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7 April 2021 How to Wear a Sandy Coat: Secretory Cells in the Dorsal Epidermis in the Sea Cucumber Holothuria atra (Echinodermata: Holothuroidea)
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Abstract

Holothuria atra is a black sea cucumber commonly found on the sandy bottom of Okinawan coral reefs. The body surface of H. atra is usually covered with sand; however, sand never covers the body of another black congener, Holothuria leucospilota, which is sympatrically distributed with H. atra. The epidermal structures were examined in these two species by means of transmission electron microscopy to determine how sand adheres to the surface of H. atra. While the epidermis was basically composed of support cells bearing microvilli and vacuolated cells probably corresponding to mucus cells, two types of granular cells, type 1 and 2, were also found at the tip of the tube feet. These granular cells were closely similar in structure to secretory cells that have been supposed to secrete adhesive substances in other holothurians. Type 1 granular cells were also found in the dorsal epidermis of H. atra but not in H. leucospilota. Therefore, adhesive secretion by type 1 granular cells probably enables the attachment of sand to the H. atra body.

© 2021 Zoological Society of Japan
Nodoka Aruga and Euichi Hirose "How to Wear a Sandy Coat: Secretory Cells in the Dorsal Epidermis in the Sea Cucumber Holothuria atra (Echinodermata: Holothuroidea)," Zoological Science 38(3), 252-258, (7 April 2021). https://doi.org/10.2108/zs200171
Received: 14 December 2020; Accepted: 2 February 2021; Published: 7 April 2021
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