Gill morphology and ultrastructure of the prawn, Palaemonetes argentinus Nobili, 1901 (Decapoda, Caridea)

Abstract

A morphological and ultrastructural study was performed on the gills of Palaemonetes argentinus from the Sotelo stream, a tributary of the Mar Chiquita coastal lagoon (Argentina, 37 • 45 S 57 • 26 W). This species possesses a phyllobranchiate gill, in which the central axis is triangular and has one row of flattened lamellae on each side. There are one afferent channel, two efferent channels, and several tegumental glands along the axis. Nephrocytes are only present in the stem, associated with the efferent haemolymph. Mature nephrocytes have a voluminous vacuole, surrounded by satellite vacuoles, a lateral nucleus, and pedicels on the surface. In the lamellae, the principal cells have apical extensions with deep infoldings and a neck-like zone with bundles of microtubules. The nucleus is in a basal expansion of the cell and the basolateral membranes of neighbouring cells are interdigitated, with large numbers of mitochondria in the interdigitations. The cells show characteristics of both respiratory and ion-regulatory epithelium; they also have a structural role in directing the haemolymph flow and in supporting the lamellae. The thicker cuticle near the marginal channel increases mechanical support. The ultrastructure of the lamellar epithelium appears to be related to the capability of P. argentinus of living in freshwater and adapting to media with variable salinity. RESÚMENSe realizó un estudio morfológico y ultraestructural de las branquias del camarón Palaemonetes argentinus del arroyo Sotelo, tributario de la laguna costera de Mar Chiquita (Argentina, 37 • 45 S 57 • 26 W). Esta especie posee filobranquias, cuyo eje central tiene forma triangular y posee una hilera de laminillas aplanadas a cada lado. Hay un canal aferente, dos canales eferentes y glándulas tegumentarias a lo largo del eje. Se observaron nefrocitos asociados con la hemolinfa eferente en el eje central. Los nefrocitos maduros tienen una vacuola voluminosa rodeada por vacuolas satélite, un núcleo lateral y pedicelos en la superficie. En las laminillas las células principales tienen extensiones apicales con profundos pliegues y una zona más estrecha con numerosos microtúbulos. El núcleo se ubica en una expansion basal y las membranas basolaterales de las células vecinas se interdigitan encerrando numerosas mitocondrias. Estas células muestran características de un epitelio respiratorio y osmorregulador. También tienen una función estructural: dirigen el flujo de la hemolinfa y 3 )