Europacific Sea Biscuit, Clypeaster europacificus

[/lgc_column]Europacific Sea Biscuit, Clypeaster europacificus. Shell collected off the beach of Punta Chivato, Baja California Sur, February 2023. Size: 16.5 cm (6.5 inches) x 2.1 cm (0.8 inches). Collection courtesy of Dr. Alan Adams, Punta Chivato, Baja California Sur. Photograph and identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Phylogeny:  The Europacific Sea Biscuit, Clypeaster europacificus (H.L. Clark, 1914), is a member of the Clypeasteridae family of Sea Biscuits, The genus Clypeaster is one of four genera in this family, and there are forty-two species in this genus. They are also known as the Giant Sand Dollar and in Mexico as galleta de mar gigante.

Morphology:   Europacific Sea Biscuits are  much flattened burrowing urchins. The dorsal side of the test is slightly humped and the ventral or oral surface is flat.  In outline, adults  have a rounded pentagonal or star shape. Juveniles have a more circular outline. The 5-petalled pattern on the dorsal surface is raised. They have a mouth (located centrally on the ventral surface) and a modified Aristotle’s Lantern (complex jaw structure). Grooves, lined with cilia, direct food to the mouth. The epidermis is covered with small spines, which facilitate movement over, and through, soft substrates. The petalloid design on top is made of pairs of pores. These pores allow for respiration through specialized tube feet. This species varies in color, including tan, brown, maroon and green. This is a fairly large species, reaching a maximum diameter of 20 cm (7.9 inches).

Habitat and Distribution: Europacific Sea Biscuits are found on sand or mud. They live subtidally, and to depths up to 100 m (330 feet). Some sources extend the maximum depth to 402 m (1,320 feet). They are an Eastern Pacific species that in Mexico are found throughout the Gulf of California, and extend south to Guatemala. They are absent from the West coast of the Baja Peninsula.

Diet:    Europacific Sea Biscuits are detritivores that use their tube feet to gather organic particles, in the sediment and in the water around them, and to pass the food to their mouth.

Predators:  Europacific Sea Biscuits are a poorly studied and understood species. There is no documentation regarding their predators. Other species in this family are preyed on by fish and starfish.

Reproduction:  Europacific Sea Biscuits are gonochoric (male or female for life). They reproduce sexually through broadcast spawning, with external fertilization. The fertilized eggs hatch into planktonic larva. These larva eventually settle to the sea floor and develop into their adult form.

Ecosystem Interactions:  Europacific Sea Biscuits are a poorly studied and understood species. There is no documentation regarding their commensal, parasitic or symbiotic relationships.

Human Interactions:  Europacific Sea Biscuits have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common and widely distribution and should be consider to be of Least Concern.

Synonyms:  Clypeaster (alexandria) europacificus.