Comparative biometry and isotopy of three dominant pennatulacean corals in the Northwest Atlantic

Abstract

Baillon, S., English, M., Hamel, J.-F. and Mercier, A. 2015. Comparative biometry and isotopy of three dominant pennatulacean corals in the Northwest Atlantic. -Acta Zoologica (Stockholm) 00: 000-000.Spatial and temporal shifts in biometric features were examined in three common deep-water pennatulacean corals (sea pens) from the Northwest Atlantic: Anthoptilum grandiflorum, Halipteris finmarchica and Pennatula aculeata. These three species show different morphological characters and adaptations to their environment. Analyses of colony length, ratio of peduncle to colony length, weight/length ratio, polyp size and density as well as sclerite shape, location and abundance indicate that their phenotype is modulated by environmental factors (e.g. food availability, currents and sediment type) and antipredator strategies. Moreover, the three species had different carbon and nitrogen stable isotope signatures that could be explain primarily by their different polyp diameters and colony shapes, suggesting that they rely on slightly different food sources (varying proportions of phytodetritus and zooplankton). Finally, sclerites were found only in H. finmarchica and P. aculeata and are not known to occur in A. grandiflorum, except for minute oval bodies inside the peduncle. The Mg/Ca ratio of sclerites differed between the two species and, for P. aculeata, among types of sclerites, evoking different biomineralization pathways related to their functional roles (structural support or defence). Overall, this study provides new information on the ecology of poorly known species, which are ubiquitous and suspected to play an important ecological role in deep-water ecosystems.

Morphometry and growth of sea pen species from dense habitats in the Gulf of St. Lawrence, eastern Canada

“…We found that this ratio decreased significantly for both species with increasing colony length, being more pronounced in A. grandiflorum. This contrasts with Baillon et al (2016), who did not observe variation of the proportion of peduncle length with colony length for P. aculeata. Our results support the conclusions from Baillon et al (2016) that long sea pens do not need to be associated with long peduncles once they are wide enough to support the colony weight.…”

“…The peduncle length:colony length ratio was greater in P. aculeata than in A. grandiflorum, as observed by Baillon et al (2016). We found that this ratio decreased significantly for both species with increasing colony length, being more pronounced in A. grandiflorum.…”

“…These results reinforce the conclusion that trawls are not good sampling tools for estimating true population size distributions of sea pens due to catchability issues (Kenchington et al 2011). Nevertheless, the average colony lengths found at the mouth of the Laurentian Channel (LC) were similar to those reported in Baillon et al (2016) for the same region and species despite differences in trawl gear (i.e. different mesh lining in the codend); however, this similarity could be spurious.…”

Size metrics, longevity, and growth rates in Umbellula encrinus (Cnidaria: Pennatulacea) from the eastern Canadian Arctic.

“…Although larger colonies do have larger peduncles, percentage of peduncle tended to decrease with colony height. This negative relationship was already reported for other sea pens (Baillon et al 2016;Murillo et al 2018). From a growth perspective, it suggests that as a colony becomes larger over time, peduncle growth rates seem to be reduced.…”

Physicochemical Characterization of Biomineralized Structures of Sea Pen Pteroeides spinosum (Ellis & Solander, 1786)(Octocorallia: Pennatulidae)

“…In this study, the Mg/Ca ratio of sclerites in polyp leaves of coral P. spinosum was determined as 0.05. Mg/Ca ratios have been reported as average 0.13 and 0.17 for Pennatula aculeata and Halipteris nmarchica sclerites, respectively (Baillon et al 2016). Electron microprobe analyses of the sea pen Halipteris willemoesi showed that the inorganic fragment of the inner axis consisted of high magnesium calcite (Wilson et al 2002).…”