Reproductive patterns in the Antarctic brachiopod Liothyrella uva

The Antarctic gastropods Marseniopsis mollis (Smith, 1902) and Torellia mirabilis (Smith, 1907) lay eggs in the late austral summer and autumn; these hatch the following late winter and early summer. Field observations indicate that M. mollis lays eggs in the tests of ascidians in January to March. Ascidians with M. mollis broods were collected in April and held in culture. Larvae hatched between mid-October and mid-December, a brooding period of 8 to 11 mo. T. mirabilis egg masses laid in aquaria in April took 6 to 7 mo to hatch. Both species released large veliger larvae (presumably planktotrophic). Natural phytoplankton were provided, but feeding was not confirmed. These larvae were maintained in culture for 25 to 50 d, during which period they were regularly offered a range of substrata, but no settlement behaviour was observed. Metabolism was estimated in individual larvae using microrespirometers of 30 to 45 µl volume, and a couloximeter system to measure water oxygen-content. Average M. mollis veligers contained 14.1 µg ash-free dry mass (AFDM) and consumed 310 pmol O 2 h -1. Corresponding values for T. mirabilis veligers were 17.6 µg AFDM and 221 pmol O 2 h -1 . The periods of protected development here were shorter than those previously reported for Antarctic gastropods, including T. mirabilis, by a factor of ×4, although previous reports were for species hatching as juveniles. The protected periods here were, however, around 5 time longer than for temperate gastropods. The oxygen-consumption rates for M. mollis and T. mirabilis veligers were around ×10 less than those for comparable temperate gastropod and bivalve veligers.

Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Metabolism and development of pelagic larvae of Antarctic gastropods with mixed reproductive strategies

Peck¹,

Clarke²,

Chapman³

2006

“…Some of these have shown considerable inter-annual variation in reproductive effort, e.g. Liothyrella uva (Meidlinger et al 1998) and Adamussium colbecki (Chiantore et al 2002). The Southern Ocean is characterised by environmental variation on a range of frequencies.…”

Section: Introductionmentioning

confidence: 99%

Long-term interannual cycles of the gametogenic ecology of the Antarctic brittle star Ophionotus victoriae

Grange¹,

Tyler²,

Peck³

et al. 2004

Spermatogenesis, oogenesis and fecundity are described and the gonad index calculated for 10 individuals from each month using histological and image analysis techniques for the Antarctic brittle star Ophionotus victoriae (Bell 1902). Individuals were collected between September 1997 and December 2000 from a shallow water population (15 to 20 m) on the west of the Antarctic Peninsula. Both male and female gonad index varied seasonally, where proportions of large oocytes and mature sperm decreased markedly between November and December of each year, indicating the spawning period. Although the annual timing of reproduction was consistent among years, O. victoriae displayed considerable inter-annual variation in reproductive effort. This variability was notable in the gonad and gut index of both males and females and in female fecundity, which showed no discernible change in some years, but varied more than an order of magnitude in others. We identify 3 main aspects to the reproductive ecology of O. victoriae: (1) spawning was synchronous and annually consistent; (2) long periods were required for gamete development, with oocytes requiring 18 to 24 mo to mature; (3) there was clear inter-annual variability in reproductive effort and nutritional condition, which could be associated with the extent of the preceding organic sedimentation event. Subsidiary effects may also have been felt from the seasonal ice profile and temperature signal. A combination of all or some of these patterns may be an adaptation to the distinct seasonality and low level resource supply characteristic of the Antarctic and the long-term cycles intrinsic in polar environmental variables.KEY WORDS: Inter-annual variation · Reproductive effort · Sedimentation events · Antarctica · Ophionotus victoriaeResale or republication not permitted without written consent of the publisher

“…This will affect the calculation of reproductive effort depending on whether gamete number or mass is used. Long-term studies of reproduction in Antarctic brachiopods (Meidlinger et al 1998) and brittle stars (Grange et al 2004) also revealed dramatic interannual variation in reproductive output. However, the only 2 studies of reproductive output in Antarctic echinoderms (McClintock 1989, Brockington 2001 both produced values that are comparable with the highest figures for temperate species (Brockington 2001).…”

Section: Resultsmentioning

confidence: 99%

“…Although these results suggest that low water temperature does slow gametogenesis, other environmental factors (photoperiod, food availability) affect both timing of the initiation of gametogenesis and subsequent tempo. Environmental predictability was recently demonstrated to have a marked effect on the timing of biological events and the tempo of life histories in Antarctic environments (Peck et al 2006), and many studies have shown that markedly extended periods are required for gametogenesis in other taxa from high latitudes including the starfish Odontaster validus (Pearse 1965), the brachiopod Liothyrella uva (Meidlinger et al 1998), the amphipod Bovallia gigantean (Clarke 1988) and the brittle star Ophionotus victoriae (Grange et al 2004). To date, the only species to show annual gametogenesis is the scallop Adamussium colbecki (Tyler et al 2003).…”

Section: Resultsmentioning

confidence: 99%

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

Brockington¹,

Peck²,

Tyler³

2007

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