Loxothylacus panopaei

History of Spread

Loxothylacus panopaei was described in 1884 from specimens on the xanthid crab Panopeus lacustris (then known as P. herbsti), taken from Tampa FL (Gissler 1884; Hines et al. 1997). Its native range extends through the Gulf of Mexico, into the Caribbean at Venezuela (Boschma 1955), and northward on the Atlantic coast to Cape Canaveral FL (Hines et al. 1997). The reported host range of L. panopaei includes at least 9 species of xanthid crabs: Eurypanopeus depressus (Flatback Mud Crab), Dyspanopeus sayi (Say's Mud Crab), Panopeus lacustris (Knotfinger Mud Crab), P. obessus, P. occidentalis (Furrowed Mud Crab), P. simpsoni (Oystershell Mudcrab), Rhithropanopeus harrisi (Harris Mud Crab), Tetraplax quadridentatus, andTetraxanthus rathbunae (Inflated Mud Crab) (Hines et al. 1997). In 2006, L. panopaei was reportedly found on a grapsid crab (Aratus pisoniis in Recife, Brazil, extending its range southward, possiby introduced by shipping (Farrapeira et al. 2008). However, genetic analysis of L. panopaei populations indicate that this name refers to a complex of lineages or cryptic species. Among Atlantic and Gulf populations, the lineage infecting R. harrisii and E. depressus (ER), and introduced to Chesapeake bay and the Atlantic Coast, appears to be distinct from the lineages(P1, P2) infectng crabs of the genus Panopeus (Kruse and Hare 2007; Kruse et al. 2012). Crabs (E. depressus or R. harrisii carrying the parasite are believed to have been transported northward with transplants of oysters from the Gulf of Mexico, following mortalities of native Atlantic Coast oysters due to the Haplosporidium nelsoni (MSX) parasite (Van Engel et al. 1966; Hines et al. 1997; Kruse et al. 2011).

In 1964, Loxothylacus panopaei was collected in the York River, lower Chesapeake Bay (Van Engel et al. 1966), and in 1974 it was collected from brackish water in the vicinity of Beaufort NC (Turquier and Payen 1978). In 1983-86, L. panopaei was found to be absent along the United States Atlantic coast south of Bogue Sound NC to Cape Canaveral FL. However, a more recent survey (Kruse and Hare 2007) found L. panopei in 6 additional estuaries in Florida and Georgia, north of Cape Canaveral. Genetic analysis suggested that the source of the Atlantic coast populations was not the eastern Gulf of Mexico (Kruse and Hare 2007). However, further sampling found parasites of the invading lineage on R. harrisii and E. depressus in Louisiana, supporting the hypothesis that the invading parasites originated in the Gulf of Mexico (Kruse et al. 2012). Atlantic coast introductions are summarized below from south to north:

FL-GA sounds:

Cove Harbor FL; Jacksonville/FL/St. Johns River estuary; St. Marys/FL/St. Marys River, Brunswick/GA/St. Simons Sound (2004-2005, Kruse and Hare 2007); Sapelo Island/GA/Sapelo Sound; ;GA/Savannah River (2004-2005, E. depressus; P. herbstii Kruse and Hare 2007)

Bogue Sound NC- Loxothylacus panopaei was discovered and found to be abundant in 1983; 47.4% of sampled Eurypanopeus depressus were found to be parasitized (Hines et al. 1997).

Neuse River NC - Six parasitized crabs (Rhithropanopaeus harrisi) were found in 1974; 'dozens' in 1976, but only one parasitized E. depressus (Turquier and Payen 1978). No parasitized crabs were found in April 1986 (Hines et al. 1997), but L. panopaei was abundant in 1993 among R. harrisi, 22% of sampled crabs were parasitized.

Chesapeake Bay:

Lower Bay- Loxothylacus panopaei was first reported in the York River at Gloucester Point VA in 1964, on E. depressus. At this time, it was not found in other rivers, or in older preserved samples of xanthid crabs (Van Engel et al. 1966). By 1967-68, the parasite ranged from Lynnhaven Bay to the mouth of the Potomac (Point Lookout MD), and from Old Plantation Creek (Cape Charles City VA) to Deal Island MD. Loxothylacus panopaei was seen on E. depressus (37% of crabs examined) and R. harrisii (5%), but not on Panopaeus herbsti or Dyspanopaeus sayi (Daugherty 1965). In 1983 survey including 5 lower Bay stations, from Hampton VA to Great Rock (Tangier Sound MD), prevalence averaged 9.7% for E. depressus, but 1.6% of D. sayi were also parasitized (Hines et al. 1997). Considerable year-to year variability and spatial patchiness has been noted in the occurrence of L. panopaei in lower Chesapeake Bay and elsewhere (Daugherty 1969; Hines et al. 1997).

Upper Bay - Crabs were examined for L. panopaei in the Rhode River MD from 1979 to the present. They were absent until 1986, when they were found at low prevalence, but then disappeared again until 1990. In 1991 they reached 70% prevalence on R. harrisi, but then declined to lower levels (30-40%) in 1992-93 (Hines et al. 1997). Loxopanopeus panopaei was not seen in the Rhode River for several years around 2000 (Hines unpublished data), but is now common (Amy Fowler 2011, personal communication).

Adjacent Atlantic Coast - Daugherty did not find any L. panopei on crabs collected on the 'ocean coast' (Oyster - Floyds Bay) of VA in 1967-68, but one was collected in Chincoteague Bay in 1969 (Daugherty 1969). In 1986, the parasite was found in 83% of E. depressus collected at Quinby VA (near Hog Island Bay) and in 17% of E. depressus at Chincoteague VA. In 1983 sampling, was not found at sites further north along the coast: Cape Henlopen DE, Cape May NJ, Ocean City NJ (Hines et al. 1997). However, in August 2012, 12 mud crabs (E. depressus), infected with L. panopaei were collected in Hempstead Harbor, Long Island Sound, New York, a substantial range extension for this parasite. Loxothylacus panopaei was not found in 3 other sites on Long Island (Freeman et al. 2013).

History References - Boschma 1955; Daugherty 1969; Gissler 1884; Hines et al. 1997; Turquier and Payen 1978; Van Engel et al. 1966

Invasion Comments