Sexual dimorphism and some special traits of spawning behavior of the Arctic Lamprey Lethenteron camtschaticum

Abstract

The sexual dimorphism and the role of secondary sexual characters in the spawning period of the Arctic Lamprey Lethenteron camtschaticum from the Utkholok basin (Kamchatka) are studied for the first time. The importance of the urogenital papilla in males and of the keel in females during egg fertilization and in con- struction of the redd is shown. By visual observations, underwater and above water videography, two forms of spawning behavior are revealed: group behavior in the current and paired behavior in the inshore part of the river, where the current is slower. The typically anadromous form, the anadromous forma praecox, and river lamprey reproduce together. The strategy of the spawning behavior is directed first of all towards better fertili- zation of eggs and finally towards reproductive success of the species.