Direct evidence of cutaneous resistance to evaporative water loss in amphibious mudskipper (family Gobiidae) and rockskipper (family Blenniidae) fishes from Pulau Hoga, southeast Sulawesi, Indonesia

Rockskippers (family Blenniidae) and mudskippers (family Gobiidae) are amphibious fishes common to tropical intertidal zones. While their emergence patterns differ, both groups spend considerable time on land where they are subject to desiccation. Using a gravimetric wind tunnel method we determined total and cutaneous resistance to evaporative water loss of lined, Istiblennius lineatus (Valenciennes in Cuvier and Valenciennes, 1836), and Ambon, Paralticus amboinensis (Bleeker, 1857), rockskippers as well as barred, Periophthalmus argentilineatus Valenciennes in Cuvier and Valenciennes, 1837, and common, Periophthalmus kalolo Lesson, 1831, mudskippers from Hoga Island, southeast Sulawesi, Indonesia. These fishes exhibited mean total resistance values ranging between 0.82 and 0.61 s/cm; values significantly higher than their agar replicas. Mean cutaneous resistance estimates ranged from 0.38 to 0.25 s/cm. Total and cutaneous resistances were statistically similar between species (p = 0.125 and 0.480, respectively). Water loss resistance, while marginal, likely plays an important role in extending fish emergence times. Having greater resistance values may not be compatible with cutaneous respiration or necessary for fishes that frequently return to pools to eliminate nitrogenous wastes. This is the first direct evidence of evaporative water loss resistance in fishes.

Research highlights
► Mudskipper and rockskipper fishes exhibit significant skin resistance values.
► Water loss resistance allows these fish to exploit austere intertidal environments.
► Respiration and excretion needs encourage low levels of water loss resistance.
► Water conservation tactics support differing emergent patterns in amphibious fish.