Distribution and Characterization of Ion Transporting and Respiratory Filaments in the Gills of Procambarus clarkii

Abstract

Individual gill filaments of the freshwater crayfish Procambarus clarkii were determined to be either predominantly respiratory or transporting. Silver staining revealed that the filaments within the central bed of the gills formed silver deposits whereas filaments at the margins and the entire sixth pleurobranch formed no deposits. Designation of the silver staining gills as predominantly transporting and unstained filaments as predominantly respiratory was substantiated by ultrastructural analyses and measurements of ATPase and transepithelial potentials. Presumptive transporting filaments had an epithelium subjacent to the cuticle that was relatively thick and dominated by abundant mitochondria. Lacunae were delineated by pillar structures and served as collateral pathways for the movement of blood from the afferent to efferent blood channels, which were separated by a thin septum. Presumptive respiratory filaments had an extremely thin epithelium with few organelles, but a relatively thick septum. Present in both types of filaments were nerves and podocytes. The values for Na, K-ATPase were significantly higher in the transporting filaments than in those designated as respiratory. The measurement of transepithelial potentials showed both filaments to be cation selective with the respiratory filaments slightly more positive and the transporting filaments slightly more negative than the diffusion potential for Na.

Osmoregulation in the Hawaiian anchialine shrimpHalocaridina rubra(Crustacea: Atyidae): expression of ion transporters, mitochondria-rich cell proliferation, and hemolymph osmolality during salinity transfers

“…This is notable as brachyuran gills are typically either respiratory or osmoregulatory in nature, with AgNO 3 staining typically confined to just the osmoregulating gills. For example, only the posterior gills undergo staining in C. sapidus and many other brachyurans (Copeland and Fitzjarrell, 1968), and while some lamellae in all gills show staining in FW crayfish, it is localized to the central filaments of each gill (Dickson et al, 1991;Khodabandeh et al, 2005). AgNO 3 staining of larval H. rubra revealed that ion-transporting gills develop at late zoeal stages (i.e.…”

“…However, all gills in crayfishes and shrimps possess MRCs and are involved in osmoregulation, although some areas of individual gills remain specialized for respiration (Wheatly and Henry, 1987;Dickson et al, 1991;McNamara and Lima, 1997;Ordiano et al, 2005;Huong et al, 2010). Active salt absorption in the MRCs is accomplished via a suite of ion transporters and supporting enzymes (Evans et al, 2005;Henry et al, 2012): in this context, Na + absorption occurs via a combination of apical Na + /H + exchange, Na + /K + /2Cl -co-transport, Na + channels and the basolateral Na + /K + -ATPase (NKA), while Cl -absorption is accomplished via apical co-transport, Cl -/HCO 3 -exchange and basolateral Cl -channels (reviewed in Freire et al, 2008;Charmantier et al, 2009;Henry et al, 2012;McNamara and Faria, 2012).…”

“…For example, while marine species tend to have gill epithelia with high conductance ('leaky'), resulting in high rates of diffusive ion loss in low salinity, FW species typically have low conductance ('tight') epithelia, which hinders ion loss (reviewed in Henry et al, 2012). NKA activity is also uniformly distributed across all gills in the euryhaline FW crayfishes Pacifastacus leniusculus and Procambarus clarkii (Wheatly and Henry, 1987;Dickson et al, 1991), unlike their marine counterparts (see above). Moreover, crayfishes tend to produce hypo-osmotic urine to prevent further salt loss in lower salinities while most marine euryhaline crustaceans produce isoosmotic urine (Riegel, 1968;Cameron and Batterton, 1978;Wheatly and Henry, 1987).…”

Ontogeny of osmoregulation in embryos of intertidal crabs(Hemigrapsus sexdentatusandH. crenulatus, Grapsidae,Brachyura): putative involvement of the embryonic dorsal organ

“…Silver staining has been used to identify putative osmoregulatory epithelia in a number of insects (Krogh, 1939) and crustaceans (Koch, 1934;Ewer and Hatlingh, 1952;Talbot et al, 1972;Barra et al, 1983;Felder et al, 1986;Dickson and Dillaman, 1991;Kikuchi and Matsumasa, 1993;Lindhjem et al, 2000;Haond et al, 2001). The appearance of the silverstaining patch on the surface of the embryo at gastrulation coincided with the acquisition of hyper-osmoregulatory capacity, tempting the suggestion that the patch is concerned with ion transport.…”

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“…Many studies have shown that gills are the primary organs for salt transport in crabs 8,9,10 and lobsters 11 . They utilize apical membrane branchial Na /HCO 3 -exchange powered by a basal membrane Na + / K + -ATPase.…”