Universal antisera for immunocytochemical identification of two different gonadotrophs in acanthopterygian fishes

Abstract

Pituitaries of various teleosts belonging to 25 orders were immunostained with antisera raised against synthetic fragment peptides corresponding to conservative regions of gonadotropinβ subunits (mummichog FSHβ 50-60 and mummichog LHβ 91-106). Both immunoreactive FSH cells and immunoreactive LH cells were successfully identified in the fishes of almost every order of the superorder Acanthopterygii and several species of the superorders Paracanthopterygii and Polymixiomorpha, such as mullet, alfonsino, flyingfish, mackerel, flounder, cod, beardfish, etc. These antisera are therefore considered as universal antisera for immunocytochemical application to acanthopterygian fishes. Extensive diversity in the abundance of the FSH cells and the LH cells among species was noted even in fishes with similar gonadal stages, indicating the possibility that the respective roles of FSH and LH may vary considerably among species in advanced teleosts. Evident but generally weak immunoreactivities to anti-mummichog LHβ 91-106 were observed in the fishes of the superorder Cyclosquamata; and slight or weak immunoreactivities to the antiserum were observed in the fishes of several more primitive taxa (superorder Stenopterygii, Protacanthopterygii, Ostariophysi, subdivision Clupeomorpha, and subdivision Elopomorpha). No immunoreactivity to anti-mummichog FSHβ 50-60 was observed in these fishes. These results are consistent with the phylogenetic status of the fishes and the degree of conservativeness in the amino acid sequences of the antigen regions.