Daily Archives: Friday,December 7, 2001

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)

Mediaster aequalis: Vermillion star–The Race Rocks Taxonomy

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Mediaster in its habitat. Photo by Dr.A..Svoboda

Snail predation

 

Vermillion stars are seen frequently by divers in the 0-15 meter depth at Race Rocks.

 

Information.
Bright red (vermillion in fact) with large plates along its five arms. To 20 cm. Common just below the surface on low tides but hardly ever high and dry. These are abundant subtidally – you may find plenty after storms or extreme tides.

This Vermillion star male was emitting sperm while in the tank at Pearson College in early January 2004 . This went on for more than three hours. Millions of sperm are broadcast into the water where they may have a chance encounter with eggs which are simultaneously released into the current by the females. Of the great numbers of eggs and sperm released only a few are fertilized and actually make it to maturity. This is a good example of
r-selection in the population.

– http://www.wavelengthmagazine.com/1998/jj98neigh.htm

Mediaster aequalis is one of the smaller sea stars ranging in size from three to seven inches. It is found on many types of beaches at very low tides.

– http://www.geocities.com/oscmarinetech/Animals.htm#Vermillion%20Star

The vermillion sea star is common in shallow subtidal waters. Its feeding area stretches to nearly the tip of each arm on the underside. The vermillion star, so named because of its colour can be found from the Alaskan Peninsula, south to southern Caifornia.

Colour: Vermillion aborally, more orange orally; tube feet red to flesh colour.

Habitat: common on rocks shell, sand, gravel, pebbles and mud.

Feeding: diet varies with substrate and season; eats encrustin sponges and bryozoans on ock; seapen.

Reproduction: breeds from March to May; number of eggs in 65mm sea star estimated at 1,800 per year. the eggs measure 1 to 1.2mm and are bright opaqe orange. It is estimated that Vermillion sea stars reach sexual maturity within four years.

Speed: The sea star can move anywhere between 27 and 40 cm per minute.

Reference: The Sea Stars of British Columbia, Lambert, 1981, British Columbia Provincial Museum, Victoria

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.

Dec 2001 Damien Guihen (PC yr 27)

Henricia leviuscula The Race Rocks Taxonomy

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Blood stars are seen frequently by divers in the 0-15 meter depth at Race Rocks. They are planktonic feeders.

Kingdom Animalia
Phylum Echinodermata
Class Stelleroidea
Sub Class Asteroidea
Order Spinulosida
Sub Order Leptognathina
Family Echinasteriade
Genus Henricia
Species Leviuscula
Common Name Blood Star

The Blood Star is characterized by its brilliant red or reddish-orange color. Its comparatively small and graceful its body is only 10 to 12 cm from the tip of one ray to the tip of the one across from it. It has an arm radius to 8.9 cm, usually less; its disk is small, its arms are long, tapering, and are usually five in name (sometimes four or six); it has an absent pedicellariae; its aboral surface has a tan to orange-red or purple color., often banded with darker shades, and bearing many groups of short spinlets arranged in a fine network.
Habitat: Common on protected sides of rocks, under rocks, and in caves and pools, more frequently where rock is encrusted with sponges and bryozoans, low intertidal zone, subtidal to over 400 m.

The sea star feeds on bacteria and other tiny particles, which are captured in mucus and swept to the mouth by ciliated tracts. It may also feed by applying the stomach to the surfaces of sponges and bryozoa.

Breeding habits in the sea star vary with size. Smaller females brood their eggs in a depression around the mouth formed by arching the arms. Larger females discharge eggs directly into the water and do not brood them. The sperm have spherical heads and the eggs are orange-yellow and yolky, and development is direct.

REFERENCES CITED:

1. Robert H. Morris, Donald P. Abbott, and Eugene C. Haderlie,Intertidal Invertebrates of California, 1980, Stanford University

LINKS:

http://elib.cs.berkeley.edu/photos/fauna/sci-invertebrate.html

http://enature.com/fieldguide/showSpeciesSH.asp?curGroupID=
8&shapeID=1072&curPageNum=9&recnum=SC0074

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.

 Dec 2001Tania Melendez (PC yr.27)

Strongylocentrotus purpuratus: Purple sea urchin– The Race Rocks Taxonomy

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Purple Urchins and Californianus sp mussels at a “zero” level tide on the west side of Great Race Rocks.
July 2000

The purple sea urchin is about 10 cm. across, spines up to 2cm. and is bright purple. Its body “skeleton”, called the test, is shell like with bumps and holes from which the moveable spines and tube feet extend .The spines are used for protection, movement and for trapping drifting algae. It has a claw like mouth with 5 teeth-like plates. It is composed of over 60 shells and is called Aristotle’s lantern and is located on the underside or oral side of its body. The anus and the genital pores are on the aboral side of the sea Urchin.

In February, 2004 we had a note from CECIERJ requesting permission to use our video of the purple sea urchin in media being prepared for their undergrad distance learning courses. By offering these courses, the consortium CEDERJ contributes to bringing high quality free education to the inner cities of the Rio de Janeiro State. As well as permitting such use of our resources, we have added for them, an introduction by one of our Brazilian students, Rita who helped us make this video in Portuguese about the Sea Urchins and Echinoderms..

Diet: The Sea Urchin feeds on algae, plankton, kelp, periwinkles, and occasional tiny barnacles or mussels.

They are eaten by crabs, sunflower stars, snails, sea otters, some birds, fish, and people.

Reproduction: Fertilization in Sea Urchin is external, the female release several million tiny, yellow jelly-coated eggs at a time. The gametes join the water column as planktonic forms .

Behaviour: Although they often live in sheltering holes that they have worn in the rocks and they have also been observed to makes holes in solid steel, this behaviour is not evident at Race Rocks. Most of them live in shallow water here, They move surprisingly fast on their tube feet and spines. Moving their feet by a hydraulic water vascular system which creates suction in the end of the foot by pulling water out of the madreporite. They can also regrow broken spines.

The following images show the structural features on the test of a dead purple sea urchin. The image was produced by scanning.


This image shows the aboral view of a purple sea urchin.The dark patch in the middle is the anus. These were dead specimens.Thus the spines are missing.

Domain Eukarya
Kingdom Animalia
Phylum Ecinodermata
Class Echinodea
Order Echinoida
Family Strongylocentrotidae
Genus Strongylocentrotus
Species purpuratus
common name Purple Sea Urchin

The lower image shows the oral view of a purple sea urchin. The hole in the middle is its mouth with the sharp edges its 5 teeth. Note the pentaradial symmetry.