Distribution of Opheliid Polychaete Ophelina amiculata Oersted, 1843 (Polychaeta: Opheliidae) in the Intertidal Zone of Sriracha Coastal Area, Chon Buri

Abstract

The distribution and density of opheliid polychaete, Ophelina acuminata Oersted, 1843 in the intertidal zone of Sriracha coast area, Chonburi Province, were investigated in February and July 2016, representing dry and wet seasons, respectively. The highest density of opheliids, O. acuminata was found at a distance of 100 m from shore (80-210 inds m-²), followed by at a distance of 50 m
from shore (21-96 inds m-²), but at distance of 10 m from shore was not found. The opheliid polychaete density in the dry season was lower than that in the rainy season. The sediment properties, including silt-clay fractions and organic matter content, were the main factors related to the distribution and density of opheliids in the area. The number of chaetiger, body length and body weight of O. acuminata ranged from 53-76 chaetigers, 10-38 mm, and 0.004-0.09 g, respectively. The smallest size at reproduction of females within the mature eggs in the coelomic cavity of opheliid polychaete was 53 chaetigers, 20 mm, and 0.004 g, respectively. The reproductive period of O. acuminata in the area spans from February (dry season) to July (wet season).