Defecation Behavior of the Hairy Urchin, ＂Tripneustes gratilla＂

白棘三列海膽的排便行為

趙世民(Shyh-Min Chao) ； 陳邦欽(Bang-Chin Chen)

《Platax》 2013卷 (2013/12) Pp. 89-93

https://doi.org/10.29926/PLATAX.201312_2013.0007

摘要

白棘三列海膽是印度洋到西太平洋珊瑚礁區很常見的海膽，主要以大型藻類、珊瑚紅藻及底沙中的有機物為食，牠的肛門位於身體上方正中央。大多數海膽排便時常會利用棘刺及管足將糞便緩緩移走，這種過程需要消耗一些能量。在2011年8月無風浪的月份，我們在台灣南端的後壁湖地區的潟湖中拍到26%（n=50）的白棘三列海膽將身體立起30~90度的特殊行為，糞便由肛門口排出，直接掉落海底。糞便的成份為細沙及未完全消化的藻類。12月風浪較強的月份，則沒有這種直立行為（n=50）。這種直立排便行為的好處是糞便直接掉落，省去棘刺及管足的運送。

關鍵字

海膽 ； 白棘三列海膽 ； 排便行為

並列摘要

The hairy urchin, ＂Tripneustes gratilla＂ (Linnaeus 1758), is a common sea urchin in the shallow waters of Indo-West Pacific reefs. Its anus is centered on top of its body. During a windless period in August 2011, we photographed 26% (n=50) sea urchins lifting up their bodies 30-90 degrees in the Houbihu Lagoon, southern Taiwan (21°56'57＂N, 120°44'53＂E). Upon close examination of these animals, we saw feces dropping from the anus directly to the substrate. The feces content was subsequently identified in the laboratory as undigested algae and fine sand. During a windy period in December 2011, no sea urchins displayed this defecation behavior. It is postulated that the defecation behavior of these urchins ensures the deposition of feces directly on the substrate. Discharging feces this way could be more energetically efficient than removing feces with tube feet and spines as observed in other urchin species.

並列關鍵字

Sea urchin ； ＂Tripneustes gratilla＂ ； defecation behavior