New insights into reproductive physiology in Antarctic fish: a trial in Lepidonotothen nudifrons

NOVILLO, MANUEL; ELISIO, MARIANO; MOREIRA, EUGENIA; MACCHI, GUSTAVO; BARRERA-ORO, ESTEBAN

POLAR BIOLOGY

SPRINGER

Año: 2021

0722-4060

The knowledge of reproductive biology in notothenioids arises exclusively from macroscopic and histologic descriptions, without the complement of hormonal analysis. Our study provides for first time in Lepidonotothen nudifrons adult females, information on oocyte growth and change in testosterone and estradiol plasma levels throughout the ovarian growth. Sampling included near 100 specimens caught at Potter Cove (PC), South Shetland Islands (SSI), from November to late March of 2016-2018. Histological analysis confirmed the macroscopic characteristic of two distinct cohorts of oocytes: one leading clutch of large orange vitellogenic oocytes, to be spawned in the upcoming reproductive season, and a second clutch of smaller whitish previtellogenic oocytes. In March, females (n=17) attained gonado-somatic index of 13-20% (16.73±4.20), total fecundity of 2196-4652 oocytes/female and leading clutch oocytes with a diameter of 1.7-2.1 mm. The leading clutch oocytes growth was significantly associated with photoperiod, with no diameter variation until the summer solstice, when they began to grow linearly with an estimated rate of 0.01 mm/day. Testosterone and estradiol increased together with the oocyte growing throughout the analyzed seasons, with a higher rise rate during March. The significant plasma level increase of both sex steroids observed in March and the reproductive effort data suggest that: (1) specimens were at a late vitellogenesis stage, just prior to the oocyte final maturation, and thus L. nudifrons spawning period might onset in March at SSI; (2) PC is likely a spawning site for L. nudifrons, which reinforce the hypothesis that nearshore areas are spawning grounds for some notothenioids.