Influence of salinity on the larval development of the fiddler crab Uca vocator (Ocypodidae) as an indicator of ontogenetic migration towards offshore waters

Abstract

Larvae of many marine decapod crustaceans are released in unpredictable habitats with strong salinity Xuctuations during the breeding season. In an experimental laboratory study, we investigated the inXuence of seven diVerent salinities (0, 5, 10, 15, 20, 25 and 30) on the survival and development time of Wddler crab zoea larvae, Uca vocator, from northern Brazilian mangroves. The species reproduces during the rainy season when estuarine salinity strongly Xuctuates and often reaches values below 10 and even 5. Salinity signiWcantly aVected the survival rate and development period from hatching to megalopa, while the number of zoeal stages remained constant. In salinities 0 and 5, no larvae reached the second zoeal stage, but they managed to survive for up to 3 (average of 2.3 days) and 7 days (average of 5.1 days), respectively. From salinity 10 onwards, the larvae developed to the megalopal stage.However, the survival rate was signiWcantly lower (5-15%) and development took more time (average of 13.5 days) in salinity 10 than in the remaining salinities (15-30). In the latter, survival ranged from 80-95% and development took 10-11 days. Given the 100% larval mortality in extremely low salinities and their increased survival in intermediate and higher salinities, we conclude that U. vocator has a larval 'export' strategy with its larvae developing in oVshore waters where salinity conditions are more stable and higher than in mangrove estuaries. Thus, by means of ontogenetic migration, osmotic stress and resulting mortality in estuarine waters can be avoided.

Duração dos estágios do desenvolvimento pós-embrionário de Porcellana sayana leach, 1820 (Anomura: Porcellanidae) em laboratório

“…Porém, nos seus estágios larvais finais a mesma se torna estenohalina, ou seja, não suportam grandes variações do gradiente de salinidade. Desta forma, a mudança de ambiente (estuarino para o laboratorial) pode ser um fator facilitador para o aumento das taxas de sobrevivência quando se pretente manipular este organismo para estudos, pois envolve maior controle dos parâmetros e relações que condicionam maior sobrevivência dos estágios zoeais, e que consequentemente, aumentam a taxa de sobrevivência do estágio megalopal (Rodrigues, 1982;Diele & Simith, 2011). Para os crustáceos, a sobrevivência dos estágios larvais iniciais estão diretamente relacionados com altos valores de salinidade, pois esses organismos aprensentam ciclo de vida associado a regiões estuarinas (Rieger & D'Incao, 1991).…”

Larval dispersal of Brachyura in the largest estuarine / marine system in the world

“…This family export strategy to the adjacent continental shelf is already known [4,[138][139][140]. These larvae are unable to survive in the low salinity of the estuarine environment for a long time, as experimentally verified for Austruca annulipes (H. Milne Edwards, 1837) [141], Leptuca leptodactyla (Rathbun, in Rankin, 1898) [142], Minuca minax (Le Conte, 1855) [143], M. rapax [144], Minuca vocator (Herbst, 1804) [145] and U. cordatus [146]. Except for L. cumulanta, which retains all larval stages in the estuary [29], so that ZI and ZII larvae may have been accidentally dragged by currents to the continental shelf, thus justifying the single occurrence 23 km from the coast.…”

Response of planktonic copepods of the White Sea to the water salinity changes in acute and chronic experiments

“…Up to date, the studies are focused either on copepod embryos (Charmantier and Charmantier-Daures, 2001) or adult stages (Calliari et al, 2019;Dutz and Christensen, 2018) with the only exception for Eurytemora affinis from the Baltic Sea (Karlsson et al, 2018). Different response to the osmotic stress in ontogeny is reported for isopods (Charmantier and Charmantier-Daures, 1994), shrimps (Torres et al, 2011;Vázquez et al, 2016), and crabs (Charmantier et al, 1998;de Jesus de Brito Simith et al, 2012). It is obvious that this problem needs a complex approach in regard to Copepoda as applied so far for other crustaceans in order to assess possible adaptations through the species lifespan.…”