Sammy De Grave

Regional scale speciation reveals multiple invasions of freshwater in Palaemoninae (Decapoda)

Ashelby, C.W., Page, T.J., De Grave, S., Hughes, J.M. & Johnson, M.L. (2012) Regional scale speciation reveals multiple invasions of freshwater in Palaemoninae (Decapoda). —Zoologica Scripta, 41, 293–306.

Phylogenetic position, systematic status, and divergence time of the Procarididea (Crustacea: Decapoda).

Bracken, H. D., De Grave, S., Toon, A., Felder, D. L. & Crandall, K. A. (2009). Phylogenetic position, systematic status, and divergence time of the Procarididea (Crustacea: Decapoda). —Zoologica Scripta, 39, 198–212.

A re-appraisal of the systematic status of selected genera in Palaemoninae (Crustacea: Decapoda: Palaemonidae)

Recent phylogenetic work (Ashelby et al., 2012) has demonstrated the need for a fresh appraisal of the systematic status of some Palaemoninae genera. In the present contribution the accumulated morphological as well as molecular evidence is reviewed. The genera Palaemonetes, Exopalaemon and Coutierella are demonstrated to be junior synonyms of Palaemon, which now contains 83 species. As a result of this systematic re-arrangement, two replacement names are needed. Palaemon kwantung nom. nov. now replaces Exopalaemon guangdongensis Guo, Wang & Zhang, 2005, nec Palaemon guangdongensis Liu, Liang & Yan, 1990. Palaemon mundusnovus nom. nov. is the replacement name for Palaemonetes intermedius Holthuis, 1949, nec Palaemon intermedius (Stimpson, 1860).

Unweaving hippolytoid systematics (Crustacea, Decapoda, Hippolytidae): resurrection of several families

The Hippolytidae is the fourth largest family within the Caridea, currently containing over 330 described species in 37 genera, and the classification of this family has been rather controversial. In this study, sequences of two nuclear protein‐coding genes, enolase and sodium‐potassium ATPase α‐subunit, and the mitochondrial 16S rRNA gene (totalling 1405 bp) from 29 hippolytid species in 20 genera plus 17 species from eight other caridean families were used to examine the phylogenetic status of Hippolytidae sensu lato. Our results clearly reject the monophyly of Hippolytidae and support the recognition of the Lysmatidae Dana, 1852, Thoridae Kingsley, 1879, Bythocarididae Christoffersen and Merguiidae Christoffersen .

Symbioses of decapod crustaceans along the coast of Espírito Santo, Brazil

Potential host species were searched for decapod crustaceans along the coasts of Espirito Santo State, Brazil. On five species of sea anemones checked, nine species of decapods were encountered. On three species of black coral checked, two decapod species were encountered. On six species of gorgonians checked, three species of decapods were encountered. In nine species of bivalves and one species of gastropod checked, one decapod species was encountered. On three sea urchin species checked, three decapod species were encountered. A further seven potential host species investigated did not have macroscopically visible symbiotic decapods. Four of these 18 symbiotic decapod species represent new records for the State of Espirito Santo, five species represent new records for Brazil, and at least one species (probably three) were new for science. The sea anemone Condylactis gigantea harboured the largest number of symbionts (eight species) and the shrimp Neopontonides sp. occurred on the largest number of hosts (four different species of gorgonians).

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).

Faunal relationships with seagrass habitat structure: a case study using shrimp from the Indo-Pacific

Caridean shrimp were used as a model group to investigate the effects of seagrass floral habitat complexity on Indo-Pacific fauna. Relationships between shrimp and seagrass habitat characteristics were explored using both multivari- ate and multiple linear regression modelling approaches. Epifaunal shrimp assemblages were sampled in the Wakatobi Marine National Park, Indonesia. Seagrass habitat complexity had a significant positive impact on shrimp abundance (F3,59 = 17.51, P < 0.001) and species richness (F3,59 = 10.88, P < 0.001), while significantly altering shrimp assem- blage structure (ANOSIM global R = 0.397, P < 0.001). In contrast to studies from other bioregions and faunal groups, species diversity and evenness were inversely related to habitat complexity. Changes in shrimp abundance, diversity and assemblage structure with habitat complexity are considered to reflect changes in individual species habitat specialisation. High complexity habitats were dominated by habitat specialists, whereas low complexity seagrass had higher numbers of habitat generalists. Generalist species may be more adapted to the reduced food availability and increased predatory pressures associated with reduced habitat complexity. Although similar patterns were observed at all sites, inter-site dif- ferences in shrimp abundance were observed. This indicates that although the present study demonstrates the importance of small-scale changes in seagrass habitat complexity to faunal assemblages, other factors related to larger spatial-scales are also important.

Multiple host switching events shape the evolution of symbiotic palaemonid shrimps (Crustacea: Decapoda)

The majority of the almost 1,000 species of Palaemonidae, the most speciose family of caridean shrimp, largely live in symbioses with marine invertebrates of different phyla. These associations range from weak epibiosis to obligatory endosymbiosis and from restricted commensalism to semi-parasitism, with the specialisation to particular hosts likely playing a role in the diversification of this shrimp group. Our study elucidates the evolutionary history of symbiotic palaemonids based on a phylogenetic analysis of 87 species belonging to 43 genera from the Indo-West Pacific and the Atlantic using two nuclear and two mitochondrial markers. A complementary three-marker analysis including taxa from GenBank raises this number to 107 species from 48 genera. Seven larger clades were recovered in the molecular phylogeny; the basal-most one includes mostly free-living shrimp, albeit with a few symbiotic species. Ancestral state reconstruction revealed that free-living forms likely colonised cnidarian hosts initially, and switching between different host phyla occurred multiple times in palaemonid evolutionary history. In some cases this was likely facilitated by the availability of analogous microhabitats in unrelated but morphologically similar host groups. Host switching and adaptations to newly colonised host groups must have played an important role in the evolution of this diverse shrimp group.

Let’s be pals again: major systematic changes in Palaemonidae (Crustacea: Decapoda)

In recent years the systematic position of genera in the shrimp families Gnathophyllidae and Hymenoceridae has been under debate, with phylogenetic studies suggesting the families are not real family level units. Here, we review the molecular evidence as well as the morphological characters used to distinguish both families, leading to the conclusion that neither family is valid. Further, we studied the structural details of the single morphological character which distinguishes the two subfamilies (Palaemoninae, Pontoniinae) in Palaemonidae, as well as their phylogenetic relationship. As the supposed character distinction plainly does not hold true and supported by the phylogenetic results, the recognition of subfamilies in Palaemonidae is not warranted. As a consequence, all three supra-generic taxa (Gnathophyllidae, Hymenoceridae, Pontoniinae) are thus herein formally synonymised with Palaemonidae.

ON THE SYSTEMATIC POSITION OF GALATHEACARIS ABYSSALIS (DECAPODA: GALATHEACARIDOIDEA)

Abstract The systematic status of Galatheacaris abyssalis is assessed on the basis of recently collected material. Mitochondrial DNA analysis reveals that the 16S rRNA sequence from one specimen is identical with that of Eugonatonotus chacei, while the COI sequences of the two taxa diverge only by 0.6% (3 bp), indicating that the two taxa are conspecific. Based on the morphological development of specimens attributed to G. abyssalis, we conclude that this taxon represents the megalopal stage of E. chacei. Therefore, the family Galatheacarididae and the superfamily Galatheacaridoidea should be abandoned.