Abstract
The parasitic dinoflagellate Hematodinium perezi infects the American blue crab Callinectes sapidus and other decapods along the Eastern seaboard and Gulf of Mexico coast of the USA. Large juvenile and adult blue crabs experience high mortality during seasonal outbreaks of H. perezi, but less is known about its presence in the early life history stages of this host. We determined the prevalence of H. perezi in megalopae and early benthic juvenile crabs from multiple locations along the Virginia portion of the Delmarva Peninsula. The DNA of H. perezi was not detected in any megalopae collected from several locations within the oceanic coastal bay complex in which H. perezi is found at high prevalence levels. However, prevalence levels were high in early benthic juveniles from 2 oceanic coastal embayments: South Bay and Cobb Bay. Prevalence levels were lower at locations within Chesapeake Bay, including Cherrystone Creek, Hungars Creek, and Pungoteague Creek. Sampling over different seasons and several consecutive years indicates that disease transmission occurs rapidly after megalopae settle in high-salinity bays along the Delmarva Peninsula during the late summer and fall. Infected juvenile crabs can overwinter with the parasite and, when subjected to increasing water temperatures in spring, infections progress rapidly, culminating in transmission to other crabs in late spring and early summer. In high-salinity embayments, H. perezi can reach high prevalence levels and may significantly affect recruitment of juvenile blue crabs into the adult fishery.
Highlights
The blue crab Callinectes sapidus is an abundant, highly mobile, benthic predator with a complex life history
The purpose of the current study was to determine if megalopae had infections of H. perezi and to assess the prevalence levels in early benthic juveniles from both intermediate- and high-salinity locations along the Virginia portion of the Delmarva Peninsula
Crabs were collected from Cherrystone Creek and Hungars Creek, 2 moderate-salinity (18−22 psu) locations on the Chesapeake Bay side of the Delmarva Peninsula (Fig. 1), by suction sampling, transported to the Virginia Institute of Marine Science (VIMS), and frozen at −20°C
Summary
The blue crab Callinectes sapidus is an abundant, highly mobile, benthic predator with a complex life history. The species is distributed from Nova Scotia (Canada) to Brazil (Williams 1984) and supports economically important fisheries along the Eastern seaboard and Gulf of Mexico coast of the USA. There have been major declines in harvest yields of many blue crab fisheries in the USA. Fishing pressure and habitat loss contribute greatly to those declines, but disease and environmental processes affecting blue crab populations have not been thoroughly researched, both have contributed to declines and changes in population cycles in other crustacean fisheries (Shields 2012). Few studies have examined the effects of pathogens upon settlement of postlarvae or new recruits, yet pathogens are often most prevalent in and damaging to the early juvenile stages of crustaceans
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