Lunina A.A., Kulagin D.N., Vereshchaka A.L.* 2025. Evolutionary traits of planktonic Eucarida // Invert. Zool. Vol.22. No.2: 340–359 [in English].
Institute of Oceanology of Russian Academy of Sciences, Nakhimov Prospekt 36, Moscow 117997 Russia.
Anastasiia Lunina: yalunina@list.ru ORCID https://orcid.org/000-0002-1105-8027
Dmitry Kulagin: kulagin.dima@gmail.com ORCID https://orcid.org/0000-0002-5521-8598
Alexander Vereshchaka: alv@ocean.ru ORCID https://orcid.org/0000-0002-6756-2468
* Сorresponding author
doi: 10.15298/invertzool.22.2.09
ABSTRACT: The pelagic realm is the most voluminous biome on Earth and a deeper insight into evolutionary traits of dominant planktonic taxa such as Eucarida (Decapoda and Euphausiidae) is indispensable to understanding evolution on our planet. We recorded synapomorphies of all major fully planktonic eucarid groups — Euphausiidae, Oplophoroidea, Pasiphaeoidea, Sergestoidea, and Benthesicymidae — at three clade levels corresponding to families, genera, and species groups. We divided morphological synapomorphies into eight groups and examined which of them provided evolutionary success in the pelagic or benthopelagic biotopes. Morphological diversification was mainly driven by copulatory structures in Benthesicymidae, pereopods and copulatory structures in Euphausiidae and Sergestoidea, carapace, pleon, and mouthparts in Oplophoroidea and Pasiphaeoidea. Proportional contribution of these characters to diversification was unique for each taxon. Morphological characters coevolve as three functional units: copulatory structure (mating); photophores, antennula, and eye (perception and communication); mouthparts, pereopods, pleon, and carapace (feeding and defense). A benthopelagic ambit for a diverged clade may be predicted by the presence of pleon-linked synapomorphies. Species group level clades are characteristic for pelagic biotopes where niche diversity is low and number of habitats is limited due to relatively homogenous environment, which canalizes within-generic evolution through infrageneric taxa such as species groups. In contrast, evolution in the ecologically more diverse benthopelagic biotope occurs through adaptations to ecologically diverse habitats and through speciation without certain infrageneric taxa.
KEY WORDS: Decapoda, Eucarida, evolutionary traits, morphological analysis, morphological characters, krill, phylogeny, planktonic groups.