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

Abstract

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.

A New Host and Range Record for the Gall CrabFungicola fageias a Symbiont of the Mushroom CoralLobactis scutariain Hawai‘i

“…A host switch is therefore more probable, but it is unclear when and where this could have happened, either in the Hawaiian Islands or in more westward localities. Host switches have also been reported from other crustacean taxa, such as pea crabs (Becker and Tü rkey 2017), xanthid crabs (García-Hernández et al 2016), and palaemonid shrimps (Brinkmann and Fransen 2016, Horká et al 2016, Hoeksema and Fransen 2017.…”

Towards a revision of the genus Periclimenes: resurrection of Ancylocaris Schenkel, 1902, and designation of three new genera (Crustacea, Decapoda, Palaemonidae)

“…Although several molecular studies were recently constructed (Kou et al 2013, Gan et al 2015, Horká et al 2016) to examine intrageneric relationships of the genus Periclimenes , a full resolution has not been achieved yet, partly due to incomplete coverage of species diversity, partly due to the low basal support of some clades within the analysis. Excluding the species recently allocated to Echinopericlimenes Marin & Chan, 2014 and Bathymenes Kou, Li & Bruce, 2016, only about 25 species of Periclimenes are involved in the analyses representing about 20% from the almost 130 species presently in the genus.…”

Designation of a new genus Michaelimenes (Decapoda: Caridea: Palaemonidae), with new host record and range extension of its type species, M. perlucidus (Bruce, 1969)

“…Within marine palaemonid shrimps, it is the most species-rich genus comprising over 150 species (De Grave and Fransen, 2011). However, Gan et al (2015) and Horká et al (2016) suggested that Periclimenes is a polyphyletic taxon on the basis of molecular evidence. High morphological diversity is also shown within the genus, and Periclimenes is divided into some species groups, for instance, Periclimenes obscurus Kemp, 1922, Periclimenes diversipes Kemp, 1922, and Periclimenes iridescens Lebour, 1949 (Bruce, 1989;De Grave and Anker, 2009;Eilbracht and Fransen, 2015).…”