Three copepod associates are reported from shallow-water ophiuroids at Belize, Central America. Two are cancerillid siphonostomatoids: Ophiopsyllus latus, new species, and Ophiopsyllus reductus. The third is a pseudanthessiid poecilostomatoid, Pseudanthessius deficiens.
The last species, previously known from Ophioderma cinereum, was also found on Ophioderma brevispinum. In contrast, species of Ophiopsyllus appear be to host-specific. Ophiopsyllus reductus is found exclusively on Ophiocoma echinata. Ophiopsyllus latus
is found only on Ophiocomella ophiactoides (with the exception of two doubtful records from Ophiocoma pumila). Previous records of Ophiopsyllus reductus on Ophiocomella ophiactoides are incorrect. Comparisons between Jamaican and Belizean populations of Ophiopsyllus
latus reveal similarities and differences and suggest that the parasitic effects of the species are minimal. On approximately 17–57% of O. ophiactoides examined there are 1–4 O. latus, which generally clasp the first or second arm joint near the edge of
the disk. They face toward the mouth of the host, possibly orienting to the currents emanating from the bursae or to food in the oral region. In Belize, only one instance of physical injury to the host was noted, although parasitic damage has been reported in Jamaica. Furthermore, a published
report that O. latus inhibits the sexual reproduction of the host appears to be unwarranted.
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