Abstract
The dynamics and microdistribution of faunal assemblages at hydrothermal vents often reflect the fine-scale spatial and temporal heterogeneity of the vent environment. This study examined the reproductive development and population structure of the caridean shrimp Rimicaris hybisae at the Beebe and Von Damm Vent Fields (Mid-Cayman Spreading Centre, Caribbean) using spatially discrete samples collected in January 2012. Rimicaris hybisae is gonochoric and exhibits iteroparous reproduction. Oocyte size-frequency distributions (21-823 µm feret diameters) varied significantly among samples. Embryo development was asynchronous among females, which may result in asynchronous larval release for the populations. Specimens of R. hybisae from the Von Damm Vent Field (2294 m) were significantly larger than specimens from the Beebe Vent Field. Brooding females at Von Damm exhibited greater size-specific fecundity, possibly as a consequence of a non-linear relationship between fecundity and body size that was consistent across both vent fields. Samples collected from several locations at the Beebe Vent Field (4944–4972 m) revealed spatial variability in the sex ratios, population structure, size, and development of oocytes and embryos of this mobile species. Samples from the Von Damm Vent Field and sample J2-613-24 from Beebe Woods exhibited the highest frequencies of ovigerous females and significantly female-biased sex ratios. Environmental variables within shrimp aggregations may influence the distribution of ovigerous females, resulting in a spatially heterogeneous pattern of reproductive development in R. hybisae, as found in other vent taxa.
Highlights
IntroductionDeep-sea chemosynthetic environments supporting chemosynthesis-based faunal assemblages are distributed widely but patchily throughout the global ocean
Deep-sea chemosynthetic environments supporting chemosynthesis-based faunal assemblages are distributed widely but patchily throughout the global ocean.Reproduction is an essential process for the establishment and maintenance of isolated populations of specialist vent, seep and whale-fall fauna
To assess spatial variation in population structure and reproductive features, samples of Rimicaris hybisae were collected from two vent fields at the Mid-Cayman Spreading Centre, Caribbean, during the 18th voyage (16th leg) of the RV ‘Atlantis’
Summary
Deep-sea chemosynthetic environments supporting chemosynthesis-based faunal assemblages are distributed widely but patchily throughout the global ocean. Reproduction is an essential process for the establishment and maintenance of isolated populations of specialist vent, seep and whale-fall fauna. More than 400 new faunal species have been described from deep-sea hydrothermal vents since the 1970s [5], and aspects of life-history biology have been elucidated in more than 90 species from vents, seeps, and whale falls (Copley, Nye et al, unpublished data). The Beebe Vent Field (,4960 m) is situated on the axis of the MCSC and it consists of a sulfide mound (,80 m diameter, 50 m height) surmounted by several active black-smoker chimney complexes and areas of diffuse flow [7]. The Von Damm Vent Field (,2300 m) is a conical mound (,150 m diameter, 70 m height) venting clear, buoyant fluids, located off-axis (approximately 13 km away from the Beebe Vent Field) on the upper slopes of the Mount Dent oceanic core complex [7]
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