Colonization of epizoic diatoms on larvae of Aliger gigas (Mollusca: Gastropoda)

Colonización de diatomeas epizóicas sobre larvas Aliger gigas

Abstract

Background. In Mexico, few studies have been carried out on epibiosis. Epizoic diatoms are used as biological indicators of ecosystems due to their apparent epibiont specificity with host animals. Little is known about this specificity in the planktonic larval phases. There have been no studies focused on epizoic diatoms on the marine gastropod Aliger gigas larval shells. Goals. The objective of this work was to determine the species composition of epizoic diatoms in the larvae of A. gigas in the Xel-Há cove, the Mexican Caribbean. Methods. Mollusk egg masses were collected from their natural environment, and the larvae were cultured in seawater filtered through a 5 µm mesh under controlled conditions and fed with the eustigmatophycean alga Nannochloropsis oculata (1000 cells/ml). Shell surface of 60 larvae aged between 2 and 42 days was analyzed using scanning electronic microscopy. A relative abundance index was calculated to quantify diatoms. Results. In total, 83% of the examined larvae carried diatoms. Twenty-four diatom species were found: 68% were mobile, 24% were erect sessile and 8% were adnate species. Conclusions. The highest richness and abundance of epizoic diatoms in the A. gigas larvae were observed on bigger shells due to a larger available colonization area and a more stable substrate.