to be "sit and wait" predators, taking slow-moving shrimp that wander too close. By contrast, the fish at the Daikoku Seamount seem to be more active, opportunistic foragers; they do not eat many crustaceans and have been observed scavenging on dying fish that fall to the bottom after coming into contact with the volcanic plume
s. Snail
s and sponge spicule
s have also been found in the stomach
s of a few individuals, and in captivity they are known to consume any food offered to them. The large numbers of S. thermophilus found on sulfur crusts where there are no obvious prey items may feed directly on filaments of chemosynthetic bacteria. If so, this would represent a hitherto unknown behavior for vent fish species.
measuring 0.9 mm in diameter. The developmental speed of the eggs increases with temperature: they hatch in one day at 26°C, in 3 days at 20°C, and in 14 days at 12°C. The newly hatched fry are initially sustained by a yolk sac
, and have a completely developed mouth
, eye
s, and digestive system by 7 days of age. The migration of the eyes begins after 30 days. Compared to other flatfish, S. symphurus is slow-growing and long-lived, with a lifespan
upwards of 10 years. Growth differs between populations, due to availability of food and consequent activity level. Over half their growth in length is accomplished in the first three years, with the growth rate slowing down afterwards. Both sexes likely attain sexual maturity
at around 4.4 cm long and one year of age.
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 tonguefish
Tonguefish
Tonguefishes are a family, Cynoglossidae, of flatfishes. They are distinguished by the presence of a long hook on the snout overhanging the mouth, and the absence of pectoral fins...
, 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...
Cynoglossidae, notable for being the only flatfish
Flatfish
The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
known to be an obligate
Obligate
Obligate means "by necessity" and is used mainly in biology in phrases such as:* Obligate aerobe, an organism that cannot survive without oxygen* Obligate anaerobe, an organism that cannot survive in the presence of oxygen...
inhabitant of hydrothermal vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s. It is known from several widely dispersed locations in the western Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and occurs in great numbers. They are tolerant of harsh conditions and are often found in close association with elemental
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
, including molten sulfur pools that exceed 180°C in temperature. As they are not significantly different in appearance and feeding habits from other tonguefishes, they are thought to be relatively recent colonizers of vent ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s.
These fish were first observed in nature in 1988, and were provisionally assigned to the species Symphurus orientalis before being recognized as a new species. The species name thermophilus is from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
thermos meaning "heat" and philos meaning "lover", referring to its association with hydrothermal vents.
Distribution and habitat
This species has a wide, disjunct distribution in the western Pacific, from the Kaikata Seamount near the Bonin Islands off southeastern JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, to the Rumble 3 and Macauley Submarine Volcanoes on the Kermadec Ridge off northern New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, including the Nikko Seamount near Minami-Iohjima Island
South Iwo Jima
South Iwo Jima is the southernmost island of the Volcano Islands group of the Ogasawara Islands, 60 km south of Iwo Jima. It is 1300 km south of Tokyo, 330 km SSW of Chichijima. Its area is 3.4 km², shore length, 7.5 km, and highest point 916m, the highest in the...
, the Minami-Ensei Knoll in the Mid-Okinawa Trough, the Kasuga-2 and Daikoku Seamounts in the Marianas Islands arc, and the Volcano-1 and Volcano-2 Seamounts in the Tonga arc. It is likely that S. thermophilus also occurs at yet-unexplored vent sites between these locations.
Adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....
s and juveniles
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
are found in the same habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s. Unusually for a vent fish, S. thermophilus favors environments that are rich in sulfur; they have been observed oriented vertically on solid sulfur walls, resting on beds of newly congealed sulfur adjacent to a rivulet of molten sulfur, and even on a thin crust of consolidated sulfur pebble
Pebble
A pebble is a clast of rock with a particle size of 4 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered to be larger than granules and smaller than cobbles . A rock made predominantly of pebbles is termed a conglomerate...
s overlaying a molten sulfur bed with a temperature of 187°C (though the crust is considerably cooler).
While many flatfish species prefer a fine substrate
Substrate (marine biology)
Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
to burrow in, S. thermophilus frequent coarse substrates and are sometimes found over solid surfaces. At the Kaikata Seamount, S. thermophilus was observed on coarse sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
bottoms where water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
of 19-22°C was percolating
Percolation
In physics, chemistry and materials science, percolation concerns the movement and filtering of fluids through porous materials...
through the sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
. At the Minami-Ensei Knoll, this species was found on white metachromatic sediments in water 5-10°C warmer than the ambient seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
. At the Kasuga-2 Seamount, it occurred on a variety of dark and light-colored gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
sediments and on bacterial mats.
Where it occurs, S. thermophilus is often extremely abundant; it is the most numerous obligate
Obligate
Obligate means "by necessity" and is used mainly in biology in phrases such as:* Obligate aerobe, an organism that cannot survive without oxygen* Obligate anaerobe, an organism that cannot survive in the presence of oxygen...
vent vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
known to date. At the Kaikata Seamount, they are found in such numbers that the fish overlap one another on the bottom. Point densities at the Daikoku Seamount have been recorded as high as 392 individuals per square meter; these densities are an order of magnitude
Order of magnitude
An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. In its most common usage, the amount being scaled is 10 and the scale is the exponent being applied to this amount...
higher than flatfish densities reported anywhere else.
Description
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, caudal, and anal fins. Both eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s, which are fairly large and rounded in this species, are located on the left side of the head in adults. The pectoral fins and lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
are absent, and there is only a single, right-side pelvic fin. The head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
is moderately long, with a blunt snout
Snout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
and long, broadly arched jaw
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s. There are 4-5 rows of teeth on the upper and lower jaws of the blind side, and 2-3 and 1 rows on upper and lower jaws respectively of the eyed side. The teeth are sharp and recurved, and better developed on the blind-side jaws.
The body is notably deep compared to other Symphurus species. The origin of the dorsal fin is located above the eyes and contains 88-94 rays. The dorsal fin pterygiophores and neural spines have a 1-2-2-2-2 interdigitation pattern. The pelvic fin is moderately long, contains 4 rays, and is connected to the body by a delicate membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
. The anal fin contains 74-80 fin rays. The caudal fin is relatively long and contains 14 rays. The scale
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s are small and strongly ctenoid in shape, numbering 47-56 rows transversely and 100-112 rows longitudinally.
The eyed side of the body is medium to dark chocolate brown in color, mottled with numerous dark, irregularly shaped blotches and white speckles. There are also five to eight darker, complete or incomplete crossbands. Some individuals have a white patch over two-thirds of the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
, sometimes with bluish-green tints and bordered posteriorly by a black blotch. The abdominal area posterior to the gill opening
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
is blackish brown and much darker than the rest of the body. Occasionally there are one or two irregular to nearly circular white spots along the body midline. The fin rays are dark at the base and lighter towards the tips, and there is an irregular dark spot at the base of the caudal fin. The blind side of the body is white, with scattered dark melanophores.
The maximum known length is 8.7 cm for a male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
and 11.2 cm for a female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
. The fish from the Nikko Seamount are nearly twice as large as those from the Kasuga-2 and Daikoku Seamounts. This may be because of the higher biological productivity at Nikko, or because Kasuga-2 and Daikoku were recently colonized.
Biology and ecology
The vent communities that co-occur with S. thermophilus differs greatly between seamounts. They co-occur with large numbers of the snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
Oenopota ogasawaarna at the Daikoku Seamount, and with the abundant shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
Opaepele loihi at the Nikko Seamount. They also frequently occur with the crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
Austinograea yunohana, which are found at Nikko, Daikoku, and Kasuga-2. Large bythograeid
Bythograeidae
Bythograeidae is a small family of crabs which live around hydrothermal vents. The family contains 14 species in 6 genera. Their relationships to other crabs are unclear...
crabs have been observed attempting attacks on the fish, though not successfully. S. thermophilus likely experiences little to no predation pressure, which coupled with the high food biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
available allows their high densities.
The affinity of this species for native sulfur has yet to be explained. The morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of S. thermophilus does not show any differences from other deepwater Symphurus species that would suggest adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
s to its unique habitat. However, S. thermophilus likely possesses extensive physiological
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
and biochemical
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
adaptations for coping with the harsh conditions around hydrothermal vents, such as temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
fluctuations, and exposure to heavy metals. In particular, they must have high hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
affinities and efficient respiratory system
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
s to deal with the toxic hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
in venting fluid. S. thermophilus is also capable of tolerating pH as low as 2, akin to sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
, and can rest over pools of molten sulfur without harm. Individuals of S. thermophilus often show skeletal abnormalities such as undeveloped fin rays or fused bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s, likely attributable to the vent environment.
Feeding
The dietDiet (nutrition)
In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. With the word diet, it is often implied the use of specific intake of nutrition for health or weight-management...
of S. thermophilus varies significantly from seamount to seamount, with the only constant being polychaete worms, which are most important for individuals on Daikoku and Volcano-1 Seamounts. Other population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
s feed predominantly on crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s; the main prey item of S. thermophilus on the Nikko Seamount is the alvinocaridid shrimp
Alvinocarididae
Alvinocarididae is a family of shrimp, originally described by M. L. Christoffersen in 1986 from samples collected by DSV Alvin, from which they derive their name. Shrimp of the family Alvinocarididae generally inhabit deep sea hydrothermal vent regions, and hydrocarbon cold seep environments....
Opaepele loihi, and on the Kasuga-2 Seamount they eat mostly palaemonid shrimp
Palaemonidae
Palaemonidae is a family of crustaceans of the order Decapoda. They belong to the infraorder Caridea, which contains the true shrimp; while some freshwater palaemonid species are known as "prawns", the family belongs to the suborder Pleocyemata like all true shrimp, whereas the true prawns are...
. The fish at these sites appear to be "sit and wait" predators, taking slow-moving shrimp that wander too close. By contrast, the fish at the Daikoku Seamount seem to be more active, opportunistic foragers; they do not eat many crustaceans and have been observed scavenging on dying fish that fall to the bottom after coming into contact with the volcanic plume
Volcanic plume
Volcanic plume may refer to:* Eruption column, or volcanic plume, a column of hot volcanic ash and gas emitted into the atmosphere during an explosive volcanic eruption...
s. Snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s and sponge spicule
Spicule
Spicules are tiny spike-like structures of diverse origin and function found in many organisms, such as the copulatory spicules of certain nematodes or the grains on the skin of some frogs.In sponges, spicules perform a structural function....
s have also been found in the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
s of a few individuals, and in captivity they are known to consume any food offered to them. The large numbers of S. thermophilus found on sulfur crusts where there are no obvious prey items may feed directly on filaments of chemosynthetic bacteria. If so, this would represent a hitherto unknown behavior for vent fish species.
Reproduction
Reproduction is oviparous, with females releasing buoyant eggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
measuring 0.9 mm in diameter. The developmental speed of the eggs increases with temperature: they hatch in one day at 26°C, in 3 days at 20°C, and in 14 days at 12°C. The newly hatched fry are initially sustained by a yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
, and have a completely developed mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
, eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s, and digestive system by 7 days of age. The migration of the eyes begins after 30 days. Compared to other flatfish, S. symphurus is slow-growing and long-lived, with a lifespan
Life expectancy
Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...
upwards of 10 years. Growth differs between populations, due to availability of food and consequent activity level. Over half their growth in length is accomplished in the first three years, with the growth rate slowing down afterwards. Both sexes likely attain sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at around 4.4 cm long and one year of age.