Global diversity and phylogeny of pelagic shrimps of the former genera Sergestes and Sergia (Crustacea, Dendrobranchiata, Sergestidae), with definition of eight new genera.

Alexander L Vereshchaka,Jørgen Olesen,Anastasia A Lunina,John F Valentine

doi:10.1371/journal.pone.0112057

Abstract

We revise the global diversity of the former genera Sergia and Sergestes which include 71 valid species. The revision is based on examination of more than 37,000 specimens from collections in the Natural History Museum of Denmark and the Museum of Natural History, Paris. We used 72 morphological characters (61 binary, 11 multistate) and Sicyonella antennata as an outgroup for cladistic analysis. There is no support for the genera Sergia and Sergestes as they have been defined until now. We define and diagnose eight genera of the former genus Sergia (Sergia and new genera Gardinerosergia, Phorcosergia, Prehensilosergia, Robustosergia, Scintillosergia, Challengerosergia, and Lucensosergia) and seven genera of the former genus Sergestes (Sergestes, Deosergestes, Eusergestes, Allosergestes, Parasergestes, Neosergestes, and a new genus Cornutosergestes). An identification key is presented for all genera of the family Sergestidae. The phylogeny of Sergestidae is mainly based on three categories of characters related to: (1) general decapod morphology, (2) male copulatory organs, and (3) photophores. Only simultaneous use of all three character types resulted in a resolved tree with minimal Bootstrap support 75 for each clade. Most genera are interzonal mesopelagic migrants, some are benthopelagic (Scintillosergia, Lucensosergia), bathypelagic (Sergia), or epipelagic (Cornutosergestes). Within each of meso- and benthopelagic genera there is one species with panoceanic distribution, while most species ranges are restricted to a single ocean. The genera demonstrate two different strategies expressed both in morphology and behavior: protective (Eusergestes, Sergestes, Cornutosergestes, Prehensilosergia, Scintillosergia, Lucensosergia, Challengerosergia, Gardinerosergia, Robustosergia, Phorcosergia, Sergia) and offensive (Neosergestes, Parasergestes, Allosergestes, Deosergestes).

Highlights

The decapod suborder Dendrobranchiata (Crustacea, Malacostraca) includes shrimps that have an important role both ecologically and economically in marine and estuarine ecosystems
Milne-Edwards, 1830 (Fig 1b) and synapomorphies: either general morphological (Sergia) Stimpson, 1860 (Fig. 1c), together most certainly form a monophyletic group based on a number of synapomorphies such as the presence of an organ of Pesta and dermal photophores [4] – [8] and comprise 71 species, i.e. two-thirds of all known recent sergestids
The taxonomic status of Sergestes and Sergia and the phylogenetic relationship of their constituent species are the object of the present paper

Summary

Introduction

The decapod suborder Dendrobranchiata (Crustacea, Malacostraca) includes shrimps that have an important role both ecologically and economically in marine and estuarine ecosystems. Species of the Sergestidae are among the most common in many ecosystems [2] – [3] and important objects of fisheries in some areas, such as Sergestes lucens in Japan (Fig. 1a). Despite their importance, the sergestids are still poorly understood with regard to higher level classification and phylogenetic relationships. Later researchers mostly followed Yaldwyn’s classification at least until the mid-1970s, when Omori [6] reviewed the differences between Yaldwyn’s subgenera Sergestes and Sergia both with respect to morphology and ontogeny and raised their taxonomic status to the generic level. Most recent authors have followed the separation of the two genera (for example, [7] – [8], [18])

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Conclusion