The Question of Functional Homology of Hatschek's Pit of Amphioxus (Branchiostoma belcheri) and the Vertebrate Adenohypophysis

Using antibodies to the beta subunit of human luteinizing hormone (hLHβ) and human chorionic gonadotropin, immunocytochemical evidence was obtained for gonadotropin activity in Hatschek's pit of amphioxus, Branchiostoma belcheri. This confirms the claim by C. Y. Chang et al. [1, 2] of vertebrate-like gonadotropin in this structure, an open groove in the dorsal part of the oral cavity. If this evidence is accepted at face value, a scenario can be constructed for the evolutionary pattern of the vertebrate adenohypophysis from the protochordate Hatschek's pit (cephalochordates) or neural gland (ascidians). Both of these structures are open to water currents in the mouth cavity. Thus, they may be able to sample thermal, chemical or pheromonal seasonally cycling clues and by gonadotropic stimulation, synchronize reproductive activity with such seasonal clues. Additional support for the idea that the early vertebrate adenohypophysis was a chemoreceptive organ comes from the fact that in cyclostomes and elasmobranchs it develops as part of the same epithelial layer and is directly contiguous with the olfactory organ. Advancement from the protochordate to vertebrate type of reproductive control involves the eventual use of sense organs and the nervous system to sample environmental changes, and the linkage of adenohypophysial function to central nervous control. The adenohypophysis then can be closed off from the mouth and direct environmental contact

The Question of Functional Homology of Hatschek\u27s Pit of Amphioxus (Branchiostoma belcheri) and the Vertebrate Adenohypophysis(Endocrinology)

Volume: 9Start Page: 387End Page: 39

Distribution of LHRH-like Immunoreactivity in the Brain of the Japanese Eel (Anguilla japonica) with Special Reference to the Nervus Terminalis

The brain of the Japanese eel, Anguilla japonica, was studied immunocytochemically using antisera generated against the synthetic luteinizing hormone-releasing hormone (LHRH) of mammals. LHRH-positive perikarya were observed in both the distal and proximal ganglia of the nervus terminalis and in the ventrolateral portions of the ventral telencephalon and preoptic area. LHRH-positive perikarya of the distal and proximal ganglia of the nervus terminalis sent their fibers to the olfactory nerve, ventral telencephalon, preoptic area, and optic tectum. LHRH-positive fibers, originating from the ventral telencephalon and preoptic area, proceeded toward the olfactory bulb, dorsolateral part of the rostral telencephalon, preoptic area, neurohypophysis, and optic tectum. LHRH-positive fibers were also observed in the optic nerve. These findings are discussed in comparison with recent anatomical findings by others in other teleosts. Further, possible participation of nervus terminalis in reproductive behavior is discussed