A New Shrimp Genus (Crustacea: Decapoda) from the Deep Atlantic and an Unusual Cleaning Mechanism of Pelagic Decapods

Alexander Vereshchaka,Dmitry Kulagin,Anastasiia Lunina

doi:10.3390/d13110536

Alexander Vereshchaka, Dmitry Kulagin + Show 1 more

Open Access

https://doi.org/10.3390/d13110536

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Abstract

The deep sea is the largest biome on Earth and hosts the majority of as yet undescribed species; description of these may trigger a new mindset about evolution and function of characters. We describe and diagnose a new genus and species Sclerodora crosnieri sp. nov. belonging to the superfamily Oplophoroidea. We examined and coded 81 characters for morphological analyses and used four gene markers for molecular analyses involving the new taxon and representatives of all other genera of Oplophoroidea. Retrieved morphological and molecular trees were similar and suggested that the new genus is a sister group to Hymenodora and both form a clade sister to the rest of Acanthephyridae. We provide an amended key to all genera of Oplophoroidea. We found an unusual chelate structure on the dactyl of the fifth pereopod, tested and confirmed a hypothesis that this structure is common for the whole family Acanthephyridae. We suggest that this derived structure is linked to an active cleaning of branchia—a function associated with chelipeds in some other carid shrimps. Convergent chelate structures are likely efficient for cleaning branchia, whichever appendage is adapted for these functions. In Oplophoridae (sister to Acanthephyridae), cleaning function is carried out by well-developed epipods.

Highlights

The deep sea is the largest biome on Earth; the deeppelagic domain accounts for nearly 94% of the habitable volume of the World Ocean [1], whereas only 16% of all named species on Earth are marine [2]
The deep sea is the largest biome on Earth and hosts the majority of as yet undescribed species; description of these may trigger a new mindset about evolution and function of characters
Convergent chelate structures are likely efficient for cleaning branchia, whichever appendage is adapted for these functions

Summary

Introduction

The deep sea (i.e., below 200 m in depth) is the largest biome on Earth; the deeppelagic domain accounts for nearly 94% of the habitable volume of the World Ocean [1], whereas only 16% of all named species on Earth are marine [2]. An alternative mechanism (an active one) is linked to grooming chelipeds: one pair is generally used in body grooming and cleaning the gills when epipod-setobranch complexes have been lost [5,6]. The specimen has a very specialized dactyl of the fifth pereopods: short and forming a very characteristic chelate structure We hypothesized that this character may mirror an alternative active cleaning mechanism involving the fifth pereopod, not the chelipeds as in other carids. In order to test this hypothesis, we checked structure of epipods and fifth pereopods in all other species of the superfamily Oplophoroidea, ran phylogenetic analyses, and mapped these characters on the resulting trees. Oplophoroidea was recently revised on the basis of both morphological and molecular analyses ([7,9,10,11]) and the finding of an undescribed genus and species belonging to this superfamily is surprising

Morphological Analysis

Morphological Analyses and Supporting Synapomorphies

Molecular Analyses

Taxonomic Implication

Key to Genera of Oplophoroidea

A New Suggested Cleaning and Grooming Mechanism