The Cephalocarida and Crustacean Phylogeny
1957; Oxford University Press; Volume: 6; Issue: 3 Linguagem: Inglês
10.2307/sysbio/6.3.112
ISSN1076-836X
Autores Tópico(s)Marine and fisheries research
ResumoCRUSTACEAN phylogeny has in I ~~ trigued zoologists for almost one hundred years. Despite the long sustained interest, this problem still remains largely unclarified due to the fact that each subclass forms a sharp, clearly defined taxonomic unit. Initial observations (Sanders, 1955) on the newly described crustacean Hutchinsoniella macracantha seemed to disclose affinities with the more primitive representatives of the subclasses Branchiopoda, Malacostraca and Copepoda. In an effort to indicate crustacean phylogeny as well as to illustrate the affinities of the Cephalocarida with the extant subclasses of Crustacea, this second paper will compare the Paleozoic arthropods, particularly the Crustacea, with the crustacean subclass Cephalocarida, as exemplified by Hutchinsoniella. Subsequent to the original description, which was based on eight individuals, 320 additional specimens, representing all free-living stages of Hutchinsoniella macracantha, have been collected from Long Island Sound, and more recently, Buzzards Bay, Massachusetts by this investigator. On the basis of this material a few observations on the life history of Hutchinsoniella and some additional pertinent details on cephalocarid anatomy can now be discussed. These animals are found subtidally in soft mud where the benthic fauna is dominated by the polychaete Nephthys incisa and the lamellibranch Nucula proxima. A description of development from hatching to maturity will be presented in a subsequent paper. Recent studies reveal that Hutchinsoniella is a hermaphrodite with entirely separate functional ovaries and testes (manuscript in preparation). Individuals are ovigerous from June through September and carry two ovisacs each attached by a short stalk to the limb rudiments of the genital segment. Each ovisac contains a single embryo. Observations in the laboratory indicate that a female can bear only three broods or six embryos during the breeding season. This is a remarkably small recruitment for a marine invertebrate.
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