Sperm allocation pattern during a reproductive season in the copulating marine cottoid species, Alcichthys alcicornis

Abstract

The sperm allocation pattern of a copulating marine cottid fish, Alcichthys alcicornis, was investigated. A total of 86 mating events using six males were conducted in aquarium tanks over 10 days, and in 36 of them, spermatozoa were collected using a false copulation method. Males released 3-8×10 8 spermatozoa in early events, with the number decreasing gradually during subsequent mating events. This sperm allocation was represented as an "early investment and tapering" pattern. It was discussed why males have significantly higher sperm release in early spawning events. The reproductive behavior consists of spawning and subsequent copulation. Spermatozoa have the ability to fertilize eggs from multiple clutches, and in earlier produced clutches the level of sperm competition should be relatively low. In addition, if early spawn happens to be the first spawn with a female, spermatozoa that are released into the water column after spawning are responsible for fertilizing the female's first clutch. The probability of this occurring should decrease dramatically as the season progresses, due to the highly synchronous seasonal spawning of females. All of these factors should select for high sperm numbers in early ejaculates. Based on such reproductive ecology of A.alcicornis we hypothesize that this sperm allocation pattern is an adaptive reproductive strategy in response to egg availability and sperm competition occurring within the ovarian cavity.

Mating Season, Egg-Laying Season, and Internal Gametic Association in the Sympatrically Occurring Fluffy Sculpin (Oligocottus snyderi) and Rosy Sculpin (O. rubellio)

“…Indeed, Al. alcicornis are likely to exhibit synchrony in peak GSI between the sexes (Koya et al, 1994;Munehara and Murahana, 2010). Alternatively, IGA species with maternal care (Radulinopsis taranetzi: Abe and Munehara, 2005) and those with no care (five species of Pseudoblennius, two species of Furcina, and one species of Vellitor: Koya et al, 2015;Awata et al, 2019;Orthonopias triacis: Awata et al, 2022) exhibit delayed timing of spawning from timing of mating.…”