Uca Rapax Research Articles

Negative outcomes of novel trophic interactions along mangrove range edges.

Tropicalization is a phenomenon that is changing the structure of ecosystems around the world. Mangrove encroachment is a particular form of tropicalization that may have cascading consequences for resident fauna in subtropical coastal wetlands. There is a knowledge gap regarding the extent of interactions between basal consumers and mangroves along mangrove range edges and the consequences of these novel interactions for consumers. This study focuses on the key coastal wetland consumers, Littoraria irrorata (marsh periwinkle) and Uca rapax (mudflat fiddler crabs), and their interactions with encroaching Avicennia germinans (black mangrove) in the Gulf of Mexico, USA. In food preference assays, Littoraria avoided consuming Avicennia and selectively ingested leaf tissue from a common marsh grass, Spartina alterniflora (smooth cordgrass), a preference that was also previously documented in Uca. The quality of Avicennia as a food source was determined by measuring the energy storage of consumers that had interacted with either Avicennia or marsh plants in the lab and the field. Littoraria and Uca both stored ~10% less energy when interacting with Avicennia, despite their different feeding behaviors and physiologies. The negative consequences of mangrove encroachment for these species at the individual level suggest that there may be negative population-level effects as encroachment continues. Many studies have documented shifts in floral and faunal communities following mangrove replacement of salt marsh vegetation, but this study is the first to identify physiological responses that may be contributing to these shifts.

Bioaccumulation and biomagnification of potential toxic elements (PTEs): An Avicennia germinans–Uca rapax trophic transfer story from Jobos Bay, Puerto Rico

In southern Puerto Rico along the coastline bordering the Jobos Bay National Estuarine Research Reserve, environmental encroachment has exposed mangrove forest to different sources of pollution. Potentially toxic element concentrations from the F1Tess (exchangeable), F4Tess (oxidizable), mangrove leaf litter (MLL), and fiddler crab whole body soft tissue were analyzed to assess the fate and transport of pollutants from the environment and its transition into flora-fauna via trophic transfer. Geo-accumulation factor values suggest the bay has experienced limited to no pollution when combining the concentrations of potentially toxic elements extracted from the F1Tess and F4Tess sediment fractions. These geochemical sedimentary compartments are considered “bioavailable” to flora-fauna as evidenced by the bioaccumulated Cd-Ba-V-Cu-Zn-As-Se in the leaf litter of the black mangrove Avicennia germinans and in the fiddler crab Uca rapax. The biota-sediment accumulation factor (F1Tess + F4Tess) demonstrated that Uca rapax behave like a de-concentrator for most pollutants and as a macro-concentrator for Cu-As, while the bioconcentration factors identified only Cu-As-Se as being actively bioaccumulated in the fiddler crabs. Of all the potentially toxic elements studied, As is the only one to be biomagnified via sediment-Avicennia germinans leaf litter-Uca rapax food chain. An unexpected find of this study was that the excavated sediment “pellets” by Uca rapax contained up to 4x the concentrations of Cd-Ba-V-Cr-Co-Ni-Cu-Zn-As-Se when compared to the F1Tess sediment fraction from the surface, thus suggesting a variable redox boundary within the fiddler crab’s burrow.

Landscape Ecology of Rhipicephalus (Boophilus) microplus (Ixodida: Ixodidae) Outbreaks in the South Texas Coastal Plain Wildlife Corridor Including Man-Made Barriers.

Landscape features and the ecology of suitable hosts influence the phenology of invasive tick species. The southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), vectors causal agents of babesiosis in cattle and it infests exotic, feral nilgai, Bosephalus tragocamelus Pallas, and indigenous white-tailed deer, Odocoilus virginianus (Zimmerman), on the South Texas coastal plain wildlife corridor. The corridor extends from the Mexico border to cattle ranches extending north from inside Willacy Co. Outbreaks of R. microplus infesting cattle and nondomesticated ungulate hosts since 2014 in the wildlife corridor have focused attention on host infestation management and, by extension, dispersal. However, there is a knowledge gap on the ecology of R. microplus outbreaks in the South Texas coastal plain wildlife corridor. Ixodid distribution on the wildlife corridor is strongly influenced by habitat salinity. Saline habitats, which constitute ≈25% of the wildlife corridor, harbor few ixodids because of occasional salt toxicity from hypersaline wind tides and infrequent storm surges, and from efficient egg predation by mud flat fiddler crabs, Uca rapax (Smith). Rhipicephalus microplus infestations on nilgai were more prevalent in part of the corridor with mixed low salinity and saline areas than in an area that is more extensively saline. The different levels of R. microplus infestation suggest that man-made barriers have created isolated areas where the ecology of R. microplus outbreaks involve infested nilgai. The possible utility of man-made barriers for R. microplus eradication in the lower part of the South Texas coastal plain wildlife corridor is discussed.

White spot syndrome virus in decapods from Mississippi Sound, USA, and susceptibility of Palaemonetes pugio and Uca panacea to a Chinese isolate.

The presence and quantity of white spot syndrome virus (WSSV) was surveyed using TaqMan real-time PCR to assess the extent of the virus in Mississippi Sound, USA. A total of 3577 wild decapods comprising 11 species was collected between November 2012 and August 2015: WSSV was present in 10 of the 11 species. Prevalence ranged from 5.1% in Uca rapax to 38.8% in U. spinicarpa. Viral load ranged from 1.8 to 7.3 log10 copies of WSSV µg-1 total DNA. Two Gulf species, Palaemonetes pugio and U. panacea, were injected with a series of doses of a virulent WSSV isolate from China to determine relative susceptibility and virulence because continuing translocation of highly pathogenic isolates of WSSV poses risk to native species. Survival was 0-65% for P. pugio and 5-60% for U. panacea. Median survival time was lower for P. pugio than U. panacea at all doses. Mean (±SD) lethal load was 9.0 ± 8.9 log copies of WSSV µg-1 total DNA in P. pugio and 8.2 ± 8.3 in U. panacea. Mean viral load in survivors was higher in U. panacea than in P. pugio (5.8 ± 6.1 vs. 3.2 ± 3.0 log copies of WSSV µg-1 total DNA); mean viral load was lower in wild individuals of those species (2.9 ± 3.2 for P. pugio and 4.9 ± 5.0 for U. panacea). U. panacea is potentially more tolerant of WSSV than P. pugio and may serve as an important reservoir host in the community.

Behavioral patterns of two fiddler crab species Uca rapax and Uca tangeri in a seminatural mangrove system.

Zoos increasingly transform their exhibitions from traditional one‐species enclosures to more natural exhibits, that is, environments that capture part of an ecosystem including a selection of animals and plants that occur there. Thus, enhancing the experience of its human visitors while also allowing its residents to possibly show more natural behavior. In 2017 Royal Burger's Zoo (Arnhem, The Netherlands) created and opened a mangrove‐like environment containing fiddler crabs. Fiddler crabs display a broad range of behaviors, and this research examines which wild‐type behavior and behavioral patterns can be observed on a seminatural mudflat. The behavior shown by Uca rapax and Uca tangeri on the mudflat was counted each hour between 07:00 and 17:00. An asymmetric tidal regime was present in the enclosure including two high water periods. Various known fiddler crab behaviors, including waving and combat, were observed but no copulation. A clear pattern in exposed crabs on the mudflat was found, with low numbers visible in the early morning and the highest numbers present in the early afternoon, while number of visitors did not have a significant effect on this pattern. Interestingly, the highest abundances were not observed around the ebbing tide (07:00–09:00), as observed in the wild, but somewhat later, possibly due to the asymmetric tidal scheme or the interaction of tidal and daily rhythms. This study shows that in captivity, fiddler crabs indeed show a range of natural behaviors which is linked to the tidal and possibly daily rhythm as well.

Relationships of Salinity, Relative Humidity, Mud Flat Fiddler Crabs, Ants, and Sea Ox-Eye Daisy With Ixodid Distribution and Egg Survival on the South Texas Coastal Plains.

The South Texas coastal plains are mostly dominated by mesquite-thorn scrub from the Mexican border to cattle ranches extending north from Willacy Co. A wildlife corridor on the plains, composed of natural habitat, supports hosts of many ixodid species. Occasional wind (not lunar) tides and infrequent storm surges inundate coastal plain areas with hypersaline water from the Lower Laguna Madre, creating large areas of saline soil. Laboratory and field experiments and observations were used to identify relationships between salinity and other abiotic and biotic factors that influence ixodid distribution. Exposure of lone star tick, Amblyomma americanum (L.), and Rhipicephalus microplus (Canestrini) eggs to hypersaline water is lethal. Although intermittent hypersaline flooding kills ixodid eggs, saline soil was not particularly toxic. When relative humidity is relatively low, desiccation causes high egg mortality on dry soil, regardless of salinity. Substantial year-round populations of mud flat fiddler crabs, Uca rapax (Smith) (Decopoda: Ocypodidae), occur on saline soil and eliminated ≈80% of A. americanum egg masses overnight. On saline and low-salinity soils predatory formicids, including the red imported fire ant, Solenopsis invicta (Buren), were indifferent to the eggs. Saline soils were dominated by the sea ox-eye daisy, Borrichia frutescens (L.) DC, and its color allowed production of a GIS-based map. At least 24.4% of the wildlife corridor supports heavy stands of B. frutescens which is indicative of high U. rapax populations. Ixodid populations were negligible on heavy B. frutescens stands because of associated salt water toxicity, desiccation, and predation by U. rapax on eggs.

Effects of metal contamination in situ on osmoregulation and oxygen consumption in the mudflat fiddler crab Uca rapax (Ocypodidae, Brachyura)

The contamination of estuaries by metals can impose additional stresses on estuarine species, which may exhibit a limited capability to adjust their regulatory processes and maintain physiological homeostasis. The mudflat fiddler crab Uca rapax is a typical estuarine crab, abundant in both pristine and contaminated areas along the Atlantic coast of Brazil. This study evaluates osmotic and ionic regulatory ability and gill Na+/K+-ATPase activity in different salinities (<0.5, 25 and 60‰ S) and oxygen consumption rates at different temperatures (15, 25 and 35°C) in U. rapax collected from localities along the coast of São Paulo State showing different histories of metal contamination (most contaminated Ilha Diana, Santos>Rio Itapanhaú, Bertioga>Picinguaba, Ubatuba [pristine reference site]). Our findings show that the contamination of U. rapax by metals in situ leads to bioaccumulation and induces biochemical and physiological changes compared to crabs from the pristine locality. U. rapax from the contaminated sites exhibit stronger hyper- and hypo-osmotic regulatory abilities and show greater gill Na+/K+-ATPase activities than crabs from the pristine site, revealing that the underlying biochemical machinery can maintain systemic physiological processes functioning well. However, oxygen consumption, particularly at elevated temperatures, decreases in crabs showing high bioaccumulation titers but increases in crabs with low/moderate bioaccumulation levels. These data show that U. rapax chronically contaminated in situ exhibits compensatory biochemical and physiological adjustments, and reveal the importance of studies on organisms exposed to metals in situ, particularly estuarine invertebrates subject to frequent changes in natural environmental parameters like salinity and temperature.

Secondary production of the fiddler crab Uca rapax from mangrove areas under anthropogenic eutrophication in the Western Atlantic, Brazil

Fiddler crabs Uca rapax were analyzed in three mangrove areas located in both a lagoon and estuarine system in order to study the influence of eutrophication on their population dynamics and production. Populations at the three sites showed a biased sex ratio. Densities were similar at the three sites, but biomass was higher at the lagoon system. Despite biomass being higher at the most eutrophic site, this site exhibited the lowest production. Regarding age structure, the population inhabiting the less eutrophic site mainly comprised younger crabs. The lower production and smaller P/B ratio found in the more eutrophic site were most likely consequences of a high mortality rate and an aged population. Our study evidences the high plasticity of the fiddler crab U. rapax, and confirms secondary production and P/B ratio estimates as useful tools to assess the effects of environmental change.

Ingested microplastics (>100 μm) are translocated to organs of the tropical fiddler crab Uca rapax

Microplastics, which are accumulating in marine sediments, are assumed to pose a risk for deposit feeding invertebrates. We tested whether the fiddler crab Uca rapax ingests and retains microplastics in its body. Furthermore, we investigated whether retention rates depend on (a) the quality of the marine environment in which the plastics were pre-weathered and on (b) their abundance. For this, polystyrene pellets were submersed at a polluted and a pristine site near Niterói, Brazil, for 2weeks. Then specimens of U. rapax were, in laboratory experiments, exposed to fragments (180–250μm) derived from these pellets for 2months. After this period, microplastics were observed in the gills, stomach and hepatopancreas of the animals. However, fragment retention was not influenced by the two factors that we manipulated. The presence of microplastics in different organs of the crab supports the assumption that these particles have the potential to harm marine invertebrates.

First record of bilateral hypertrophy in chelas of Uca rapax male specimen (Crustacea, Decapoda, Ocypodidae) on the Brazilian coastline – ERRATUM

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First record of bilateral hypertrophy in chelas of Uca rapax male specimen (Crustacea, Decapoda, Ocypodidae) on the Brazilian coastline

An adult male specimen ofUca rapax(Crustacea, Decapoda, Ocypodidae), containing bilaterally hypertrophied chelipeds, was found in the mangrove area of the Rio Grande do Norte state, north-eastern Brazil. The chelipeds are subequal in size and similar to the major cheliped of normal male specimens ofUca rapax. This paper is the first record of the aforementioned anomaly for the species from the Brazilian coastline.

A new species of &lt;i&gt;Microphallus&lt;/i&gt; (Trematoda: Microphallidae) from Venezuela

During 1997-1999, a total of 94 crabs, Uca rapax were collected from La Sabana, La Ceiba and El Paujil, Sucre State, Venezuela. Of these 36 were infected with metacercariae. Two parasites were located in the abdominal muscles and one under the tissue of carapace and gonad. These metacercariae grew to adults in the following genera: Levinseniella, Microphallus and Maritrema, in the period of 2-5 days after feeding experimentally to the rat Rattus norvegicus, mice Mus musculus and duck Cairinia moschata. Specimens of the genus Microphallus were described herein as a new species M. sabanensis. The life cycle of M. sabanensis sp.nov. were studied experimentally using rat, mice and duck. All developmental stages and the adult are described. In addition, M. sabanensis was collected from wild birds Anas discors, Pluvialis squatarola, Butorides striatus, Egretta caerulea and Nycticorax violaceus from the same localities.

Is larval dispersal a necessity for decapod crabs from the Amazon mangroves? Response of Uca rapax zoeae to different salinities and comparison with sympatric species

Salinity may play an important role in the larval Biology and Ecology of many brachyuran decapod crustaceans. Usually, ontogenetic changes in salinity tolerance represent a good indicator of larval dispersal in marine coastal ecosystems. In an experimental laboratory study, we investigated the effects of eight different salinities (Sal. 0–35) on zoeal development of the neotropical fiddler crab Uca rapax from a northern Brazilian estuary. In the study area the species reproduces year-round, including the wet season when low salinities (≤5) are frequent, resulting from heavy tropical rainfalls and input of freshwater mostly from the Amazon River. Larval survival and development duration from hatching to megalopa of U. rapax were significantly affected by salinity. All larvae died in Sal. 0–20, while they successfully developed through five zoeal stages to megalopa in higher salinities (Sal. 25–35). However, in Sal. 25 the survival rate was still significantly lower (33.8±4.8%) and the zoeal development duration was longer (13.7±0.5days) than in salinities 30 and 35, where >90% of the larvae successfully survived after an average of 11.8–12.4days of development, respectively. Our results strongly suggest that the early life-history stages of U. rapax perform ontogenetic migrations towards adjacent coastal or fully marine waters to develop in favourable high salinities. Comparison with two other sympatric crab species, e.g. Ucides cordatus and Uca vocator, suggests that the larval ‘export’ strategy is a convergent adaptation exhibited by decapod species in the Amazon region to avoid mass mortality within parental mangroves that are frequently subjected to strong salinity fluctuations caused by the specific meteorological and hydrological conditions.

A case of malformation on the third maxilliped of Uca rapax (Smith, 1870) (Decapoda: Ocypodidae)

This paper evaluates the malformation in the left third maxilliped of a specimen of the fiddler crab Uca rapax from Venezuela. There are some hypotheses and the cause of the malformation remains unknown, but the results are indicative that is most likely due to errors in morphogenetic processes.

South American homogeneity versus Caribbean heterogeneity: population genetic structure of the western Atlantic fiddler crab Uca rapax (Brachyura, Ocypodidae)

The majority of marine species, including fiddler crabs, are thought to be genetically homogeneous due to their planktonic larval stages. However, recent studies have uncovered genetically structured populations in other littoral crabs thriving in mangroves. To determine the population genetic structure of the widespread mudflat fiddler crab Uca rapax, Smith, 1870 along the western Atlantic and the Caribbean Sea, mitochondrial Cox 1 sequence data of seven populations were compared and analyzed. We computed a haplotype network, nucleotide and haplotype diversities and conducted an AMOVA. While the three mainland populations examined (Brazilian states of São Paulo and Pará; Suriname) are genetically indiscernible as expected, populations from four Caribbean islands (St. Martin, Hispaniola, Jamaica, Cuba) showed significantly restricted gene flow among each other as well as compared to the mainland populations. Our data suggest the absence of possible barriers to gene flow between mainland sites, whereas a hindrance to genetic exchange seems to be present between mainland and Caribbean islands as well as among the islands.

Comparative morphology of the first zoea of twelve brachyuran species (Crustacea: Decapoda) from the Amazon region

The laboratory-hatched first zoeal stage of twelve brachyuran species collected in the estuarine area of the Caeté River in the Amazonian region are described and illustrated in the present study: P. americanus Saussure, 1857, Eurytium limosum (Say, 1818), Sesarma curacaoense De Man, 1892, S. rectum Randall, 1840, Armases rubripes (Rathbun, 1897), Aratus pisonii (H. Milne Edwards, 1837), Ocypode quadrata (Fabricius, 1787), Uca rapax (Smith, 1870), U. maracoani (Latreille, 1802), U. thayeri Rathbun, 1900, Ucides cordatus (Linnaeus, 1763) and Pachygrapsus gracilis (Saussure, 1858). Through intraspecific comparisons of the respective larval stage, an identification key was generated and provided. Most of the studied species presented morphological differences (e.g. type and presence or absence of setae) when compared to the same species previously described in the literature.

Fiddler crab burrow defence: A robot simulation

Fiddler crab burrow defence: A robot simulation

Sediment Bioturbation Potential of Uca rapax and Uca uruguayensis as a Result of Their Feeding Activity

Bioturbation of mangrove sediments by Uca uruguayensis (Nobili, 1901) and U. rapax (Smith, 1870) was compared based on the grain-size composition and organic content in surface sediment around the burrow and feeding pellets in two mangrove zones of the Sao Vicente Estuary, state of Sao Paulo, Brazil. For each species, 25 burrows with active crabs were selected. All pellets within a 15-cm radius of each burrow were carefully collected; samples of substrate were taken; and the crab occupant was excavated, sexed, and measured for carapace width (CW). The number of spoon-tipped setae on the second maxilliped of each species was estimated; U. uruguayensis showed more of these setae than U. rapax. For both species, the sediment post-processed by feeding activity (feeding pellets) showed a similar increase of coarser fractions and a smaller organic content. However, U. uruguayensis was more efficient in removing organic matter (88.1%) from the sediment than U. rapax (37.5%). These results suggest that different numbers of spoon-tipped setae on the second maxillipeds of the fiddler crabs do not affect the potential for grain-size selection, but result in differing abilities to remove organic matter from the sediment.

Sediment Particle Selection During Feeding by Four Species of UCA (Brachyura, Ocypodidae)

Differences in sorting of sediment grain-size during the feeding activity of fiddler crabs were investigated experimentally in four Uca species that have different numbers of spoon-tipped setae on the second maxillipeds. Uca leptodactylus had the highest number of spoon-tipped setae, followed by Uca rapax and Uca thayeri; whereas Uca vocator had no setae of this type. The crabs were allowed to feed for 48 h, in containers filled with three types of sediments with different particle-size composition. The feeding pellets formed in each type of sediment were collected, and the proportion of each granulometric fraction was compared with the substrate in the container. The diameters of the sediment particles found in the crab stomachs were measured and compared among the species and the types of sediments. The granulometry of the feeding pellets in each substrate was similar among the species. The size of particles ingested by fiddler crabs reflected the granulometric composition of the experimental substrate. Only U. leptodactylus ingested the smallest grains in coarser sediments. Therefore, the variation in the number of spoon-tipped setae on the second maxilliped seems not to affect the ability of fiddler crabs to manipulate and sort different particle sizes during feeding.

Population Dynamics and Secondary Production of Uca rapax (Brachyura: Ocypodidae) in a Tropical Coastal Lagoon, Southeast Brazil

Abstract The population dynamics and secondary production of the fiddler crab Uca rapax Smith, 1870 in the Itaipu Lagoon (Southeast Brazil) were studied. Samples were taken monthly over a period of 12 months, in order to test latitudinal gradient predictions about secondary production and P/B ratio. Males and females showed the same growth rates (K = 2.083) and reached the same asymptotic size (15.57 mm). However, females showed higher total (Z = 3.20) and annual mortality (A = 0.96 ind·year−1) than males (Z = 1.89; A = 0.85 ind·year−1). Recruitment occurred in all months, except in June, 2007. Secondary production was estimated in 113.4 g AFDW·m−2·year−1 and the production to biomass ratio (P/B) was 15.09. The production and P/B ratio estimated in the present study did not agree with the latitudinal gradient literature predictions.