Ontogenetic development of the crinoidPoliometra prolixain the Arctic deep sea

Abstract

Poliometra prolixa is a common species of comatulid crinoid in the Arctic deep sea. In this study, we characterize the ontogenetic development through the cystidean and pentacrinoid stages, using specimens from the LTER (Long‐Term Ecological Research) observatory HAUSGARTEN in the Fram Strait, Arctic Ocean. While embryos and early larval stages (e.g., the doliolaria) were not observed, both post‐settlement stages and adults of P. prolixa were observed on the same moored experimental platform at 2,500 m water depth, suggesting that larvae of P. prolixa do not disperse far from their mothers. This indicates that doliolariae may have an abbreviated pelagic duration period or may be brooded in this species. The cystidean has a short, translucent stalk with a star‐shaped attachment disc and a diamond‐shaped translucent head. Metamorphosis from the cystidean to the pentacrinoid is characterized by the formation of brachial ossicles from oral ossicles and by fusion of the basal and radial ossicles to form the calyx. The pentacrinoid stalk is opaque and first develops synarthrial joints at the distal end. Late pentacrinoids have a xenomorphic stalk, bifurcated arms with pinnules, and cirri. We discuss the reproductive and ecological niche of P. prolixa and also consider the question of whether cystidean and pentacrinoid stages undergo metamorphosis.

New strategies for the new environment. Stowaway feather star on crab Hyas sp. - Spitsbergen (Arctic)

“…Crinoids and other suspension feeder invertebrates often colonize elevations on the seabed (Meyer 1980;Genin et al 1986;Messing et al 1990;Messing 2004;Meyer et al 2014). At such heights, the ow of current is faster and more laminar, thanks to which these organisms get a feeding advantage (Vogel et al 1996;Meyer-Kaiser et al 2021). We observed this behavior with the rst crinoid attached to the edge of the platform and the next two attached to the carapace of the crab (Fig.…”

The campylogomphosis: A new kind of joint in echinoderms

“…Generations of echinoderm researchers have referred to ossicle “fusion” in the formation of fixed joints of various groups of echinoderm (Clark & Downey, 1992; Fell, 1963a, 1963b; Fewkes, 1887; Hendler, 1978, 2018; Hotchkiss & Glass, 2012; Hyman, 1955; Irimura & Fujita, 2003; Meyer‐Kaiser et al, 2021; Murakami, 1963; Smith et al, 1995; Stöhr & Martynov, 2016). In much of the literature, it is unclear what the authors meant by “fusion.” It is likely that fusion has been inferred from failure of ossicles to separate upon treatment with bleach (e.g., Mortensen, 1933).…”

Corrigendum for Meyer‐Kaiser et al. 2019

“…Since the publication of this article, it has been revealed that the crinoid specimens do not belong to Bathycrinus carpenterii but rather the comatulid species Poliometra prolixa (Meyer‐Kaiser et al 2021). In addition, the “small round white sponge” in our 2019 paper is an hexactinellid sponge, possibly Caulophacus arcticus , whereas sponges called “small round white sponge” by other authors working in the HAUSGARTEN belong to the demosponge species Tentorium semisuberites (e.g., Bergmann et al 2011, Taylor et al 2017).…”