Sponge-dwelling Snapping Shrimps Research Articles

Comparative mitochondrial genomics of sponge-dwelling snapping shrimps in the genus Synalpheus: Exploring differences between eusocial and non-eusocial species and insights into phylogenetic relationships in caridean shrimps.

The genus Synalpheus is a cosmopolitan clade of marine shrimps found in most tropical regions. Species in this genus exhibit a range of social organizations, including pair-forming, communal breeding, and eusociality, the latter only known to have evolved within this genus in the marine realm. This study examines the complete mitochondrial genomes of seven species of Synalpheus and explores differences between eusocial and non-eusocial species considering that eusociality has been shown before to affect the strength of purifying selection in mitochondrial protein coding genes. The AT-rich mitochondrial genomes of Synalpheus range from 15,421bp to 15,782bp in length and comprise, invariably, 13 protein-coding genes (PCGs), two ribosomal RNA genes, and 22 transfer RNA genes. A 648bp to 994bp long intergenic space is assumed to be the D-loop. Mitochondrial gene synteny is identical among the studied shrimps. No major differences occur between eusocial and non-eusocial species in nucleotide composition and codon usage profiles of PCGs and in the secondary structure of tRNA genes. Maximum likelihood phylogenetic analysis of the complete concatenated PCG complement of 90 species supports the monophyly of the genus Synalpheus and its family Alpheidae. Moreover, the monophyletic status of the caridean families Alvinocaridae, Atyidae, Thoridae, Lysmatidae, Palaemonidae, and Pandalidae within caridean shrimps are fully or highly supported by the analysis. We therefore conclude that mitochondrial genomes contain sufficient phylogenetic information to resolve relationships at high taxonomic levels within the Caridea. Our analysis of mitochondrial genomes in the genus Synalpheus contributes to the understanding of the coevolution between genomic architecture and sociality in caridean shrimps and other marine organisms.

The complete mitochondrial genome of the eusocial sponge-dwelling snapping shrimp Synalpheus microneptunus

In the marine realm, eusociality is only known to have evolved within a clade of sponge-dwelling snapping shrimps in the genus Synalpheus. Deciphering the genomic underpinnings of eusociality in these marine shrimps has been limited by the sparse genomic resources in this genus. Here, we report, for a eusocial shrimp Synalpheus microneptunus, a complete mitochondrial genome (22X coverage) assembled from short Illumina 150 bp paired-end reads. The 15,603 bp long mitochondrial genome of S. microneptunus is AT-rich and includes 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, 22 transfer RNA genes and an 834 bp intergenic region assumed to be the D-loop. The gene order is identical to that reported for most caridean shrimps and corresponds to the presumed Pancrustacean ground pattern. All PCGs showed signs of purifying selection, with KA/KS <<1 across the whole PCGs and most sliding windows within PCGs. Maximum-likelihood and Bayesian inference phylogenetic analyses of 13 PCGs and 68 terminals supports the monophyly of the Caridea and the family Alpheidae. The complete mitochondrial genome of the eusocial shrimp Synalpheus microneptunus will contribute to a better understanding of the selective pressures and rates of molecular evolution in marine eusocial animals.

Synalpheus amintae sp. nov., a new species of sponge-dwelling snapping shrimp(Crustacea: Decapoda: Alpheidae) from Parque Nacional Natural Isla Gorgona, Pacific Coast of Colombia.

A new species of sponge-dwelling snapping shrimp, Synalpheus amintae sp. nov. from the Parque Nacional Natural Isla Gorgona, Pacific coast of Colombia, is described. This new species pertains to the denominated Synalpheus "Gambarelloides" species group sensu Coutière (1909)-previously known as "Laevimanus" group. It was collected in the southern part of the Island, during episodes of extreme low tides, known locally as "puja". Synalpheus amintae sp. nov. is closely related to the only two other known species of the S. "Gambarelloides" species group from the eastern Pacific: Synalpheus occidentalis Coutière, 1909, from Gulf of San José, Lower California, and Synalpheus mulegensis Ríos, 1992, from Bahía Concepción, Gulf of California, and can be differentiated from them by the poorly developed distal portion of pollex of the major cheliped, the armature of the distal segment of third maxilliped, and the number of acute teeth of exopodal uropod. A discriminative analysis dealing with other three species of Synalpheus from the western Atlantic, with distinctive pollex of major chela reduced, is presented. A dichotomous key was elaborated to identify the species of Synalpheus "Gambarelloides" species group from the eastern Pacific. The number of valid species described of Synalpheus from the eastern Pacific is increased to 23.

Social transitions in sponge-dwelling snapping shrimp.

Sociality is exceedingly rare in the marine environment, with true eusociality found only within a single genus of sponge-dwelling snapping shrimp. This genus is socially diverse and exhibits multiple independent evolutionary origins of both eusociality and communal breeding from pair-forming ancestors. Ecology was critical to the evolution of shrimp sociality, as the transition from host specialization to generalism preceded the evolution of eusociality, and the transition from small to large host sponges favored the evolution of communal breeding. Moreover, a change in life history from planktonic to non-dispersing, crawling larvae only occurred in eusocial species. Here, we present a hypothesis describing the evolutionary transitions toward sociality in shrimp that serves to illustrate how ecology and life history interact to shape social evolution more broadly.

Reproductive skew drives patterns of sexual dimorphism in sponge-dwelling snapping shrimps

Sexual dimorphism is typically a result of strong sexual selection on male traits used in male-male competition and subsequent female choice. However, in social species where reproduction is monopolized by one or a few individuals in a group, selection on secondary sexual characteristics may be strong in both sexes. Indeed, sexual dimorphism is reduced in many cooperatively breeding vertebrates and eusocial insects with totipotent workers, presumably because of increased selection on female traits. Here, we examined the relationship between sexual dimorphism and sociality in eight species of Synalpheus snapping shrimps that vary in social structure and degree of reproductive skew. In species where reproduction was shared more equitably, most members of both sexes were physiologically capable of breeding. However, in species where reproduction was monopolized by a single individual, a large proportion of females--but not males--were reproductively inactive, suggesting stronger reproductive suppression and conflict among females. Moreover, as skew increased across species, proportional size of the major chela--the primary antagonistic weapon in snapping shrimps--increased among females and sexual dimorphism in major chela size declined. Thus, as reproductive skew increases among Synalpheus, female-female competition over reproduction appears to increase, resulting in decreased sexual dimorphism in weapon size.

Embryo production in the sponge-dwelling snapping shrimp Synalpheusapioceros (Decapoda, Alpheidae) from Bocas del Toro, Panama.

Caridean shrimps of the genus Synalpheus are abundant and widely distributed in tropical and subtropical regions, but knowledge of their reproductive biology remains scarce. We report reproductive traits of Synalpheus apioceros from Bocas del Toro, Panama, based on collections in August 2011. The 46 ovigerous females that were analyzed ranged in size from 3.8 to 7.4 mm in carapace length. Fecundity varied between 8 and 310 embryos and increased with female size. Females invested 18.6 ± 10.3% of their body weight in Embryo production. Embryo volume increased considerably (77.2%) during embryogenesis, likely representing water uptake near the end of incubation period. Compared to Synalpheus species with abbreviated or direct development, Synalpheus apioceros produced substantially smaller embryos; however, Synalpheus apioceros seems to have a prolonged larval phase with at least five zoeal stages, which may explain the combination of relatively small and numerous embryos. We did not find nonviable, minute, chalky embryos, previously reported for Synalpheus apioceros specimens obtained from the northwestern Gulf of Mexico, which supports the hypothesis that the production of this type of embryos may be a physiological response of this warm-water species to the temperature decrease near to its latitudinal range limit.

Sponge-dwelling snapping shrimps of Curaçao, with descriptions of three new species

Sixteen species of sponge-dwelling snapping shrimp in the genus Synalpheus (gambarelloides group) were collected from sites spanning the south coast of Curaçao, including three new to science. Synalpheus hoetjesi sp. nov. belongs to a species complex that includes Synalpheus pandionis, S. dardeaui, S. yano, S. goodei, S. longicarpus, and S. ul. Synalpheus kuadramanus sp. nov. is a distinctive shrimp characterized by a short, square moveable finger on the major first pereopod and by brilliant turquoise embryos in females. Synalpheus orapilosus sp. nov. is a shrimp most morphologically similar to Synalpheus barahonensis—both species share the distinctive character of a tuft of setae on the distal end of the third maxilliped, instead of a distal circlet of spines—but can be distinguished from the latter by the number of carpal segments on the second pereopod. Although eusocial Synalpheus species (defined here as species that live in large colonies with strong reproductive skew) are often the most numerically abundant Synalpheus collected from sponges at other sites, only pair-bonding Synalpheus species were recorded from our collections in Curaçao.

The sponge-dwelling snapping shrimps (Crustacea, Decapoda, Alpheidae, Synalpheus) of Discovery Bay, Jamaica, with descriptions of four new species

The sponge-dwelling snapping shrimps (Crustacea, Decapoda, Alpheidae, Synalpheus) of Discovery Bay, Jamaica, with descriptions of four new species

The sponge-dwelling snapping shrimps (Crustacea, Decapoda, Alpheidae, Synalpheus) of Discovery Bay, Jamaica, with descriptions of four new species

Twenty-two species of sponge-dwelling shrimp in the genus Synalpheus were collected in the vicinity of Discovery Bay, Jamaica. Four of these species are new to science. Synalpheus thele n. sp., S. corallinus n. sp., and S. plumosetosus n. sp. belong to a group of morphologically similar species that also includes S. brooksi, S. bousfieldi, S. carpenteri, and S. chacei. Synalpheus irie n. sp. is a highly distinctive shrimp most similar to S. mcclendoni, but can be distinguished from the latter by the unique bowl-shaped fingers of the major chela and the two-pronged distal protuberance on the palm of the major chela. Synalpheus belizensis and S. regalis are reported for the first time from outside their type localities in Belize, while S. bocas and S. duffyi are reported for the first time outside their type localities in Caribbean Panama.

Microsatellite development suggests evidence of polyploidy in the social sponge‐dwelling snapping shrimp Zuzalpheus brooksi

We isolated and characterized 33 novel, polymorphic microsatellite loci from the social sponge-dwelling snapping shrimp Zuzalpheus brooksi. We screened all 33 loci in approximately 31 individuals from a population of Z. brooksi from the Florida Keys, USA and found an average of 16 alleles per locus. Approximately 25% of the loci showed more than two bands per individual, suggesting evidence of high gene duplication, or more likely, polyploidy, which is common in crustaceans. The 25 disomic loci had an observed heterozygosity of 0.57 (range=0.03-1.00) and will be useful for studying the social organization in Zuzalpheus shrimp.

Two New Species of Sponge-Dwelling Snapping Shrimp from the Belizean Barrier Reef, with a Synopsis of the Synalpheus brooksi Species Complex

Two new species of sponge-dwelling snapping shrimp in the genus Synalpheus are described. Synalpheus carpenteri is based on specimens collected from the Belizean Barrier Reef, the Exuma Islands of the Bahamas, and the Atlantic Coast of Panama, while Synalpheus ruetzleri is based on specimens collected from the Belizean Barrier Reef and the Atlantic Coast of Panama. Both species belong to a group of closely related shrimp (the ‘‘Synalpheus brooksi complex’’) that includes Synalpheus brooksi, Synalpheus bousfieldi, Synalpheus chacei, and possibly additional undescribed species. All species in the complex are remarkably similar in morphology, but Synalpheus carpenteri is readily recognizable by its brilliant orange color in life, its habitation solely in sponges of the genus Agelas, its squat, wide-based telson, and the short lateral spines of its scaphocerite and basicerite. Synalpheus ruetzleri appears unique within the complex in possessing a well-developed blade on the scaphocerite. Specimens of Synalpheus brooksi and S. bousfieldi from Belize and other localities are also figured to facilitate separation of members of the brooksi complex.

Species boundaries, specialization, and the radiation of sponge-dwelling alpheid shrimp

Microevolutionary studies and natural history suggest that host-specialization has promoted the high diversity of tropical sponge-dwelling snapping shrimps (Decapoda, Alpheidae, Synalpheus). Yet the taxonomic difficulty of this genus has precluded rigorous tests of this hypothesis. S. rathbunae Coutiére is among the most abundant invertebrates inhabiting the framework of sponges and dead coral that forms the floor of Caribbean coral reefs. Even within a small area S. rathbunae exhibits the apparently wide variation in size, color, and morphology that has long frustrated efforts to identify and define species boundaries within this large (< 100 described species) genus. Here I show that sympatric populations of this nominal species occupying different sponge hosts display clear, concordant differences in allozyme genotypes and in multivariate morphometries, confirming that the populations represent three distinct biological species. Moreover, careful field sampling revealed that the three S. rathbunce taxa and the closely related S. filidigitus Armstrong showed almost no overlap in the species of hosts occupied. Interestingly, while there was significant differentiation between Belizean and Panamanian populations of the one taxon that occurred at both sites (∼1500 km apart), these populations were recognizable as conspecific using both genetic and morphological characters. These results show that (1) diversity of Synalpheus, which is already among the most species-rich crustacean genera, is probably several times higher than currendy recognized, and (2) species of sponge-dwelling Synalpheus are highly host-specific, with related species distinctly segregated among hosts. Together with previous evidence of host race differentiation within shrimp species, these results suggest a primary role for resource specialization in the origin and/or maintenance of this group's characteristically high diversity.