Category Archives: Invertebrate

Eupentacta quinquesemita:white sea cucumber–The Race Rocks Taxonomy

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Here are the tentacles extended on a cluster of Eupentaca.Their bodies are hidden. Photo by Dr.A. Svoboda

GENERAL DESCRIPTION

Eupentacta quinquesemita is stiff to touch due to abundant calcareous ossicles in the skin and tube feet. The body grows 4-8 cm in length. The non-retractile tube feet give it a spiky look. It has five rows of tube feet (four tube feet in width) with smooth skin between. The two ventral feeding tentacles are smaller than the other eight. This character is useful for identifying this species when only the tentacles are visible. The expanded tentacles are creamy white with tinges of yellow or pink at the bases.

Skin ossicles: numerous large, porous, ovoid bodies dominate the ossicles but among them are small, delicate baskets. The latter are important in differentiating this species from Eupentacta pseudoquinquesemita.

HABITAT

They are fairly common under the rocks and in cervices, low intertidal zone on rocky shores; common on concrete piles and marina floats in Monterey harbor, Vancouver (British Columbia) to Morro Bay (San Luis Obispo. Co). High densities of this species occur in strong currents. Juveniles (up to 1 cm) settle among hydroids and small algae in high current areas and on floating docks.

REPRODUCTION

Eupentacta quinquesemita is a suspension feeder. It spawns from late March to mid May. The female produces eggs greenish in color, 370 to 416 um diameter: the male releases sperm, and fertilization takes place in open water. The yolky egg develops into a non-feeding evenly ciliated larva. In culture, the larva grows to the armoured stage in 11 to 16.5 days.

 

PREDATORS

The predators of Eupentacta quinquesemita are: the Sun Star (Solaster stimpsoni), the Sunflower Star (Pycnopodia helianthoides), the Six-armed Star (Leptasterias hexactis) and the Kelp Greenling (Hexagrammos decagrammus).

BIOTIC ASOCIATION

The internal parasite, Thyonicola americana, a shell-less wormlike snail, attaches elongated coils of eggs to the intestine of E. quinquesemita. The larvae are released into the intestine and probably scape through the anus. Any parasites that are ejected by evisceration perish.

FEEDING

Is by shovelling of sediment into the mouth and digesting the microfauna within. No direct feeding is required. Is omnivore.

DomainEukarya
Kingdom Animalia
Phylum Echinodermata
Class Holothuroidea
SubclassDendrochirotacea
Order Dendrochirotida
Family Sclerodactylidae
Genus Eupentacta
Species quinquesemita
Common name White sea cucumber

REFERENCES

Lambert, P. 1997. Sea Cucumbers of British Columbia, Southeast Alaska and Puget Sound. UBC Press, British Columbia Canada. 166 pages

Morris, R., P. Abbott, and E. Haderlie.1980. Intertidal Invertebrates of California. Standford University Press, Stanford, California. 690 pages.

Kozloff, E. 1996 . Seashore Life of the Northern Pacific Coast. Fourth Edition. University Of Washington Press. Seattle and London. 370 pages.

 

Other Members of the Phylum Echinodermata at Race Rocks 
taxonomyiconReturn to the Race Rocks Taxonomy
and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

 Patricia  (PC year28)

Orthasterias koehleri: Rainbow sea star– The Race Rocks Taxonomy

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General description:

Arms radius to 21cm, gets fairly big to 50cm; disk small, with five slender arms; aboral surface bearing prominent sharp spines and a conspicuous ruff of pedicellariae, which are white; color vivid; varying from rosy pink with a gray mottling, to bright red mottled or banded with yellow, the spines whitish or lilac.

Habitat

Uncommon, on mud, sand, and kelp but occurs in the very low intertidal zone, on shaded rock surfaces. It is more common at scuba depths and extends to 250m, being found from Alaska to Southern California.

Feeding
Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Class Asteroidea
Order Forcipulatida
Family Asteriidae
Genus Orthasterias
Species koehleri
COMMON NAME: Rainbow sea star

Orthasterias koehleri feed on small snails, limpets, clams, scallops, chiton, barnacles, and tunicates. They can dig clams out of cobbled bottoms, and use the pull of the tube feet to spread apart the outer layer of a clam shell until a small opening is made between the valves. The stomach is then inserted through the opening and the clam digested.

Reproduction

To expose the gonads in a rainbow sea star, make a 1-2 inch cut in the ray near the junction with the disk, push the digestive gland gently aside to expose the underlying gonad, then firmly grasp the gonoduct with forceps and cut it free from the gonopore. Fragments of gonad can be removed, but the cut gonad will leak gametes into the body cavity. Suture the incision or leave it to heal unsutured in clean and strongly flowing seas water. Recovery is better if the insicion is small, the digestive gland is undamaged, and all air is removed from the body cavity. This method has been used with success.

References

Intertidal Invertebrates of California, Between Pacific Tides
Other Members of the Phylum Echinodermata at Race Rocks 
taxonomyiconReturn to the Race Rocks Taxonomy
and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

Esrah Ugurlu (PC year 28

Strongylocentrotus droebachiensis: Green sea urchin –The Race Rocks taxonomy

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See this green urchin in the video and compare it with the purple and red urchins

 

Green Sea Urchin: average size is 50-60 mm, but may reach a maximum size of about 85 mm.

Distribution: The green sea urchin is one of the most widely distributed of all Echinoderms. It has a circumpolar distribution, which extends into the Arctic regions of both the Atlantic and Pacific Oceans. It commonly inhabits the rocky subtidal zone from the low-tide mark down to a depth of 1200 m, but also occurs intertidally in tide pools.

 

 

Diet: The green sea urchin primarily grazes on seaweeds (kelp being its preferred food source), but will also consume a wide variety of organisms including mussels, sand dollars, barnacles, whelks, periwinkles, sponges, bryozoans, dead fish, and – when hungry enough – other sea urchins.

This shows the grazing action of sea urchin teeth, arranged in a complex assemblage of small bones, the five teeth gouged out this star pattern in the stipe of a Pterygophora.

 

The skeleton of the sea urchin is called a “.test”. The radial symmetry is reflected in the placement of all the tube feet holes. Here you can see the size of a green urchin compared to a red urchin

 

 

 

Reproduction: Green sea urchins release their gametes into the water column where the eggs are fertilized by the sperm. The sexes are separate. The resulting larva (termed an “echinopluteus”) undergoes development planktonically for a period of one to several months before settling on the sea floor and metamorphosing into the adult form. Reproduction occurs on an annual cycle with spawning occurring in the spring, generally between February and May, but sometimes as late as June.  See the Lab on Sea urchin Embryology.

This video from underwater Safari shows a wolf eel crunching a sea urchin…

Behavior: Where urchins occur at high density, destructive grazing can produce habitats devoid of seaweeds. These areas may be termed “sea urchin barren grounds”.. When sea urchins are removed from these sites, either manually or by disease, the reduction in grazing pressure often results in the development of highly productive kelp forests. These kelp beds provide shelter for a wide variety of marine organisms (e.g. fish, lobsters, crabs, sea stars, bivalves, gastropods, bryozoans) and the habitat is typically much more diverse than barren grounds. Hence, sea urchins are one of the principal factors controlling habitat diversity in the rocky subtidal environment.

Other Members of the Phylum Echinodermata at Race Rocks 
taxonomyiconReturn to the Race Rocks Taxonomy
and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

Aldo Caixeta (PC yr 28)/strong>

Scyra acutifrons: Sharp-nosed crab– The Race Rocks Taxonomy

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This individual is well camouflaged and you can see the other associated organisms around it. The red circle is a serpulid worm

Geographic range is Alaska to Mexico

Size: up to 45mm (1.7 inches)

Domain Eukarya
Kingdom Animalia
Phylum Arthopoda
Subphylum Crustacea
Class Malacostrata
Superorder Eucarida
Order Decapoda
Family Epialtidae
Genus Scyra
Species acutifrons
Common Name:Sharp-nosed crab 

This is a reasonably common crab especially around the dock and higher subtidal areas. The adult males have large claws that they seem to keep folded in. The nose is flat and pointed. The crab shells are often covered with barnacles and other growth as can be seen in this picture. This species puts relatively little effort into decorating, occasionaly placing a small pieces of material on its rostrum but generally appearing to just let organisms colonize its roughened carapace. It feeds primarily on detritus and sessile invertebrates, and sometimes it associates with sea anemones. Females with eggs have been found all months but April to May and September to October. Number of eggs carried ranges fom 2,700 to 16,300.

References:

http://www3.bc.sympatico.ca/kerryw/creature/sharp.htm

Jensen G.C. 1995. Pacific Coast Crabs and Shrimps. Sea Challengers, Monterey, CA. p. 21.

Kozloff, E.N. 1983. Seashore Life of the Northern Pacific Coast. University of Washington Press. Washington. 370 pages.

Morris, R., P. Abbott, and E. Haderlie. 1980. Intertidal Invertebrates of California. Stanford University Press, California. 690 pages.

 

Other Members of the Phylum Arthropoda at Race Rocks 
taxonomyiconReturn to the Race Rocks Taxonomy
and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

Sumak Serrano (PC year 28)

Urticina piscivora: Fish-eating anemone

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upiscivora

U.piscivora photo by Dr. A. Svoboda

Urticina piscivora is one of the largest Northern Pacific sea anemones. You can find this type of species from La Jolla, Mexico to Alaska, it can grow about 8 inches (20 centimeters)
Urticina piscivora was called Tealia Anemone. The structure of this anemone consists of a bag formed by three layers a non-cellular “mesoglea” between two tissues, an outer layer called “epidermis” and an internal called gastrodermis.The interior of the bag is the gut also known as gastrovascular cavity. Sheets of tissue or septa extend out form the body wall dividing the gut into compartments wich manifests on the surface as tentacles. Many of the anemones have their tentacles in multiples of six.

Domain Eukarya
Kingdom Animalia
Phylum Cnidaria
Class Anthozoa
Genus Urticina
Species piscivora
Common Name Fish eating anemone
urtricina

Utricina photo by Pearson College divers.

Inside the centers of septa, they are often elaborated and called septa filaments .Heavily loaded with stinging cells or nematocysts. Stinging cells are used to immobilize their prey.Urticina piscivora eats small fish.

Sexes are generally separated in sea anemones, but some species may be serial hermaphrodites, functioning males during one spawning and females at a later time. The typical reproductive pattern is to spawn into the water where fertilization occurs. Asexual reproduction occurs in some sea anemones some can reproduce by splitting by two (binary fission), and others will leave little piece of the pedal disk behind as they move, (pedal laceration),

This file is provided as part of a collaborative effort
by the students, faculty, staff and volunteers  of  Pearson College UWC.		 Feb. 2002 Nora Lozano Yr.28

Return  to the Race Rocks Taxonomy

Epiactis prolifera : Brooding Anemone The Race Rocks Taxonomy

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epiactis

Epiactis prolifers G.Fletcher photo

Brooding anemones,  Epiactis prolifera are a small species. The height of an expanded specimen does not often exceed about 3cm. The basic colour is brown to greenish brown, but it is sometimes red, pinkish, blue,  red or dull green. They are usually found in the subtidal zone (at zero tidal level, especially on intertidal rock benches or surge channels, and in rocky areas with wave action, often in areas with crustose coralline algae. Brooding anemones are also regularly found on the leaves of eelgrass. Red or pinkish red specimens are sometimes found on rocky shores, but rare on eelgrass. They are rarely exposed to the air, not being able to tolerate exposure to the air and sun. Brooding anemones, like other sea anemones, attach themselves to something solid so as not to get carried off by currents or wave action.

The oral disk of brooding anemone is generally marked with radially arranged white lines. The pedal disk and column have similar lines, though they may not be as sharp. The numerous young regularly found on the pedal disk do not originate there by asexual budding, but are derived from eggs fertilized in the digestive cavity. The motile larvae, after swimming out of the mouth, migrate down to the disk and becomes installed there until they become little anemones ready to move and be able to feed themselves. Click on the photo on the left to see a belt of these juvenile anemone around the pink adult which has retracted.

 

Brooding anemone usually spend most of their lives in one place, but some have the ability to move, they can only travel three to four inches an hour. Sometimes the brooding anemone hitch a ride on hermit crabs or decorator crabs. Brooding anemones can protect the crab and if the crab is a messy eater, the sea anemone can pick up bits of food from the crab and eat it. This is one of the biotic associations of Epiactis prolifera. This is also an example of mutualism, where both the organisms living together benefit from each other.

Brooding anemones eat small fish and shrimps. Much of their prey is crustaceans. The brooding anemones capture its prey with its deadly stinging tentacles. Its mouth and tentacles are located on the top of its body. Their stalk and tentacles are bristling with an arsenal of stinging cells, or nematocysts. The double walled microscopic stinging cells contain a hollow thread with a minute harpoon-like barb at the end. When the cell is stimulated either physically or chemically, it explodes and fires the barb and attaches the thread with incredible force into the potential predator or prey and simultaneously injects a potent poison. Usually hundreds and thousands of these stinging cells are activated at once, which can paralyze prey or deter most predators.

After being immobilized, the prey which may include shrimps, crabs, jellyfish or small fish is manoeuvred by tentacles towards the mouth where it is consumed whole. Any indigestible material or waste will be excreted through the mouth as well. Even with its formidable arsenal of nematocysts, anemones are a favoured prey for other animals. Many nudibranchs feed on anemones and are not only immune to the anemones defenses, but have the ability to absorb un-detonated packets of stinging cells which are then used for the nudibranchs own defense. Sea stars and fish are also some regular predators. If a brooding anemone, like any other sea anemones, is torn apart, then each part becomes a new brooding anemone.

References:Eugene N.Kozloff: Marine Invertebrates of the Pacific Northwest
Seashore Life of the Northern Pacific Coast
Megumi F.Strathmann: Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast
Doug Pemberton: Divers Magazine February 2001
http://divermag.com/archives/feb2001/anemones-feb01.html
Sea Anemones: http://library.thinkquest.org/J001418/anemone.html

This file is provided as part of a collaborative effort by the students, staff, faculty and Volunteers of Lester Pearson College February 2002 Sangeeta Asre Fiji IslandsPearson College: Year 28

 

Epiactis Prolifera: Brooding Anemone- The Race Rocks Taxonomy

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broodinganemone

A field of Epiactis prolifera, showing the high variability in colouration– photo by Ryan Murphy.

Brooding anemones or Epiactis prolifera are a small species: the height of an expanded specimen does not often exceed about 3cm. The basic colour is brown to greenish brown, but it is sometimes red, pinkish red or dull green. They are usually found in the subtidal zone (zero tidal zone), especially on intertidal rock benches or surge channels, and in rocky areas with wave action, often in areas with crustose coralline algae. Brooding anemones are also regularly found on the leaves of eelgrass. Red or pinkish red specimens are sometimes found on rocky shores, but rare on eelgrass. They are rarely exposed to the air, not being able to tolerate exposure to the air and sun. Brooding anemones, like other sea anemones, attach themselves to something solid so as not to get carried off by currents or wave action.

 

The oral disk of brooding anemone is generally marked with radially arranged white lines. The pedal disk and column have similar lines, though they may not be as sharp. The numerous young regularly found on the pedal disk do not originate there by asexual budding, but are derived from eggs fertilized in the digestive cavity. The motile larvae, after swimming out of the mouth, migrate down to the disk and becomes installed there until they become little anemones ready to move and be able to feed themselves. You can see the belt of juvenile anemone in several of the images above.

Domain Eukarya
Kingdom Animalia
Phylum Cnidaria
Class Anthozoa
Order Actiniaria
Family Actiniidae
Subclass Zoantharia
Genus Epiactis
Species prolifera
Common Name: Brooding Anemone
rmbrooding

Brooding Anemone photo by Ryan Murphy

Brooding anemones eat small fish and shrimps. Much of their prey is crustaceans. The brooding anemones capture its prey with its deadly stinging tentacles. Its mouth and tentacles are located on the top of its body. Their stalk and tentacles are bristling with an arsenal of stinging cells, or nematocysts. The double walled microscopic stinging cells contain a hollow thread with a minute harpoon-like barb at the end. When the cell is stimulated either physically or chemically, it explodes and fires the barb and attaches the thread with incredible force into the potential predator or prey and simultaneously injects a potent poison. Usually hundreds and thousands of these stinging cells are activated at once, which can paralyze prey or deter most predators.

After being immobilized, the prey which may include shrimps, crabs, jellyfish or small fish is manoeuvred by tentacles towards the mouth where it is consumed whole. Any indigestible material or waste will be excreted through the mouth as well. Even with its formidable arsenal of nematocysts, anemones are a favoured prey for other animals. Many nudibranchs feed on anemones and are not only immune to the anemones defenses, but have the ability to absorb un-detonated packets of stinging cells which are then used for the nudibranchs own defense. Sea stars and fish are also some regular predators. If a brooding anemone, like any other sea anemones, is torn apart, then each part becomes a new brooding anemone.

References:

Eugene N.Kozloff: Marine Invertebrates of the Pacific Northwest
Seashore Life of the Northern Pacific Coast
Megumi F.Strathmann: Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast
Doug Pemberton: Divers Magazine February 2001
http://divermag.com/archives/feb2001/anemones-feb01.html
Sea Anemones: http://library.thinkquest.org/J001418/anemone.html

This file is provided as part of a collaborative effort by the students, staff, faculty and volunteers of Lester B. Pearson College February 2002 Sangeeta Asre- Fiji Islands
Year 28

Cucumaria miniata: Orange sea cucumber–The Race Rocks Taxonomy

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The orange Cucumaria miniata sea cucumber is a common resident just off the docks at Race Rocks in 5 to 10 meters of water. In this video they occur in a high concentration relative to other areas. Each orange tuft is the tentacle mass. If disturbed, it quickly withdraws into the sea cucumber body which is always buried under loose rocks.

Note the name Cucumaria miniata should be on the following video instead of C. curata

General Description:The Orange sea cucumber received its Latin name, Cucumaria because it resembles a cucumber. The orange pigment that separates it from other sea cucumbers comes from a chemical called cinnabar or vermilion. Although it seems to be completely soft and fragile, it actually has bone-like plates in the body wall called ossicles. To stay attached to the holes between the rocks, the cucumber uses tube feet that you can see in the image above in 5 rows around the circumference of the body. If you ever want to keep one as a pet, don’t get too attached because they usually only live about 5 years, sometimes 10 if they’re lucky.

Habitat:

Sea cucumbers live in between boulders and sheltered rock formations. Because they are able to stay attached to surfaces, they prefer to live in areas with stronger currents, making it harder for predators to reach them.

Feeding:

The orange sea cucumber is a suspension feeder. This means that it catches food in its tentacles. After the food is caught, it removes the food with its eating arms and scrapes it into its mouth. Sea cucumbers eat plankton and detritus.

Reproduction:

Unfortunately, sea cucumbers aren’t very intimate creatures. In fact, their mating process can’t have any less contact. When the time comes to make a new cucumber and two cucumbers are physically (and emotionally) ready, one will release eggs into the water and the other will release sperm. From that, the two elements meet in suspension and that’s it.

Predators and Defenses:

The cucumbers main predators include fish, and even humans. That’s right kids, there are some people in the world that actually eat these things. To protect itself, the cucumber has many defenses. Their skin is some of the most amazing tissue found on an animal. The compound is made of a material called ‘catch collagen’ which can change from liquid to solid when neurologically triggered. It does this so can squeeze into small spaces and then harden again. Another defense is they “pee” out all the water in their system and shrink into a small, hard rock. The “peeing” usually occurs when the cucumber is removed from its habitat. If that’s not enough for you, they also can bust out a defense called evisceration. What happens here is if the cucumber is stressed and scared enough, it will spew its guts out. That means everything, intestines, gonads, respiratory organs, everything. Now after that, you would think that’s the end but if it can get itself to a safe habitat, it can actually regenerate its organs.

Biotic Associations

These guys are generally really passive, and they don’t really interact with any other organism or with between each other really.
References:http://oz.plymouth.edu/~lts/invertebrates/Primer/text/holothuroidea.html

http://www.afsc.noaa.gov/hodiak/photo/cuke03.html

Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Class Holothuroidea
Family Cucumariidae
Genus Cucumaria
Species miniata

Common Name: Orange Sea Cucumber

 

Other Members of the Phylum Arthropoda at Race Rocks 
taxonomyiconReturn to the Race Rocks Taxonomy
and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

 March OctoberFebruary , 2002, Andres Jennings (PC yr 28)

Metridium farcimen: Giant Plumose Anemone–The Race Rocks Taxonomy

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metridium

Metridium cluster by Ryan Murphy

 

rmmetridium1

The Metridum farcimen polyp can reach well over 30cm in length. Ryan Murphy photo

General description: The Giant Plumose Anemone is a fairly large anemone of typically white, cream, tan, orange or brown colourations. Subtidal animals can often reach 25cm in crown diameter and 50cm in height. However larger specimens have been reported around 75cm in height. Shape of the column is much longer than wide. Tentacles lining the mouth of the oral disk are quite fine, very numerous, slender and short. Tentacle colouration is typically transparent when the tentacles are expanded and take the colour of the column when contracted.Habitat: Found in both subtidal and low intertidal zones, including jetties, wharfs, harbours, breakwaters and floats. When found on wharfs, anemone communities of dense distribution are common. Larger specimens are often found solitarily in the subtidal. The Plumose Anemone ranges from Alaska to southern California and along both sides of America.

These images by Ryan Murphy show the biological associations of which they are a part.

 

Feeding: Both the small and large anemones feed primarily on zooplankton, using their stinging tentacles to catch the prey. The feeding appears non-selective. Scraps of fish and squid and small benthic (subtidal) organisms are also taken.

In this video Ben from Australia introduces us to this abundant anemone found in the waters around Race Rocks. Note the fine tentacles– ideal for trapping plankton in the high current areas. Also note that this is not Metridium senile as labelled, but Metridium farcimen 

Predators: The Plumose Anemone has few predators. Nudibranchs feed on small anemone, while in Puget Sound (Washington State) a sea star (Dermasterias imbricata) has been found to feed on larger anemones.

Reproduction: The anemone reproduces both asexually and sexually. Asexual reproduction occurs as the anemone moves about, leaving small sections of its pedal disk (base) behind, in a process described as pedal laceration. Dense colonies can be formed in this manner, with the pedal disks forming small cloned rounded anemones that feed and grow.

Sexual reproduction occurs in a broadcast spawning process whereby the males release sperm with wedged-shaped heads stimulating the females to release their eggs, about 0.1mm in diameter with a pinkish colouration. External fertilization occurs, with the zygote dividing to form a planula larva which swims in planktonic form. Adam Harding caught this process in action in July .

ahplumosespawnl2

Metridium spawning, Adam Harding photo.

 Planulae settle and metamorphose into young anemones.

Biotic Associations: Plumose Anemone symbiosis is an area in which little research has been done. Possible commensal behaviour may be similar to other anemones which have certain fish (e.g Clown Fish) which use the anemone.

Interesting behaviour: Anemones are rich in nematocysts (stinging cells) which are used in both defense and attack. The normal tentacles contain these cells used for both defense and feeding. However, in large colonies of Plumose Anemones the species bordering the colony develop a different type of tentacle; “catch” tentacles. These tentacles, which are used to repel non-cloned anemones, take about 9 weeks to develop close to the mouth and may number as great as 19 on an individual organism. If the “catch” tentacles, which contain a different type of nematocysts, touch another anenome from a separate colony a stinging tip breaks of and releases the separate complement of nematocysts. This technique is used to repel intruding anemones. Interestingly, these tentacles can expand to a possible length of 12cm.

metrid2

Domain Eukarya
Kingdom Animalia
Phylum Cnidaria
Class Anthozoa
Order Actinaria
Family Metridiidae
Genus Metridium
Species farcimen
Common Name: Giant Plumose Anemone

Reference: R.Morris, D.Abbott, E.Haderlie, Intertidal Invertebrates of California (690) pp. 62-63. Stanford University Press, Stanford, California. 1983.

 

Return to the Race Rocks Image Gallery and Taxonomy

This file is provided as part of a collaborative effort by the students, faculty, staff and volunters of Lester Pearson College UWC February 2002 Ben Dougall PC28

Psolus chitonoides: creeping pedal sea cucumber

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Predation of a Psolus chitinoides by a sea star is examined and discussed by Laura and Nadege. The stomach of the sea star surrounds the sea cucumber and the soft neck and mouth of Psolus is well inside the cavity of the sea

 

Sea cucumbers have inhabited the world’ s oceans for about 400 million years. Psolus chitonoides is an unusual species of these marine invertebrates. Its diverse characteristics have given it 4 common names: Armoured sea cucumber, Creeping armoured sea cucumber, Slipper sea cucumber and Creeping pedal sea cucumber.

Compare the tentaclesof Psolus with the end of the California Sea Cucumber to the left. Photo by Dr.A.Svoboda

Tentacles of P.chitinoides

A-Description

As all echinoderms, the creeping pedal cucumber has a spiny skin. Also, its appearance is closer to a chiton than to a sea cucumber (here is the origin of its name “chitonoides“).

1-External features:an oval body (7cm long to 5.8 cm wide) domed dorsally with stiff, shingle-like scales, flat, flexible sole ventrally. Its tentacles(8-10) are dendritic, equal in size, or 8 large and 2 small. Also observing the body, it could be compared to an elongate cylinder lying on its side with the mouth at one end and the anus at the other. The rows of tube feet run the length of the body

2-Internal features: the tentacle ampullae, the rete mirable and cuverian organs are absent . On the other hand, we can observe the presence of retractor muscles. Respiratory trees are “y shaped”. Note that its madreporic body is attached to a dorsal mesentery. Its internal calcareous skeleton is composed as following:calcareous ring with anterior processes only. Psolus chitonoides is characterized by typical skin ossicles, where one type of circular perforated plate (some with knobs coalesced into a raised network) occur only in the ventral sole.

Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Class Holothuroidea
SubclassAspidochirotacea
Order Dendrochirotida
Family Psolidae
Genus Psolus
Species chitonoides
Common Name: Creeping pedal sea cucumber
B-Physiology and Biology

1-Suspension feeder: tentacles trap larger particles (larger than 2mm) by bending inwards to form a cagelike enclosure. The mouth lips extend toward the particle as the nearest tentacle pushes it into the mouth .

2-Reproduction : the reproductive organs of a sea cucumber generally consist of 1 or 2 tufts of elongated tubules in the forepart of the body cavity.Spawning occurs annually, from mid March ot late May, commonly in the early morning. A spawning male will swab its genital papilla with its tentacles, then lift the tentacles to disperse the sperm . Females release long ropes of brick red eggs; fertilized eggs develop into pelagic lecithotrophic vitellaria larvae. Late larvae and early juveniles are negatively phototatic and settle gregariously.

3- Respiratory system: its water vascular system is a hydraulic system made up of tubes and valves that operate rows of extendible tube feet . As other sea cucumbers, Slipper sea cucumbers respire through their tube feet, body wall and respiratory trees.

4-Chemicals: there are toxic chemicals (saponins) on its tentacles, discouraging predators from nipping the tentacles. For example, even the Kelp Greenling (Hexagrammos decagrammus), which feeds on sea cucumbers, avoids this species.

C-Predators, parasites and commensals

1-Sea stars and fish are the main predators of the Psolus chitonoides.

2-Parasitic forms of flatworms and snails can live inside the sea cucumber

3-Commensal organisms are mostly scales that mimic the colour of sea cucumbers, and crawl on their skin.

D-Habitat

From exposed coast to sheltered inlets; although it seems to prefer clean, vertical rock that is free of sediment. Its soft, flat sole enables it to attach firmly to rock.

E-Range

Aleutian Islands to Baja California ; intertidal to 247m ; common in shallow subtidal areas.

References:

Kozloff, E.N. Keys to the Marine Invertebrates of Puget Sound , the San Juan Archipelago, and Adjacent Regions.

Lambert, P. 1997. Sea cucumbers of British Columbia, Southeast Alaska, and Puget Sound. UBC Press,

Other Members of the Phylum Echinodermata at Race Rocks 
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and Image File
pearsonlogo2_f2The Race Rocks taxonomy is a collaborative venture originally started with the Biology and Environmental Systems students of Lester Pearson College UWC. It now also has contributions added by Faculty, Staff, Volunteers and Observers on the remote control webcams.

 March October 2003-  Rahilla (PC)