Salinity tolerance and gill histopathological alterations in Liza aurata Risso, 1810 (Actinopterygii: Mugilidae) fry

Abstract

Gill histopathological alterations in Golden Grey Mullet, Liza aurata, fry in acute salinity exposure were studied by light and scanning electron microscopy (SEM). The Golden Grey Mullet fry was obtained from the south of the Caspian Sea and acclimated to brackish water (12 ppt). Fry (adapted in 12 ppt salinity) were transferred directly to salinities of 40, 45, 50, 55, 60, 65 and 70 ppt. Mortality occurs more rapidly over a narrow range of salinity from 45 to 60 ppt. Mortality was 100% in salinity higher than 60 ppt. Histopathological gill alterations included edema of the epithelial cells with the breakdown of pillar cells, hypertrophy and hyperplasia of epithelial and chloride cells. According to SEM observation, two types of chloride cells were identified in gill of L. aurata fry. In Type I, crypts usually had large openings and were occasionally ornamented with short microvilli, and, in Type II, crypts resembled a narrow and deep hole. The number of Type II increased following elevated salinity. lethal concentration50 (LC50) 24-, 48-, 72- and 96-h values calculated with the probit method were 50.11, 49.91, 49.91 and 49.91 ppt, respectively. This study showed that the gill was the primary target organ for the acute effects of salinity. Moreover, the type of chloride cells and gill structure is affected by acute salinity such that these alterations must be one of the reasons for death in some treatments.