Global Diversity and Phylogeny of Pelagic Shrimps of the Former Genera Sergestes and Sergia (Crustacea, Dendrobranchiata, Sergestidae), with Definition of Eight New Genera

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).

Phylogeny and taxonomy of the enigmatic genusPetalidium(Decapoda, Sergestidae), with biological remarks

“…The states of characters are illustrated in Vereshchaka (), Vereshchaka et al . () and in Figures of the present study. The data matrix is presented in the Supporting information (http://onlinelibrary.wiley.com/doi/10.1111/zoj.12243/suppinfo).…”

“…Seventy‐six characters are almost identical to those in Vereshchaka (, ) and Vereshchaka et al . (); seventy‐four are novel and marked by an asterisk in the Supporting information (http://onlinelibrary.wiley.com/doi/10.1111/zoj.12243/suppinfo). The states of characters are illustrated in Vereshchaka (), Vereshchaka et al .…”

“…The family comprises: (1) seventy‐one species of the former genus Sergestes sensu H.J.H. Hansen (, ), now split into fifteen genera (Vereshchaka, Olesen & Lunina, ); (2) fourteen species of Acetes (Omori, ); (3) three species of Petalidium (Hansen, , ; Burkenroad, ); (4) three species of Sicyonella (Hansen, ; Fukuoka, Tamaki & Kikuchi, ); and (5) one species of Peisos (Burkenroad, ).…”

“…The detailed morphology of the genus was originally reconstructed from available material. The morphology of P. obesum was detailed by Hansen (), whose material fortunately included one well preserved immature male, and that of P. suspiriosum by Wasmer () who based his description on extensive collections taken off Oregon (all the individuals used were imperfect but it was possible to assemble undamaged parts from among them). The presence of three different types of characters that demonstrate nonparallel phylogeny (Vereshchaka et al ., ): (i) traditional external body characters used in carcinology (spines, setae, etc. ); (ii) a male clasping organ (modified part of Antenna I); and (iii) a petasma (male copulatory organ), which may differ in similar species and be similar in distant species.…”

Geographical distribution of pelagic decapod shrimp in the Atlantic Ocean

“…9), a distribution similar to that of the myctophid fish Benthosema glaciale . Vereshchaka (2009) recognized the Southern Ocean population as a separate species that he named Eusergestes antarcticus, but the species is not accepted in the World Register of Marine Species (http:// www.marinespecies.org/, accepted 5 December 2014).…”