Reproductive biology, oogenesis and early development in the brood-caring sea anemoneActinostola spetsbergensis (Anthozoa: Actiniaria)

Brooding sea anemones (Cnidaria: Anthozoa: Actiniaria): paragons of diversity in mode, morphology, and maternity

“…). Larvae are most often pelagic dispersers, but demersal larvae have also been reported (e.g., Riemann‐Zürneck ). Juvenile, as a general biological term, does not have a universal ontogenetic definition but is usually applied to at least some prefertility life stages.…”

“…While offspring of various actiniarian species might spend any amount of time with or within their parent from zygote through adult, this definition carries biological and ecological significance rather than serving as an arbitrary ontological cutoff. In particular, larvae are primarily life stages of dispersal (Chia ; Riemann‐Zürneck ), whereas juveniles (except for some nonbrooded parasitic forms) are benthic and relatively sessile. Therefore, the difference in dispersal capability between pelagic offspring released as eggs or early embryos and those released as larvae is much less than the difference between either of them and those released as juveniles or as adults.…”

“…Adults of Glandulactis spetsbergensis ( Carlgren 1893) brood enigmatic giant larvae, spherical propagules that approach 10 mm in diameter. Riemann‐Zürneck () reported that the developmental stages spanning zygotes through juveniles at the 24‐mesentery stage were found in the distal portion of the adult and were contained individually within “embryonal envelope[s]” (p. 359). At the same time, mature stages, including those with tentacles (24 of which appear simultaneously) are held within the gastrovascular cavity near the base of the adult, apparently having hatched from the envelope.…”

A Functional Biology of Sea Anemones

“…These anemones have yolky eggs >400 11m in diameter, a fact that might be related to their cold-water distributions (see Thorson, 1936). In the arctic species Actinostola spetsbergensis, large eggs and viviparity are associated with greatly reduced fecundity (Table 6.1), which is offset by parental protection of very large offspring (Riemann-Ziirneck, 1976). In the arctic species Actinostola spetsbergensis, large eggs and viviparity are associated with greatly reduced fecundity (Table 6.1), which is offset by parental protection of very large offspring (Riemann-Ziirneck, 1976).…”

Developmental pathways of anthozoans

“…They might also derive nutrition from the parent. Although this may appear energetically unlikely, the parent already having invested in the offspring (as yolk in sexual, and as tissue in asexual progeny), elaborate envelopes surrounding embryos invite speculation about nutritive relationships (e.g., Gohar & Roushdy, 1961, Riemann-Zlrneck, 1976a, 1976bKojis, 1986;Benayahu etal., 1989a). Once able to feed, an embryo may benefit by being in a food-rich environment (either in or on a parent), with the opportunity to share prey too large for it to capture (e.g., Chia & Rostron, 1970;Spaulding, 1972;Dunn, 1975).…”