Sea Urchins

The National Science Foundation has created a wonderful interactive website on the sea urchin complete with anatomy, details on how to do the fertilization experiments, tutorials about microscopy and games.  There is also a section on teacher resources. Gulf Specimen has been listed by Stanford University as a sea urchin supplier. We highly recommend this exceptional free electronic educational resource.

microcompare_borderSea urchin and sand dollar videos on
Sea Urchin 2 . Sea Urchin Cleavage Stage Embryos . Sea Urchin flipping
Sea Urchin fishing . Sea Urchin . Sea Urchin
Sand Dollar moving across sand . Sand Dollar at Sannibel Island . Living Sand Dollar

Care And Feeding

Sea urchins do well in a standard marine aquarium. A powerful outside filter that assures good circulation is recommended for quantities of 50 or more (one urchin per one gallon of seawater is an ideal density). As long as their spines are erect and they’re moving about the aquarium feeding, they’re in good condition. If water quality deteriorates, their spines will collapse. Both Arbacia and Lytechinus eat ravenously, gnawing on blue-green algae, sea grass, sargassum weed, and diatoms with their powerful teeth located in their complex Aristotle’s lantern. Leafy green algae such as Ulva or Enteromorpha make the best food. Lytechinus is one of the few direct consumers of turtle grass in the marine ecosystem. The size of the gonads are directly correlated with the relative abundance of food. To some extent, urchins absorb free amino acids from the sea water, and hence may stay fertile when food sources are scarce. If marine algae is not available, chopped lettuce or vitamin E-enriched grain made up of small cakes of agar and placed beneath the urchins will suffice.

Sea Urchin Embryology

Providing a routine supply of fertile, usable sea urchins for embryology is a cooperative venture between the scientific supplier and the researcher or teacher. Fertility is often a seasonal affair, governed by a variety of environmental factors.

Arbacia punctulata is generally fertile during the colder months from mid-January through April, and Lytechinus variegatus produces good eggs and sperm from May through September, and sometimes into October and November. However, there are transitional periods when one urchin is nearing the end of its season, and the other is just beginning. Unless otherwise specified we will provide whichever sea urchin is more fertile at the time of shipment. The larger the quantity ordered, the better the chances of a successful fertilization experiment, since there are tremendous variations within any given population during these transitional periods.

During transition you are likely to get smaller volumes of sperm and eggs from each animal and likely to receive smaller percentages of cleavage. The urchins are more easily stressed and need more careful handling than usual, including acclimation.

There may be an interval of a few weeks when both species are infertile, and we cease shipping. A phone call to check on current urchin fertility is advisable. We will be most happy to help you plan your lab around the time you are most likely to receive fertile urchins, but long-range projections are anyone’s guess.

To ensure that our urchins arrive alive, unbroken, and in usable condition, they are carefully packed in several layers of plastic bags of seawater and charged with oxygen. During warmer weather, ice is packed to retard premature gamete discharge

Care and Handling Of Arbacia and Lytechinus Eggs

1. Sea urchins can be easily held in the laboratory in running seawater or in clean aerated seawater.

2. The animals may be induced to spawn by several methods. The following has proven to be most effective. Prepare a solution of 0.5M K Cl. Isolate the animals. Inject the solution through the soft tissue surrounding the mouth, and if the “orange” eggs begin to appear, invert the animal over a fingerbowl of seawater. If the “white” sperm appears, collect it “dry” in a watch glass on wet ice.

3. Mix 0.2cc (about 2 drops) of sperm in about 10cc of seawater. You must use this within 10 minutes. Add two drops of this diluted sperm to a fingerbowl of seawater containing eggs and gently stir.

4. Sperm penetration is rapid and occurs anywhere on the egg. The temperature will determine the rate at which cleavage proceeds. The first cleavage occurs (at 20 degrees C.) in about 50-55 minutes, the second in 100 minutes and the third in about 145 minutes.

They are a sleek saltwater catfish that cleans up the bottom. Adult males carry and hatch the eggs in their mouths. Size 10-30 cm.


Since there are no fresh water echinoderms, this is one of the most popular phylogenetic assortments, with collections of writhing brittlestars lashing their snaky arms, bristling sea urchins and burrowing sand dollars. Sea cucumbers, shaped as their name implies, tunnel through the sediments like earthworms taking up nutrients and starfish creep up the aquarium glass, wrapping their arms around tunicates, or chopped clams. Sand stars emerge from sand and “speed” along the bottom, on raised tubed feet when a bit of food is dropped in the tank. These assortments usually include two or three of every listing, and sometimes there are surprises such as sea biscuits and other echinoderms.


Included are amphipods, isopods, barnacles, crabs, shrimp, hermit crabs, and horseshoe crabs.


Includes colorful anemones from our tanks, hydroid, corals, gorgonians, sea pansies and if scyphozoan jellyfish are pulsating in our bay, they are included along with shimmering examples of the phylum Ctenophora.


Includes an array of brightly colored sponges that can range from different shades of green, blue, pink or yellow. Species may include red beard, yellow ball, devil’s finger and crumb of bread sponge.


  • Included are chitons, clams, mussels, whelks, snails, and nudibranchs. When abundant, scaphopods and/or frilled sea hares may be included.


Create your own botanical gardens with our collection of semi-tropical macroscopic benthic marine algae. Phyla represented include Chlorophyta, Rhodophyta, Phaeophyta, and Cyanophyta.


The greatest diversity of fish form and function is found among marine species. Here the flat fishes, flounders, hog chokers, tonguefish, represent the epitomy of depression, and eels are the most elongate. Blowfish inflate themselves, and pipefish, looking like blades of grass, are perfect in camouflage. While these examples are likely to turn up in our fish assortment, there is no predicting the diversity and variety that will be provided. It is always a pleasant surprise.


Includes non-vertebrate chordates: solitary, colonial, and encrusting tunicates and amphioxus


Colorful anemones from our tanks, hydroid, corals, gorgonians, sea pansies and if scyphozoan jellyfish are pulsating in our bay, they are included along with shimmering examples of the phylum Ctenophora.


Arius felis

They are a sleek saltwater catfish that cleans up the bottom. Adult males carry and hatch the eggs in their mouths. Size 10-30 cm.

Each Dozzen small ---123

Each Dozzen small ---123

Each Dozzen small ---123

Each Dozzen small ---123


Hardhead sea catfish (Arius felis)

Spheroides nephelus

A drab smooth-skinned fish that will inflate itself into a tight, buoyant, impregnable ball when handled. Size: 10-14 cm.


Southern puffer (Spheroides nephelus)

Lactophrys tricornis

It has a fused armor giving it a hard-shelled, triangular un-fishlike body. Colorful blue, green and yellow fish with two prominent horns over its eyes.


A cowfish (Lactophrys tricornis)

Balistes capriscus

Known mostly for their sharp “triggered” dorsal spine, these territorial grey triggerfish are a sight to see both locally in the Gulf of Mexico and ranging throughout the western Atlantic Ocean.


Grey triggerfish (Balistes capriscus) at Gulf Specimen Marine Lab and Aquarium.

Monacanthus hispidus

Their names come from their sandpapery skin, fishermen once used their hides to strike matches. Their dorsal spine has a trigger-like mechanism that makes it spring erect when they are threatened. Size: 4-8 cm.


Gobiesox strumosus

Small fish shaped like a skillet; with a broad head and narrow body. The pelvic fins are actually a large, broad suction disc. Clingfish are usually found hiding in or on the shells around oyster bars and seagrass beds. Size: 4-6 cm.


Clingfish or skilletfish (Gobiesox strumosus)

Symphurus plagiusa

Small, flat, left-eyed fishes that taper to a point — “tongue-shaped” — hence the name. They are bottom-dwelling fish, common in the muddy bottoms of bays and estuaries feeding on small crustaceans and polychaete worms. Size 6-12 cm.


Trinectes maculatus

This flatfish stays buried and looks like a baby flounder but seldom grows larger than six inches. Probably named from the days when hogs roamed the beaches and gobbled up fish as fast as seine fishermen dragged their catches up on the beaches. The scales, which make the fish stick to the deck, also could lodge in a hog’s throat. Very hardy and vigorous. Size: 6-12 cm.


Hogchoker (Trinectes maculatus)

Paralichthys oblongus

Unlike the common gulf flounders, these flatfishes have four large, dark and round spots on their bodies.


Four-spotted flounder (Paralichthys oblongus)

Paralichthys albigutta

Flounders belong to the group of fishes known as “flat fishes.” Their most unique feature is the placement of their eyes. As the young larvae develop, one eye migrates across the head toward the other. Depending on the species, flounders and other flatfishes are “right-eyed” or “left-eyed.” Lying flat on the sea bottom, flounders are masters of camouflage, changing their coloration to blend in with the substrate; hiding from predators or aggressively ambushing small fishes and crustaceans with their mighty tooth-studded jaws.


Mugil cephalus.

Often seen jumping out of the water, mullet are the cows of the fish world, and are the main food fish of the northern Gulf Coast. They browse along the bottom, feeding on algae and tiny creatures that live in mud.


Serranus subligarius

The smallest of the Sea Basses they are 5 inches long at maximum, but mature at 2 inches. Common in warm Atlantic and Caribbean waters to depths of 60 feet. Found around rocky jetties and over sand flats. Their common name comes from the large white patch on their belly. Size: 3-6 cm.


Belted sandfish (Serranus subligarius)

Chasmodes saburrae and other species

A large group of small, fish (2-4 inches), common along the shells of oyster bars. Also found on shallow flats and seagrass beds. Females lay hundreds of tiny golden colored eggs in empty shells, which the males aggressively guard. Size: 3-8 cm.


Feather blennie (Hypsoblennius henzi)

Halichoeres bivittatus

Has beautiful green coloration. Will bury itself in the sand substrate to hide. Size 6-10cm.


Green wrasse (Halichoeres bivittatus) at Gulf Specimen Marine Lab in Panacea, FL.

Prionotus scitulus, P. tribulus

Swims along the sand bottoms with its wing-like pectoral fins expanded. The modified ventral fins act like fingers, feeling the bottom for prey. Size: 6-12 cm.


Bighead searobin (Prionotus tribulus)

Scorpaena brasiliensis

Red, orange, and brown, they blend into the sea bottom, and ambush passing shrimp. Although bristling with poisonous spines, they are a popular aquarium specimen.


A scorpionfish (Scorpaena brasiliensis)

Chaetodipterus faber

Common to Florida and Caribbean water, schools of spadefish are frequently seen nibbling on jellyfish, hydroids, and feeding on small crabs and shrimp when the fish matures.


Atlantic spadefish (Chaetodipterus faber)

Diplodus holbrookii

Less common than the regular pinfish but still very common. Found in coastal grass beds. Size 6 to 12 cm


Lagodon rhomboides

3 inches to 6 inches, a very common aggressive fish available throughout the year. Hardy species that does well in aquariums.


Lagodon rhomboides

A large bag of preferred species (whichever species is available at the time of shipment) is collected and shipped in water. One bag per two dozen urchins is recommended for a month.


They have long formidable looking spines which rapidly moves about the aquarium. Their powerful teeth scrape away algae, and chew into sponges. Although they add action and beauty to the salt water aquarium, they have been classically used in embryology. Specimens are fertile January through March.


Handsomely pink and white, with an explosion of short spines emanating from a fat round body. Eggs are remarkably clear and easy to study, particularly for demonstrating mitotic spindles. Huge volumes of eggs can be produced from a single large specimen, hence it is also prized by seafood loving gourmets. Specimens are fertile March through October.


This sluggish, nocturnal sea urchin has thick, wooden like spines. It feeds primarily on algae and coral but they can feed on small invertebrates as well. They are a very hardy species and can range from a light brown to a reddish brown.


Arbacia loves to gnaw on the protein rich green tissues full of symbiotic algae. The sponge colony often stays alive until it is completely consumed.