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 pe… Show more
“…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.…”
For the first time, this study monitored six sites in a wide transect with approximately 240 km radius on the Amazon Continental Shelf (ACS) every three months. The objective was to analyze the larval composition of Brachyura, its abundance in shallow/subsurface and oblique hauls, the extent of larval dispersion related to the estuary/plume, and to predict the probability of occurrence and abundance for the temperature, salinity, and chlorophyll- a profiles of the water column. A total of 17,759 identified larvae are distributed in 8 families and 25 taxa. The water salinity was the best predictor of larval distribution. The statistical models used indicated that Panopeidae and Portunidae larvae are more frequent and more likely to occur in shallow water layers, while Calappidae occur in deeper layers, and Grapsidae, Ocypodidae, Sesarmidae, Pinnotheridae and Leucosiidae occur similarly in both strata. The larval dispersion extent varies among families and throughout the year while the groups are distributed in different salinities along the platform. The probability of occurrence of Portunidae is higher in ocean water (> = 33.5); Grapsidae, Panopeidae, and Pinnotheridae is higher in intermediate and ocean salinity waters (25.5 to 33.5); Ocypodidae, Sesarmidae and Calappidae is higher in estuarine and intermediate salinity waters (5 to 25.5), whereas Leucosiidae, euryhaline, occur in all salinities (5 to 33.5). Furthermore, the Amazon River seasonal flow and plume movement throughout the year not only regulate the larval distribution and dispersion of estuarine species but are fundamental for the ACS species, providing the necessary nutrient input for larval development in the region plankton.
“…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.…”
For the first time, this study monitored six sites in a wide transect with approximately 240 km radius on the Amazon Continental Shelf (ACS) every three months. The objective was to analyze the larval composition of Brachyura, its abundance in shallow/subsurface and oblique hauls, the extent of larval dispersion related to the estuary/plume, and to predict the probability of occurrence and abundance for the temperature, salinity, and chlorophyll- a profiles of the water column. A total of 17,759 identified larvae are distributed in 8 families and 25 taxa. The water salinity was the best predictor of larval distribution. The statistical models used indicated that Panopeidae and Portunidae larvae are more frequent and more likely to occur in shallow water layers, while Calappidae occur in deeper layers, and Grapsidae, Ocypodidae, Sesarmidae, Pinnotheridae and Leucosiidae occur similarly in both strata. The larval dispersion extent varies among families and throughout the year while the groups are distributed in different salinities along the platform. The probability of occurrence of Portunidae is higher in ocean water (> = 33.5); Grapsidae, Panopeidae, and Pinnotheridae is higher in intermediate and ocean salinity waters (25.5 to 33.5); Ocypodidae, Sesarmidae and Calappidae is higher in estuarine and intermediate salinity waters (5 to 25.5), whereas Leucosiidae, euryhaline, occur in all salinities (5 to 33.5). Furthermore, the Amazon River seasonal flow and plume movement throughout the year not only regulate the larval distribution and dispersion of estuarine species but are fundamental for the ACS species, providing the necessary nutrient input for larval development in the region plankton.
“…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.…”
Section: Sampling Of Minuca Mordax and Leptuca Leptodactylamentioning
confidence: 99%
“…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).…”
Section: Genetic Analysesmentioning
confidence: 99%
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
The dispersal mode of estuarine invertebrates has a strong effect on genetic variability and phenotypic expression, potentially maintaining gene flow among widely separated populations or limiting connectivity among close ones. Understanding the dispersal strategies effects can support adequate strategies for environment management and understand the evolutionary history of the studied species. A comparative study on the effect of larval dispersal strategies (export vs retention) along the overall geographic distribution ranges of adult populations of two co‐distributed fiddler crab species was performed. Geometric morphometric techniques were used to evaluate morphological differentiation in the shape of the carapace and major cheliped propodus in 10 populations of Minuca mordax and five populations of Leptuca leptodactyla. Potential genetic differentiation was assessed using DNA sequence data from up to 170 fiddler crab specimens, corresponding to the mitochondrial gene cytochrome c oxidase subunit 1 (COX1). Patterns of genetic and morphological characteristics diverged among populations of both species. In terms of morphology, populations of both species showed intraspecific variation in the shape of the carapace and, to a lesser extent, in the major cheliped propodus. This observed intraspecific variation followed a clear geographic pattern of morphometric differentiation, in which the geographic origin is associated with a phenotypic response to the environmental diversity along the extended Brazilian coast. In contrast, there are shared haplotypes in populations separated by more than 4000 km, but with significant ΦST values among most populations of L. leptodactyla and M. mordax, suggesting a moderate to high level of gene flow. Therefore, it can be concluded that the split of the Central South Equatorial Current has not acted as an efficient long‐term barrier to the dispersal of larvae in both species. In M. mordax, a slight limitation of genetic exchange can be observed between the southernmost populations and the remaining ones. This first evidence of genetic structuring within this widely distributed species is consistent with its documented strategy to retain larvae in the estuarine environments. However, occasional transport of larvae to more open coastal waters seems to maintain stepwise gene flow between neighboring populations. Overall, our results still provide evidence of more pronounced genetic homogeneity in a species with a larval export strategy (L. leptodactyla) compared to a species with a larval retention strategy (M. mordax). This suggests that larval dispersal strategies, coupled with the microhabitat in which the respective species occur, have a noticeable effect on the degree of gene flow. Most likely, these biological aspects are further influenced by the estuarine and coastline geomorphology.
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