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A new tantulocaridan, Itoitantulus misophricola Huys, Ohtsuka et Boxshall gen. et sp. nov., (Crustacea) ectoparasitic on a hyperbenthic misophrioid copepod, Misophriopsis okinawensis Ohtsuka, Huys, Boxshall et Itô, 1992, is described from Kume Island, Okinawa, South Japan. This is the first record of Tantulocarida from the North Pacific region. The new tantulocaridan is placed in the Deoterthridae on account of the 1-segmented abdomen, the absence of a rostrum in the tantulus larva, the segmentation of the rami of the thoracopods, and the position of the expanded trunk sac in the male. The new genus can be distinguished from other deoterthrid genera by the absence of a lobate endite of thoracopod 1 and the presence of the dorsally directed, recurved spine on the apex of the sixth thoracopod in the tantulus larva.

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Comparative analysis of the development of antennulary segmentation and setation patterns across six orders of copepods revealed numerous common features. These features are combined to produce a hypothetical general model for antennulary development in the Copepoda as a whole. In this model most compound segments result from the failure of expression of articulations separating ancestral segments. In adult males, however, compound segments either side of the neocopepodan geniculation are typically formed by secondary fusion at the last moult from CoV (stage 5). The array of segments distal to the articulation separating segments XX and XXI is highly conserved both in ontogeny and phylogeny: typically the distal segmentation of the adult female is already present in the CoI. A maximum of three setae is added to the distal array during the entire copepodid phase. This morphological conservatism is interpreted as evidence of the functional continuity of the distal setal array as a mechanosensory system providing early warning of approaching predators. Sexual dimorphism typically appears late in development; the male undergoing modifications especially at the final moult to sexual maturity. These modifications include the formation of the neocopepodan geniculation at the XX to XXI articulation and, in some orders, the formation of a proximal geniculation at the XV to XVI articulation. A proximal geniculation is reported here from the Calanoida for the first time. The geniculations allow the male to grasp the female during any mate guarding and during spermatophore transfer. Particular setae on segments either side of the neocopepodan geniculation are modified as basally fused spines in at least some representatives of the Calanoida, Misophrioida, Cyclopoida, Harpacticoida and Siphonostomatoida. The antennulary chemosensory system, comprising primarily the aesthetascs, is enhanced at the final moult in many male copepods. In planktonic copepods this enhancement may take the form of a doubling of the aesthetascs on almost every antennulary segment, as in the eucalanid calanoids, or of an increase in size of existing aesthetascs, as in the siphonostomatoid Pontoeciella, or of the transformation of possibly originally bimodal, seta–like elements into distally thin–walled, more aesthetasc–like elements, as in some calanoids, harpacticoids and poecilostomatoids. Enhancement of the chemosensory capacity of adult males appears to be linked with their mate–locating role. Copepods inhabiting the open–pelagic water column are more likely to exhibit enhancement of the chemosensory system than neritic or benthic forms. Enhancement may confer a greater sensitivity to chemosensory signals, such as pheromones produced by receptive females, which may retain their directional information at lower concentrations and, therefore, for longer periods, in oceanic waters than in more turbulent neritic waters. Aesthetascs appear to be more evolutionarily labile than other setation elements, apparently being lost and regained within well–defined lineages. Caution is urged in the use of aesthetasc patterns in phylogenetic analysis. The ontogenetic analyses suggest that the timing of expression of intersegmental articulations during development may in future provide the most informative characters for phylogenetic study, rather than either segment numbers or the patterns of fused or undivided segments.

A new misophrioid copepod Misophriopsis okinawensis (Crustacea) is reported from Kume Island. Okinawa, South Japan. A full description of the new misophrioid is presented together with supplementary notes on the males of Misophria pallida Boeck, 1864. Consideration of the phylogeny of the new species led to a reassessment of the affinities between all the named species of Misophria Boeck, 1864 and Misophriopsis Boxshall. 1983. A new genus, Stygomisophira, is recognised based on Misophria kororiensis Boxshall et Iliffe, 1987. Diagnoses are presented of all three genera.

The deep-sea planktonic copepod Paralubbockia longipedia is redescribed from the type specimens, and a new family of Poecilostomatoida is proposed to accommodate it. The Paralubbockiidae fam. nov. is characterized by two unique plesiomorphies, the ventrally located fifth legs and the retention of a separate maxillulary palp, and by the apomorphic states of the endopods of the swimming legs and of the antenna. The sister group of the Paralubbockiidae is identified as the family Oncaeidae. These are the only two poecilostomatoid families that have retained a vestige of the geniculation mechanism in the antennules of the male. The genus Laitmatobius Humes is here regarded as incertae sedis within the lineage comprising the Oncaeidae and the Parulubbockiidae.