Category Archives: Invertebrate

Haliclystus salpinx –Stalked jellyfish: The Race Rocks Taxonomy

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These animals are best desribed as “upside down” medusae, with their bell extended into a stalk which is attached, in the case of this species, mostly to surfgrass leaves. They occur from low intertidal to the subtidal littoral. They feed mostly on caprellid amphipods. Natural size up to 1cm :

 

Stalked Jellyfish Haliclystus salpinx

Stalked Jellyfish Haliclystus salpinx

Note update on Taxonomy of :STAUROZOA*

“Stauromedusae are little stalked jellyfishes that spend their entire life attached to the substrate (rock or algae, usually), rather than swimming freely up in the water column like most other jellyfish. They have long been considered to be in the Order Stauromedusae in the Class Scyphozoa of the Phylum Cnidaria, but recent morphological and molecular studies (Marques and Collins, 2004; Collins and Daly, 2005) argued convincingly that they should be elevated to a rank equal to both the Scyphozoa and Cubozoa, as the Staurozoa. For those who prefer to apply taxonomic ranks, these might now all be considered Classes, but many scientists are pulling away from the concept of tight adherence to the old hierarchies of rank, in which case just “Staurozoa” will do.” (C.Mills)

rm18910stalked

Image by Ryan Murphy of the habitat of this animal, showing attachment to eel grass. Taken at Swordfish Island at 4 metres depth.

The Haliclystus salpinx is among the order of cnidarians which the more commonly known are jelly fish. Unlike jelly fish however this family of cnidarians is not free floating but more or less fixed, and always attached to the blade of eelgrass. It occurs frequently in the eelgrass bed around Swordfish island and Emdyck Pass near Bentinck island adjacent to Race RocksIt moves on very slowly or by somersaulting itself from one plant to another. Its physiological makeup has not been studied in enough detail at the present time how ever it shares some characteristics with more documented species. The Haliclystus salpinxas can be seen by the photo appears as an upside down medusae or in common terms jelly fish with its tentacles pointing outwards. The bell of the hydroid is then attached to a stalk that is stationery on the eel grass. It is found in the tidal and intertidal zones rendering it more conducive to shallow water as opposed to deep water.

Domain Eukarya
Kingdom Animalia
Phylum Cnidaria
Class Staurozoa*
Order Stauromedusae
Suborder Eleutherocarpida
Family Lucernariinae
Genus Haliclystus
Species salpinx   (Clark, 1863)
COMMON NAME: Stalked Jellyfish

RANGE:

It is located most abundantly in the North Atlantic, Europe and Asia where areas are generally free external influences on rocky coasts. They are generally found in intertidal and tidal zones attached to surf grass.

REFERENCES CITED:

Mills, C.E. Internet 1999-2001. Stauromedusae: list of all valid species names. Electronic internet document available at http://faculty.washington.edu/cemills/Stauromedusae.html Published by author, web page established October 1999, last updated December 2nd 2001.

This file is provided as part of a collaborative effort by the students, faculty, volunteers and staff of Lester B. Pearson College– Dec 2001, by Sarah Gross

 

 

Epizoanthus scotinus : zooanthid anemone–

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epizooanthus2

Epizoanthus scotinus photo by Ryan Murphy

Description

The Epizoanthus is an anemone of the phylum Cnidaria. The class Anthozoa, into which it falls, has the literal meaning of flower animals, hence the Epizoanthus scotinus is a flower animal. Most Anthozoa belong to the subclass zoantharia with about 1000 species of sea anemones and 2500 species of stony corals that have been identified. Typical of the subclass zoantharia, Epizoanthus scotinus is colonial. The bases of the polyps in each group are connected having a column with sand or other foreign material embedded in it. The anemone are abundant along sea coasts but zoantharia occur in deep water as well. At Race Rocks, we typically find this species in darkened protected spaces, such as along the base of a vertical rock or under a protecting overhang. They are not very common but when they do occur, they will occupy up to 900 square centimeters. They also occur in very shallow water at Weir Point in Pedder Bay

 This short video taken by the divers shows a close up view, showing the density of the colony. They are a rather primitive looking, small anemone,.

 

Domain Eukarya
Kingdom Animalae
Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order Zoanthinaria
Genus Epizoanthus
Species scotinus
Common Name Zooanthid anemone
rmepizooanthus

A large colony of Epizoanthus scotinus on a boulder. Photo by Ryan Murphy

Return to the Race Rocks Taxonomy Index

This file is provided as part of a collaborative effort by the students, faculty, staff and volunteers  of Lester B. Pearson College Dec. 2001 Sikhululekile Hlatshwayo,
PC yr 27

Orange hermit crab

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In this video, the orange hermit crab inhabits the shell of an Oregon triton


The Elassochirus gilli (Benedict 1892), commonly known as the Orange Hermit Crab, is commonly found in the waters around Race Rocks. Hermit crabs are abundant around the world. They have soft rear ends that need the protection of the hard snail shell for survival. Hermit crabs carry their shell homes on their backs and tuck themselves away inside for protection using their strong stomach muscles. Sometimes, hermit crabs experience housing problems. As the crab outgrows one shell, it must find another often running into serious competitions for available homes in the right size range. Once it has found a suitable home it will not look again for some time. In any case, hermit crabs will fight for exclusive rights to empty shells. However, they will never displace a live snail from its home.In the video above, the crab inhabits the shell ot the Oregon triton snail, Fusitriton oregonensis .They have two sets of legs that they extend outside their shell for walking and two pairs of legs tucked away inside that they use to move their body around inside their shell.
The right cheliped surface of the Elassochirus gilli is smooth (without small spines) with its shield equal in length and width. The eyestalk of the crab is stout and its cornea is not inflated. The left hand is oval with a wide fixed finger. However, its greatly expanded and flattened right claw is a distinguishing feature. The walking legs of the crab are compressed and yet another distinguishing feature of the species is its bright blue upper leg. The Elassochirus gilli is usually rather uniformly orange to red.

The size of the male crab, is on average, about 20.4m in length. In this secies, the males are without paired pleopods and the females are without paired gonoppores.

The Elassochirus gilli prefers bedrock in areas of fast moving current. As such, its primary habitat is in rocky areas.
Domain Eukarya
Kingdom Animalia
Phylum Arthropoda
Class Crustacea
Order Decapoda
Infraorder Anomura
Superfamily Paguroidea
Family Paguridea
Genus Elassochirus
Species gilli
COMMON NAME: Orange Hermit Crab

WEBSITES AND REFERENCES ON ELASSOCHIRUS GILLI

http://www.oceanlink.island.net/oinfo/biodiversity/hermitcrab.html

Kozloff, Eugene N. Seashore Life of the Northern Pacific Coast, University of Washington Press (1996), p.410

Hart, Josephine F. Crabs and their Relatives of British Columbia, British Columbia Provincial Museum, Victoria (1982), p.124

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. Dec 2001- N’kiru Okagbue

 

Haliotis kamtschatkana: Northern Abalone–The Race Rocks Taxonomy

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Cryptic Coloration of Abalone
Associated organisms with abalone.

Domain Eukarya
Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Prosobranchia
Order Archaeogastropoda
Suborder Pleurotomariina
Family Haliotidae
Genus Haliotis
Species kamtschatkana
Common Name: Northern Abalone

Paulina and the PC Divers go in search of abalone for our population tagging program. The opportunity arises to demonstrate the escape response of the Northern Abalone, when it is presented with a Pycnopodia, the giant sunflower star.

Scott Wallace did research in 1997 and 1998 at Race Rocks with Pearson College divers. He studied the population dynamics of the Northern Abalone, Haliotis kamtchatkana. His research was done as part of a PhD thesis in Resource Management from the University of British Columbia in Vancouver. In May of 2000, he returned to Race Rocks for a dive with Garry and Hana and an interview with Stephanie Paine and Director Julia Nunes for the Discovery Channel. In this video he demonstrates the measurement technique he used in his research

Link to Abstract of Scott’s Paper
Wallace, Scott, S. 1999, Evaluating the Effects of Three Forms of Marine Reserve on Northern Abalone Populations in British Columbia, Canada. Conservation Biology, Vol 13 No 4, August, 1999, pages 882-887.
An article by Scott Wallace:
Out of Sight, Out of Mind, and Almost out of Time out of sight out of mind–mpa

 

 

 

n 1998, we began a long term research program, initiated by Dr. Scott Wallace, on the population dynamics of the Northern Abalone
(Haliotis kamtschatkana).

For several years, the Pearson College divers monitored the population. In this video, Pearson College graduate Jim Palardy (PC yr.25) explains the process.

Carmen Braden and Garry find a Northern Abalone exposed at low tide in June in the intertidal zone of the east side of Race Rocks. They talk about its adaptations and the problem of overharvesting which has resulted in the endangered status.

This abalone was filmed by Felix Chow as it was rasping off diatoms from the glass wall of the aquarium. A small tongue or radula scrapes the algae from the walls.

General information:

Northern or Pinto abalones (Haliotis kamtschatkana) belong to the class of mollusks having a shell that consists of one piece. The genus they belong to is Haliotis, which means “sea ear” and refers to the flattened shape of the shell.

abaloneshellDescription:

Pintos are the smallest abalones and they are commonly about 4 inches long, however the biggest individuals can grow as big as 6 inches long (12 cm). The shell is oval or rounded with a large dome towards one end; it is also irregularly mottled and narrow. The colour of the shell exterior is mottled greenish brown with scattered white and blue. The shell has a row of respiratory pores through which the abalone takes in water and filters dissolved oxygen from the surrounding water with its gills. Water that passes through the body leaves through the respiratory holes carrying away waster from the digestive system. Pinto abalones have from 3 to 6 open holes in their shells. The shape of these respiratory holes is oval and they are raised. The colour of the pinto abalones’ epipodium is mottled greenish tan or brown. The tentacles are thin and the colour of them can vary from yellowish brown to green. Abalones’ muscular foot has a strong suction power that permits the abalone to clamp tightly to rocky surfaces.

Habitat:

Pinto abalones have definite preferences in locations and habits. Pinto abalones range from Sit ka, Alaska to Monterey, California. The only member of the genus is likely to be found in the Puget Sound region., on the open coast of Vancouver Island and Washington. Farther south pinto abalones become strictly sub tidal. Pinto abalones can be found clinging to rocks in kelp beds along open coastal environments that have a good water circulation. Their habitat is between the low inter tidal zone and sub tidally down to 70 feet (18 meters depth).

Life cycle:

The life cycle of an abalone begins from an egg. Abalone female releases millions of eggs, but only about 1% (or even less) of the offspring survive the many challenges they have to face before maturity. The eggs turn into a free living larva and then after drifting with the currents about a week the abalone larva settles to the bottom and begins to develop the adult shell form.

Predators:

Abalone have many predators. They get eaten by other animals (crabs, lobsters, octopuses, starfish, fish and snails) and crushed to the rocks by strong waves. The sea otter was traditionally one of the most significant predators of abalones, although they have not yet moved into the Strait of Juan de Fuca, from the re-introduction several years ago to northern Vancouver Island.

Nutrition:

Pinto abalones, as all abalones, are herbivores. They use their large, rough radulas (“tongues”) to scrape pieces of algae and other plant material from the rock surfaces. The adult abalone feeds on loose pieces of algae drifting in water. Abalones prefer large brown algae; mainly different kind of kelps and seaweed. The colour banding on many abalone shells is caused by the changes in the type of algae that the abalone has eaten.

Threats:

Pinto abalones used to be subject to sports and commercial fishery . They suffered from over harvesting and habitat loss and poaching. There is now a permanent closure on all abalone fishing on the B.C. Coast. For the Pacific North West Coast First Nations People, the beautiful shells of abalone were used for jewelry and abalone also were a seafood delicacy. They occur sub tidally and only in remote areas.

See the Abalone measurement and statistics exercise at RaceRocks:
http://www.racerocks.com/racerock/research/abalone/abalonemeas.htm

See our abalone exercise for middle school.

References Cited:

Kozloff, Eugene N., Marine Invertebrates of the Pacific Northwest, University of Washington Press, Seattle and London, 1996.

Kozloff, Eugene N., Seashore life of the Northern Pacific Coast, University of Washington Press, Seattle and London, 1996.

Meglitsch, Paul A., Invertebrate Zoology; second edition, Oxford University Press, 1972.

Snively, Gloria, Exploring the Seashore in British Columbia, Washington and Oregon, Gordon Soules Book Publishers Ltd., Vancouver/London, 1981.

http://www.pacificbio.org/ESIN/OtherInvertebrates/NorthernAbalone/NorthernAbalone_pg.html ( available at this URL in 20101)

http://www.sonic.net/~tomgray/describe.html

Other Members of the Phylum Mollusca 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. Salla Vornanen, PC yr 27

 

Anthopleura elegantissima: Aggregating Anemone-Race Rocks taxonomy

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rm18910anthopleura

Anthopleura growing in a moist crevasse. Photo by Ryan Murphy.

One of the many organisms found at Race Rocks are sea anemones. Sea anemones belong to the phylum known as the Cnidaria, from the cnida or stinging cells that are present in this major group of animals that also include corals, jellyfish, hydroids, medusae, and sea fans. Sea anemones, corals and their allies form the class know as the Anthozoa. Anthopleura elegantissima is abundant on rock faces or boulders, in tide pools or crevices, on wharf pilings, singly or in dense aggregations (Smith and Carlton, 1975)

 

 

 

 

 

anthopleur       Link to extended essay of Santiago on Anthopleura distribution in the intertidal zone.

 

 

 

 

maliha   Link to  the extended essay by Maliha Zahid on Anthopleura-elegantissima-Distribution

 

 

 

 

Kingdom Animalia
Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order Actiniatia
Family Actiniidae
Genus Anthopleura
Species elegantissima
Common Name Aggregating Anemone

 

Characteristics:

  • The aggregating anenome is 2-5 cm in column diameter and 4-5 cm high in its clonal form.
  • The tentacular crown is roughly 8 centimeters in diameter.
  • The species presents numerous short tentacles, in five or more cycles, which are variously colored.
  • At the bases of its tentacles are bulbous structures where certain types of stinging capsules are concentrated.
  • The column is light green to white, and twice as long as wide when extended, with longitudinal rows of adhesive tubercles (verrucae)
  • Rock, sand, and shell fragments accumulate on anenome by adhering to the tubercles on the column.
  • The anenome is a green or olive colour depending on the algae living in its tissues.

Habitat:

It is a species characteristic of middle intertidal zone of semi protected rocky shores of both bays and outer coast from Alaska to Baja California.

Reproduction:

Anthopleura elegantissima reproduces both sexually and asexually. In sexual reproduction, ova are present as early as February and grow steadily until their release in July; the ovarian is then resorbed and new eggs do not appear until the following February. Sperm are released through the summer. The asexual reproduction occurs by longitudinal fission. This process results in aggregations or clones of anemones pressed together in concentrations of several hundred per square meter.

Ecological Niche:

  • Anthopleura elegantissima is a carnivore, feeding on small crustacians such as copepods, isopods, amphipods, and other small animals that contact the tentacles.
  • It is preyed upon by the nudibranch Aeolidia papillosa, which usually attacks the column, by the nail Epitonium tinctum, which attacks the tips of the tentacles, and by sea stars such as Dermasterias imbricata that can engulf an entire small anemone.
  • Moreover, in some anemones, small pink amphipods, Allogaussia recondita, make a home in the gastro vascular cavity. Two types of unicellular algae live in the tissues ofAnthopleura elegantissima in a symbiotic relationship. It is these algae that give the anenome its distinctive green or olive colour.

Interesting Further Studies:

  • Ecological niche study was conducted by Santiago, Pearson College Student 1998-2000../../research/santiago/santiago.htm
  • The US Environmental Protection Agency (EPA) has investigated using aggregating anenome as a test for salinity. This bioindicator would be used to see the freshwater influx in ocean environments. http://es.epa.gov/ncer/fellow/progress/99/cohenri00.html
  • The behaviour of Anthopleura elegantissima at different depths.
  • The reproduction cycle of Anthopleura elegantissima.
  • Further study of aggregating anenomes at Race Rocks.

References:

  • Kozloff, Eugene N. Seashore Life of the Northern Pacific Coast. (Seattle: University of Washington Press, 1983).
  • Kozloff, Eugene N. Keys to the Marine Invertebrates of Puget Sound, the San Juan Archipelago, and Adjacent Regions. (Seattle: University of Washington Press, 1974).
  • Morris, R.H. etal. Intertidal Invertebrates of California. (Stanford: Stanford University Press, 1980).

 

Enteroctopus dolpheni: Giant Pacific Octopus: The Race Rocks Taxonomy

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rmoctopus eye

Enteroctopus dolpheni: Giant Pacific Octopus: The advanced eye of a mollusc. Photo by Ryan Murphy

Getting up close and personal was one of the things that former Ecoguardian Ryan Murphy was able to do very well underwater.. Consequently he produced the following interesting images from underwater.

We frequently encounter Octopus while diving at Race Rocks. They blend in very well with the algae and can change colors rapidly. Often the best way to see them is to spot their large (1-2 cm) white suckers in a crevice or cave. According to the website below, “Although it is very unusual to find an individual over 45kg, one large individual captured just near Victoria in 1967 weighed 70 kilograms (156 pounds) and was almost 7.5 meters ( 23 feet ) from arm tip to arm tip.

Smaller animals occur occasionally in low intertidal pools on rocky shores, larger individuals generally subtidal to depths of 100m; along North Pacific rim from northern Asia to California;

One of the largest octopus species known, the largest specimen on record with a total arm spread of 9.6m and a weight of 272 kg; dorsal mantle length usually over 20 cm; weight sometimes exceeding 50 kg; body ovoid, with extensive skin folds, red to reddish brown above, pale below; ocelli absent; arms 3-5 times body length, lacking specialized enlarged suckers and large truncate papillae; hectocotylus large, about one-fifth the length of the third right arm; with 12-15 lamellae on the outer demibranch of each gill; gill lamellae 25-29; ink dark brown; eggs measuring 6-8 mm by 2-3 mm, planktonic larva with a single row of chromatophores on each arm; borne in capsules on long stalks, these entangled and cemented together to form long festoons.

The Giant Pacific Octopus, (Enteroctopus dofleini , Hochberg, 1998) was formerly classified as : Octopus dofleini (Wulker, 1910)

 

Giant Pacific Octopus frequently appear at Race Rocks in the subtidal waters. They are also seen occasionally washed up in the intertidal zone where they contribute to the energy flow of the gulls and eagles. This individual which had died recently in June 2002, became the subject of a webcast and an impromptu dissection on the shore.

Video on Octopus necropsy

Domain: Eukarya
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order Octopoda
Suborder: Incirrata
Family :Octopodidae
Genus: Enteroctopus
Species: dofleini (Hochberg, 1998)
Common Name:  Giant Pacific Octopus
Although E.dofleini has been used extensively in laboratory studies, its natural history is still poorly known. The life cycle is thought to be 4-5 years. Eggs are laid throughout the year, though mainly in the winter, and development takes 5-7 months; hatching peaks in the early spring. The young are pelagic for a short period, probably about 1 month.

The three images above of a baby Octopus were taken in the intertidal zone near the docks by
Ryan Murphy in July 2004.

The adults feed on crustaceans (shrimps and crabs), mollusks (scallops, clams, abalones, moon snails, and small octopuses, and fishes ( rockfishes, flat fishes, and sculpins). Large crabs are stalked and then caught with a sudden flick of one or more arms; empty crab carapaces, shiny shells, and bones often litter the entrance to a lair. The octopus takes smaller shrimps and fishes by slowly arching its body over a seaweed bed, then suddenly pouncing, and enclosing the area in a canopy formed by the web membrane that joins the basal parts of adjacent arms. The sensitive arm tips are then inserted into the impounded area to search for food.

  • Two mesozoan parasites charactersictically occur in the kidneys of E. dofleini: Dicyemennea abreida and Conocyema deca.

This octopus is fed upon by seals, sea otters, dogfish sharks, lingcod, and man. It supports small commercial fisheries in Alaska, Canada, Washington, Oregon, and Northern California. Locally, it is also used by halibut fishers as bait.

Literature Cited:

Robert H. Morris, Donald P. Abbott, and Eugene C. Haderlie, Intertidal Invertebrates of California

Eugene N. Kozloff, Marine Invertebrates of the Pacific Northwest

octopus and diverLink to an assignment on Biodiversity submitted to us by
Shawna Millard Biology 202 at Bellevue Community College, Washington.

 

 

Return to the Race Rocks Taxonomy

This file is provided as part of a collaborative effort by the students, faculty and volunteers of Lester B. Pearson College .  This file was started by: Amanda Muscat PC yr 27, Dec. 2001.

Gersemia rubiformis: Sea strawberry–The Race Rocks Taxonomy

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gersem

Gersemia rubiformis –Photo by Dr. A.Svoboda

In the following video, the soft pink coral Gersemia rubiformis is highlighted. It grows at 7-10 meters over a 3 square meter area off peg #3.  note the retraction of the colony when it is disturbed. Also note the other associated invertebrates in the same area.

The following video shows in close details the characteristics of the soft pink coral (Gersemia rubiformis) found at Race Rocks. Soft corals are mostly sub-tidal. A soft coral has spicules of calcium carbonate within it, so it is moderately firm, but it does not have a completely calcified skeleton, like that of reef-building corals of warmer seas, or even like that of the cup coral of our coast. The polyps of soft corals have eight tentacles, each with delicate side branches. This establishes their relationship to sea pens and to most of the colonial reef-building corals. This colonial invertebrate forms a lumpy colony, sometimes 10 or 15 cm in diameter, whose colors range from cream through orange to deep pink elsewhere, but are consistently deep pink here at Race Rocks. The lumps, when the polyps have withdrawn, slightly resemble raspberries, which belong to the genus Rubus; hence the specific name rubiformis. Extended, the individual polyps stick out about 5mm beyond the lump to which they belong.   Filmed by Jean-Olivier Dalphond and Damien Guihen on a sunny day at Race Rocks.


Gersemia rubiformis – a soft coral found underwater at Race Rocks. Usually it is found at the depth of 8 to 10 meters with an amazing variety of many other invertebrates. Here, no invertebrate is found growing on its own, they always occur in association with other invertebrates.

Gersemia occurs in fairly big pink patches in rather greater depths in the ocean but there are some small patches of it along the North cliff of Race Rocks. The lumpy colonies it forms usually are 10 to 15 cm in diameter.

Gersemia grows at the shallow depth because of the availability of nutrients there. Emerging from the walls are small pale pink polyps

Extended, the individual polyps stick out about 5 mm beyond the lump to which they belong. These polyps have small tentacles at the end. Each polyp has 8 of them, each with delicate branches which are able to catch masses of plankton for food. The vertical structure of the colony allows the polyps to be filter feeders and strain out plankton and other drifting organisms from the water column.

Embedded within the body wall of the polyp are millions of microscopic, photosynthetic organisms, known as zooxanthellae. They live symbiotically, provide food and fuel and absorb many of the waste products of the polyp. Without the zooxanthellae, the corals could not exist. It is the zooxanthellae that contains necessary chemicals for the adequate production of calcium carbonate, for reef forming types of corals. However Gersemia does not have a completely calcified skeleton, like that of reef-building corals of warmer seas. Zooxanthellae are also responsible for providing much of the colour in corals, which usually range from cream through orange to deep pink elsewhere, but are consistently deep pink in Race Rocks.
CLASSIFICATION:
Domain: Eukarya
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Alcyonacea
Family: Nephtheidae
Genus: Gersemia
Species: rubiformis
Common name: Sea Strawberry

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. Ania Pawlicka——- PC yr 27, 2001

 

Ligia pallasii: Sea Slater –The Race Rocks Taxonomy

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video of sampling of populations of Ligia sp

 

During the Johan Ashuvud project 2004, students explored the intertidal with Garry. They examined various organisms as well as the artificial tidepool.

In this video, we also get a chance to meet all the students taking part in the project

The central part of this video has a section on Ligia sp.

Sexual dimorphism in body proportions is marked in L.pallasii. Males, with their large, laterally expanded ephemeral plates, have a length/width ratio of about 1.6; females and immature males are narrower, with a corresponding ratio of about 2.1. Half- moulted males are occasionally found in which the rear half of the body has moulted and is abruptly significantly wider than as yet unmoulted front half, an odd sight, usually several days after the posterior moult.On the walls of cliffs and sea caves, the larger and broader males often cover and shield the females and juveniles.

L.Pallassi prefers sea cliffs. At Race Rocks, the loose upper intertidal rocks and crevasses on the Western side of the main island provide ideal habitat. There are differences in the osmoregulatory responses shown by these species associated with their behavior and ecology.The slower -moving pallasii lives permanently in cool, moist habitats characterized by fluctuating hypo-saline condition. L.Pallasii are air breathers with gill-like pleopods not equipped with tracheal trees.The respiratory pleopods must be kept moist to function properly.This is done by immersion or by dipping the tail in water in such away that the uropods serve as capillary siphons.

Ligia species are fed upon by birds, especially gulls, and by the intertidal crab. Life span of L.pallasii is 1.5 to 2 years , with breeding occurring in spring and early summer, and the average brood size is 48 plus or minus 11 young.The overall sex ratio is 1:1.

Domain Eukarya
Kingdom Animalia
Phylum or Division Arthropods
Class Crustacea (crustaceans)
Order Isopoda
Family Ligiidae
Genus Ligia
Species pallasii
COMMON NAME:sea slater

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. Dec 2005- Palwasha Hussain Khel

 

Ophiothrix spiculata: Brittle star–The Race Rocks Taxonomy

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Ophiothrix spiculata is a common species among algal holdfasts at Race Rocks. Its arm’s spines are especially long, and each one has a number of small thorns on it. the color is extremely variable but it is generally reddish brown, there may be some orange on the disk, too. in spite of all the color variation, this species is unmistakable because of its thorny spines.

Two sets of video on brittle stars are seen here. They were observed off the docks at Race Rocks in about 10 meters of water. Note the other organisms that live in the area also.

 

This brittle star is lives on the rocky sea floor, from shallow waters to great depths. Brittle stars are related to sea stars. These marine invertebrates move very slowly along the sea bed. More than 2000 species of brittle stars exist in the world.
It has long, thin, spiny arms that radiate from a flat central disk; the arms do not touch each other at their bases. Many of the arms are forked. If a brittle star’s arm is cut off, it will regenerate.
Usually the central disk in these brittle stars is under 2 cm) in diameter. They have an exoskeleton and vary in color. They do not have a brain; they have a simple ring of nerve cells that moves information around the body. Tube feet located along the arms sense light and smells.

This juvenile brittle star was filmed in the lab by Sylvia Roach using a Digital camera attached to a dissecting microscope at 4X

Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Class Ophiuroidea
Order Ophiurida
Family Ophiodermatidae
Genus Ophiothrix
Species spiculata
COMMON NAME: brittle star

They often gather in large groups and collectively filter food from the circulating water. When roused from a hiding spot their best form of defense is to crawl away-

The projections on the five arms of this brittle star look like many tiny hairs, but are actually spines. That being said, they are gentle, very delicate creatures that do not harm humans. They are nocturnal (feed and move about primarily at night); they stretch out to catch food particles, passing the bits down to the central mouth.
To avoid predation, if a predator catches one of its legs, it has the ability to swim off, leaving that leg behind, and it can regenerate a new one!

Waving arms point out the home of the stars. Those aren’t worms, they’re brittle stars, sea star cousins that hide themselves under rocks and in the holdfasts of kelp, especially in the Pterophyga at Race Rocks.

For comparison with another species, see this image in our ecological equivalents file an image of a large 20cm species from the Galapagos:

 

 

 

Reference Cited:

Eugena N. Kozloff , Seashore Life of the North Pacific Coast

http://www.mbayaq.org/efc/living_species/default.asp?hOri=1&inhab=142

 

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.

 March October 2003-  Rahilla (PC)

Leptasterias hexactis The Race Rocks Taxonomy

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The six rayed sea star is found both intertidally and subtidally at Race Rocks. They are one of the smaller sea stars.

Domain Eukarya
Kingdom Animalia
Phylum Echinodermata
Class Asteroidea
Order Forcipulatida
Family Asteriidae
Genus Leptasterias
Species  hexactis  (Stimpson,1862)
COMMON NAME: Six- rayed Star
Introduction
Description: Radius 2″ (51 mm), 6-armed ( note the species name hexactis referring to the six arms.). Green, black, brown, or red, sometimes mottled. Disk moderate-sized with 6 fairly broad arms; spines on upper surface dense and mushroom-shaped. rarely do we find these at Race Rocks exceeding 15 cm in length.
Habitat: On rocky shores. We frequently find these when doing intertidal studies or when diving in shallow water at Race Rocks. Range British Columbia to s. California.
Discussion: L. hexactis eats small snails, limpets, mussels, chitons, barnacles, sea cucumbers, and other species, including dead animals. It produces yellow, yolky eggs that stick together in a mass after fertilization. These are brooded under the disk of the female until they hatch as miniature sea stars after 6 to 8 weeks. The small six-rayed sea stars of the West Coast are quite variable and have presented problems of identification. The only other species currently recognized is the Small Slender Sea Star (L. pusilla) which has sharp spines and longer, thinner arms than L. hexactis, and is a light gray-brown or reddish color. It also has a very limited range from San Francisco to Monterey Bay. It reaches a radius of 1″ (25 mm).
Echinoderms have a few important aspects in common. They have bony ossicles in their body. They have a water-vascular system which pumps water through the madroporite. They also have small jaws that are supported by the water-vascular system. And they have tube feet which they use to attach to objects, for protection, as well as to obtain food. They have radial symmetry and most can regenerate lost limbs.

 

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.

 December 2001(PC)