New species of the genera Synapseudes and Cyclopoapseudes with notes on morphological variation, postmarsupial development, and phylogenetic relationships within the family Metapseudidae (Crustacea: Tanaidacea)

Abstract

In addition to the characters cited in the original description of the Metapseudidae the genera of this family share the presence of mandibular molar setae; a low level of sexual dimorphism; and the presence of oostegites on pereopods 1I-V only, all oostegites participating in the formation of the marsupium. The family can no longer be considered to be a strictly warm-water taxon; one species is now known from the southern tip of South America. Metapseudes and Synapseudes are most closely related, and both show considerable affinity with Apseudomorpha; Cyclopoapseudes is appreciably different morphologically and stands apart phylogenetically from these taxa. Metapseudes aucklandiae, the single species of the type genus, is discussed; a lectotype is designated; and additional information and figures are added to the original description. A new species of Synapseudes is described; the variable structure of the pleon in this morphologically aberrant genus is reviewed; and pleopods, found primarily among the males, are reported for Synapseudes for the first time; these resemble the reduced pleopods of Metapseudes and Apseudomorpha. Chelae of unequal size, known for several species of Synapseudes and formerly thought to be restricted to males, also occur in females. The postmarsupial development of Synapseudes is partially elucidated; the sexes are recognizable from very early stages, and there is no clear evidence for protogyny or protandry. A second species of Cyclopoapseudes is described in detail; exopods are present on pereopods I and II in this genus, contrary to previous information.