Ultrastructural Evidence for Osmoregulatory Function of the Sternal Epithelia in Some Gammaridean Amphipods

Abstract

The ion-permeabilities and the ultrastructure of the sternal epithelia were studied in 7 species of gammaridean amphipods. Evidence has been obtained that the sterna can be divided into 2 categories: ion-transporting and non-ion-transporting types.The sterna of Sternomoera japonica, Grandidierella japonica, Melita setiflagella, and Corophium uenoi, belonging to the former category, are covered by ion-permeable cuticular layers lined with a thick epithelium, which is characterized by both a shallow apical infolding system (AIS) and a well-developed basolateral infolding system (BIS). The AIS is composed of frequent lamellar infoldings without mitochondrial association originating from the apical sides of the epithelia and involves virtually every part of the apical cell membrane, forming elaborate intercellular channels in the subcuticular space. In contrast, the BIS consists of deep infoldings of the basolateral cell membranes and extensive interdigitations between epithelial cells, which are both associated with a large number of mitochondria. This BIS involves the greater part of the cell membrane and constitutes a complicated, giant labyrinth of the intercellular spaces above the basal lamina. The AIS and BIS never communicate in the sternal epithelia, though they sometimes interpenetrate.On the other hand, the sterna of Jesogammarus jesoensis, Jesogammarus hinumensis, and Haustorioides sp., belonging to the latter category, are composed of an ion-impermeable, thick cuticular layer and a thin epithelium characterized by a paucity of mitochondria and complete lack of the BIS and AIS, which are common to those of the ordinary epithelium of the body surface.The results suggest a rather widespread occurrence in amphipods of a variety of extrabranchial ion-permeable areas of the body surface. They also suggest that the sterna lined with thick, specialized epithelia, together with the gills, are involved in the active transport of electrolytes in osmoregulation as well as respiration.

Ecology of ontogenetic body-mass scaling of gill surface area in a freshwater crustacean

“…No apparent effect of conductivity on gill SA scaling was observed, possibly because of limited differences in conductivity among the study springs, and because gills are not the only sites for ion regulation in crustaceans (Kikuchi and Matsumasa, 1997). However, among Gammarus species, freshwater species tend to have larger gills than marine species (Moore and Taylor, 1984).…”

Preliminary Analysis of Phylogenetic Relationships of the Asian-Pacific Endemial Subterranean Amphipod Genus Pseudocrangonyx Among Families and Genera of Crangonyctoidean Amphipods Inferred by Partial LSU rDNA Gene Sequences

“…Together with Procrangonyx (three species; Uéno, 1930;Stock and Jo, 1990;Hou and Li, 2004;Sidorov and Holsinger, 2007), these genera comprise the family Pseudocrangonyctidae. The pseudocrangonyctids are morphologically adapted for life in groundwater conditions: their body is narrow and teretial, without teeth or combs, the appendages are relatively elongate, the eyes and pigmentation are lost entirely, and sternal respiratory organs are presented by humps (or pulvinate sternal epithelium sensu Kikuchi and Matsumasa, 1997).…”

Gill ultrastructure and salinity tolerance of Caprella spp. (Crustacea: Amphipoda: Caprellidea) inhabiting the Sargassum community

“…Comparative studies on the gill structure of amphipod crustaceans, which are widely distributed in various habitats from the abyssal floor of the ocean to ancient freshwater lakes in highlands, have elucidated the wide variation of the morphology and fine structural characteristics of the gill epithelia, especially the presence/absence of two types of mitochondria-rich cells according to differences in habitat. [1][2][3][4][5][6][7] The two types of specialized mitochondria-rich cells are involved in the absorption and/ or excretion of NaCl for osmoregulation in hyperosmotic environments. 1,2,8,9 The first type of specialized epithelial cells was initially observed around the blood vessels of the coxal gills of brackish amphipod species, 2 and was considered to be involved in salt excretion.…”