NEW INSIGHTS ON REPRODUCTIVE FEATURES IN LEPIDONOTOTHEN NUDIFRONS (PISCES, NOTOTHENIOIDEI) AT THE SOUTH SHETLAND ISLANDS, SUPPORTED BY PHYSIOLOGICAL EVIDENCE

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

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar-COLACMAR 2019; 2019

COLACMAR

The Southern Ocean marine ichthyofauna is dominated by a unique costaldemersal fish group, the suborder Notothenioidei. The nototheniidLepidonotothen nudifrons is abundant in nearshore waters of the Scotia Arcregion, where it is ecologically important as relevant prey of piscivorouspredators. The knowledge of its reproductive biology arises exclusively frommacroscopic and histologic descriptions of the maturation cycle. In this study,we provide for first time in L. nudifrons adult females, information on oocytegrowth rate and change in testosterone (T) and estradiol (E2) plasma levelsthroughout their ovarian growth period in summer. Briefly, 98 specimenswere caught at Potter Cove (PC), South Shetland Islands (SSI), fromNovember to late March in the consecutive campaigns 2016/2017-2017/2018. Histological analysis of the ovaries confirmed the macroscopiccharacteristic of the two distinct cohorts of oocytes: one leading clutch (Lc) oflarge orange vitellogenic oocytes, likely to be spawned in the upcomingreproductive season, and a second clutch of smaller whitish previtellogenicoocytes. In late March, females (n=17) had gonado-somatic index valuesbetween 13 and 20% (16.73±2.10) and total fecundity ranged between 2196and 4652 oocytes/female (3209± 740), while Lc oocytes reached between1.7 and 2.1 mm. The estimated Lc oocyte diameter average growth rate was0.01 mm/day. Both, T and E2, increased together with the oocyte growingthroughout the analyzed seasons. However, E2 variation was more significantly associated with the photoperiod than with the Lc oocyte size, whereas T was better associated with this last variable. Based on physiological evidence, mainly on the significant plasma level increase of both sex steroids observed in females captured in March, and also on the reproductive effort data, we suggest that: (1) specimens from March were presumably at a late vitellogenesis stage just prior to the oocyte final maturation, and thus L. nudifrons spawning period might onset in late MarchApril at SSI, (2) the inshore locality of PC is likely a spawning site for L. nudifrons, which reinforce the hypothesis that nearshore areas are spawning grounds for some notothenioids.