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

Abstract

Petalidium (Decapoda: Dendrobranchiata: Sergestidae) is one of the least known genera of pelagic decapods. On the basis of collections taken during Dana Expedition 1920–22 and 1928–30, we revise the morphology of the genus. To understand the taxonomic status and position of Petalidium within other sergestid genera, we used 150 morphological characters (127 binary, 23 multistate). Three recognized species of Petalidium and eighteen type species representing all other genera of Sergestidae were included as terminals. Characters were polarized using Lucifer typus (Luciferidae: Sergestoidea) and Aristeomorpha foliacea (Aristeidae: Penaeoidea) as the outgroups. Phylogenetic analysis revealed monophyly of Petalidium comprising three species: Petalidium foliaceum Bate, 1881; Petalidium obesum (Krøyer, 1859); and Petalidium suspiriosum Burkenroad, 1937. Phylogenetic analyses also revealed possible monophyly of the clade including 15 new genera of the former Sergia and Sergestes and the position of Lucifer (family Luciferidae) within the clade Sergestidae. These results highlight necessity of future phylogenetic analyses of the remaining genera Lucifer, Acetes, Peisos, and Sicyonella involving all species of these genera and promise interesting changes for the classification of Sergestoidea. Morphological trends within Sergestoidea are discussed, and an emended diagnosis of Petalidium and diagnoses of the species it includes are given. All species are illustrated and biology of the genus is discussed. Keys to species of Petalidium based upon new information are presented. © 2015 The Linnean Society of London

A phylogenetic study of krill (Crustacea: Euphausiacea) reveals new taxa and co‐evolution of morphological characters

“…The use of characters of the petasma had a major impact on the result of the morphology‐based phylogenetic analysis. The same has been shown previously for other pelagic crustaceans (Vereshchaka et al., , , c, , b; Vereshchaka and Lunina, ), so the inclusion of characters of the petasma is highly recommended for phylogenetic analyses whenever possible. Indeed, the use of petasma characters in the Euphausiacea matrix doubled the number of supported clades.…”

“…In addition to standard morphological characters, we also include for the first time copulatory organ characters (e.g. of the petasma) for Euphausiacea, as such information has proven phylogenetically important for other pelagic crustaceans (Vereshchaka et al., , , c, , b; Vereshchaka and Lunina, ). We also analyse sequences of four genes and compare the resulting molecular and morphological trees.…”

A phylogeny-based revision of the family Luciferidae (Crustacea: Decapoda)

“…The character states are figured in Vereshchaka (, ), Vereshchaka et al . (), and Vereshchaka & Lunina (). We used 169 modified characters (22 new – see Appendix S2).…”

“…We used the data matrix of Vereshchaka & Lunina () as a basis for this work. The character states are figured in Vereshchaka (, ), Vereshchaka et al .…”

“…The current knowledge of the morphology and phylogeny of Luciferidae is in the same state as it was a century ago, which is unfortunate as many species are highly abundant and play a significant role in epipelagic ecosystems (Woodmansee, ; Bowman & McCain, ; Zimmerman, ; Lee, Omori & Peck, ; Antony, ; Teodoro et al ., ). Recent studies of several genera in the sister family Sergestidae (Vereshchaka, Olesen & Lunina, ; Vereshchaka & Lunina, ) yielded a data matrix with 150 morphological characters and resulted in the establishment of eight new sergestid genera. This matrix has been used in the present paper as a basis for a phylogenetic analysis and a revision of the classification of Luciferidae.…”