Reproduction, recruitment, and growth of the Arctic deep‐sea hydroid Bouillonia cornucopia

Abstract

Invertebrates in polar and deep‐sea environments that have complex life histories are exposed to unique environmental conditions that may favor non‐pelagic development and K‐strategist reproduction. Although many polar species follow this strategy, the numerically most abundant species tend to have more r‐strategist life‐history characteristics. We deployed artificial substrata over 3 years in the Arctic deep sea and collected hundreds of specimens of the athecate hydroid Bouillonia cornucopia. While this species has previously been described as rare, we report dense, patchy recruitment on artificial substrata, suggesting that B. cornucopia is highly opportunistic. This species has rapid growth compared to other sessile invertebrates in the study area, high fecundity, and continuous reproduction—all characteristics of an r‐selected life history. The species’ gonophores are simple, lacking an obvious spadix or radial canals. We observed nurse cells in histological sections of female gonophores, but no male gonophores were observed. Gonophores break away from the blastostyles in mature specimens and appear to have fertilization envelopes, suggesting that each gonophore is composed of a single oocyte and that embryological development occurs in the water column. Hydroids are typically the first invertebrates to recruit to substrata in the Arctic but are easily overgrown. The opportunistic life histories of B. cornucopia and other hydroids may be adaptive for maintaining populations in the face of high mortality. Our study demonstrates the utility of artificial substrata for collections of otherwise rare opportunistic species.

From basalt to biosphere: Early non-vent community succession on the erupting Vailulu’u deep seamount

“…Pioneer species in terrestrial ecosystems are typically r-selected species characterized by small size, rapid growth, high fecundity, high dispersive potential, and short life spans (Huston and Smith, 1987). Such r-selected life history characteristics have been documented in another deep-sea aplanulate hydroid species, Bouillonia cornucopia, consistent with the idea that some hydroids may be pioneer species in the deep sea (Meyer-Kaiser et al, 2021). Hydrozoan and bryozoan small-size species capable of colonizing bare surfaces have also been documented in higher frequency in disturbed seamounts relative to undisturbed ones.…”

Trait–environment relationships of hydroids (Cnidaria: Hydrozoa) across large spatial and environmental gradients in the Atlantic Ocean

“…Despite being small and frequently overlooked, hydroids have extensive roles in ecosystems (Di Camillo et al, 2017). They are early substrate colonizers (Fernandez et al, 2014, 2015; Meyer‐Kaiser et al, 2021; Migotto et al, 2001) and important predators of zooplanktonic and benthic populations (Gili & Hughes, 1995; Huang et al, 2020). Being among the first taxa to recolonize the substrate after disturbances, they are also important for the recovery of benthic communities (Al‐Habahbeh et al, 2020).…”