Postembryonic Apomorphies Proving the Monophyletic Status of the Copepoda
2004; Biodiversity Research Center, Academia Sinica; Volume: 43; Issue: 2 Linguagem: Inglês
ISSN
1810-522X
Autores Tópico(s)Marine Biology and Environmental Chemistry
ResumoPostembryonic characters were screened for their relevance for providing apomorphies for major maxillopodan groups with an emphasis on the Copepoda. The analysis used characters which have previously been suggested in the literature, as well as hitherto unemployed ones based on own observations. A cladogram based on postembryonic characters partly confirms and partly contradicts previous hypotheses about phylogenetic relationships within/of the Copepoda, which are mainly based on adult characters. Hypothesized naupliar apomorphies confirm the monophyletic status of the Thecostraca, Copepoda, Podoplea, Harpacticoida Oligoarthra (the Harpacticoida Polyarthra were excluded from this comparison and treated separately due to their overall plesiomorphic character states), and Calanoida. A sister-group relationship based on naupliar characters is hypothesized for the Copepoda/Thecostraca. As for copepod nauplii, the following autapomorphies are suggested: 3-segmented antennule, 2 antennal coxal setae, 1-segmented antennal endopod, postmaxillar limb buds juxtaposed medially, legs 1 and 2 present at N VI, and 6 caudal setae. A swimming mode of locomotion is suggested to represent the underived mode of locomotion among copepod nauplii and results directly in naupliar feeding. The metamorphosis to the copepodid phase in particular is unprecedented among extant Crustacea: involving somite and limb addition, and transformation of limbs which become reduced, functional, or follow changes from a locomotive to a feeding function. This provides copepod ontogeny with a peculiar way of anagenetic development, including both the naupliar and the copepodid phase, which differs from those of other Crustacea in several respects.
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