Echinoderms of Zihuatanejo

PHYLUM ECHINODERMATA

-Sea Urchins and Sea Cucumbers (Subphylum Echinozoa)

-Sea Cucumbers (Class Holothuroidea)

-Subclass (Actinopoda)

-Order (Holothuriida)

-Family (Holothuriidae)

-Genus (Holothuria)

-Sandy Sea Cucumber (Holothuria inornata)

Holothuria inornata is usually found beneath rocks, covered with a thin layer of fine sand. Some larger organisms can also be found next to rocks, over sand, and covered with fine or coarse debris mimicking the bottom. Sea Cucumbers contribute to important chemical and physical processes on the sea- floor, and promoting the continuous mixing of the sediment particles. They actively participate in the recycling of nutrients and organic matter within marine ecosystems.

Diet

Holothuria inornata is a deposit-feeding sea cucumber. It takes in sand and fine sediment with its feeding tentacles and extracts organic matter, microorganisms and detritus before passing the processed sediment through its digestive tract.
This feeding behaviour contributes to the mixing and recycling of sediments and nutrients on the seafloor.

Range

The Sandy Sea Cucumber is a tropical eastern Pacific species ranging from the Gulf of California and the Pacific coast of Mexico southward to northern Peru. It also occurs on several offshore islands, including Clarión and Socorro in Mexico, Cocos Island in Costa Rica and the Galápagos.
Holothuria inornata occurs in the Zihuatanejo area. It is associated with sandy areas around rocks, where it can remain partially covered by sediment and debris.

Habitat

It is primarily a shallow-water species, generally occurring from the intertidal zone to about 18 m depth. It favours rocky-sandy bottoms where fine sediment accumulates around rocks and reef structures.
Individuals commonly shelter beneath rocks or partially bury themselves in fine sand and sediment. Their cryptic coloration and habit of remaining partly covered can make them difficult to detect.
Around Zihuatanejo, suitable habitat includes shallow rocky reefs with sandy pockets, rubble areas and sandy bottoms adjacent to rocks.

Description

Holothuria inornata is a large sea cucumber that can reach approximately 40 cm in length. The body is elongated and cylindrical, with a distinct underside bearing numerous tube feet. It has 20 oral tentacles surrounding the mouth.
The upper surface is generally brown to very dark brown or nearly black, with four to six rows of prominent papillae. The papillae may have reddish coloration, producing a contrasting pattern against the darker body.
The underside is lighter and forms a broad, well-developed “sole” covered with numerous tube feet. The body wall contains microscopic calcareous ossicles that are important for distinguishing the species from closely similar Holothuria.