Ontogenetic changes in location and morphology of chloride cells during early life stages of the Nile tilapia Oreochromis niloticus adapted to fresh and brackish water

Abstract

Ontogenetic changes in the location, size, density and morphology of chloride cells in the Nile tilapia Oreochromis niloticus adapted to fresh and brackish water are described using Na(+) /K(+) -ATPase immunohistochemistry, light microscopy (LM), scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). The pattern of chloride cell distribution changed during development under both treatments, with chloride cell density decreasing significantly from hatch to 7 days post-hatch, but appearing on the inner opercular area at 3 days post-hatch and increasing significantly thereafter (P < 0·05). Chloride cells were always denser in fresh- than in brackish-water larvae. In both treatments, chloride cells located on the outer operculum and tail showed a marked increase in size with age, but cells located on the abdominal epithelium of the yolk sac and the inner operculum showed a significant decrease in size (P < 0·05). Chloride cells from brackish-water adapted larvae from 1 day post-hatch onwards were always significantly larger (P < 0·05) than those from freshwater-adapted larvae. SEM revealed structural differences in chloride cell apical morphology according to environmental conditions. There appears to be clearly defined temporal staging of the appearance of adaptive mechanisms that confer an ability to cope with varying environmental conditions during early development.

Confocal scanning laser microscopy with complementary 3D image analysis allows quantitative studies of functional state of ionoregulatory cells in the nile tilapia (Oreochromis niloticus) following salinity challenge

“…The significant decrease in overall MRC density following transfer to elevated salinities reported here is in agreement with previous studies which reported a decrease in density of total MRCs following seawater adaptation in gills of the adult Mozambique tilapia (van der Heijden et al, ; Lin and Hwang, ) and yolk‐sac larvae of the Nile tilapia (Fridman et al, ). However, conflicting results do exist in the literature concerning the overall density of MRCs in hypotonic and hypertonic environments.…”

“…Indeed the ontogeny of osmoregulatory capability in early life stages of teleosts is characterized by a distinct spatial shift in MRC distribution. It is generally accepted that integumental MRCs are initially responsible for osmoregulation prior to development of the adult osmoregulatory organs in O. mossambicus (Ayson et al, 1994;Shiraishi et al, 1997;Hiroi et al, 1999), O. niloticus (Fridman et al, 2011), and F. heteroclitus (Katoh et al, 2000) and, similarly, density diminishes with age in P. olivaceus (Hiroi et al, 1999), disappearing completely in adulthood (Whitear, 1970;Bullock and Roberts, 1975).…”

Influence of salinity on juvenile obscure pufferTakifugu obscures

“…It is likely that the morphology changes have to be made to maintain water and ion balance. Based on these results, we speculated that the changes in density and morphology of chloride cells caused by increased salinity help adapt to high-salinity conditions (Fridman et al 2011). An ultra-structural hallmark of the seawater chloride cells is an invagination called apical crypt, which structure is correlated with adaptation to high salinities (Carmona et al 2004).…”

Morphological and ultrastructural characterization of ionoregulatory cells in the teleost oreochromis niloticus following salinity challenge combining complementary confocal scanning laser microscopy and transmission electron microscopy using a novel prefixation immunogold labeling technique

“…The tail section of the larvae was chosen because it proved easier to cut into ultrathin sections than the yolk‐sac, as previous attempts to cut through the thicker yolk‐sac had resulted in poor sectioning, with the epithelium lifting away from the yolk mass. Previous studies in the Nile tilapia had demonstrated that MRCs were present on the tail in meaningful and measureable numbers from 3 dph onward (Fridman et al, ), therefore, this area was regarded as representative of integumental MRCs. Ultrathin sections (90 nm) were cut from each of the dissected tails and serial sections were made every 10 µm thereafter.…”