Deep-sea corals are of conservation concern in the North Atlantic due to prolonged disturbances associated with the exploitation of natural resources and a changing environment. As a result, two research cruises in the Gulf of Maine region during 2014 and 2017 collected samples of two locally dominant coral species, Primnoa resedaeformis and Paramuricea placomus, at six locations to investigate reproductive ecology. Remotely operated vehicles (ROVs) were used to collect specimens that were examined via paraffin histology, and coincident video surveys were used to determine size class distributions. Both species were identified as gonochoristic, and sampled locations exhibited dissimilarities in spermatocyst development and oocyte size except for those in close geographic proximity. Fecundities exhibited substantial ranges across sample locations and average oocyte sizes (±SD) were 140 ± 117 µm for P. resedaeformis and 64 ± 46 µm for P. placomus. In addition, colony size distributions were also significantly different across sampling locations. Notably, the Outer Schoodic Ridge sample location, with larger colony and oocyte sizes, was identified as a potential key source population of reproductive material in the Gulf of Maine. These data were used to calculate differences in reproductive potential based on relationships between colony morphology and reproductive output using height as a predictive proxy. Furthermore, calculated age at first reproduction, 7.6-19.8 years for P. resedaeformis and 20.7-37 years for P. placomus, which may be dependent on sex of the colony, provides a metric for estimating the amount of time these coral habitats will take to recover. This investigation, in response to historical population impacts and environmental change, links reproductive and morphometric relationships to inform population scale reproductive models, while also establishing an understanding of regional scale gametogenic variability within the Gulf of Maine region.
The mud star Ctenodiscus crispatus has a broad distribution from Arctic waters into the northern Atlantic and Pacific oceans. Populations in the Atlantic are well studied and show oocyte sizes indicative of continuous gametogenesis with aseasonal spawning. In contrast, knowledge on the reproductive biology of Pacific populations is lacking. Thus, this study aims to examine the reproduction of C. crispatus in the northeastern Pacific. We sampled a population from the Pacific Ocean off Oregon and confirmed the species identity through 16S and cytochrome oxidase subunit I (COI) genetic barcoding. The majority of adults were 22-27 mm in size. Oocytes were obtained from dissected gonads soaked in a 1-methyladenine solution and fertilized with spawned sperm. Other individuals were preserved whole in 10% buffered formalin, and oocytes were measured from preserved gonads. Strip-spawned oocytes had a mean diameter of $485 μm, consistent with Atlantic populations. Sperm had a mean head diameter and flagellum length of 3.1 and 65.9 μm, respectively. The time between first and second cell divisions was $2 h, but larval cultures failed, and very few embryos developed to blastulae. Both strip-spawned and preserved oocytes had a bimodal sizefrequency distribution indicative of semicontinuous gametogenesis. Comparison among individuals showed evidence of asynchrony among the population. This asynchrony and bimodal oocyte distribution may be driven by regular pulses of food, as has been postulated for other populations of this species. The reproductive plasticity seen among populations of this species in different regions could explain how it successfully inhabits such a wide geographic range.
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