![]() Unialgal cultures were maintained in PES medium 12 at 22 ☌ in a 14:10 h LD cycle at a photon flux density of 90 μE/m 2/s. Scrippsiella hexapraecingula Horiguchi et Chihara was collected from tide pools on the Turugizaki coast, Miura Peninsula, Kanagawa Prefecture, Japan, on 30 August, 1992. Kazuo Okuda, Satoko Sekida, in Progress in Biotechnology, 2001 Culture Although the terrestrial sorties in mudskippers elevate plasma cortisol above resting values and cortisol actually evokes terrestrial behavior, expression of the heat shock protein HSP90 is not elevated ( Sakamoto et al., 2002, 2011). In this case, the elimination of NH 4 + may be aided by anions (HCO 3 −) permeating the CFTR pathway. NH 4 + active secretion during aerial exposure results in astonishingly high accumulation of NH 4 + in gill fluid to 90 mM in a few hours ( Chew et al., 2007). In mudskipper Periophthalmodon schlosseri, branchial ionocytes express NKA and NKCC on the basolateral surface, but have Na +/H + exchangers NHE2, NHE3, V-type H +-ATPase, and CFTR anion channels in the apical membrane ( Wilson et al., 2000). Mudskippers and other gobies keep their dorsal sides wet by rolling periodically ( Lee et al., 2005) and restrict desiccation by spending time in their burrows ( Ikebe and Oishi, 1997).Īerial exposure also evokes changes in gill transporter distribution, an apparent evolutionary adaptation for effective excretion of ammonium ions. Behaviorally, rockskippers ( Hypsoblennius gilberti) typically emerge at night when evaporation rates are lower ( Luck and Martin, 1999) and clingfish curl up near rocks to reduce the surface area available for evaporation. During terrestrial sorties, interlamellar cell masses (ILCMs) accumulate in the gills, an effect that may reduce evaporation on land, but also reduces the effective aquatic respiratory surface area on return to the aquatic medium ( Turko et al., 2011). ![]() Aerial exposure of mangrove killifish ( Kryptolebias marmoratus) causes skin ionocytes to retract and become covered over, an effect reversible with immersion in SW ( LeBlanc et al., 2010). In response to high ammonia exposure, mudskipper ( Periophthalmodon schlosseri) skin increases levels of cholesterol and saturated fats, suggestive of a protective response to reduce NH 3 permeability with the side-effect of reduced evaporative water loss ( Randall et al., 2004). Mudskippers do not have a dry keratinized skin or waxy secretion, but there are structural modifications of the skin including increased mucus secretion and a porous corky layer that may protect against ultraviolet light ( Suzuki, 1992). Four species – blennies Istiblennius lineatus and Paralticus amboinensis and mudskippers Periophthalmus argentilineatus and Periophthalmus kalolo – all lose water at approximately the same rate, 2.6–5.6% h −1, as inanimate aqueous gel ( Dabruzzi et al., 2011), implying that these fish have not evolved significant defenses against desiccation. The mudskipper Periophthalmus cantonensis loses between 6 and 8% of body weight per hour of aerial exposure ( Gordon et al., 1978) and members of this genus die after water loss approaching 22% ( Gordon et al., 1969). There is thus a tradeoff between the need to maintain efficient cutaneous gas exchange, mostly across the wetted buccal epithelium ( Randall et al., 2004), and the need to reduce the rate of water loss. This aerial exposure can result in desiccation sufficient to cause significant concentration of the blood and tissues. Mummichogs also survive well during aerial exposure and do not resort to anaerobic metabolism, but, rather, use cutaneous respiration at approximately half the usual rate of aquatic respiration in well-aerated water ( Halpin and Martin, 1999). Intertidal species such as blennies and mudskippers do not retreat with the ebbing tide and instead take refuge in cracks and holes and beneath rocks, where they remain exposed but, relatively inactive until the return of the tide. Estuarine species have evolved to cope with short periods of osmotic and thermal stress that generally is relieved when the tide returns. In sun-exposed tide pools, resident animals can become heat stressed and hypoxic, while still needing to maintain osmoregulation. Marshall, in Fish Physiology, 2012 4.2 Aerial Exposure
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