Morphology and distribution of two epizoic diatoms (Bacillariophyta) in Brazil

Abstract

The epizoic diatoms Pseudohimantidium pacificum and Falcula hyalina, which live on copepods, were investigated using light and electron microscopes, based on material gathered from different marine environments along the Brazilian coast. Pseudohimantidium pacificum is reported for the first time for the Southwestern Atlantic Ocean, significantly enlarging its range of geographic distribution. This species usually covers the entire body surface of the copepods Corycaeus amazonicus and Euterpina acutifrons, and of cypris larvae of Cirripedia. Falcula hyalina uses a higher number of copepod hosts, particularly Oithona oswaldocruzii, Pseudodiaptomus richardii and Acartia spp. The valve morphology and biometrical data of both diatoms were within the range limits recorded in the literature, including the original publications. Both species occurred in all the sampling stations along the Brazilian coastline stretching from 12°S down to 28°S. Falcula hyalina had already been found as far as latitude 31°S in the Southwestern Atlantic Ocean.As diatomáceas epizóicas em copépodos Pseudohimantidium pacificum e Falcula hyalina foram investigadas em microscopias óptica e eletrônica de varredura, com base em amostras coletadas em diferentes ambientes marinhos da costa brasileira. Pseudohimantidium pacificum é reportada pela primeira vez no Oceano Atlântico Sul Ocidental, ampliando significativamente sua faixa de distribuição geográfica. A espécie ocorreu sobre os copépodos Corycaeus amazonicus e Euterpina acutifrons, e em larvas cypris de Cirripedia. Falcula hyalina utilizou um número maior de hospedeiros, particularmente os copépodos Oithona oswaldocruzii, Pseudodiaptomus richardii e Acartia spp. A morfologia e dados biométricos das valvas de ambas as diatomáceas estiveram dentro dos limites registrados na literatura, incluindo as publicações originais. As duas espécies ocorreram em todas as estações de coleta ao longo da região costeira entre as latitudes 12°S e 28°S. F. hyalina havia sido registrada anteriormente no Oceano Atlântico Sul Ocidental na latitude 31°S.