Journal of the Marine Biological Association of India

Studies on the distribution of three species of lancelets in the shallow waters along the Indian Ocean coast of Thailand

Volume 14 Issue 1

Twesukdi Piyakaranchana and Arom Ratanavichien

Abstract

The samples were collected during the 5th Thai-Danish Expedition along the Indian Ocean coast of Thailand during January-February 1966. The main aim of this expedition was to study the benthos communities along the continental shelf of the Indian Ocean bordering Thailand coast. Bottom samples were collected at one hundred and eighty-two stations by Smith-Mclntyre Bottom Sampler with 0.1 m² capacity. In some locations, Mouse Trap was also used in order to collect meiofauna.

 

Three species of lancelets, Branchiostorm belcheri Gray, B. malayana Webb and Epigonichthys cultellus Peters were found at only fourteen stations. Various ecological factors, such as, temperature, salinity, oxygen content, water current and the composition of the bottom sediments were brought into consideration in order to determine the cause of their distributions. It seems probable that the compositions of the bottom sediments and the water current along the coast are the main factors that limited the distribution of these three species. It was also found that these three species selected different types of sediments. B. belcheri prefers medium coarse brown sand with shell fragments and very small proportion of mud to very fine sand with large proportion of mud. On the contrary, Epigonichthys cultellus and B. malayana were found in muddy sand with or without shell gravels.

 

The evidences also show that the interspecific competition among these three species are high. B. belcheri usually occurred alone while E. cultellus and B. malayana were found together in the same type of sediment. However, in such a case, B. malayana were found more numerous than E. cultellus

Date : 30-06-1972