Histochemical observations on glycoproteins in the urinary apparatus of the bullhead Cottus gobio L. and the bull rout Myoxocephalus scorpius (L.).

The distribution of neutral and acid (sialylated and sulfated) glycoprotein in the urinary apparatus of a marine and a fresh water cottid teleost (Bull rout and Bullhead) has been studied. The renal morphology of the Bullhead Cottus gobio is similar to that of the marine Bullrout Myoxocephalus scorpius: The glomerular nephron consists of 2 tubular segments (PI and PII), leading to the collecting duct-archinephric duct system (CD/AD). Sialoglycoprotein is present in the secretion of the proximal tubule segment PII cells in breeding males of Cottus gobio, resembling the mucus production of nest building male sticklebacks Gasterosteidae. The acid mucus coat in the CD/AD system of Myoxocephalus is discussed in relation to the excretion of salts by the kidney.