Nicole A M Atherley

The Apicomplexa are obligate unicellular parasites found in terrestrial and aquatic environments. Nematopsis are found infecting marine invertebrates in a life cycle involving mollusks and crustaceans. In the present study, mantle and muscle tissues from nerite gastropods were microscopically examined for Nematopsis using wet mounts and histology. Oocysts contained one single sporozoite surrounded by an ellipsoidal wall and were surrounded by a parasitophorous vacuole within a host phagocyte. Length and width of fresh oocysts were measured and compared between host species. DNA was extracted from infected tissue, and regions of the rRNA gene were amplified using novel primers. Nematopsis‐infected tissues from scallops from Argentina and Scotland were used as controls. The sizes of oocysts observed in nerite hosts from Saint Kitts were not significantly different. DNA sequences of Nematopsis isolated from nerite hosts in this study were identical and phylogenetically related to sequences obtained from scallops. Bayesian and maximum likelihood phylogenetic analyses robustly place the Nematopsis DNA sequences from this study with Nematopsis from scallops in Florida and members of the family Porosporidae. We conclude that marine Nematopsis will group within this clade or within the Porosporidae. We have provided specific oligonucleotide primers to assist with the molecular study of the Porosporidae.

The Caribbean spiny lobster, Panulirus argus (Latreille, 1804), is an important resource in the Western Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. A nemertean egg predator of P. argus, Carcinonemertes conanobrieniSimpson, Ambrosio & Baeza, 2017, was recorded in Florida in 2017 and Colombia in 2018. This study sought to investigate the presence of C. conanobrieni in P. argus in Saint Kitts and Nevis, eastern Caribbean Sea. Nemerteans were observed in the brood masses of P. argus. Molecular techniques confirmed its presence in the P. argus population on Saint Kitts. Egg, juvenile, and adult stages of C. conanobrieni and of an undescribed Carcinonemertes sp. were found in the brood masses of 27 of 31 (87%) ovigerous P. argus. Differences in the shape of the nemertean egg masses (string versus spherical arrangement) were confirmed as two distinct species of Carcinonemertes Coe, 1902 using molecular analyses. The juvenile stage of the undescribed Carcinonemertes sp. was detected in the gills of 72 of 320 (23%) of the P. argus individuals from Saint Kitts. The prevalence of branchial nemertean infestation was not significantly different among male and female P. argus. Female lobsters with ovaries in early stages of gonadal maturation were more likely to have branchial nemerteans relative to those with ovaries in late stages of maturation, suggestive of nemertean migration from gills to egg mass once the host oviposits. This is the first report of C. conanobrieni in the Caribbean spiny lobster from the eastern Caribbean, which is approximately 1,300 miles from Florida and 1,000 miles from Colombia. This is also the first report of an undescribed nemertean worm in P. argus. The high prevalence of Carcinonemertes spp. in P. argus raises concern for the extent to which these egg predators may be impacting P. argus in Saint Kitts, an important fishery on the island.