Diatom diversity in the in situ diet of Chiton virgulatus (Mollusca: Polyplacophora) from Baja California Sur, Mexico

Abstract

Although 15 species of chitons have been recorded for Bahía de La Paz, BCS, their basic ecology is poorly known. Because most chitons are grazers and preliminary observations indicate that diatoms are an important part of their diet, the aim of this study was to determine the species diversity of diatoms that are grazed upon by Chiton virgulatus Sowerby, 1840 and to determine if any feeding preference exists. In order to do so, specimens were collected in three seasons within an area of approximately 50 m2 of Balandra beach in Bahía de La Paz. One hundred and sixty two diatom taxa were identified in the gut contents of the collected specimens of C. virgulatus; 35% were epiphytes, including: 19 Cocconeis species, 15 Amphora,14 Nitzschia and 10 Achnanthes. Typical mangrove species were also common: Diploneis (9), Lyrella (4) and Mastogloia (9). The most abundant taxa were: Nitzschia frustulum var. perminuta and Achnanthes pseudogroenlandica var. phinneyi which characterize the sampled seasons. Similarity measurements indicate that the observed seasonal differences may be clouded by different microhabitat found within the sampling area. The estimated values of H´ (2.34 - 4.44) together with the species composition indicate that the benthic diatoms found in the guts of C. virgulatus represent the typical assemblages found in the environment.