Juvenile Ascarophis (Spirurida: Nematoda) parasitizing intertidal decapod crustacea in California: with notes on prevalence and effects on host growth and survival

Inhibition of the growth and reproduction of the porcellanid crabPachycheles rudisby the bopyrid isopod,Aporobopyrus muguensis

A population approach was employed to study the effects of a bopyrid isopod,Aporobopyrus muguensis, on the growth and reproduction of its anomuran host,Pachycheles rudis. Indirect evidence, provided by the size-specific prevalence pattern, and direct evidence, provided by laboratory moult frequencies and moult-stage data, indicated that the frequency of moulting was reduced among parasitized crabs. Moult increments of parasitized crabs were less than those of non-parasitized crabs. Although parasitized femaleP. rudiswere able to reproduce, their fecundity was substantially reduced. Parasitized female hosts appeared to be delayed in their attainment of sexual maturity. Once mature, these crabs produced significantly smaller size-specific clutches than those produced by non-parasitized female crabs. Because fecundity increases with size inP. rudis, the slower growth rates of parasitized female hosts may further limit their fecundity. Potential mechanisms by whichA. muguensislimits the growth and reproduction ofP. rudisare discussed.

Larval Spirurida (Nematoda) from the crab Macrophthalmus hirtipes in New Zealand

Previously undescribed third-stage larvae of two species of Spirurida were found in the haemocoel of the stalk-eyed mud crab Macrophthalmus hirtipes (Heller) (Ocypodidae) in New Zealand. Examinations by light and scanning electron microscopy showed that the larger larvae (about 7 mm long) belonged to a species of Ascarophis van Beneden, 1871 (Cystidicolidae), the genus including parasites of fishes, whereas the smaller larvae (about 4-5 mm long) belonged to the Acuariidae, a family with species parasitic as adults mostly in aquatic birds. In a sample of 82 specimens of M. hirtipes collected in July 2002 from Papanui Inlet, on Otago Peninsula, South Island, 74 crabs (90.2%) were infected with larval nematodes with an intensity of 1-18 (mean 4.6) nematodes per crab; no distinction between nematode species was made in these estimates, although juvenile Acuariidae greatly outnumbered larval Ascarophis. Apparently, crabs play a role as intermediate hosts of these nematode species. This is the first record of larval representatives of Cystidicolidae and Acuariidae from invertebrates in the Australasian Region.

Nectonema zealandica n. sp. (Nematomorpha: Nectonematoidea) parasitising the purple rock crab Hemigrapsus edwardsi (Brachyura: Decapoda) in New Zealand, with notes on the prevalence of infection and host defence reactions

A new species of marine hairworm, Nectonema zealandica (Nematomorpha: Nectonematoidea), is described from the purple rock crab Hemigrapsus edwardsi Hilgendorf from the South Island, New Zealand. This is the first record of Nectonema in the South Pacific Ocean and the southernmost locality for the genus. The description is based on juveniles and pre-adults taken from crabs. The new species is characterised by its stomal structure, presence of four cephalic papillae, mesenchyme arranged in eight lobes in pre-adults, insertion of muscle layer increasing body diameter at the septum and translucent anterior chamber. Data on the prevalence of infection over a three-year period, rates of parasitism in relation to host sex and size, and host defence reactions are presented. A list of all reported hosts of nectonematids is included.