Species Of Fiddler Crabs Research Articles

Population Ecology of the Fiddler Crab Uca spp. in Punta, Baybay City, Leyte

A study on the population of the fiddler crabs, Uca spp. was conducted to determine their abundance, density, sex ratio, frequency and distribution pattern in the mangrove area of Punta, Baybay City, Leyte. A total of 126 individual fiddler crabs belonging to three different species were collected in a 6,000m2 mangrove area from September to December, 2 2013. The three fiddler crab species were Uca perplexa, U. triangularis, and U. crassipes. Uca perplexa had the highest density which occurred only in the landward zone while U. triangularis occurred in all three zones (seaward, middle and landward). The sex ratio of U. perplexa population did not deviate from the typical 1:1 ratio while U. triangularis did. In terms of their mean size, males of U. perplexa were significantly different from females while U. triangularis showed no significant size difference between males and females. Both U. perplexa and U. triangularis populations had non-normal overall size frequency distributions which were aggregately distributed. Distribution of U. perplexa population appeared to be influenced by substrate type while U. triangularis was not affected by this parameter.

A review of fiddler crabs (genus Uca Leach, 1814) in South Africa

Fiddler crabs occur globally across tropical and subtropical coastal habitats including mangrove swamps, which are in decline worldwide. The genus has been well-studied in the Americas, Australia and Asia, whereas information on African species is scarce. This review summarises the existing literature on fiddler crabs and highlights gaps in research for species at their southernmost distribution ranges in South Africa. Biological and ecological aspects including life cycle and reproduction, feeding ecology, biotic interactions and tolerance to environmental fluctuations and pollution are discussed. The systematics and distribution of the five fiddler crab species that occur in South Africa is provided. The St Lucia estuarine lake is presented as a case study for the effects of environmental change on Uca populations. Future research should focus on less-studied Uca populations, such as those found in the Indo-Pacific region. The effects of climate change and habitat modification on Uca populations should also be more widely investigated.

Are crabs stressed for water on a hot sand flat? Water loss and field water state of two species of intertidal fiddler crabs

Field measures of stress are needed to understand the role of behavior in stress and how behavior trades off with overall fitness. Along Atlantic shores, displaying and reproductive burrow-occupying males of the fiddler crab Uca pugilator live in high intertidal dry sandy sediments, whereas Uca pugnax live in lower intertidal wetter muddy substrata. Water loss was examined in the lab for both species. Water loss of U. pugilator males was approximately linear with time and crabs regained water completely after 2h of rehydration. Percent water loss was inversely correlated with body mass, irrespective of sex. Males of the higher intertidal U. pugilator lost proportionally less water over time than U. pugnax, which occupies muddier and wetter sediments. A field test of water state on a hot day demonstrated that males of either species seen at the surface next to mating burrows were not stressed for water, suggesting that behavior compensated adequately for water loss when displaying in the sun on the surface. Behavior can therefore compensate for what appears to be a stressful environment. However, such compensation likely comes at the cost of reproductive success, which depends upon remaining on the sediment surface in open stressful conditions. Large-sized males may be more successful in breeding territories owing to their proportionately lower water loss.

Settlement of fiddler crab megalopae on a North Carolina (USA) sandflat: species identification using multiplex PCR provides evidence for selective settlement

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 523:115-123 (2015) - DOI: https://doi.org/10.3354/meps11166 Settlement of fiddler crab megalopae on a North Carolina (USA) sandflat: species identification using multiplex PCR provides evidence for selective settlement James M. Welch1,2,*, Kathleen A. Reinsel1,2, Kristen A. Battles1, Abner O. Romero2, Jennifer M. Blaine1, Rachel L. Sendi1, Richard B. Forward Jr.2 1Department of Biology, Wittenberg University, Springfield, OH 45502, USA 2Nicholas School of the Environment, Duke University Marine Laboratory, Beaufort, NC 28516, USA *Corresponding author: jwelch@wittenberg.edu ABSTRACT: Selection of settlement sites by planktonic larvae can have important impacts on adult population distributions. Three species of fiddler crabs—Uca pugilator, U. pugnax, and U. minax—commonly co-occur in mid-Atlantic estuaries of the USA. They share a common larval life history of export to coastal waters followed by reinvasion of the estuary as postlarvae (megalopae), but their adults occupy different habitats separated by salinity and sediment type. This separation of adults could be caused by differential larval supply, selective settlement, or by post-settlement processes. We examined the species composition of planktonic postlarvae delivered to an intertidal site with a monospecific population of U. pugilator and compared it to newly settled postlarvae and first-instar crabs at this site using a new multiplex PCR technique for species identification. We found that all 3 species were present in the plankton but that almost all settled megalopae were U. pugilator, indicating that selective settlement is important for maintaining the adult population distribution at this site. In addition, all first-instar crabs were U. pugilator except for a single U. pugnax individual, indicating that megalopae that initially settle in an inappropriate habitat can leave before metamorphosis. The multiplex PCR is faster and less expensive than existing molecular methods for identifying fiddler crab larvae and juveniles to species. Future experiments should examine the behavioral bases for the selective settlement of Uca spp. megalopae. KEY WORDS: Larval transport · Larval settlement · Selective settlement · Multiplex PCR · Larval supply · Uca Full text in pdf format PreviousNextCite this article as: Welch JM, Reinsel KA, Battles KA, Romero AO, Blaine JM, Sendi RL, Forward RB Jr (2015) Settlement of fiddler crab megalopae on a North Carolina (USA) sandflat: species identification using multiplex PCR provides evidence for selective settlement. Mar Ecol Prog Ser 523:115-123. https://doi.org/10.3354/meps11166 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 523. Online publication date: March 16, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Determination of key environmental factors responsible for distribution patterns of fiddler crabs in a tropical mangrove ecosystem.

In tropical regions, different species of fiddler crabs coexist on the mangrove floor, which sometimes makes it difficult to define species-specific habitat by visual inspection. The aim of this study is to find key environmental parameters which affect the distribution of fiddler crabs and to determine the habitats in which each species was most abundant. Crabs were collected from 19 sites within the mudflats of Sepang-Lukut mangrove forest. Temperature, porewater salinity, organic matter, water content, carbon and nitrogen content, porosity, chlorophyll content, pH, redox potential, sediment texture and heavy metals were determined in each 1 m2 quadrate. Pearson correlation indicated that all sediment properties except pH and redox potential were correlated with sediment grain size. Canonical correspondence analysis (CCA) indicated that Uca paradussumieri was negatively correlated with salinity and redox potential. Sand dwelling species, Uca perplexa and Uca annulipes, were highly dependent on the abundance of 250 μm and 150 μm grain size particles in the sediment. Canonical Discriminative Analysis (CDA) indicated that variation in sediment grain size best explained where each crab species was most abundant. Moreover, U. paradussumieri commonly occupies muddy substrates of low shore, while U. forcipata lives under the shade of mangrove trees. U. annulipes and U. perplexa with the high number of spoon tipped setae on their second maxiliped are specialized to feed on the sandy sediments. U. rosea and U. triangularis are more common on muddy sediment with high sediment density. In conclusion, sediment grain size that influences most sediment properties acts as a main factor responsible for sediment heterogeneity. In this paper, the correlation between fiddler crab species and environmental parameters, as well as the interaction between sediment characteristics, was explained in order to define the important environmental factors in fiddler crab distributions.

Spatial distribution and population structure of fiddler crabs in an Indian Sundarban mangrove

Brachyuran crabs constitute the most abundant faunal component of mangrove ecosystems and support a wide range of ecosystem services. In the present study, seasonal variation of population density and biomass along with demographic categories and sex ratios of four species of fiddler crabs (Uca rosea, Uca triangularis, Uca dussumieri and Uca vocans) from Jhorkhali Island in the Sundarban mangrove were studied in relation to some major environmental parameters (salinity, nutrient content, soil organic carbon, dissolved oxygen, total dissolved solute, etc.) during bimonthly sampling for three consecutive years (2010-2012). Maximum population density and biomass of the ocypodid crabs were recorded during the pre-monsoonal month and minimum values during the monsoon. Different peaks in reproductive activity were observed among seasonal breeders (U. triangularis, U. dussumieri). For U. vocans, the sex ratio peaks declined during the ovigerous period. All four populations were characterized by significantly more males than females. Multiple regression analysis suggested a cumulative effect of several ecological parameters on seasonal fluctuations of the crab population. Breeding periodicity might be controlled by a combination of factors, including temperature, quality of the substratum, food availability for the adult and larval stages, and intertidal zonations.

Reproductive Biology and Bioturbatory Activities of Two Sympatric Species of Fiddler Crabs Uca lactea annulipes and Uca triangularis bengali (Decopada : Ocypodidae) at the East Midnapore Coastal Belt of West Bengal, India

Two sympatric species of fiddler crabs viz. Uca lactea annulipes and Uca triangularis bengali belonging to order decapoda, family ocypodidae have been taken into consideration in respect of their habitat preference, sex ratio, fecundity and role of bioturbatory activities in sustaining the coastal-estuarine-ecosystem dynamics at an ecotone (Talsari) located in the Midnapore (East) coastal belt of West Bengal, India. A distinct segregation of habitats of these two species was evident from this field study. In general, monthly sex ratios were a clearly male biased for both species. Reproductive potential and intensity of the studied fiddler crabs have been measured by quantifying the relative frequency of ovigerous females and their fecundities. These two crabs have been to be as excellent bioturbator mediators and their bioturbatory activities were found to alter geochemistry of sediments by way of making semidomes (only male of U. lactea annulipes) and mudballs (both sexes of U. triangularis bengali). These bioturbatory structures used to play some role in the social as well sexual interactions of both species.

Salt marshes

Salt marshes are unique ecosystems that are brimming with diversity, and provide crucial shelter to coastal communities.

A new species of fiddler crab from the Ogasawara (Bonin) Islands, Japan, separated from the widely-distributed sister species Uca (Paraleptuca) crassipes (White, 1847) (Crustacea: Decapoda: Brachyura: Ocypodidae).

A new species of fiddler crab (Brachyura: Ocypodidae), Uca boninensis sp. nov., is described from the Ogasawara (Bonin) Islands, Japan. The new species has previously been identified with the widely distributed U. crassipes (White, 1847), from which it differs by having a slightly differently shaped carapace, and relatively stouter male first gonopods (G1). The recognition of the new species is also supported by differences in the mitochondrial cytochrome oxidase I (COI) and control region (CR) genes. U. boninensis sp. nov., appears to be endemic to the Ogasawara Islands, and as the only known population is small, urgent conservation measures are needed for its protection. Our study brings the total number of the Japanese fiddler crab species to 12.

Density, Shell Use and Species Composition of Juvenile Fiddler Crabs (Uca spp.) at Low and High Anthropogenic Impact Salt Marsh Sites

Coastal wetlands worldwide have been negatively impacted by humans, causing decreases in the vegetation used as a refuge from predation by juveniles of many species. This study examined juvenile fiddler crab densities and species composition (Uca pugnax, Uca pugilator, and Uca minax), and their use of gastropod shells (Littorina littoraria), at three low and three high impact sites on barrier islands in southeast Georgia. On six dates in June–August 2010, samples were taken from 10 quadrats (1 m2) at each site to determine juvenile fiddler crab densities and species composition, as well as gastropod shell densities and percent shell use. Multiplex PCR was used to identify juvenile fiddler crabs to species. Juvenile fiddler crab densities were lower at high impact sites, while gastropod shell densities and shell use were similar at both low and high impact sites. Species compositions differed between low and high impact sites on the substrate and in shells, with more U. pugilator and U. minax at high impact sites. A change in fiddler crab densities and species composition could cause a substantial change in southeastern salt marshes.

Evolutionary variation in the mechanics of fiddler crab claws

BackgroundFiddler crabs, genus Uca, are classic examples of how intense sexual selection can produce exaggerated male traits. Throughout the genus the enlarged “major” cheliped (claw) of the male fiddler crab is used both as a signal for attracting females and as a weapon for combat with other males. However, the morphology of the major claw is highly variable across the approximately 100 species within the genus. Here we address variation, scaling, and correlated evolution in the mechanics of the major claw by analyzing the morphology and mechanical properties of the claws of 21 species of fiddler crabs from the Pacific, Gulf and Atlantic coasts of the Americas.ResultsWe find that the mechanics that produce claw closing forces, the sizes of claws and the mechanical strength of the cuticle of claws are all highly variable across the genus. Most variables scale isometrically with body size across species but claw force production scales allometrically with body size. Using phylogenetically independent contrasts, we find that the force that a claw can potentially produce is positively correlated with the strength of the cuticle on the claw where forces are delivered in a fight. There is also a negative correlation between the force that a claw can potentially produce and the size of the claw corrected for the mass of the claw.ConclusionsThese relationships suggest that there has been correlated evolution between force production and armoring, and that there is a tradeoff between claw mechanics for signaling and claw mechanics for fighting.

Fossil and modern fiddler crabs (Uca tangeri: Ocypodidae) and their burrows from SW Spain: ichnologic and biogeographic implications

The burrowing activity of the only European fiddler crab species, Uca tangeri (Eydoux, 1835), was studied along the shores of the estuary of the Piedra River in Lepe, southwestern Spain. Casting of burrows allowed recognition of their simple, J-shaped to irregular architecture, which displays striking similarities to fossil Pliocene burrows in the same area. The finding of body fossils of U. tangeri in contemporaneous strata indicates these trace fossils are produced by the same species and demonstrate its presence in the eastern Atlantic coast at least for the last three million years. Burrows of U. tangeri are similar to those of other Uca spp. worldwide and also to those of other brachyurans. Their architectural simplicity makes difficult their definitive recognition in the fossil record. Nevertheless, review of existing literature confirms the presence of brachyuran burrows at least since the Cretaceous.

Latitudinal differences in thermoregulatory color change in Uca pugilator

Animals can change color either rapidly in response to changes in their immediate environment or slowly as the seasons change. Such plasticity can permit local adaptation but it can also be constrained by physiological and behavioral mechanisms. Here, we explore how different temperature regimes along a latitudinal gradient spanning the natural range of a species of fiddler crab may affect the ability of crabs to change color rapidly in response to acute changes of temperature. Uca pugilator populations from New York (NY), North Carolina (NC) and Florida (FL) were exposed in air to 5°C and 35°C and carapace shade intensity (from dark to light color) and contrast was recorded. In general, individuals darkened when exposed to cold conditions, and lightened when exposed to warm conditions. Males from different populations differed in the magnitude of response to temperature, but had similar directional changes in shade (dark under cold conditions and light under warm conditions) suggesting differences among populations in the ability to change color. Females showed similar directional changes but there were no differences among populations. Differential responses of crabs to temperature suggest that crabs have local physiological adaptations and can acclimate quickly to withstand fluctuating or extreme temperatures.

The fiddler crabs (Crustacea: Brachyura: Ocypodidae: genus Uca) of the South Atlantic Ocean

The taxonomy of the 11 species of fiddler crabs [Uca (Uca) maracoani (Latreille, 1802-1803), U. (U.) tangeri (Eydoux, 1835), U. (Minuca) burgersi Holthuis, 1967, U. (M.) mordax (Smith, 1870), U. (M.) rapax (Smith, 1870), U. (M.) thayeri Rathbun, 1900, U. (M.) victoriana von Hagen, 1987, U. (M.) vocator (Herbst, 1804), U. (Leptuca) cumulanta Crane, 1943, U. (L.) leptodactyla Rathbun, 1898 and U. (L.) uruguayensis Nobili, 1901] of the South Atlantic Ocean is reviewed. Keys for identification, updating the keys for the Atlantic Ocean are proposed, including the species recently described. Comments reporting morphological variations among types and additional material and among populations of different localities are included. The Atlantic species are divided into three subgenera: Uca s. str., Minuca and Leptuca. The eastern Atlantic species U. (U.)tangeri is included in subgenus Uca s. str. due to the presence of a proximal spine opposing the spoon-tipped setae of the second maxilliped, which is considered an apomorphic character of the subgenus Uca s. str.

Morphological diversity of setae on the second maxilliped of fiddler crabs (Decapoda: Ocypodidae) from the southwestern Atlantic coast

AbstractFiddler crabs are deposit feeders, and use the setae on their mouth appendages to manipulate sediment particles to extract food. The number of spoon‐tipped setae on the second maxilliped is frequently related to the distribution of fiddler crabs on estuarine sediments, but no study has compared the morphological diversity of these setae among multiple fiddler crab species. Here, we describe and classify the setae of the second maxillipeds of the nine Uca spp. known from the Brazilian coast. The second maxilliped of each species was examined by scanning electron microscopy. Six types of setae (five papposerrate, and one pappose) were described on the meropodite of the second maxilliped. Among the papposerrate setae, one type had a spoon‐like tip, and the morphology of this type, especially the degree of curvature, differed between species. Members of Uca leptodactylus, U. uruguayensis, and U. maracoani had highly concave spoon‐tipped setae. In U. rapax and U. cumulanta, the setal tip was moderately curved, while in U. thayeri, U. burgersi, and U. mordax, this curvature was slight. At the other extreme, the meropodite of the second maxilliped of U. vocator lacked setae altogether. This is the first study that describes differences in the degree of curvature of spoon‐tipped setae in fiddler crabs. This trait may be strongly related to the distribution of these fiddler crabs on different estuarine substrates.

Reducing error in reproductive timing caused by temperature variation: interspecific differences in behavioural adjustment by fiddler crabs

Many organisms time reproduction with physical and biological cycles that affect offspring survival. In the marine environment, a common pat- tern is the release of planktonic larvae during large- amplitude nocturnal tides, which may reduce losses due to predation. However, if the duration of embry- onic development depends on temperature, changes in temperature can lead to errors in timing. Organ- isms may reduce such errors either by changing the timing of onset of incubation or by selecting the temperatures to which embryos are exposed. We conducted field and laboratory experiments with 2 species of fiddler crabs to examine the effects of temperature and temperature variation on the timing of larval release and synchrony of release among females. As expected, the duration of incubation increased with decreasing temperature in both spe- cies. In the field when temperature was low, Uca terpsichores released larvae earlier than expected, indicating that shifts in timing of mating reduced potential errors in timing of release. However, when temperature changed during incubation, accuracy and precision in the timing of release decreased. U. deichmanni maintained timing and synchrony of release despite variable temperature in the field, but in cold water in the laboratory, they incubated eggs longer than in the field and released larvae late. These differences suggest that U. deichmanni regu- lates the incubation period in the field. U. terpsi- chores may be less able than U. deichmanni to adjust to rapid variation in temperature that may accom- pany climate change, which could result in large- scale interspecific differences in larval survival and recruitment.

Paternity analysis of two male mating tactics in the fiddler crab, Uca mjoebergi

The fiddler crab Uca mjoebergi mates both underground in male-defended burrows and on the surface near female-defended burrows. The reproductive tract of Uca species facilitates last-male precedence, suggesting that males that do not guard-mated females are likely to gain very little paternity if the female re-mates with another male. Here, we test the reproductive success of burrow and surface matings using paternity analysis. We found that 100 % of the females that mated in burrows extruded a clutch of eggs. Furthermore, we show conclusively, for the first time in a fiddler crab species, that last-male sperm precedence results in the majority of the female’s eggs being fertilised by the burrow-mated male. In contrast, surface matings resulted in significantly fewer females extruding eggs (5.6 %). Paternity analysis also revealed that more than half of the clutches from burrow-mated females showed low levels of extra-pair paternity from previous matings. Although multiple matings appear common in U. mjoebergi, burrow-mated males that guard females are guaranteed a successful mating with extremely high rates of assured paternity. Surface matings therefore appear to be an opportunistic tactic that may increase male reproductive success in a highly competitive environment.

The effects of neighbor familiarity and size on cooperative defense of fiddler crab territories

Cooperation between neighbors in territory defense is expected when the cost of helping a neighbor is less than that of establishing new boundaries with a successful usurper of a neighboring territory. Cooperation has been documented in 3 species of fiddler crab and is understood to depend strongly on the relative sizes of participants—large residents will help smaller neighbors repel intermediate-sized intruders. Simply meeting these criteria does not, however, guarantee that helping occurs, and additional factors are likely to affect the benefits of providing help. We tested whether the likelihood that a large resident would help his smaller neighbor was affected by neighbor familiarity or the relative size of the smaller neighbor, by replacing neighbors with smaller, larger, or size-matched individuals and then simulating intrusions onto their territories. The likelihood of helping did not differ between familiar and unfamiliar neighbors of the same size, but it decreased when the replacement resident differed in size from the original resident. These results suggest that although residents do not recognize their neighbors individually, size acts as a cue to neighbor identity.

Shell use by juvenile fiddler crabs Uca pugnax and U. pugilator

The present study documents for the first time shell use by juvenile fiddler crabs in the salt marsh. Twenty visits were made to six salt marsh sites at Tybee Island, Georgia between 2007 and 2009. One hundred empty Littorina irrorata shells were collected at each site on each field trip. Juvenile carapace width was measured, crabs sexed, and species identification completed using RFLP analysis. Shell use of up to 79% was observed. Two species of fiddler crabs were found in empty shells, Uca pugnax and U. pugilator. U. pugnax was the dominant species at all sites representing 62–84% of the juvenile fiddler crab population. Juvenile sex ratios were female-biased (1.7:1) at all six sites. Juvenile size did not vary significantly between species but males of both species were significantly larger than females. Size frequency distribution of carapace width revealed that shell use varied with size and sex. In the 3 to 4 mm size class, juvenile females outnumbered juvenile males in empty L. irrorata shells while in the 5 to 6 mm size class and greater, juvenile males outnumbered juvenile females in shells. Significantly more juvenile fiddler crabs were found in empty shells during flood than ebb tide at 3 of the sites. This discovery illuminates the resourcefulness of juvenile fiddler crabs and provides another mechanism that might enhance survival.

The effect of sewage discharge on the ecosystem engineering activities of two East African fiddler crab species: Consequences for mangrove ecosystem functioning

A number of studies have suggested that mangrove forests and their faunal components may be pre-adapted to the impact of organic waste discharge, making them possible natural wastewater treatment wetlands. However, the results from recent research are contradictory. Some studies have shown that negative effects, sometimes subtle and difficult to observe, can be detected on specific biotic components of forests subjected to organic pollution. Therefore, the aim of the present study was to investigate possible alterations in the ecosystem engineering activities of a fiddler crab community dominating the landward belts of Kenyan mangrove forests. The total processed sediment produced by burrowing and foraging activities in a population from a peri-urban mangrove area receiving untreated domestic sewage was compared with that from a forest not affected by urban wastewater. The results showed how the peri-urban site hosted a higher biomass of crabs, which produced a significantly lower amount of processed sediment compared with the pristine site, resulting in a lower total top sediment mixing activity of the crabs. Thus, the present study showed a link between sewage exposure and top sediment reworking by crabs, which is potentially beneficial for mangrove growth and ecosystem functioning. This represents a possible example of cryptic ecological degradation in mangal systems.