TWAInv12

Invertebrates, Algae and Vascular Plants of The Tropical West Atlantic: Bahamas to Brazil, Part 12

To: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13, Part 14, Part 15,

Bob Fenner

Echinoderms

Crinoids: Sea Lilies, Feather Stars: Often misidentified as brittle stars or entirely overlooked as hidden or decorative ornaments due to their plant-like appearance, immobile/anchored sea lilies and the related, mobile feather stars make up the most ancient class of the phylum echinodermata, the Crinoidea (cry-noi-day-ah).

Due to easy breakage, suspension feeding habits and shy and retiring behavior these animals are considered challenging to keep. Most are doomed from difficulties accumulated from the time of their collection to delivery to your outlet. Feather stars need not be impossible however, as you will see.

Davidaster rubiginosa, the Golden Crinoid. 7-10 inches, twenty arms of variable color, found in water of 30-130 foot depth. Cozumel image. Arm/pinnule close-up by Di.

Nemaster grandis, the Black & White Crinoid. Tropical west Atlantic; southern Caribbean. Forty arms that are darkish/black with white tips. Live completely exposed night and day, perched on top of sponges, corals, reefs for filter feeding. Bonaire pix.

Sea Stars: Completely marine echinoderms of obviously overall pentaramous symmetry. Live oral side down, feeding on a myriad of sedentary invertebrates and detritus, detrital infauna.

Consider the Reticulated Seastar (Oreaster reticulatus), a large starfish common in the Turtle grass beds of the tropical west Atlantic. Growing to twenty inches in diameter, it consumes mollusks, even oysters in heavily calcified, tightly shut shells, methodically and with a voracious appetite. Like others in this fascinating Class, the Reticulated Seastar possesses a cleverly evolved arsenal of hydraulic tube feet connected to an elaborate water-vascular system that encircles the animal's mouth and extends via five radial canals down the center of each arm. Below: an Oreaster in Belize's shallows, an individual at night off Cozumel, and an aquarium specimen.

Linckia guildingi Gray 1840, the Green Linckia. Usually with five (sometimes 4 or 6) arms that are cylindrical in cross section. Skin appears smooth but is coarse with low, hard nodules. Though called "green" occurs in other colors (tan, beige, brown, blue, reddish). Big Island Hawaii pix.

Brittle/Serpent and Basket Stars. The Brittle or Serpent Stars are grouped as the Class Ophiuroidea, characterized by having highly mobile arms that can be used to assist in (relatively) rapid motion. These starfish-like echinoderms are decidedly quicker and more delicate than asteroids. Their common name is derived from their sinuous, snake-like movements, and the fact that they're truly brittle and break away easily if they come under attack. The podia in this class are generally used as sensory organs, rather than for active feeding as with their kin, the asteroids. There are more than 2,000 described species worldwide, and they're found congregating throughout shallow reef environments, hiding under rocks and within and between other living organisms.

Ophiocoma paucigranulata, the Spiny Brittle Star. Tropical West Atlantic. 4-6 inches in diameter. Have pale colored arms in their middles. Found in association with living corals. Cozumel image at night.

Ophiothrix suensonii, the Sponge Brittle Star. Tropical West Atlantic. 2 1/2- 3 1/2". Live principally on sponges. Also found on fire coral and gorgonians. Arms bear a dark line running down their mid-line. Cozumel pix.

Basket Stars:

One fast mention of the bizarre Basket Stars. Though some folks have reported reasonable success in their husbandry (see references below), these nocturnal animals are by no means easy to keep in captive conditions. They require specialized, large facilities, and diligence in their food preparation and administration.


The Basket Star Astrophyton muricatum in the Bahamas. Here "sleeping" by day on a gorgonian.	The same species in a typical daytime spot; curled up inside a brown sponge. This one in Belize.	Night time, and it's time to unfurl your arms into the incoming current and strain out your meal. Here in St. Lucia.

Sea Urchins and Sand Dollars, Class Echinoidea: Friends and associates who know me to be an avid diver frequently ask whether I'm concerned with potential encounters with sharks, rays, giant squids and the like. My standard reply is that hour per hour spent the most dangerous activity we all engage in is driving on the freeway. In all honesty, in the way of moments spent underwater, other than your dive buddy, Sea Urchins are the most realistically harm/hurtful organisms.

Family Diadematidae: Astropyga, Diadema, Echinothrix.

Astropyga magnifica, the Magnificent Urchin. Tropical West Atlantic. To nearly ten inches in diameter counting the spines. Deeper water (65-130 ft.) This one off St. Lucia at night.

Diadema antillarum, the Long-Spined Urchin. Tropical West Atlantic. 4-8 inch diameters with spines. Come out at night to feed, hide during the day within rock crevices. Younger ones with white banded spines. Cozumel images during the night and a juvenile showing white and black spine banding in Bonaire.

Family Echinometridae: Colobocentrotus, Echinometra, Heterocentrotus.

Echinometra lacunter, the Rock-Boring Urchin. Dark colored with red highlights. 2-3 inches in diameter. Relatively short, pointed spines. Tropical West Atlantic.

Echinometra viridis, the Reef Urchin. 2-3 in. diameter. Pointed purple to brownish spines with a white ring around their base. Tropical West Atlantic. Feed during the night (hide in coral, rock by day) on algae. Cozumel image.

Family Toxopneustidae: Lytechinus, Toxopneustes, Tripneustes.

Lytechinus variegatus (Leske 1778), the Variegated Urchin. Family Toxopneustidae. Tropical West Atlantic; Bermuda to Brazil, including the Gulf of Mexico. Lives in mud to rocky substrates. Eats algae and animal based foods. Temp.: 22-28 C. A good choice for TWA biotopic presentations.

Tripneustes ventricosus (Lamarck 1816), the (West Indian) Sea Egg. Tropical East and West Atlantic coasts. Up to eight inches in diameter. Juveniles inhabit rocks, adults moving out to sand, grass beds. Cozumel at night and close up in the Bahamas.

Family Cicaridae:

Eucidaris tribuloides (Lamarck 1816), Mine, Pencil, Club Urchin. Tropical West Atlantic. Solitary, hiding by day. Live on algae, bryozoans, sponges, tunicates in the wild. Algae and opened shellfish in captivity. To about three inches in diameter. Cozumel, aquarium and Bonaire photos.

Order Spatangoida: Heart Urchins

Meoma ventricosa, the Red Heart Urchin. Covered with short reddish-brown spines. Tropical West Atlantic. 4-6 inches in diameter. Upperside bears a pentagonal petal design. Here is the under and upper side to a test (dead exoskeleton) found scuba diving off Cozumel.

Order Clypeasteroida: Sand Dollars

Clypeaster subdepressus, the Sand Dollar. Filter feeders that live under the sand by day, emerging at night to feed generally. 3/4 inch diameter. Tropical West Atlantic. Cozumel image.

Sea Cucumbers, Class Holothuroidea: With body shapes ranging from spherical to long and worm-like, bizarre rings of tentacles circling a non-descript head-end, these slow-moving, drab to brightly colored and marked invertebrates are well-known at least by sight, by most aquarists.

Genus Actinopyga: "Toothed Sea Cucumbers", named for the series of five teeth ringing their anus.

Actinopygia agassizii, the Five-Toothed Sea Cucumber. Have five square teeth surrounding the anus. Short, knobby podia on back, sides. Brown to yellow on top, lighter colored sides. Bahamas pic.

Genus Holothuria:

Holothuria mexicana (Ludwig 1875), the Donkey Dung Sea Cucumber. Tropical West Atlantic. Detritivorous. Found singly on grass and sandy beds. To twenty inches in length. This one in Belize.

Holothuria thomasi (Pearson 1914), the Tiger Tail Sea Cucumber. Tropical West Atlantic, in holes, crevices, beneath rocks. Can move quickly. To two meters in length... stretched out. This one in the Bahamas.

To: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 13, Part 14, Part 15,

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