The following information was supplied regarding data availability: Faulkes, Zen : Polypocephalus infection of hippoid crabs. Abstract Two digging decapod crustaceans, the sand crab species Lepidopa benedicti and the mole crab species Emerita benedicti, both live in the swash zone of fine sand beaches. They were examined for two parasites that infect decapod crustaceans in the region, an unidentified nematode previously shown to infect L. Lepidopa benedicti were almost always infected with both parasite species, while E. This difference in infection pattern suggests that tapeworms are ingested during sediment feeding in L. Larger L.

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Search Menu Abstract Mole crabs of the genus Emerita Family Hippidae inhabit many of the temperate and tropical sandy beaches of the world. The nine described species of this genus are rarely sympatric, and most are endemic to broad biogeographic regions.

The phylogenetic relationships among the species have not yet been investigated. Based on presumed morphological synapomorphies, it has been suggested that the species inhabiting the New World constitute a monophyletic group, as do the species inhabiting the Old World. The relationships within the New World species were previously studied using sequence data from Cytochrome Oxidase I and 16S rRNA mitochondrial genes; the results strongly suggested that one of the species, Emerita analoga, was very divergent from the other taxa examined.

This observation prompted uncertainty about monophyly of the New World species. The goal of the present study was to elucidate the relationships among the species within the genus Emerita. Phylogenetic analyses suggest that E. Mole crabs of the genus Emerita Scopoli, , are medium-sized benthic crustaceans of the family Hippidae Anomura: Hippoidea that live in intertidal and upper subtidal sandy marine environments.

Historically, taxonomy of the genera Hippa and Emerita has been dynamic, with movement of species from one genus to the other. When initially described, the genus Emerita had as type species a taxon that is now assigned to the genus Hippa. Morphologically, the major difference between Hippa and Emerita is the shape of the carapace: it is dorsoventrally flattened, oval, and moderately convex in Hippa species and not flattened, cylindrical, and very convex in Emerita species.

In addition, compared to Hippa species, Emerita species have longer ocular peduncles, longer flagella on the antennae, and smoother lateral margins of the carapace Calado, The external morphology of these structures suggests that Hippa and Emerita are sister genera.

There are no described fossils that provide information regarding the history of Emerita species or the origin of the genus. On the basis of a molecular clock, it has been suggested that all species in the genus evolved before the mid- to late-Pliocene Tam et al.

Emerita species are distributed along most marine temperate coasts Fig. In the regions where Emerita species are absent, mole crabs of the genera Hippa and Mastigochirus may be present; these genera are distributed throughout the temperate and tropical seas of the world Miers, Three species are found along Old World coasts: E.

Geographic distribution of the nine species of the genus Emerita based on Efford and Tam et al. Open in new tab Download slide Geographic distribution of the nine species of the genus Emerita based on Efford and Tam et al. Two conflicting phylogenetic hypotheses have been proposed Fig. On the basis of morphological traits and distribution of species, Efford suggested that Emerita analoga, E.

Emerita talpoida and E. Efford suggested that E. Open in new tab Download slide Phylogenetic hypotheses for species of Emerita. The relationships suggested by the molecular analyses of Tam et al. A Efford suggested that Emerita analoga, E. Together these were hypothesized to form a sister clade to the Old World species E. B Tam et al. Emerita analoga is external to the other New World species of Emerita. The second hypothesis Fig. Their results suggest that E. Tam et al. Schmitt did a comparative study of the joint of the antennal peduncle in mole crabs.

He found that in Emerita analoga, the shape of the second joint is similar to that of E. The rest of the New World species have a second joint of the antennal peduncle that is similar in shape to the one in E. This suggestion is in agreement with Tam et al. The hypotheses presented by Efford and by Tam et al. The present work uses mtDNA to investigate the level of genetic divergence within the genus Emerita. The 16S rRNA gene has been used to gain insights into the phylogenies of numerous crustacean taxa at both high and low taxonomic levels i.

Similarly, the COI gene has been successfully used to generate phylogenetic hypotheses at the species level in many crustacean groups Palumbi and Benzie, ; Meyran et al. For a wide diversity of taxa, the COI gene is the most conserved in terms of sequence variation of the mitochondrial protein-coding genes Simon et al.

Samples for New World species were characterized by Tam et al. Amplification reactions were performed following standard protocols described by Tam et al. All sequences are a consensus of two sequencing reactions one in each direction. Bacterial colonies with inserts were cultured in SOC media overnight, following which plasmids were purified using the Plasmid Miniprep Kit Qiagen, Inc.

Presence of the correct-size insert was verified using PCR followed by agarose gel electrophoresis. Plasmid preparations that had the correct-size inserts were sequenced as previously described. The genus Hippa is considered to be the sister taxon to the genus Emerita A. Harvey, personal communication. The Pacific mole crab Hippa pacifica Dana, , widespread in the Indopacific region, was investigated as the sister taxon in the present study.

Several anomuran species belonging to the families Porcellanidae and Paguridae were also used as outgroup taxa. Table 1 lists the species examined and the associated GenBank accession numbers. Table 1. List of taxa, collection localities for Emerita species, and GenBank accession numbers for all species.


Benedict Sand Crab



Emerita benedicti






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