Reproductive biology of the bathyal asteroid Ctenodiscus crispatus in the northeastern Pacific

Abstract

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 size-frequency 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.