The amphipod genus Alexandrella (Amphipoda, Stilipedidae): taxonomic status, allometric growth and description of two new species

Abstract

Two new species of the genus Alexandrella are described: A. mandibulata and A. martae. One species, A. mixta, is considered a junior synonym of the type species A. dentata. The genus now comprises six species, all of which are restricted to either the Antarctic or sub‐Antarctic region or the South Pacific. Oostegites are observed to be present on pereopod 1 in two Alexandrella species. This is a novel morphological trait among the Amphipoda. Developmental information is presented for two other Alexandrella species, in which the mandibular incisor is seen to be modified from strongly toothed in marsupial young to totally smooth in mature specimens. Also the armature dorsally on their body and the morphology of the telson undergo conspicuous allometric changes. A key to all known Alexandrella species is provided.

Keywords:

• Alexandrella
• allometry
• Amphipoda
• Stilipedidae
• taxonomy

Acknowledgements

We are grateful to Ellen Beck for her help with the illustrations and to William Moser (NMNH, Washington, DC), Prof. De Broyer (IRSCNB, Belgium) and Dr Coleman (Zoological Museum, Berlin) for their help in providing material. Prof. Geoff Moore and one anonymous referee offered constructive and useful criticism on earlier drafts of the manuscript.