Identification, Taxonomic Redescription, and Phylogenetic/Phylogeographic Analyses of Parasitic Monogenoids of Cryptic Sphyrna spp. (Sphyrnidae) from the Southwestern Atlantic Ocean (South Carolina, USA)

Kaitlyn M. Dalrymple, Emanuel L. Razzolini

& Walter A. Boeger

Monogenoid parasites were collected and preserved in ethanol or formalin between 2018-2019 from the gills of sympatric neonates of two cryptic species of hammerhead sharks (Sphyrnidae), Sphyrna lewini and Sphyrna gilberti, and their hybrids captured from a nursery off the coast of South Carolina by South Carolina Department of Natural Resources.These parasites were subsequently identified as two species of Erpocotyle (Hexabothriidae) and one species of Loimosina (Monocotylidae) - they have been redescribed morphologically and confirmed using molecular sequencing. Prevalence data for each family was collected and confirmed that Loimosina wilsoni was the only monogenoid to not infect all three host species (i.e. it was not found to infect S. gilberti, but was found in S. lewini and hybrids). Fragments of cytochrome oxidase 1 mitochondrial DNA (COI) were sequenced for specimens of L. wilsoni and analyzed to identify signals of host-range expansion via formation of distinct lineages in hybrid hosts (a result of Founder’s effect or selection), however this signal was not detected and thus we conclude that L. wilsoni uses both hybrids and S. lewini indiscriminately. Fragments of 18S rDNA have been sequenced for our Erpocotyle spp. specimens and a phylogeny is being constructed using these and sequences from other members of the family (Hexabothriidae) obtained from GenBank, to be compared with a morphological phylogeny. All literature on the family Hexabothriidae is being reviewed and data is being compiled to construct a phylogeography of the parasites based on host range data.