Reginald B. Blaylock

KUDOA HYPOEPICARDIALIS N. SP. (MYXOZOA: KUDOIDAE) AND ASSOCIATED LESIONS FROM THE HEART OF SEVEN PERCIFORM FISHES IN THE NORTHERN GULF OF MEXICO

Kudoa hypoepicardialis n. sp. infects the space between the epicardium and the compact myocardium and, in intense infections, the pericardial chamber of man-of-war fish (Nomeus gronovii) (Nomeidae) (the type host), blue runner (Caranx crysos) (Carangidae), Warsaw grouper (Epinephelus nigritus) (Serranidae), Atlantic tripletail (Lobotes surinamensis) (Lobotidae), northern red snapper (Lutjanus campechanus) (Lutjanidae), black drum (Pogonias cromis) (Sciaenidae), and bluefish (Pomatomus saltatrix) (Pomatomidae) in the northern Gulf of Mexico. This is the first report of a Kudoa sp. from the heart of a fish in the Gulf of Mexico, and of these hosts, only the bluefish was previously identified as a host for a species of Kudoa. Spores of the new species varied slightly in size among these hosts but were regarded as conspecific based on their nearly identical (99.9%) small-subunit (SSU) ribosomal DNA (rDNA) sequence. The new species differs both from the 4 nominal species of Kudoa reported from fishes in the Gulf of Mexico and from K. pericardialis, an allopatric species that infects the pericardial cavity, by the combination of having a large spore, a small polar capsule, and a polar filament with a single coil. The new species is morphologically and genetically most similar to K. shiomitsui, an allopatric species that infects the heart and pericardial cavity, but is distinguished from it based on a 4.2% difference in the SSU rDNA sequence. Heart lesions primarily were restricted to the vicinity of plasmodia and included a layer of fibrinous inflammation characterized by lymphocytes, macrophages, and granulomas as well as epithelioid encapsulations around plasmodia. Heavily infected hosts had melanin-like deposits and adipose cells beneath the epicardium, and the epicardium was discontinuous and apparently breached by plasmodia in some regions. Cardiac muscle, gill, liver, spleen, intestine, and kidney were normal.

Mycoses in red snapper (Lutjanus campechanus) caused by two deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum)

We report two species of deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum) concurrently infecting the swim bladder and posterior kidney and causing erratic behavior in two specimens of wild-caught, tank-held red snapper (Lutjanus campechanus). Lesions produced by both species infiltrated the immediately surrounding tissue and produced severe pathological changes; however, the infection apparently was not systemic. Only P. corylophilum grew in the initial culture from the swim bladder and only C. sphaerospermum grew in the initial culture from the kidney. Infection may have occurred upon penetration of a syringe to deflate the swim bladder. There was no horizontal transmission to 13 other specimens of red snapper held in the same tank. This suggests that these fungi are not primary pathogens. Injection of each species into various sites in the Gulf killifish, Fundulus grandis, failed to produce infections within 1 month, suggesting differences in susceptibility among species.

Margolisianum bulbosum n. gen., n. sp. (Nematoda: Philometridae) from the Southern Flounder, Paralichthys lethostigma (Pisces: Bothidae), in Mississippi Sound, USA

A new species of a philometrid nematode, Margolisianum bulbosum, is described from the subcutaneous tissue in the mouth (larvigerous females), head (males, ovigerous, and larvigerous females), and eye (preovigerous females) of the southern flounder, Paralichthys lethostigma, from Mississippi Sound. It is placed in a new genus diagnosed by the combination of 8 large, paired but separate cephalic papillae; no inner cephalic papillae; an esophagus with a separate, muscular anterior bulb; a prominent mononuclear esophageal gland; and variable, irregularly distributed cuticular bosses in the females, as well as a vestigial rectum, particularly in larvigerous females. Some female specimens exhibit rows of lateral grooves and longitudinal ridges near the posterior end. Males have 2 small slightly subequal spicules, a barbed gubernaculum, 4 pairs of small cephalic papillae, and a bipartite hypodermal extension within a membranous cuticle on the posterior end. Males, ovigerous females, and larvigerous females appear to be present year round in this sporadic infection in Mississippi.

Counter-Insurgents of the Blue Revolution? Parasites and Diseases Affecting Aquaculture and Science

Abstract:  Aquaculture is the fastest-growing segment of food production and is expected to supply a growing portion of animal protein for consumption by humans. Because industrial aquaculture developed only recently compared to industrial agriculture, its development occurred within the context of a growing environmental awareness and acknowledgment of environmental issues associated with industrial farming. As such, parasites and diseases have become central criticisms of commercial aquaculture. This focus on parasites and diseases, however, has created a nexus of opportunities for research that has facilitated considerable scientific advances in the fields of parasitology and aquaculture. This paper reviews Myxobolus cerebralis, Lepeophtheirus salmonis, white spot syndrome virus, and assorted flatworms as select marquee aquaculture pathogens, summarizes the status of the diseases caused by each and their impacts on aquaculture, and highlights some of the significant contributions these pathogens have made to the science of parasitology and aquaculture.

Feeding Performance of Juvenile Hatchery-Reared Spotted Seatrout Cynoscion nebulosus

The feeding performance of individual hatchery-reared (HR) and wild juvenile spotted seatrout Cynoscion nebulosus was compared across a series of six 1·5 h feeding exposures over a 3 day period in a controlled experiment. The predation cycle served as a context for discerning feeding performance elements. The experimental design facilitated assessments of the effects of experience, motivation due to hunger or satiation and prey density and encounter frequency. Although feeding success improved significantly across successive trials for both groups of C. nebulosus, wild C. nebulosus successfully captured and consumed significantly more Palaemonetes spp. prey and completed most performance metrics more efficiently than HR C. nebulosus. Total exposure time decreased with experience for both groups of C. nebulosus; however, HR C. nebulosus took longer to complete feeding exposures. Underpinning this difference was the time spent by HR C. nebulosus in non-search mode and for completing various foraging behaviours. Nevertheless, juvenile HR C. nebulosus exhibited sufficient foraging plasticity to switch from a pelleted diet to live novel prey.

Population Model for Amyloodinium ocellatum Infecting the Spotted Seatrout Cynoscion Nebulosus and the Red Snapper Lutjanus campechanus

The dinoflagellate Amyloodinium ocellatum, a major pathogen in warm water mariculture, has a trophont, a tomont and a dinospore life history stage. This paper presents a population model for A. ocellatum infecting spotted seatrout Cynoscion nebulosus and red snapper Lutjanus campechanus and evaluates the relative effect of each vital rate on the A. ocellatum population growth rate. The vital rates were estimated by incubating trophonts in vitro and tracking their development through the successive life history stages at 25°C and 33 ppt. The A. ocellatum population growth rate was 1.90 d-1 for spotted seatrout and 1.92 d-1 for red snapper. Highest elasticity values (0.24 and 0.23 in spotted seatrout and red snapper, respectively) corresponded to transitions from the dinospore to the trophont stage, the trophont stage to the tomont stage and the tomont stage back to the dinospore stage in both host species (self-loops not included). A 50% change in vital rates showed that the mean number of dinospores produced by a tomont had the largest effect on the A. ocellatum population growth rate (15%), followed by the dinospore infection rate (14%), the tomont sporulation rate (12%) and the dinospore mortality rate (10%) in both host species. A comparison of modeled and experimental vital rate threshold values revealed a 2.5- (spotted seatrout) or a 2.6-fold (red snapper) difference in the values for dinospore mortality, which is the smallest difference among all the modeled and experimental vital rates. Therefore, measures that increase dinospore mortality have a greater likelihood of influencing the outcome of an epidemic.

SUSCEPTIBILITY AND TOLERANCE OF SPOTTED SEATROUT, CYNOSCION NEBULOSUS, AND RED SNAPPER, LUTJANUS CAMPECHANUS, TO EXPERIMENTAL INFECTIONS WITH AMYLOODINIUM OCELLATUM

abstract:  Amyloodinium ocellatum is a parasitic dinoflagellate that infects warm-water marine and estuarine fishes and causes mortalities in aquaculture. Its life cycle consists of 3 stages: a feeding trophont that parasitizes the gills and skin where it interferes with gas exchange, osmoregulation, and tissue integrity; a detached reproductive tomont; and a free-swimming infective dinospore. We compared the susceptibility and tolerance of juvenile spotted seatrout, Cynoscion nebulosus, and red snapper, Lutjanus campechanus, to this parasite by individually exposing fish in 3-L aquaria (at 25 C and 33 practical salinity units) to several dinospore doses over different time periods and quantified the size and number of resulting trophonts. We estimated the trophont detachment rate and trophont size at detachment, the 24-hr dinospore infection rate, the dinospore 48-hr median lethal dose (LD50), and the trophont lethal load at the 48-hr LD50. There were no significant differences in dinospore infection rates or dinospore lethal doses between spotted seatrout and red snapper; however, trophonts remained attached longer and attained a larger size in red snapper than in spotted seatrout. The trophont lethal load was significantly higher in spotted seatrout than in red snapper. A proposed model simulating the trophont dynamics reflected our experimental findings and showed that A. ocellatum reproductive success is linked both to the number of dinospores and the size of the trophont, factors that, in turn, are linked to the time the trophont spends on the host and the number of trophonts the host can tolerate.

Effects of release procedures on the primary stress response and post‐release survival and growth of hatchery‐reared spotted seatrout Cynoscion nebulosus

To help explain the apparent poor post-release success of hatchery-reared (HR) spotted seatrout Cynoscion nebulosus, this study examined the effects of handling, transport and release procedures on the stress response of two age classes [48 and 80 day post-hatch (dph)] of HR C. nebulosus, as measured by cortisol concentrations and the post-release survival and growth of 48 and 80 dph HR C. nebulosus. As a proxy for stress, tissue cortisol was measured at various times during the handling, tagging (80 dph), transport, acclimation and release process. To consider the implications of the pre-release stressors, growth and survival were monitored in separate field experiments for each age class of acclimated post-transport C. nebulosus using control C. nebulosus that only experienced anaesthesia, transport, acclimation and a net release v. experimental C. nebulosus that underwent the entire routine procedure, including anaesthesia, tagging, transport, acclimation and gravity release through a pipe. For 48 dph C. nebulosus, mean cortisol varied significantly throughout handling and transport, increasing more than six-fold from controls before decreasing in mean concentration just prior to release. For 80 dph C. nebulosus, cortisol varied throughout handling, tagging and transport, first increasing more than three-fold compared with control C. nebulosus, before decreasing and rising slightly just prior to release. For 48 dph C. nebulosus within field enclosures, survival was high and similar for control and experimental groups; experimental C. nebulosus, however, were shorter, lighter and lower in condition than control C. nebulosus. For 80 dph C. nebulosus within field enclosures, fewer experimental C. nebulosus survived and those that did survive were of lower condition than C. nebulosus from the control group. Small untagged C. nebulosus may survive the release procedure better than larger C. nebulosus carrying a coded-wire tag. These findings document some ways in which pre-release practices may translate into detrimental effects on post-release success of HR C. nebulosus.