Pterygophora californica
Encyclopedia
Pterygophora californica is a large species
of kelp
, commonly known as stalked kelp or southern palm kelp. It is the only species in its genus
Pterygophora (Ruprecht, 1852). It grows in shallow water on the Pacific coast of North America where it forms part of a biodiverse
community in a "kelp forest".
and has a single, tough, woody stipe
or stem up to two metres long and 2cm (0.8in) in diameter. It is a long-lived perennial plant which may survive for twenty-five years, and annual growth rings can be seen in the stipe. There are a number of smooth blades arranged on either side of the top half of the stipe. These are sporophyll
s and bear reproductive organs called sporangia in which the spores are formed. The terminal blade is linear, has a midrib and is larger than the others, growing up to 90cm (33in) long.
of the west coast of North America from British Colombia south to Mexico
at depths down to about ten metres.
. Microscopic zoospores are produced in the sporangia. After release, these settle on the sea bed and develop into haploid gametophyte
s. These produce male and female gamete
s the fertilisation of which results in zygote
formation and the growth of the diploid sporophyte
s, the stipe and blades.
s with other brown algae including the annual
species, bull kelp (Nereocystis luetkeana) and giant kelp (Macrocystis pyrifera
). Brown seaweeds are photosynthetic
organisms and their growth is mainly restricted by the availability of light. Various algae try to get a head start by attaching themselves to P. californica well above the ocean floor. These include red algae (Rhodophyte spp.), bull kelp (Nereocystis luetkeana) and sea belt (Saccharina latissima). The most common cause of death of P. californica is being torn from the rocks during storms. This is made more likely by the drag caused by the epiphyte
burden. P. californica and other Laminariales attempt to reduce their epiphytic load by periodically sloughing off their surface layers and by the production of "antifouling" substances such as phenols in their tissues.
At Race Rocks, near Vancouver Island
, it was found that during the winter, the only remains of the kelp forest was the bare stipes of P. californica, the annual seaweeds having been broken down and dispersed. By mid summer however, the fast growing N. luetkeana formed the canopy while P. californica and S. latissima formed a middle storey layer. In a research study in that location, it was found that much of the N. luetkeana was growing epiphytically on P. californica with their holdfasts attached to the blades and upper portions of the stipes. S latissima was also epiphytic but occupied the middle part of the stipe. Neither was present on the lower regions of the stipe and it was thought that this was due to grazing pressure from benthic
macrofauna such as sea urchins.
Herbivore
s feed on P. californica and other kelps, the predominant grazers
being sea urchins. If the population size of these becomes too great, "barren grounds", with no large algal species, can develop and may remain in existence for years. A reduction in the number of predators
or a diminution in the quantity of drift algae may encourage hungry urchins to overexploit and potentially eradicate the kelp. The sea urchins Strongylocentrotus purpuratus
and Strongylocentrotus droebachiensis
graze on P. californica at the northern end of its range.
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 kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
, commonly known as stalked kelp or southern palm kelp. It is the only species in its 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...
Pterygophora (Ruprecht, 1852). It grows in shallow water on the Pacific coast of North America where it forms part of a biodiverse
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
community in a "kelp forest".
Description
P. californica is a large brown seaweed and may grow to about three metres in height. It is attached to a rocky substrate by its holdfastHoldfast
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. ...
and has a single, tough, woody stipe
Stipe (botany)
In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described....
or stem up to two metres long and 2cm (0.8in) in diameter. It is a long-lived perennial plant which may survive for twenty-five years, and annual growth rings can be seen in the stipe. There are a number of smooth blades arranged on either side of the top half of the stipe. These are sporophyll
Sporophyll
A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls bear either megasporangia , or microsporangia...
s and bear reproductive organs called sporangia in which the spores are formed. The terminal blade is linear, has a midrib and is larger than the others, growing up to 90cm (33in) long.
Distribution
P. californica is found in the sublittoral zoneNeritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
of the west coast of North America from British Colombia south to Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
at depths down to about ten metres.
Biology
Reproduction in P. californica involves an alternation of generationsAlternation of generations
Alternation of generations is a term primarily used in describing the life cycle of plants . A multicellular sporophyte, which is diploid with 2N paired chromosomes , alternates with a multicellular gametophyte, which is haploid with N unpaired chromosomes...
. Microscopic zoospores are produced in the sporangia. After release, these settle on the sea bed and develop into haploid gametophyte
Gametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
s. These produce male and female gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s the fertilisation of which results in zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
formation and the growth of the diploid sporophyte
Sporophyte
All land plants, and some algae, have life cycles in which a haploid gametophyte generation alternates with a diploid sporophyte, the generation of a plant or algae that has a double set of chromosomes. A multicellular sporophyte generation or phase is present in the life cycle of all land plants...
s, the stipe and blades.
Ecology
P. californica grows in underwater kelp forestKelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....
s with other brown algae including the annual
Annual
Annual or yearly is a word often used to describe something that happens once a year. Circannual describes events that take place over the course of one year and repeat year after year."Annual" may be an abbreviation for:*Yearbook*Annual plant...
species, bull kelp (Nereocystis luetkeana) and giant kelp (Macrocystis pyrifera
Macrocystis pyrifera
Macrocystis pyrifera, commonly known as Giant kelp or Giant bladder kelp, is a species of kelp , and one of four species in the genus Macrocystis...
). Brown seaweeds are photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
organisms and their growth is mainly restricted by the availability of light. Various algae try to get a head start by attaching themselves to P. californica well above the ocean floor. These include red algae (Rhodophyte spp.), bull kelp (Nereocystis luetkeana) and sea belt (Saccharina latissima). The most common cause of death of P. californica is being torn from the rocks during storms. This is made more likely by the drag caused by the epiphyte
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
burden. P. californica and other Laminariales attempt to reduce their epiphytic load by periodically sloughing off their surface layers and by the production of "antifouling" substances such as phenols in their tissues.
At Race Rocks, near Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
, it was found that during the winter, the only remains of the kelp forest was the bare stipes of P. californica, the annual seaweeds having been broken down and dispersed. By mid summer however, the fast growing N. luetkeana formed the canopy while P. californica and S. latissima formed a middle storey layer. In a research study in that location, it was found that much of the N. luetkeana was growing epiphytically on P. californica with their holdfasts attached to the blades and upper portions of the stipes. S latissima was also epiphytic but occupied the middle part of the stipe. Neither was present on the lower regions of the stipe and it was thought that this was due to grazing pressure from benthic
Benthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...
macrofauna such as sea urchins.
Herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s feed on P. californica and other kelps, the predominant grazers
Grazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
being sea urchins. If the population size of these becomes too great, "barren grounds", with no large algal species, can develop and may remain in existence for years. A reduction in the number of predators
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
or a diminution in the quantity of drift algae may encourage hungry urchins to overexploit and potentially eradicate the kelp. The sea urchins Strongylocentrotus purpuratus
Strongylocentrotus purpuratus
The purple sea urchin, Strongylocentrotus purpuratus, lives along the eastern edge of the Pacific Ocean extending from Ensenada, Mexico to British Columbia, Canada. This sea urchin species is deep purple in color and lives in lower intertidal and nearshore subtidal communities...
and Strongylocentrotus droebachiensis
Strongylocentrotus droebachiensis
Strongylocentrotus droebachiensis is commonly known as the green sea urchin because of its characteristic green color. It has the longest genus-species names in the animal kingdom...
graze on P. californica at the northern end of its range.