Reproductive biology of the isopod Excirolana braziliensis at the southern edge of its geographical range
In: Helgoland Marine Research. Springer: Berlin; Heidelberg. ISSN 1438-387X; e-ISSN 1438-3888, more
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| Keywords |
Biological development > Embryonic development
Body size
Developmental stages
Periodicity > Seasonality
Population characteristics > Biomass
Reproduction
Reproductive cycle
Sandy beaches
Topographic features > Landforms > Coastal landforms > Beaches
Excirolana braziliensis Richardson, 1912 [WoRMS]
ASW, Uruguay [Marine Regions]
Marine/Coastal |
| Author keywords |
sandy beaches; isopods; reproduction; embryonic development |
| Abstract |
A full analysis of the reproductive biology of the isopod Excirolana braziliensis Richardson 1912 was conducted in a sandy beach of Uruguay, located at the southernmost edge of its distributional range in the Atlantic Ocean. Reproductive and recruitment periods of E. braziliensis were concentrated in austral summer. Females with oostegites appeared in November, whereas total biomass, individual sizes and fecundity of ovigerous females peaked between December and January. These concurrent traits were responsible for the significant peak of juveniles in January. The size at maturity was 9.88 mm. Four embryonic developmental stages were described and identified: mean length linearly increased from stages I to III, whereas dry weight exponentially decreased from stages I to IV. The high reproductive output (0.41-0.58), reported for the first time in this isopod, exceeds the rates documented for other isopods. Reproduction of E. braziliensis at the southern edge of its range is semelparous: females produce one brood during the reproductive season, exhaust their energy reserves during incubation, and probably die at the end of the reproductive season. A macroscale comparison suggests that E. braziliensis at the southern edge of its range counteracts its narrow reproductive period by a short incubation period with larger individual mature female and embryo sizes, higher fecundity and a higher percentage of ovigerous females than in subtropical and tropical populations. These extreme reproductive indicators could be attributed to the internal retention of embryos that assures offspring survival, coupled with a high adaptation capability to environmental variations across its range. |
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