Immunolocalization of Na+/K+-ATPase, carbonic anhydrase II, and vacuolar H+-ATPase in the gills of freshwater adult lampreys, Geotria australis

As adults, anadromous lampreys migrate from seawater into freshwater rivers, where they require branchial ion (NaCl) absorption for osmoregulation. In teleosts and elasmobranchs, pharmological, immunohistochemical, and molecular data support roles for Na⁺/K⁺-ATPase (NPPase), carbonic anhydrase II (CAII), and vacuolar H⁺-ATPase (V-ATPase) in two different models of branchial ion absorption. To our knowledge, these transport-related proteins have not been studied in adult freshwater lampreys, and therefore it is not known if they are expressed, or have similar functions, in lampreys. The purpose of this study was to localize NPPase, CAII, and V-ATPase in the gills of adult freshwater lampreys and determine if any of these transport-related proteins are expressed in the same cells. Heterologous antibodies were used to localize the three proteins in gill tissue from pouched lamprey (Geotria australis). Immunoreactivity (IR) for all three proteins occurred between, and at the base of, lamellae in cells that match previous descriptions of mitochondrion-rich-cells (MRCs). NPPase-IR was always on the basolateral side of cells that did not stain for CAII or V-ATPase. In contrast, CAII-IR was always on the apical side of cells that also contained diffuse V-ATPase-IR. Therefore, we have identified two types of MRC in adult freshwater lamprey gills based on immunohistochemical staining for three transport proteins. A model of ion transport, based on our results, is proposed for adult freshwater lampreys. 

Histological health indices : linking complex pollutant exposure with tissue alteration in sand flathead Platycephalus bassensis

Port Phillip Bay, Victoria, is a pollutant-impacted environment that is extensively fished both professionally and recreationally. Consumption of contaminated fish represents a potential threat to human health, and fish exposed to environmental contaminants may themselves be affected in a similar fashion. This study describes a fish health index based on histological alterations identified in multiple organs of the sand flathead Platycephalus bassensis. Alterations were evident in tissues from all individuals assessed, with common pathologies observed in the gills, skin, kidney, liver and spleen. Alterations commonly present included necrosis, melanomacrophage centres, inflammation and multiple alterations of the gill epithelium (e.g. hyperplasia and hypertrophy). Fish health, calculated using severity of histological alterations, differed significantly across Port Phillip Bay, with heavily industrialized regions of Altona and St. Helens showing greatest alteration prevalence across multiple organs. This study indicates that the health of P.bassensis from Altona, St. Helens, and Mornington to a lesser extent, are currently compromised, potentially due to complex pollutant exposures which require further investigation