Old Dominion University ODU Digital Commons Biological Sciences Faculty Publications Biological Sciences 2019 Parasitic Dinoflagellate Hematodinium perezi Prevalence in Larval and Juvenile Blue Crabs Callinectes sapidus from Coastal Bays of Virginia H. J. Small J. P. Huchin-Mian K. S. Reece K. M. Pagenkopp Lohan Mark J. Butler IV Old Dominion University, [email protected] See next page for additional authors Follow this and additional works at: https://digitalcommons.odu.edu/biology_fac_pubs Part of the Biology Commons, Marine Biology Commons, and the Parasitology Commons Original Publication Citation Small, H. J., Huchin-Mian, J. P., Reece, K. S., Lohan, K. M. P., Butler, M. J., & Shields, J. D. (2019). Parasitic dinoflagellate Hematodinium perezi prevalence in larval and juvenile blue crabs Callinectes sapidus from coastal bays of Virginia. Diseases of Aquatic Organisms, 134(3), 215-222. doi:10.3354/dao03371 This Article is brought to you for free and open access by the Biological Sciences at ODU Digital Commons. It has been accepted for inclusion in Biological Sciences Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. Authors H. J. Small, J. P. Huchin-Mian, K. S. Reece, K. M. Pagenkopp Lohan, Mark J. Butler IV, and J. D. Shields This article is available at ODU Digital Commons: https://digitalcommons.odu.edu/biology_fac_pubs/391 Vol. 134: 215–222, 2019 DISEASES OF AQUATIC ORGANISMS Published online June 6 https://doi.org/10.3354/dao03371 Dis Aquat Org OPENPEN ACCESSCCESS Parasitic dinoflagellate Hematodinium perezi prevalence in larval and juvenile blue crabs Callinectes sapidus from coastal bays of Virginia H. J. Small1,*, J. P. Huchin-Mian1,3, K. S. Reece1, K. M. Pagenkopp Lohan1,4, M. J. Butler IV2, J. D. Shields1 1Virginia Institute of Marine Science, William & Mary, PO Box 1346, Gloucester Point, VA 23062, USA 2Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA 3Present address: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Noria Alta s/n, Guanajuato 36050, Mexico 4Present address: Marine Disease Ecology Laboratory, Smithsonian Environmental Research Center, Edgewater, MD 21037, USA 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 out- breaks 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 consecu- tive 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 signif- icantly affect recruitment of juvenile blue crabs into the adult fishery. KEY WORDS: Dinoflagellate · Parasite · Crustacea · Endemic · Infection 1. INTRODUCTION USA. Fishing pressure and habitat loss contribute greatly to those declines, but disease and environmen- The blue crab Callinectes sapidus is an abundant, tal processes affecting blue crab populations have not highly mobile, benthic predator with a complex life been thoroughly researched, although both have con- history. The species is distributed from Nova Scotia tributed to declines and changes in population cycles (Canada) to Brazil (Williams 1984) and supports eco- in other crustacean fisheries (Shields 2012). In parti - nomically important fisheries along the Eastern cular, few studies have examined the effects of patho- seaboard and Gulf of Mexico coast of the USA. In the gens upon settlement of postlarvae or new recruits, yet last decade, however, there have been major declines pathogens are often most prevalent in and damaging in harvest yields of many blue crab fisheries in the to the early juvenile stages of crustaceans. © The authors 2019. Open Access under Creative Commons by *Corresponding author: [email protected] Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited. Publisher: Inter-Research · www.int-res.com 216 Dis Aquat Org 134: 215–222, 2019 The blue crab serves as a host for a variety of 2. MATERIALS AND METHODS pathogens, including viruses, bacteria, fungi, proto- zoa, helminths, and other crustaceans (Shields & 2.1. Collection and treatment of Overstreet 2007). Most pathogens cause little patho- experimental animals logical alteration to the host, but several have the capacity to cause serious disease and significantly In 2008 and 2009, juvenile blue crabs were affect host populations and their associated fisheries. obtained from colleagues studying the relationship For instance, the parasitic dinoflagellate Hemato- between submerged aquatic vegetation (SAV) cover dinium perezi causes widespread blue crab mortali- and juvenile crab density (Ralph et al. 2013). Crabs ties during annual seasonal outbreaks (Messick were collected from Cherrystone Creek and Hungars 1994, Messick & Shields 2000, Lee & Frischer 2004). Creek, 2 moderate-salinity (18−22 psu) locations on The parasite was first documented in blue crabs by the Chesapeake Bay side of the Delmarva Peninsula Newman & Johnson (1975) and was later shown to (Fig. 1), by suction sampling, transported to the Vir- have a broad distribution on the Eastern seaboard of ginia Institute of Marine Science (VIMS), and frozen the USA and Gulf of Mexico coast (Messick & Shields at −20°C. Samples were then thawed and sorted, and 2000, Pagenkopp Lohan et al. 2013). The parasite is individual crabs were measured (carapace width endemic in crabs living in areas of high salinity [CW] including epibranchial spines) prior to their (>20 psu), and infections are rarely found in waters preservation in 70% ethanol. In 2011 and 2012, early where salinity is below 18 psu (Newman & Johnson benthic juvenile crabs were collected from SAV habi- 1975, Messick & Sindermann 1992, Messick & tats in Cherrystone Creek and South Bay, a high- Shields 2000). The parasite also infects several other salinity (32− 34 psu) oceanic coastal embayment on crustacean species, including decapods and amphi - the Delmarva Peninsula. Crabs were captured using pods (Johnson 1986, Messick & Shields 2000, Shep- dip nets and immediately stored in coolers contain- pard et al. 2003, Pagenkopp Lohan et al. 2012). ing ambient seawater for transport to VIMS for H. perezi can be highly pathogenic in its blue crab assessment. Upon return to the laboratory, crabs host, with mortality rates up to 87% in naturally and were preserved whole in 95% ethanol. All subse- experimentally infected mature blue crabs (Messick & quent collections from SAV habitats (2014−2017) Shields 2000, Shields & Squyars 2000). Infections and were conducted in the same manner. Over this crab mortalities have historically been reported from period, crabs were also collected from Cobb Bay, large juvenile and adult crabs due to their ease of cap- which abuts South Bay. In fall 2016, juvenile crabs ture in commercial traps; few studies have examined were also collected from Pungoteague Creek and larval and early benthic juvenile stages. Messick Gwynn’s Island, 2 moderate-salinity locations (16− (1994) documented prevalence levels up to 100% in 18 psu) on the Chesapeake Bay side of the Delmarva early benthic juveniles sampled in 1992 and 1993 Peninsula and on the western shore of Chesapeake from coastal bays near Ocean City, Maryland, and Bay, respectively. At the laboratory, crabs were Franklin City, Virginia. Little is known about whether measured and assessed for obvious in juries prior to the parasite can infect larval stages. Sullivan et al. dissection. They were then bisected sagittally along (2016) and Sullivan & Neigel (2017) detected Hemato- the carapace length using a sterile razor blade on a dinium DNA associated with blue crab megalopae clean glass microslide. Half of the crab was placed collected from inshore locations in Louisiana, but their into Bouin’s solution and the other half was placed studies did not demonstrate whether the positive PCR into 95% ethanol for later processing. The dissection assays were associated with internal infections. smear was then stained with 0.3% neutral red in The purpose of the current study was to determine physiological saline and assessed for the presence of if megalopae had infections of H. perezi and to assess the parasite. the prevalence levels in early benthic juveniles from Megalopae were collected from several high-salin-