Changes in the activity budget of the fiddler crab Leptuca uruguayensis throughout the reproductive period in temperate estuaries.

Animal reproductive success implies the performance of several behaviours, such as courting, mate searching, copulation, offspring production and care. These behaviours usually have high energetic and ecological costs. Therefore, to maximise their reproductive success, animals should make choices throughout their lives, such as deciding how much energy to invest in different activities, according to their conditions and needs. In temperate estuaries, the fiddler crab L. uruguayensis has a short reproductive period, with two synchronous spawning events. Considering that reproductive behaviours incur high energetic cost to fiddler crabs, we estimated how this species manages its activity budget throughout the reproductive period, to quantify trade-offs between the time spent on reproductive behaviours versus time spent on other activities. By analysing videos of females and males recorded in the field at different moments of the reproductive period, we observed that pre-copulatory behaviours, such as female wandering and male waving were more intense at the beginning of the reproductive period, suggesting that most matings occurred before the first spawning event but not before the second one. The ecological conditions during the breeding season and the individual strategies adopted by males and females mostly determine when and how much time to spend on courtship behaviours, and behavioural plasticity can be expected whenever the conditions change. The strategy used by L. uruguayensis for energy management, females' ability to store male gametes and environmental temperatures might have been the main factors determining the relative time spent in courtship behaviours during the reproductive period.

Thin-fingered fiddler crabs display a natural preference for UV light cues but show no sensory bias to other hypertrophied claw coloration.

Although color cues play an important role in sociosexual signaling, when communication is exploited as a foraging cue by predators, prey must pay the due cost for sustaining information interchange. In this regard, fiddler crabs draw attention by having flashy enlarged claws that could potentially attract the interest of many predators. Surprisingly, the adaptive function of claw coloration in fiddler crabs is not entirely understood and have barely been studied in American species. Here, we examine the spectral reflectance of thin-fingered (Leptuca leptodactyla) fiddler crabs' hypertrophied claws and evaluate whether female conspecifics prefer UV-light or other color cues. We test whether male claws reflect UV light and whether females use UV light and/or other color cues when making mating decisions. Our results reveal that only the most flamboyant enlarged claws should be detected by female conspecifics, which show a clear preference for male UV signals. Moreover, while the anterior portion of the enlarged claws (pointing towards conspecifics) reflect UV light, claws' dorsal portion and carapaces (which possibly point upwards and might attract airborne predators) do not show an UV peak. We also discuss the possibility of hypertrophied claws working as honest aposematic signals or playing an important role as decoys.

Mortality of the Atlantic ghost crab Ocypode quadrata (Fabricius, 1787) due to vehicle traffic on sandy beaches: A road ecology approach.

Sandy beaches are not roads, but they have been used as such worldwide, threatening endemic fauna such as ghost crabs (Crustacea: Ocypodidae). The objective of the present study was to identify the spatial factors influencing the incidence of ghost crabs (Ocypode quadrata) killed by vehicles. This study included a systematic study of carcasses with clear signals of crushing by cars on beaches with distinct urbanization levels and on dirt roads crossing low-urbanized beach stretches. Predictive variables (e.g., tyre tracks on the sand, proxies of urbanization, distance from coastal lagoons and beach width) were obtained for the kill points and random points. Generalized linear models with binomial distributions showed that the number of tyre tracks nearby (positive correlation) and indicators of urbanization in the environment (negative correlation) were the main variables explaining ghost crab kills on the beach. Similarly, the likelihood of finding crabs killed by vehicles on the dirt road was associated with the areas with the densest ghost crab populations (higher beach width and low-urbanized areas). Therefore, as an important conservation strategy and mitigation action, vehicle traffic must be severely controlled mainly on low-urbanized beaches, both on the sand and dirt roads crossing natural beach vegetation.

Characterization of the complete mitochondrial genome of Uca lacteus and comparison with other Brachyuran crabs.

Brachyuran crabs comprise the most species-rich clade among the crustacean order Decapoda and are divided into several major superfamilies. However, the monophyly of the superfamilies Ocypodoidea and Grapsoidea in their current compositions within the Brachyura remains inconclusive. In this study, the complete mitochondrial genome (mitogenome) of Uca lacteus (Ocypodoidea, Ocypodidae) was sequenced, annotated, and compared with those of other Brachyuran crabs. The circular mitogenome of U. lacteus is 15,661 base pairs long and contains the entire set of 37 genes and an A + T-rich region typically observed in decapod mitogenomes. Secondary structures of several tRNAs are partly missing (trnS1), and the number of bases is significantly decreased (trnD and trnF), as discovered in many other metazoans. We compared the gene order of U. lacteus with other species of Ocypodidae and found that they are consistent. The gene rearrangement of Ocypodidae is also identical to that of the ancestor of Brachyura. However, the order of the trnH gene varies from the rearrangement of ancestral Decapoda. Accordingly, we hypothesized that this rearrangement of trnH underwent a translocation during the evolution from Decapoda to Brachyura. The phylogenetic relationship of the 81 Brachyura species and one outgroup was recovered based on 13 protein-coding genes. This analysis confirmed that U. lacteus belongs to the family Ocypodidae and established a paraphyletic relationship between Ocypodoidea and Grapsoidea.

Evidence of marine debris usage by the ghost crab Ocypode quadrata (Fabricius, 1787).

Sandy beaches are sites of marine debris stranding, but the interaction of beach biota with waste is poorly studied. The objective of this study was to investigate whether the ghost crab Ocypode quadrata selects marine debris by types using a non-destructive method on sandy beaches of Southeastern Brazil. We found marine debris in 7% of 1696 surveyed burrows, and the ghost crabs selectivity was mainly by soft plastic (30%), straw (11%), rope (6%) and foam (4%). Burrows with marine debris showed higher occupation rate (~68%) compared to burrows without debris (~28%), indicating that these materials may increase the capacity of ghost crabs to memorize their burrows placement (homing). The percentage of marine debris was not always related to their amount in the drift line, but ghost crabs used more debris near urbanized areas. Future studies should test whether ghost crabs are using marine debris for feeding, homing or other mechanisms.

Analysis of complete mitochondrial genome of Ocypode cordimanus (Latreille, 1818) (Decapoda, Ocypodidae).

Complete mitochondrial genome of smooth-handed ghost crab Ocypode cordimanus (Latreille, 1818) has been sequenced and phylogenetic relationships evaluated due to mitochondrial protein coding genes. This is the second record of complete mitochondrial genome from the genus. The size of mitochondrial genome for O. cordimanus is 15,604 bp and the nucleotide distribution of the mitochondrial genome is 31.8% A, 21.8% C, 11.9% G and 34.5% T.

Ontogenetic and seasonal shifts in the diet of the pemecou sea catfish Sciades herzbergii (Siluriformes: Ariidae), from a macrotidal mangrove creek in the Curuçá estuary, Northern Brazil

The feeding ecology of pemecou sea catfish (Sciades herzbergii) was studied bimonthly from September 2003 to July 2004 in a macrotidal mangrove creek at Curuçá estuary, Brazil. Feeding activity and relative importance of prey groups were assessed in 528 and 226 specimens (6.2 to 36.0 cm total length), respectively, using stomach contents. A total of 1 820 specimens were caught. The fish left the creek with an average of 2.2 % of their body weight in prey. Feeding activity was lower in the dry season (September and November 2003) than in the rainy season (January to May 2004). The diet was dominated by Ocypodidae and Grapsidae. Feeding strategies of the pemecou sea catfish indicated a slight variation between the diets of adults and juveniles; however; the main factor leading to diversification in the diet were the seasons. Opportunistic feeding behavior was observed in the dry season, shifting to more specialized feeding in the wet season. This temporal diet shift may be explained by the environmental seasonal variations (e.g. transparency of the water, high water level) in the intertidal mangrove creek habitat. Rev. Biol. Trop. 56 (2): 861-873. Epub 2008 June 30.

Estudiamos la ecología trófica del bagre guatero Sciades herzbergii, con periodicidad bimestral, desde septiembre de 2003 a julio de 2004, en un canal de marea del estuario del río Curuçá, norte de Brasil. Del total de 1820 ejemplares capturados, analizamos la actividad alimentaría y la importancia de las diferentes fuentes de alimento por evaluación de los contenidos estomacales de 528 y 226 ejemplares (longitud corporal 6,2 a 36,0 cm), respectivamente. S. herzbergii sale del canal de marea con un valor promedio de 2,2 % de su peso corporal como alimento. El ritmo alimentario fue menor durante el período seco (septiembre a noviembre de 2003) que en el lluvioso (enero a mayo de 2004). Los análisis de los contenidos estomacales de 226 ejemplares indicaron una dieta con predominio de Ocypodidae y Grapsidae. Las estrategias alimentarías de S. herzbergii mostraron pequeñas diferencias entre las dietas de los adultos y de los jóvenes, pero la variación estacional fue el factor que mejor definió la diversificación de la dieta. En el período seco hubo un comportamiento oportunista en la alimentación, cambiando a una dieta mas especializada durante el período lluvioso. Esta variación temporal en la dieta corresponde con la variación estacional en los hábitats del canal de marea.