Ecological Effects and Genetic Diversity of the Invading Rhizocephalan Parasite Loxothylacus panopaei in the Flatback Mud Crab Eurypanopeus depressus
Date of Award
Master of Science in Coastal Marine and Wetland Studies
Coastal and Marine Systems Science
Erin J. Burge
Juliana M. Harding
Kevin S. Godwin
The rhizocephalan barnacle Loxothylacus panopaei (Gissler, 1884) is a parasite of xanthid crabs. Infection results in parasitic castration and anecdysis of the host. Loxothylacus panopaei is invasive to the US Atlantic coast. The parasite's range was expanded by introduction of infected crabs to Chesapeake Bay in the mid-1960s, and now extends from Long Island Sound, New York to Cape Canaveral, Florida. Monthly flatback mud crab (Eurypanopeus depressus Smith, 1869) collections over 13 months (January 2012-January 2013) at three South Carolina locations found an overall parasite prevalence of 24.2% (391 of 1,615), and provided the first reports of L. panopaei at Waties Island, Murrells Inlet and North Inlet. North and South Carolina parasite DNA sequence analysis revealed the presence of four mitochondrial DNA cytochrome c oxidase subunit I (COI) haplotypes (one of which was a new haplotype), and indicates that the Carolina populations are the result of a range expansion from the original Atlantic coast introduction in Chesapeake Bay. To investigate ecological relationships between Eurypanopeus depressus hosts and their parasites, prey consumption was compared between parasitized (externa-bearing) and unparasitized (externa-lacking) E. depressus 8-13 mm carapace width. Parasitized crabs consumed significantly fewer (median = 2) mussels than unparasitized crabs (median = 4) over 72 hours (Kruskal-Wallis, H = 5.94, d.f. = 1, p = 0.02). Relationships between host size, parasite externa color, and developmental stages of the externa were examined. Of the total externae collected (n = 476), 35.5% were placed into the oldest (purple) developmental category. Size of L. panopaei externae tended to increase with increasing E. depressus carapace width (Spearman rank order correlation, p < 0.001, r = 0.65), suggesting that the externa exists based on the balance of two laws: (1) The parasitic externa must grow large enough to produce nauplii in amounts that will ensure infection of new hosts; and (2) the externa must remain small enough to allow host mobility to forage in between the small oyster crevices and avoid predation.
O'Shaughnessy, Kathryn A., "Ecological Effects and Genetic Diversity of the Invading Rhizocephalan Parasite Loxothylacus panopaei in the Flatback Mud Crab Eurypanopeus depressus" (2013). Electronic Theses and Dissertations. 39.