Echinoderms

 

One of the most familiar groups of marine invertebrates. All are marine and most are shallow bottom dwellers, characterized by a striking five membered radial symmetry. The parts of the body are radially arranged around a central region in which the mouth is located. All have an internal calcareous skeleton that normally bears projecting spines or tubercles that five the body surface a warty or spiny appearance. Hence, the name "echinoderm" is derived from two words, "echino" (spiny) and "derm" (skin) or "spiny skin."

(Brittle Star Album)

The name of this class is derived from words meaning "serpent tail like" and is applied to serpent stars and brittle stars because of their long, slender, snake like arms. In brittle stars the arms break very easily if handled or disturbed. The digestive and reproductive organs are limited to the central disk and do not extend into the arms as they do in the seastar. One opening in the center of the lover surface serves as both the oral and anal opening.

(Feather Star Album)

The bodies of these animals are cup shaped, with many branched arms attached to the rim of the cup. The mouth faces upward and the pinnately branched arms spread out to feed on detritus or small planktonic organisms. Stlakless crinoids are anchored while young, but eh adults break loose from the stalk and yet continue to cling to a rock and feed as do stalked forms. They can creep slowly over rocks or coral and, if disturbed, detach themselves and move to another location. Some crinoids are known to be commensal with a species of brittle star that live on its oral surface. Usually live in deep water but in the tropics, they are a conspicuous part of the coral reef community. All are free living and unstalked in their adult stage, thus being feather stars. Although free living, they change positions very slowly. Sea feathers are considered harmless except that the tentacles opposite the anus will stick to one's skin when touched. Best observed at night. They are plankton feeders. The group on the whole is difficult to identify without close inspections of both the pinnules and cirri.

(Sea Cucumber Album)

Visually, sea cucumbers seem to have little in common with seastars or sea urchins, but they may be thought of as an elongated echinoderm without hard spines or a skeleton. Most sea cucumbers are black or brown, while some display elaborate patterns and brighter colors. They range in length from 2 cm to 1 meter. Some feed by sweeping the bottom surface with their mucus covered tentacles; others feed by leaving their tentacles expanded, ingesting the microscopic organisms floating in the water. The internal space (cloaca) at the end of the alimentary tract of the sea cucumber makes a good place for smaller commensal animals to live. Small fish, pea crabs, and polychaete worms are known to reside in the cloacae of certain holothurians. When molested some sea cucumbers (e.g., Stichopus) have a peculiar habit of extruding all of their internal organs through the anal opening. They are then regenerated within 2 months. Sea cucumbers have few natural enemies and people probably take the heaviest toll. Dried and sold in tropical markets, they are popular with Chinese people who call them trepang. Stichopus Chloronotus is best represented in the Philippines, an all black animal with an underlying deep green tinge. Plentiful on sand substrates, it is reported to have a toxin in its tissues that is weakened or destroyed by cooking.

(Sea Urchin Album)

All are armed with movable spines that vary from very short to more than 30 centimeters in length. Some are sharp and mildly toxic, presenting a hazard if they break one's skin. As in seastars, the mouth of the sea urchin is located on its underside and the anus on the upper side. Exceptions are the heart urchins and sand dollars in which both the mouth and the anus are on the underside. The principal enemies of the echinoids are seastars and people. Sea urchin eggs are eaten by people and because the quantity of meat (gonads) per sea urchin is small, many urchins are collected to comprise a meal. Most sea urchins tend to e less conspicuous during the day than at night. Most take cover under a coral head or rock outcropping while some have devised interesting methods of hiding during the day.

(Star Fish Album)

Free moving animals have a structure consisting of a central body area that typically radiates out into five arms, although the number of arms may vary from four to forty, in a few species. The mouth is located in the center of the under surface of the body and the anus on the upper surface. Under ideal conditions seastars can regenerate an entire body from on detached arm. One seastar found in the Philippine reefs and Indo-Pacific region is the Pacific blue seastar, Linckia Laevigata. Other seastars include  the distinctive pillow or pincushion seastar, Culcita. It has no apparent arms and looks like a flattened sphere with a green to red quilt like pattern: it is sometimes observed among small coral heads or out on the open sand.

 

Phylum Echinodermata

Class Asteroidea (Seastars) (Philippine Translation: Koros-Koros, Padpad)

Uncategorized: (1) (2)

Acanthaster Planci Sp. (Crown Of Thorns) (Philippine Translation: Dap-Ag, Salamay) This seastar is capable of denuding coral areas when it reaches plague proportions; the spines are poisonous to humans. The animal leaves the corals white and dead after it feeds on them. 10-20 rays and elongate spines, is immediately distinctive. The spines can inflict a painful wound to divers when the skin is punctured by the crown of thorns. In some areas of the south and western Pacific, population explosions of this species have resulted in the local decimation of living reefs. (1) (2)

Choriaster Granulatus Sp. (Granular Seastar) Has distinctive swollen arms and fees on coral polyps and other invertebrates. A large species of sea star with broad rays, usually pinkish gray with orange or rust mottling in the central region. A common resident of shallow, living reefs. Appears to be a scavenger on dead animal material. (1) (2)

Culcita Novaeguineae Sp. (Pillow Seastar, Pincushion Seastar) This seastar can right itself if rolled over by inflating half of its body until the tube feet can get a grip. As it grows it loses the rudimentary arms and becomes nearly spherical. Is the most widespread and common species of cushion star. It is extremely variable in its coloration and ranges from red to green and brown. Common inhabitant of shallow patch, barrier and fringing reefs. The commensal shrimp, Periclimenes Soror is commonly found on the oral or aboral surface of this species. (1) (2) (3) (4) (5) (6) (7) (8)

Fromia Monilis  Sp. One of the most striking species with cream to yellow pigment and a bright red disk area. Common species of Fromia in the western Pacific, where it is found on shallow reefs in the open. Depth 1-35m. (1)

Linckia Laevigata Sp. (Pacific Blue Star) It is the most common on coral reefs. This species is variable in color, ranging from bright blue to green, pink or yellow. It appears to be a scavenger and also to feed upon algae and microbes. It may have specimens of Periclimenes Soror on its oral surface. The commensal shrimp are generally the same color  as the sea star. The parasitic snail, Thyca Crystallina may be found on the oral side of the animal partially imbedded in the ambulacral grooves. Depth to 60 meters. (1) (2) (3)

Linckia Sp. Similar to the Linckia Laevigata except different color variations. (1) (2)

Class Ophiuroidea (Brittle Stars, Basket Stars)

Order Ophiotrichidae (Brittle Stars, Serpent Stars)

Ophiothrix Sp. (Brittle Starfish) Has hairy lateral projections on the arms and is associated with sponges and soft corals. (1) (2)

Class Echinoidea (Sea Urchins)

Uncategorized: (1) (2)

Asthenosoma Ijimai Sp. This species  has much more uniformly arranged spines that are more similar in size. Able to inflict painful stings. Found on shallow living reef and rock habitats. Depth 1-20 m. (1) (2) (3)

Diadema Setosum Sp. (Long Spine Sea Urchin)  (Philippine Translation: Tuyom) Has long, sharp spines that contain toxins and can cause painful wounds. In many areas, dense aggregations may form next to the shore after sunset. Most diagnostic is the bright orange or red ring surrounding the anal opening. Abundant in shallow water in areas that have been recently disturbed also. (1)

Tripneustes Gratilla Sp. On of the most common and variable species of Indo Pacific Urchin. It has white and reddish spines, separated by areas of pedicillaria which are variable in width. The color of the animal may be black, white or greenish. Commonly found in shallow water lagoons and bays. This species frequently covers itself with debris and a wide variety of objects. One specimen, near a harbor entrance in  Hawaii, was observed covering itself with a pair of under shorts. (1) (2)

Echinothrix Calamaris Sp. (Variable Sea Urchin)  (Philippine Translation: Tuyom) Has a dark and white spotted anal sac. The spines are tubular with open distal tips and may be banded frequently.  Found under coral heads and coral rubble in shallow reef habitats. Also capable of inflicting painful puncture wounds. (1) (2)

Class Holothuroidea (Sea Cucumbers)  (Philippine Translation: Balat)

Actinopyga Obesa Sp. Can be recognized by its reddish brown or yellowish brown body color. Its dorsal surface is often partially covered by a dusting of sand particles. Found in areas of rubble and sand interface in 15-30 m of water. (1) (2) (3)

Bohadschia Graeffei Sp. (Graeffe's Sea Cucumber)  (Philippine Translation: Balat) Common long sea cucumber is tan with brown patches and spots. Radically changes its appearance in its transition from a juvenile to an adult. The changes in appearance of this species are related to the mimicry of juveniles to several nudibranchs of the Phyllidiidae, including Phyllidia Coelestis and P. Varicosa. Once the sea cucumber exceeds the maximum size of the nudibranch it begins altering its appearance, as the mimicry is no longer effective. (1) (2) (3)

Cucumaria Miniata or Colochirus Robustus Sp. ? (Yellow Sea Cucumber) Is frequently found in groups, with their tentacles fully extended when feeding. Relatively small holothurian, rarely exceeding 60 mm in length. It is bright yellow with green pigment on the five highly branched tentacles. Forms dense aggregations on reef faces and wall in areas with strong current. (1) (2)

Euapta Godeffroyi Sp. This species lacks tube feet. The body is translucent cream with brown bands in enlarged "beaded" areas of the skin. The pinnate tentacles are cream. Found in shallow water, sandy habitats and in grass beds. It is active at night and may extend its body length to 1.5m. (1)

Holothuria (Halodeima) Atra or Stichopus Chloronotus Sp. ? (Black Sea Cucumber) Can be recognized by its uniform black color and sausage shape. The body is frequently dusted with sand grains. One of the most common sea cucumbers in the Indo-Pacific tropics. Animals may form dense aggregations in shallow water sandy habitats, just below the low tide mark. (1)

Synaptula Sp. (Sponge Synaptid, White Sea Cucumber?) Animal lives on large barrel and encrusting sponges where in large numbers it can almost cover the sponge. (1) (2)

Synaptula Lamperti Sp. (Sponge Synaptid, Banded White Sea Cucmber?) This species has an opaque white body with dark burgundy longitudinal stripes. The same colors are present on the tentacles. Is found in association with massive sponges in relatively shallow water. (1) (2)

Thelenota Ananas Sp. (Spiny Sea Cucumber)  (Philippine Translation: Balat) Red sea cucumber has a body with numerous projections, which provide shelter for a number of symbiotic organisms. Large species, reaching half a meter in length. Found in 5-30 m depth, where it inhabits the interface between reefs and sand. (1)

Thelenota Anax Sp. Most massive holothurian in the Indo-Pacific, reaching one meter in length. The body is cream with scattered orange blotches. It has a warty texture. Inhabits sandy bottoms. Periodically more than half of the animal will rear up off the surface. In this spawning posture, it resembles and elephant's trunk. (1) (2) (3)

Bohadschia Argus Sp. (Spotted Sea Cucumber) Is often covered with small stones and coral rubble and ejects a bundle of sticky threads when disturbed. Inhabits shallow water reef and rubble habitats.

Holothuria (Halodeima) Edulis Sp. Is one of the edible species of sea cucumbers served as "sea slugs, "trepang" or "beche de mer." It can be recognized by its reddish or beige undersurface and darker, often black, dorsal surface. A common inhabitant of shallow water rocky and sandy habitats.

Neothyonidium Magnum Sp. Can be distinguished by its massive tentacular crown, often the only part of the animal that is visible.  The body is creamy white with dark brown tentacles and the tube feet. Found largely buried in clean sand, often with only the tentacles exposed.

Class Crinoidea (Feather Stars, Sea Lilies)

Crinoid Sp. (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17)

*Reference: Philippine Coral Reefs A Natural History Guide By Alan T. White & Coral Reef Animals Of The Indo-Pacific By Terrence M. Gosliner, David W. Beherens, Garry C. Williams

*Photos: Are Full Moon Divers. All Rights Reserved.

+[Home]+