Gametogenesis and gonad mass cycles in the common circumpolar Antarctic echinoid Sterechinus neumayeri

Abstract

Polar conditions (low and stable seawater temperature coupled with highly seasonal primary productivity) constrain reproduction in benthic invertebrates. The reproductive cycle of the common Antarctic sea urchin Sterechinus neumayeri was investigated at monthly intervals over a 2 yr period in relation to seasonality of chlorophyll standing stock and ability to feed. Competence to spawn increased gradually throughout the austral winter to peaks in September to November. Gonad mass varied strongly, both seasonally and among 3 geographically close sites. Spawning occurred between October and January at each site, and was strongest in November of both years. Spawning was not always accompanied by a reduction in gonad mass because of simultaneous feeding and deposition of nutritive tissue for the forthcoming winter. Spawning was annual but there was also strong evidence for longer, multi-year periodicity in reproductive output. Histological analysis indicated an 18 to 24 mo vitellogenic cycle, with oocytes developing from 20 to 50 µm in the first winter, and from 50 to 120 µm in the second winter. Of total oocyte volume increase (vitellogenesis), 93% occurred within the last 12 mo. Spermatogenesis took 12 mo. S. neumayeri does not feed during the austral winter, and vitellogenesis is therefore predominantly decoupled from energy intake. Much of the cost of reproductive synthesis is met at a time of severe energy limitation. KEY WORDS: Gonad mass · Seasonality · Reproductive cycle · Vitellogenesis · UrchinResale or republication not permitted without written consent of the publisher

The reproductive ecology of the Antarctic bivalve Aequiyoldia eightsii (Protobranchia: Sareptidae) follows neither Antarctic nor taxonomic patterns

“…nanoplankton production, acts as a selective pressure driving a superimposed seasonal reproduction, recent evidence of a multi-year cycle in shell growth of the protobranch bivalve (Román-González et al 2017) suggests the reproductive asynchrony observed in females is not underpinned by environmental factors. Nor can this reproductive pattern be explained by the accepted paradigm of an 18-to 24-month period needed for oogenesis in several other Antarctic invertebrates (Peck et al 2005; for examples see Grange et al 2004Grange et al , 2007Brockington et al 2007;Orejas et al 2007). The reproductive ecology of A. eightsii also differs from other shallow-water and deep-sea nuculanid protobranch bivalves that have a 12-month gametogenic cycle, often with seasonal investment in reproduction (Tyler et al 1992;Nakaoka 1994;Jaramillo and Thompson 2008;Scheltema and Williams 2009).…”

Contributions of genetic and environmental variance in early development of the Antarctic sea urchin Sterechinus neumayeri in response to increased ocean temperature and acidification

“…Sterechinus neumayeri were collected (20-25 m depth) by scuba diving from Winter Quarters Bay, Ross Island, Antarctica (77°50′S, 165°0′E) in November 2013 during their peak spawning period (Brockington et al 2007). For environmental conditions for the site of collection see Kapsenberg et al 2015.…”

Vulnerability of Antarctic shelf biodiversity to predicted regional warming

“…Reproduction and other processes are generally lengthier in polar waters. An egg development period of 24 mo appears widespread compared with 12 mo or less in temperate species, and this has been demonstrated in the starfish (Odontaster validus), the ophiuroid (Ophionotus victoriae), the sea urchin (Sterechinus neumayeri), the infaunal bivalve (L. elliptica), the limpet (Nacella concinna), the brachiopod (Liothyrella uva) and the octocoral (Ainigmaptilon antarcticum) (Orejas et al 2002, Brockington et al 2006 and references therein). There are a few exceptions, and the scallop (Adamussium colbecki ) matures its eggs in 1 season (Tyler et al 2003), as do some amphipod species (Clarke 1988) Fig.…”