Larval export strategy as an indication of ontogenetic migrations towards open sea of the fiddler crab Leptuca leptodactyla (Rathbun, in Rankin, 1898) (Crustacea, Ocypodidae) from Guaratuba Bay, southern Brazil

Abstract

The influence of salinity on the survival of the larvae of Leptuca leptodactyla (Rathbun, in Rankin, 1898) from zoea (Z) to megalopa (M) stage was analyzed in order to deduce the larval dispersal strategy of the species. Larvae were obtained from 10 ovigerous females captured in the mangrove of Guaratuba Bay, southern Brazil. Five salinity treatments were conducted from 0 to 35 PSU (S0, S5, S15, S25 and S35). The larvae were individually raised in plastic cell culture plates, totaling 120 experimental units per treatment, kept under natural photoperiod (12:12 h) and constant water temperature (26.3 ± 0.82°C), and fed with microalgae, rotifers and Artemia nauplii. While all larvae died at S0, S5 and S15, complete larval development until the M stage was only observed at S25 and S35. The highest survival rate was recorded at S35 (18 M from 120 newly-hatched Z, survivorship 15%) and the lowest at S25 (2 M, 1.66%). No significant difference in the total duration was observed between S25 (28.5 ± 0.70 days) and S35 (23.61 ± 3.05 days). The life cycle of L. leptodactyla is based on a larval exportation strategy as they need to perform ontogenetic migrations to the coastal area.

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.…”

Comparing the effect of larval dispersal strategies on morphological versus genetic differentiation in two neotropical fiddler crabs

“…Samples from five populations of Leptuca leptodactyla were obtained from São José do Ribamar, Maranhão (MA); Natal, Rio Grande do Norte (RN); Maceió, Alagoas (AL); Guaratuba, Paraná (PR) and Itapoá, Santa Catarina (SC) (Table 1 and Figure 1). Crabs were manually collected, identified based on Martins et al (2020) and preserved in 95% ethanol.…”

“…Salinity is recognized as one of the most important factors interfering with larval dispersal, and in consequence, a large variation in the tolerance levels to different salinities can be observed in planktonic larvae of coastal decapods (e.g., Anger, 2001Anger, , 2003. L. leptodactyla has a larval export strategy and thus exhibits higher larval survival probabilities in high salinities during zoeal development (optimal salinity = 35 PSU; Martins et al, 2020). On the other hand, M. mordax larvae follow a retention strategy and exhibit higher survival rates in intermediate salinities (optimal salinity = 20 PSU; Martins, 2014).…”

“…The reproduction occurs from September to March (Masunari, 2006; Nogueira, 2017). It also has a larval phase with five to six zoeal stages and one megalopa and a mean development time of 24 days, but with higher survival rates at salinities around 35 ppt (Martins et al., 2020). The different salinity optima for larval development suggest a retention strategy of the first species and an export strategy of the second one.…”

“…We expect a retention strategy in species with greater affinity to low salinity due to larval higher survival probability in estuarine areas and lower in marine coastal areas, which reduces the survival of larvae outside estuarine waters resulting in higher chances of larval retention inside estuarine systems. Furthermore, while adults of M. mordax settle in the innermost part of the estuaries, with salinities close to freshwater (Crane, 1975; Martins, 2014), adults of L. leptodactyla occupy more exposed polyhaline areas of the same embayments, facilitating the export of larvae to the open sea (Martins et al., 2020). The contrasting microhabitat use and larval dispersal strategies of these semiterrestrial crab species (Martins, 2014; Martins et al., 2020) make them an interesting case study to evaluate the effects of dispersal strategies and of natural barriers on larval distribution potential, the consequences in genetic structuring and phenotypic variation, and its influence on demographic history.…”