In situ rates of DNA damage and abnormal development in Antarctic and non-Antarctic sea urchin embryos

Laboratory experiments suggest that calcifying developmental stages of marine invertebrates may be the most ocean acidification (OA)-sensitive life-history stage and represent a life-history bottleneck. To better extrapolate laboratory findings to future OA conditions, developmental responses in sea urchin embryos/larvae were compared under ecologically relevant in situ exposures on vent-elevated p CO 2 and ambient p CO 2 coral reefs in Papua New Guinea. Echinometra embryos/larvae were reared in meshed chambers moored in arrays on either venting reefs or adjacent non-vent reefs. After 24 and 48 h, larval development and morphology were quantified. Compared with controls (mean pH (T) = 7.89–7.92), larvae developing in elevated p CO 2 vent conditions (pH (T) = 7.50–7.72) displayed a significant reduction in size and increased abnormality, with a significant correlation of seawater pH with both larval size and larval asymmetry across all experiments. Reciprocal transplants (embryos from vent adults transplanted to control conditions, and vice versa ) were also undertaken to identify if adult acclimatization can translate resilience to offspring (i.e. transgenerational processes). Embryos originating from vent adults were, however, no more tolerant to reduced pH. Sea temperature and chlorophyll- a concentrations (i.e. larval nutrition) did not contribute to difference in larval size, but abnormality was correlated with chlorophyll levels. This study is the first to examine the response of marine larvae to OA scenarios in the natural environment where, importantly, we found that stunted and abnormal development observed in situ are consistent with laboratory observations reported in sea urchins, in both the direction and magnitude of the response.

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Micromeres are required for normal vegetal plate specification in sea urchin embryos

Development ◽

10.1242/dev.121.10.3215 ◽

1995 ◽

Vol 121 (10) ◽

pp. 3215-3222 ◽

Cited By ~ 13

Author(s):

A. Ransick ◽

E.H. Davidson

Keyword(s):

In Situ Hybridization ◽

Sea Urchin ◽

Direct Evidence ◽

Cleavage Stage ◽

Sea Urchin Embryos ◽

Normal Manner ◽

Whole Mount

Vegetal plate specification was assessed in S. purpuratus embryos after micromere deletions at the 4th, 5th and 6th cleavages, by assaying expression of the early vegetal plate marker Endo 16, using whole-mount in situ hybridization. After 4th cleavage micromere deletions, the embryos typically displayed weak Endo16 expression in relatively few cells of the lineages that normally constitute the vegetal plate, while after 5th and 6th cleavage micromere deletions the embryos exhibited strong Endo16 expression in larger fractions of cells belonging to those lineages. When all four micromeres were deleted, the embryos were severely delayed in initiating gastrulation and sometimes failed to complete gastrulation. However, if only one micromere was allowed to remain in situ throughout development, the embryos exhibited strong Endo16 expression and gastrulation occurred normally, on schedule with controls. Additional measurements showed that these microsurgical manipulations do not alter cleavage rates or generally disrupt embryo organization. These results constitute direct evidence that the micromeres provide signals required by the macromere lineages for initiation of vegetal plate specification. The specification of the vegetal plate is completed in a normal manner only if micromere signaling is allowed to continue at least to the 6th cleavage stage.

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