The physiological tolerance of the grey carpet shark (<Emphasis Type="Italic">Chiloscyllium punctatum</Emphasis>) and the epaulette shark (<Emphasis Type="Italic">Hemiscyllium ocellatum</Emphasis>) to anoxic exposure at three seasonal temperatures

The epaulette shark (Hemiscyllium ocellatum) and the grey carpet shark (Chiloscyllium punctatum) are commonly found in periodically hypoxic environments. The ecophysiological time available for these animals to safely exploit these niches during different seasonal temperatures was examined. The time to loss of righting reflex (T _LRR) was examined in response to an open ended anoxic challenge at three seasonal temperatures (23, 25 and 27°C). Ventilation rates were measured in an open ended anoxic challenge at 23°C and during 1.5 h of anoxia followed by 2 h of re-oxygenation at 23 and 25°C. The mean T _LRR of epaulette and grey carpet sharks was inversely proportional to temperature. The T _LRR was similar between species at 23°C; however, grey carpet sharks had significantly reduced T _LRR at higher temperatures. During the standardised anoxic challenge, epaulette sharks entered into ventilatory depression significantly earlier at 25°C. During re-oxygenation, epaulette sharks exposed to anoxia at 23°C had no significant increase in ventilation rates. However, after anoxic challenge and re-oxygenation at 25°C, epaulette sharks showed a significant increase in ventilation rates during re-oxygenation. Grey carpet sharks displayed no evidence of ventilatory depression during anoxia. However, during re-oxygenation, grey carpet sharks had significantly elevated ventilation rates above pre-experimental levels and control animals. These data demonstrate that the anoxia tolerance times of both species were temperature dependent, with a significant reduction in the T _LRR occurring at higher temperatures. Epaulette sharks had a significantly greater T _LRR at higher temperatures than grey carpet sharks, which did not enter into a ventilatory depression.     

Melanomacrophages in three species of free-ranging sharks from the northwestern Atlantic, the blue shark Prionacae glauca (L.), the shortfin mako, Isurus oxyrhinchus Rafinesque, and the thresher, Alopias vulpinus (Bonnaterre)

The melanomacrophage aggregates or cells (MMC) are commonly used as biomarkers of exposure to pollution in fish, albeit their numbers and morphological characteristics can be influenced not only by environmental toxins but also by a range of physiological parameters and pathological conditions. Accordingly, before we can use MMC as biomarkers in any fish species, their normal, 'background' characteristics have to be established in apparently healthy fish. The knowledge of MMC in sharks is minimal. The aim of this study was to characterize MMC from 51 free-ranging, large pelagic sharks from the northwestern Atlantic, including shortfin mako, Isurus oxyrhinchus , thresher, Alopias vulpinus and blue shark, Prionacae glauca . The rationale of this study was twofold. First, because, sharks have life histories predisposing them to the accumulation of environmental toxins they constitute good sentinel species of the health of the global marine ecosystem. Second, because many shark populations are in decline or threatened by extinction, we need to expand our understanding of their health status in order to develop appropriate protective measures. All sharks were collected by sports fishing gear between June and August in 2007. Their health condition was assessed by necropsy, morphometrics, and by microscopic examination of gonads, livers, spleens and kidneys. Routine, haematoxylin and eosin and/or Pearl's reagent-stained paraffin embedded sections were studied by light microscopy. Our results provide the first data on the morphometric and morphological characteristics of MMC in viscera of apparently healthy free-ranging sharks from the northwestern Atlantic.     

Fish meal replacement by plant and animal by-products in diets for the Australian short-finned eel, Anguilla australis australis (Richardson)

In this experiment, 23% of fish meal protein was replaced with protein from Australian soybean meal (SBM), lupin meal (LM), corn gluten meal (CGM) and meat meal (MM) in nutritionally balanced experimental diets. Growth and growth efficiencies of juvenile Australian short‐finned eel Anguilla australis australis (Richardson) elvers (2.23±0.4‐g average wet weight) were compared. Elvers were fed twice a day to a total of 5% body weight per day for 63 days. Total weight gain (g), specific growth rate (% day^?1), protein efficiency ratio (%) and productive protein value (%) were significantly higher (P<0.05) for elvers fed the MM diet than for those fed the LM diet. There were no differences in diurnal ammonia‐nitrogen excretion rates. However, diurnal urea‐nitrogen excretion rates were significantly (P<0.05) affected by diet and rates were two to three times higher for all diets, except CGM, 4 h following the afternoon feed. Diet significantly affected apparent digestibility (AD); ADs of protein for SBM and LM were significantly (P<0.001) higher than for control diet, CGM and MM; AD of energy for LM was significantly (P<0.05) lower than for all the other diets. Fish meal protein was replaced by CGM, SBM and MM without compromising growth rates of the Australian short‐finned eel. However, whole lupin seed meal (LM) depressed growth and growth efficiencies most likely because of the high indigestible carbohydrate content.     

Henneguya shaharini sp. nov. (Protozoa: Myxozoa), a parasite of marble goby, Oxyeleotns marmoratus (Bleeker)

Abstract. Henneguya shaharini sp. nov. is described from marble goby, Oxyeleotns marmoratus , collected in the State of Selangor, Malaysia. Cysts occurred in the gill filaments. The histopathological examination revealed intralamellar and inter-lamellar forms of infection. A host tissue response against the parasite was seen in some fish.     

Sanguinicola fontinalis sp nov. (Digenea: Sanguinicolidae): a blood parasite of brook trout, Salvelinus fontinalis (Mitchill), and longnose dace, Rhinichthys cataractae (Valenciennes)

Abstract. Sanguinicola fontinalis sp. nov., from the branchial, renal and cardiac blood vessels of brook trout. Salvelinus fontinalis (Mitchill), and longnose dace, Rhinichthys cataractae (Valenciennes), is described. The new species most closely resembles, hut differs from, Sanguinicola davisi of steelhead and rainbow trout, Salmo gairdneri Richardson. The adult differs from all known North American species in having 29–33 lateral tufts of blunt spines. The snail host is Leptoxis (Mudalia) carinata (Bruquière, 1792). Lodged and migrating miracidia caused considerable gill damage in the brook trout, resulting in high mortality when the fish were moved. To remove the hazard, the most severely affected brook trout were destroyed and the ponds drained and disinfected. Adult worms from Pennsylvania brook trout and West Virginia longnose dace were studied, as well as infected snails.     

Infection of the Carpathian brook lamprey (Eudontomyzon danfordi Regan, 1911) with a dermocystid parasite in the Tisza River Basin,Hungary

The Carpathian brook lamprey (Eudontomyzon danfordi Regan, 1911) is an endemic protected species of Cephalaspidomorphi in the Carpathian Basin. No parasites have become known from these jawless vertebrates to date. Here, the authors describe an infection from a single specimen manifesting in protuberant skin cysts 7–10 mm in diameter, scattered on the body surface. Similar dermal infection was observed in 25 of the 274 lampreys recorded in the population survey. Skin cysts filled with round spore-like structures of a dermocystid parasite were found. These particles measured 8–14 µm in diameter and had an about 0.5 µm thick wall, and containing mainly a granular mass and a relatively scarce plasma. No hyphae were recorded. Despite conspicuous morphological changes in the skin, no inflammatory reactions were found. The molecular analysis of 18S rDNA showed similarity to dermocystid species of several fish species but differed from them approximately by 2%. This is the first record of a dermocystid parasite infecting a jawless vertebrate.     

Comparison of histological features, and description of histopathological lesions in thyroid glands from three species of free-ranging sharks from the northwestern Atlantic, the blue shark, Prionace glauca (L.), the shortfin mako, Isurus oxyrhinchus Rafinesque, and the thresher, Alopias vulpinus (Bonnaterre)

Histomorphological features of piscine thyroids are widely accepted and frequently used as bioindicators of environmental pollution. This despite the fact that there is marked variation in thyroid morphology resulting from numerous pathological and physiological conditions. Our hypothesis was that there will be variations in histological features in thyroids collected from different shark species during the summer season in the northwestern Atlantic. To test our hypothesis, we examined histological features encountered in grossly normal thyroids from three species of sharks, the shortfin mako, Isurus oxyrhinchus , thresher, Alopias vulpinus and blue sharks, Prionace glauca . In addition, microscopic lesions from these thyroids were described. Ninety-four sharks were collected in summer 2001, 2002 and 2004. Routine, haematoxylin and eosin-stained paraffin-embedded sections were studied by light microscopy. We found inter-species but not intra-species variation in histological patterns of thyroids, which were distinct enough to allow 'blind' assignment of a thyroid to the specific species. The most common lesions encountered were lymphofollicular hyperplasia and chronic thyroiditis. In addition, one case each of intravascular larval nematodes and a myxosporean infection was found. Our results provide the first data on species-specific morphology of thyroids collected during summer months from sharks. The results indicate that familiarity with normal thyroid morphology is crucial before using shark thyroids in biomonitoring of environmental contamination or interpreting data from this gland in shark-health studies.     

Ecological and histopathological aspects of Didymodiclinus sp. (Trematoda: Didymozoidae) parasite of the dusky grouper,Epinephelus marginatus (Osteichthyes: Serranidae), from the western Mediterranean Sea

The dusky grouper Epinephelus marginatus (Lowe) is an ecologically and commercially important fish species of the Atlantic and Mediterranean coastal rocky habitats. Despite records of didymozoid infections in several grouper species, the identification and pathogenesis of these parasites in E. marginatus are lacking. The aim of this study is to characterize the didymozoids of E. marginatus, particularly their mechanisms of infection and histopathological features. Dusky groupers (n = 205) were caught off Majorca Island (western Mediterranean Sea) and examined for parasites. Of the fish sampled, 45% were infected with white and yellow didymozoid capsules and brown nodules, found on the gills and pseudobranchs. Parasite abundance had a strong positive relationship with the fish length; only fish larger than 20 cm were infected, suggesting infection via consumption of an intermediate host, for which E. marginatus size was a limiting factor. The capsules contained two convoluted viable adult trematodes, identified as Didymodiclinus sp., in close contact with host capillary vessels, with no evidence of the tissue inflammatory response. Conversely, nodules containing degraded parasites were surrounded by an intense inflammatory infiltrate. The findings suggest that Didymodiclinus sp. have the potential to evade the host's immune system by inhibiting the inflammatory response.     

Characterization of a host response to the myxosporean parasite, Ceratomyxa shasta (Noble), by histology, scanning electron microscopy and immunological techniques

Abstract. The tissue response of Salmo gairdneri Richardson, against the myxosporean parasite. Ceratomyxa shasta (Noble), was investigated using histological techniques, scanning electron microscopy and immunological methods. The progress of infection in C. shasta -susceptible and resistant steelhead and rainbow trout was examined by standard histological techniques and by indirect fluorescent antibody methods using monoclonal antibodies directed against C. shasta antigens. Trophozoite stages were first observed in the posterior intestine and there was indication that resistance was due to the inability of the parasite to penetrate this tissue rather than to an inflammatory response. Examination of a severely infected intestine by scanning electron microscopy showed extensive destruction of the mucosal folds of the posterior intestine. Western blotting and indirect fluorescent antibody techniques were used to investigate the immunological component of the host response. No antibodies specific for C. shasta were detected by either method.