Study on the biology of the ghost shrimp, Nihonotrypaea japonica (Ortmann 1891) (Decapoda: Thalassinidea: Callianassidae), distributed on intertidal Sandflats in Ariake Sound, Kyushu, Japan

Abstract

Nilumotrypaea jfll)Onica (Ortmann 1891) is one of the commonest members of large­sized benthic fauna. inhabiting intertidal sandflats largely in the middle one-third of A.riake Sound, Kyushu, Japan, while the habitats of its congeneric species, N. hann(!ndi, range from Ariake Sound (estuary) through Tachibana Bay (intermediate waters) to the East China Sea (open sea). However, there is a little overlap in their distribution margins. The two shrimps construct and reside in complex tubular branching burrows for shelter, reproduction and feeding. Accompanied with their activities during burrow construction or maintenance and/or feeding, unwanted sediment is ejected from the burrow, forming mounds on substratum surface. Those activities are often called bioturbation. Whilst the importance of bioturbation has been recognized, there are still relatively few detailed studies of the shrimps' biology. This is particularly true of N. japonica. The aim of the present study was to elucidate the biology of N. japonica, including (l) taxonomy, (2) spatial distribution and (3) life history, in the light of comparative viewpoint to those of N harmandi. The results of the three subjects are presented in three chapters after Chapter I (General Introduction), i.e. Chapter II, Chapter ill ;md Chapter IV, respectively. Chapter ll - For the two calliaoassid shrimps, Nihonotrypaea japonica and N harmandi, morphometric character variations [carapace length (CL), total length (TL), abdomen width (AW), eyestalk width (EsW), cornea width (CoW), and rostrum angle (RA)] were examined based on the materials collected from sandflats in western Kyushu, Japan. Allometric relationships were established between each combination of two morphometric characters for each species, in which CL was fixed on the abscissa as a reference variable; the values of TL, AW, EsW and CoW lnearly increase with the CL..dst