The shrimp superfamily Sergestoidea: a global phylogeny with definition of new families and an assessment of the pathways into principal biotopes.

A. L. Vereshchaka

doi:10.1098/rsos.170221

Abstract

The phylogenetic analysis of Sergestoidea based on 253 morphological characters and encompassing all 99 valid species confirmed all previously recognized genus-level clades. Analysis retrieved five major robust clades that correspond to families Luciferidae, Sergestidae, Acetidae fam.n., Sicyonellidae fam.n. and Petalidiumidae fam.n. Synonymy, emended diagnoses and composition of revealed family-level clades are provided. Three types of morphological characters were important in the phylogeny of the Sergestoidea: general external characters, copulatory organs, and photophores. Novel metrics to quantify the contribution of these character types were tested. General external characters were significant in supporting the major clades (80% of the families and nearly half of the genera). Copulatory organ characters and photophores greatly supported the medium-level clades: Lucifer, Belzebub, Petalidium, Neosergestes, Challengerosergia (copulatory organ characters) and Lucensosergia, Challengerosergia, Gardinerosergia, Phorcosergia (photophores). An evolutionary model of the Sergestoidea showing their pathways into their principal biotopes is proposed: the major clades evolved in a vertical direction (from epi- to bathypelagic); further divergence at the genus level occurred within vertical zones in a horizontal direction, with the invasion of the benthopelagic and neritic (shelf and estuarine) habitats and speciation within these domains.

Highlights

The order Decapoda includes two suborders, Pleocyemata and Dendrobranchiata, the latter encompassing two superfamilies, Sergestoidea and Penaeoidea
The material used for this study is from the extensive collections of pelagic crustaceans taken during the Danish ‘Dana I’ (1920–1922) and ‘Dana II’ (1928–1930) Expeditions stored at the Natural History Museum of Denmark; some type specimens were requested from other museums
The present data show that the family Luciferidae is a natural group, whilst the remainder of the Sergestoidea

Summary

Introduction

The order Decapoda includes two suborders, Pleocyemata and Dendrobranchiata, the latter encompassing two superfamilies, Sergestoidea and Penaeoidea. The Sergestoidea hereby represents a significant part of the decapod phylogenetic tree, while phylogeny and even taxonomy (e.g. the proper position of Lucifer) within this superfamily remains unclear [1]. This is partly because of the poorly resolved systematics of two speciose groups (genera) in the family Sergestidae (see details in [2,3,4]), previously known as Sergestes and Sergia (over 70 species). Species of the Sergestidae are among the most common in many marine ecosystems and important targets of fisheries in some areas [5,6,7] Despite their importance, the Sergestoidea are still poorly understood with regard to higher level classification and phylogenetic relationships. The phylogenetic study of the whole Sergestoidea at species level can be completed by assembling the rich dataset of morphological characters (approx. 250) that have been coded during previous studies, and this is the first objective of this paper

Objectives

Methods

Results

Conclusion