Research study 1
Brittle stars Amphiodia urtica in Santa Monica Bay, California host a gut-inhabiting parasitic coppod Caribeopsyllus amphiodiae. No aspects of its biology are known. Photo of A. urtica courtesy Bill Austin, Khoyotan Marine Laboratory, Victoria.
NOTE the authors have named this previously undescribed copepod species after the genus name of its host
NOTE thanks to rearing experiments by researchers at the Natural History Museum and Hyperion Treatment Plant in the Los Angeles area, we actually do know a lot about this most unusual parasite. After 5mo in the host’s stomach (in Petri-dish culture at 15oC), during which time gonads develop, the larvae metamorphose to the first of 5 non-feeding copepodite stages, leading after only about 3d to the adult, both sexes non-feeding. At some point, either late-stage copepodite or adult, the parasite emerges from the host, probably via its mouth. Because the host brittle star usually lies buried in shallow sediment, parasite departure may occur when the host emerges to the sediment surface, or possibly it occurs by the parasite leaving the stomach and crawling upwards through the mud. The adults live freely for only 2wk. Eggs appear in female ovisacs after just 1d. These hatch to naupliar larvae within about a week (6 naupliar stages altogether), and these then transform to metanauplii (see photograph). Infestation of a new host brittle star Amphiodia urtica likely occurs during late metanauplius stage, perhaps involving burrowing from open water into the sediment containing the host. The metanauplius is negatively buoyant and appears able to crawl only weakly. Usually only a single metanauplius is present within each Amphiodia. Within the host’s stomach the metanauplii (up to about 1mm in length) feed on stomach tissue, gastric secretions, or the host’s food, but appear not to inflict damage on the host. The authors suggest that the long larval life relative to that of the adult is an example of paedomorphosis, an evolutionary process involving delayed metamorphosis and early onset of reproductive maturity. Breeding is throughout the year in the southern California area. 5. Photograph of metanauplius courtesy the authors.
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