Larval Hysterothylacium sp. (Nematoda, Anisakidae) and trematode metacercariae from the amphipod Paracorophium excavatum (Corphiidae) in New Zealand

Abstract

Previously undescribed fourth-stage larvae of anisakid nematodes were found in the haemocoel of the amphipod Paracorophium excavatum (Thomson, 1884) (Corophiidae) in New Zealand. Morphological examination by light microscopy showed that the worms belonged to a species of Hysterothylacium Ward et Magath, 1917, based on several characters including the presence of interlabia, the location of the excretory pore posterior to the nerve ring, and the characteristics of the intestinal caecum and ventricular appendix. Interestingly, several male specimens showed precocious sexual development. This is the first record of fourth larval stage and precocious adult male specimens of Hysterothylacium in an invertebrate host, as well as the first record of anisakid larvae in New Zealand crustaceans. In addition, metacercariae of two trematode species, Coitocaecum parvum and Microphallus sp., are recorded for the first time from the amphipod P. excavatum.

Hysterothylacium larvae (Nematoda, Anisakidae) in the freshwater mussel Diplodon suavidicus (Lea, 1856) (Mollusca, Unioniformes, Hyriidae) in Aripuanã River, Amazon, Brazil

“…However, these authors investigated the gastropod mollusc Gundlachia radiata (Guilding, 1828) and identified the larvae as belonging to the Contracaecum genus. Luque et al (2007) recorded the presence of Hysterothylacium larvae in amphipods in New Zealand. However, the prevalence found by Thiengo et al (2000) and Luque et al (2007) were low compared to this study.…”

“…Luque et al (2007) recorded the presence of Hysterothylacium larvae in amphipods in New Zealand. However, the prevalence found by Thiengo et al (2000) and Luque et al (2007) were low compared to this study. From the 65 Gundlachia radiata specimens collected, only three were parasitized by Contracaecum larvae and with a maximum intensity of two larvae per host.…”

“…From the 65 Gundlachia radiata specimens collected, only three were parasitized by Contracaecum larvae and with a maximum intensity of two larvae per host. From the amphipods collected by Luque et al (2007), around one to 10% of the hosts were parasitized, depending on the sampling site, with one or two nematodes being found per host.…”

“…According to Luque et al (2007) adult Hysterothylacium are found parasitizing fish. The larvae can be found in marine and freshwater fish as well as some invertebrates that, in this case, act as intermediate hosts.…”

Guide to the Parasites of Fishes of Canada Part V: Nematoda

“…In common with some other aquatic ascaridoids, species of Hysterothylacium have evolved remarkable flexibility in completing the life-cycle. For example, Luque et al (2007) reported L4 of Hysterothylacium sp. in the haemocoel of amphipods, Paracorophium excavatum, from New Zealand waters.…”