Hematological and plasma biochemical parameters of aquarium-maintained cownose rays

Noninvasive, epigenetic age estimation in an elasmobranch, the cownose ray (Rhinoptera bonasus)

Age data are essential for estimating life history parameters and are thus critical for population assessment, management, and conservation. Traditional vertebrae-based age estimation in elasmobranchs can be costly, time intensive, of low accuracy, and is by necessity lethal. Herein, epigenetic clocks were developed for an elasmobranch, the cownose ray (Rhinoptera bonasus), using aquarium-born individuals (n = 42) with known dates of birth (age range: 7-7,878 days or 0-21 years) and two tissue types (fin clips and whole blood) that can be sampled in a relatively non-invasive manner. Enzymatically-converted restriction site-associated DNA sequencing (ECrad-seq) was used to identify CpG sites that exhibited age-correlated DNA methylation. The epigenetic clocks developed were highly accurate (mean absolute error, MAE, < 0.75 years) and precise (R2 > 0.98). Age-associated CpG sites were identified across tissues, and a multi-tissue clock was also highly accurate (MAE < 1 year) and precise (R2 = 0.97). Using the developed fin clip clock, three wild-caught individuals of unknown age but managed in aquariums for > 22 years were predicted to be 22.10-23.49 years old. Overall, the results have important implications for future epigenetic clock development and noninvasive age estimation in elasmobranchs.

Hematological and plasma biochemical profile of two species of freshwater stingrays from the Amazon

The evaluation of hematological and plasma biochemical parameters and the subsequent establishment of reference intervals facilitate the diagnosis of the health status of animals. This work aimed to determine the blood parameters of wild specimens of the stingrays Potamotrygon motoro and Potamotrygon orbignyi from the lower Solimões River region, Amazonas, Brazil. One hundred forty-one stingrays were captured, 92 specimens of P. motoro and 49 of P. orbignyi, of both sexes and at different stages of development. No effect of sex was observed on the blood parameters of juvenile animals for both species. P. motoro neonates presented a distinct hematological and biochemical profile, with significantly lower hematocrit values, hemoglobina, number of erythrocytes, mean corpuscular hemoglobin concentration, monocytes, plasma glucose, total proteins, albumin, and globulin. On the other hand, total cholesterol and urea levels were significantly higher in this same group compared to juveniles of the same species. Comparison between species revealed lower values of triglycerides and total cholesterol in P. orbignyi of both sexes. The results obtained are pioneering for these Amazonian species in white water environments and will serve as a basis for evaluating the health status of wild stingrays. Thus, from the analysis of the blood of the P. motoro and P. orbignyi stingrays, it was possible to observe good health conditions.

Effect of photobiomodulation therapy as a multimodal approach to treatment of dermal abrasions in cownose rays (Rhinoptera bonasus)

Photobiomodulation therapy (PBMT) has become increasingly utilized in the zoo and aquarium fields to treat ailments in various species; however, its use in teleosts and elasmobranchs is relatively underrepresented in the literature. This study examined the efficacy of PBMT as an adjunct treatment to reduce the healing time of dermal abrasions in cownose rays (Rhinoptera bonasus). Ten cownose rays were included in this study and separated into control (n = 5) and treatment groups (n = 5). Animals in both treatment and control groups received intramuscular injections of enrofloxacin every 72 h to provide broad-spectrum antibiotic coverage. Cownose rays in the treatment group additionally received PBMT using the Companion® CTC-12 unit using the large, noncontact head. Control group rays were subjected to identical handling without the use of PBMT. A total of 196 Joules were delivered at a power of 2 W based on a dose of 5 J/cm2 at each session. Observational analysis revealed a lack of appreciable difference in healing time between the treatment and control groups in the aforementioned settings; however, it is recommended that PBMT protocols should be re-evaluated if there is little to no response in healing after three to four sessions. PBMT use on acute superficial dermal abrasions in cownose rays was well-tolerated in this study and may have utility in a multimodal treatment approach to wound healing. This study also produced a wound scoring metric based on photographs captured at each treatment. Future studies should utilize increased fluence (J/cm2) and irradiance (W/cm2) and incorporate synchronous histological analysis and increased sample size.

Blood collection under anesthesia, peripheral blood cells, plasma biochemistry, and plasma protein electrophoresis in a living fossil: the Spotted Ratfish (Hydrolagus colliei)

This report describes the safe and effective handling under anesthesia, blood collection and main clinical pathology values determination for three adult Spotted Ratfish (Hydrolagus colliei) (two males and one female) successfully maintained under human care for more than 20 years. The anesthetic MS-222 diluted in tamponed salt water at 50 ppm provided deep narcosis with mean induction and recovery times of 5 and 20 min, allowing safe handling and blood collection in the three animals sampled. Major leukocyte types were similar to other teleost and elasmobranch species, identifying lymphocytes as the predominant leukocyte (75.5%), followed by the fine eosinophilic granulocytes (10.25%), the coarse eosinophilic granulocytes (9.75%), and a small percentage of monocytes (5.50%). Plasma biochemistry values in this species were like those seen in elasmobranchs, with the highest levels of blood urea nitrogen described in any Chondrichthyes (mean 679.7 mmol/l). Plasma protein electrophoresis analysis in the Spotted Ratfish showed five consistent fractions, like those previously described in other fish species, with a negligible quantity of proteins migrating in the region equivalent to albumin, and with fraction 4 (mean 53.20%) as the predominant fraction. Despite the limitations imposed by the small sample size and the challenging access to the studied species under human care, this study will shed light on and enhance clinical knowledge regarding Ratfish handling, anesthesia, blood collection, and analysis. It aims to deliver a comprehensive clinical pathology description, presenting valuable data for professionals engaged in the care and management of Chimaerans.

Diagnostic agreement between three point-of-care glucose and β-hydroxybutyrate meters and reference laboratory methods in stingrays

Point-of-care (POC) glucose and β-hydroxybutyrate (β-HB) meters can potentially provide rapid insight into an elasmobranch's metabolic state in clinical and field research settings. This study evaluated the diagnostic agreement of three commercial POC meters against reference laboratory methods for glucose and β-HB concentrations in stingrays. Blood was collected during anesthetized exams from 28 stingrays representing four species: cownose rays (Rhinoptera bonasus), Atlantic stingrays (Hypanus sabina), southern stingrays (Hypanus americanus), and yellow stingrays (Urobatis jamaicensis). Glucose and β-HB concentrations were measured with each POC meter using whole blood and plasma; in parallel, plasma glucose and β-HB concentrations were measured via reference laboratory methods. Agreement between POC meters and reference laboratory methods was assessed using Bland-Altman methods, Passing-Bablok regression, observed total error, percent relative error, and linear mixed effect models. Plasma glucose and β-HB concentrations determined by reference laboratory methods ranged from <20-63 mg/dL to 0.05-5.38 mmol/L, respectively. One human POC meter-the Precision Xtra-showed the greatest agreement with reference laboratory methods when measuring glucose with whole blood [mean bias and 95% CI: 0 (-3-4) mg/dL] and β-HB with plasma [mean bias and 95% CI: 0.1 (-0.04-0.2) mmol/L]. Stingray sex, weight, buffy coat, and packed cell volume did not significantly affect the agreement between POC meters and reference laboratory methods. Across all three POC meters, mean bias and imprecision for plasma β-HB concentrations were relatively small (0-0.1 mmol/L and 0%, respectively). Utilizing POC meters to measure glucose and β-HB in stingrays may be viable when reference methods are unavailable.

Establishment of preliminary reference intervals and cytochemical staining of blood cells in big-bellied seahorses (Hippocampus abdominalis)

BACKGROUND

Despite their popularity, hematology reference intervals (RIs) have not been established in big-bellied seahorses (Hippocampus abdominalis).

OBJECTIVE

The objectives of this study were to establish hematologic RIs to compare values between sex in regard to cytochemical staining of blood cells. We also sought to compare white blood cell concentrations using the Natt and Herrick technique vs blood smear estimates.

METHODS

Forty-three healthy individuals from the Aquarium du Québec (22 females and 21 males) were included. Normal health status was confirmed by an unremarkable physical examination in five individuals and by necropsy of five other individuals, of which all were excluded from further analyses. Venipuncture was performed from the ventral coccygeal vein in the remaining 33 individuals without anesthesia using heparinized insulin syringes. A blood volume of 0.05 to 0.1 ml was collected to prepare Wright Giemsa-stained blood smears and hematocrits immediately after venipuncture. Whole blood was stored in heparinized Eppendorf tubes to determine red and white blood cell concentrations using the Natt and Herrick technique with a hemocytometer in 10 individuals; these results were compared with blood smear estimates. Additional blood smears were stained with alkaline phosphatase substrate, periodic acid Schiff, and toluidine blue stains.

RESULTS

The reference intervals included the packed cell volume (27.4-67.5%), thrombocyte count (19.5-197.7 × 10⁹ /L), and white blood cell (WBC) count (2-54.8 × 10⁹ /L), including neutrophils (1.1-21.3 × 10⁹ /L), lymphocytes (2.7-45.5 × 10⁹ /L), and monocytes (0-2.2 × 10⁹ /L). The WBC hemocytometer counts showed no correlation with blood smear estimates (Spearman's rho = 0.2). There was also no significant difference between the sexes.

CONCLUSIONS

These preliminary reference intervals will help assess the health of seahorses.

Baseline Health and Nutritional Parameters of Wild Sand Tigers Sampled in Delaware Bay

Species-specific hematological reference values are essential for diagnosis and treatment of disease and maintaining overall health of animals. This information is lacking for many species of elasmobranchs maintained in zoos and aquaria, thus reducing the effectiveness of care for these animals. Descriptive statistics and reference intervals were calculated for hematocrit and complete blood cell counts, biochemistry and protein electrophoresis parameters, trace minerals, vitamins, heavy metals, reproductive hormones, and fatty acids in the blood of 153 wild Sand Tigers Carcharias taurus of both sexes and a range of sizes caught in Delaware Bay (Delaware, USA). Mean hematocrit, total white blood cell counts, lymphocyte differentials, glucose, phosphorus, amylase, and aspartate aminotransferase levels were significantly higher in juveniles than in adults. Levels of estradiol, progesterone, testosterone, and differences in selenium and eicosapentaenoic acid (a polyunsaturated fatty acid) between males and females suggest that they are important parameters for improving Sand Tiger breeding success in managed care. Finally, blood metal levels for arsenic, cadmium, lead, and mercury suggest low levels of contaminant exposure for Sand Tigers during their summer residence in Delaware Bay. The results of this study provide baseline health parameters for wild Sand Tigers that will aid in effective maintenance of aquarium animals and contribute to a greater understanding of the biology of these sharks and efforts to accomplish sustainable management of their populations.

Hematology and Plasma Chemistry Reference Values in Nursehound Shark (Scyliorhinus Stellaris) Maintained Under Human Care

Studies determining baseline hematological reference intervals (RI) in elasmobranchs are very limited. In this study, blood samples were collected from 94 clinically healthy Nursehound Shark (Scyliorhinus stellaris) maintained under human care. Median (RI) in major leukocyte types were similar to other Carcharhinid sharks as lymphocytes were the predominant leukocyte with 38.0 (28.2–53.5)%, followed by coarse eosinophilic granulocytes with 20.0 (12.2–31.7)%, fine eosinophilic granulocytes with 6.0 (1.2–12.8) %, monocytes with 2.0 (0.0–6.0)%, and neutrophils with 2.0 (0.0–6.0)%. Nursehound Shark produced granulated thrombocytes, which were classified as granulocytes and represented 28.5 (12.4–39.7)% of all leukocytes. Median (RI) manual red blood cell and white blood cell counts were 177.50 (132.50–210.00) x 109 cells/l and 8.26 (5.24–14.23) x 109 cells/l, respectively. Median (RI) plasma chemistry values showed alkaline phosphatase 7.7 (4.2–13.0) U/l, aspartate aminotransferase 7.6 (3.3–17.1) U/l, blood urea nitrogen 281.6 (261.2–305.0) mmol/l, calcium 3.97 (3.59–4.47) mmol/l, total cholesterol 2.04 (1.02–3.91) mmol/l, chloride 233.0 (215.2–259.0) mmol/l, iron 3.79 (1.74–6.93) μmol/l, glucose 0.87 (0.47–1.44 mmol/l), potassium 3.8 (2.9–4.6) mmol/l, sodium 243.0 (227.7–271.0) mmol/l, phosphorus 1.58 (1.13–2.10) mmol/l, total protein 24.0 (20.0–35.0) g/l, and triglycerides 0.97 (0.49–3.35) mmol/l. Creatine kinase, gamma glutamyl transferase, and lactate dehydrogenase levels were below the instrument reading range.

Protein electrophoresis of non-traditional species: A review

EPH has been demonstrated to be a useful tool in companion animals while providing an opportunity to characterize globulinemias, including paraproteinemia. In EPH of non-traditional species, these same applications are important, but the primary use is to gauge the acute-phase and humoral immune responses. This includes the valid quantitation of albumin as well as the examination of fractions reflective of increases in acute-phase reactants and immunoglobulins. Agarose gel EPH and, more recently, capillary zone EPH have been applied to samples from these species. Performing these analyses provides special challenges in the placement of fraction delimits, generation of RIs, and interpretation of results. Recommended as part of routine bloodwork, EPH can also provide key results that are helpful in clinical and field-based health assessments as well as in prognostication.

Hematology and blood biochemistry profile of the freshwater stingray Potamotrygon magdalenae as a tool for population assessment in artificial environments

Hematological and blood biochemical reference information is important to establish physiological status of freshwater stingray populations and improve care and management protocols in artificial environments. Here, we used a commercial freshwater stingray with high mortality rates in the market (Potamotrygon magdalenae), as an example to understand how artificial environments and handling protocols influence physiological status of captive freshwater stingrays. To this purpose, blood from five adult males and six adult females was collected to perform complete blood counts and blood chemistry analyses. All sampled animals showed good body condition with no differences between sexes. Differences between sexes were only found for the differential count of lymphocytes. Red blood results were consistent with previously studied potamotrygonids while white blood results showed higher values of leukocytes, thrombocytes, heterophils and lymphocytes in P. magdalenae compared to other Potamotrygonids. All types of leukocytes described for elasmobranchs were found except neutrophils and basophils. Blood metabolites showed an influence of ex situ diet in total protein, triglycerides and cholesterol. Glucose results were consistent while urea showed lower levels than those recorded for other freshwater stingrays. These results highlight the importance of physical, physiological and health analysis in freshwater stingrays as a part of welfare assessment to improve monitoring protocols and survival rates in public or private aquaria.

Serum Protein Analysis of Nurse Sharks

Serum protein electrophoresis (EPH) is used to assess relative concentrations of blood proteins in clinical and biological studies. Serum EPH fractions have been determined for elasmobranchs using mammalian albumin, alpha 1-, alpha 2-, beta-, and gamma-globulin fractions, and have been deemed fractions 1 through 5, respectively. However, serum EPH fraction concentration reference intervals (RIs) have not been widely established for different elasmobranch species. In this study, RIs for fractions 1 through 5 were determined from 45 wild-caught Nurse Sharks Ginglymostoma cirratum (27 females and 23 males) in South Florida. Serum samples were isolated from whole blood following caudal venipuncture. Body condition was also measured in the field to assess the relative health of the individuals sampled. There was no relationship between body condition and serum EPH fraction concentrations. In addition, there was no difference in body condition or serum EPH fraction concentrations between females and males. Total solids and total protein values were significantly different (P < 0.001). Nurse Shark serum EPH fraction 1 was found within the mammalian albumin migrating band distance and was negligible. Fraction 2 showed no peak in the mammalian alpha 1-globulin range. A thin, medium peak in the mammalian alpha 2-globulin range represented fraction 3. In the mammalian beta-globulin range, fraction 4 consisted of the majority of protein observed. It was represented by a smooth, broad peak. A short, medium broad peak in the mammalian gamma-globulin range represented fraction 5. The Nurse Shark serum EPH fraction RIs provided in this study may be utilized to clinically evaluate the health of Nurse Sharks in captivity and in the wild, and to compare the health of their populations around the world experiencing various anthropogenic stressors and other environmental impacts.

Advances in Exotic Animal Clinical Pathology

Over the last 10 years, exotic animal clinical pathology has been evolving, improving health assessment in avian, mammal, fish, reptile, and amphibian patients. These advances are reviewed in this article. Species-specific reference intervals for blood parameters are becoming more available (eg, for ionized calcium, endocrine panels, and vitamin D plasmatic concentrations). In addition, new technologies are being developed to facilitate targeted metabolite detection and result acquisition by veterinarians. Novel techniques, biomarkers, and clinical changes related to disease have been described in avian, mammal, fish, reptile and amphibian species. The use of mobile applications may also be helpful.

EVALUATION OF HEALTH PARAMETERS IN COWNOSE RAYS ( RHINOPTERA BONASUS) HOUSED IN A SEASONAL TOUCH POOL HABITAT COMPARED WITH AN OFF-EXHIBIT HABITAT

Cownose rays ( Rhinoptera bonasus) are commonly displayed in zoo and aquarium touch pool exhibits; however, there is a gap in our understanding of how these practices might impact the health of these animals. The aim of this study was to evaluate and compare selected health parameters in cownose rays housed in a seasonal outdoor exhibit touch pool system with abundant public contact and an indoor off-exhibit holding system with minimal human contact. All animals underwent physical examination, ultrasound, cloacal wash and cytology, and blood collection for complete blood counts, point-of-care blood analysis, plasma protein electrophoresis, and plasma cholesterol electrophoresis in May and October 2014. Physical examination, ultrasound, and cloacal wash cytology findings were all unremarkable for both groups of animals. Significant differences in health parameters among animals by location and time point were few and included decreased heart rate ( F = 12.158, P = 0.001), increased lactate ( F = 6.838, P = 0.012), and increased low-density lipoproteins ( F = 19.961, P = 0.000) in touch pool animals over time. Based on these results, cownose rays inhabiting a touch pool exhibit and an off-exhibit system remained in comparable planes of health based on routine diagnostic modalities with few differences in measured health parameters.

WHOLE BLOOD TRANSFUSIONS TO TREAT SEVERE ANEMIA IN SEVEN COWNOSE RAYS ( RHINOPTERA BONASUS) AND ONE SHORT-TAIL STINGRAY ( DASYATIS BREVICAUDATA)

Blood transfusions can provide life-saving treatment to severely anemic animals. Due to limited availability and the difficulty of storing whole blood and blood products, such as fresh frozen plasma and packed red blood cells, exotic animals often receive fresh whole blood transfusions. Little is known about elasmobranch blood types and transfusions. Conspecific cross-matches within several different elasmobranch species were negative, indicating that in an emergency situation a single whole blood transfusion may be possible without causing a transfusion reaction. Experimental transfusions between healthy conspecific Atlantic rays ( Dasyatis sabina) showed no adverse reactions and autotransfusions in marbled electric rays ( Torpedo marmorata) were successful. There are no published reports of blood transfusions performed on clinically abnormal elasmobranchs. The following case series documents blood transfusions performed on seven cownose rays ( Rhinoptera bonasus) and one short-tail stingray ( Dasyatis brevicaudata). All rays were treated with the same protocol, which included pretreatment with steroids and antibiotics followed by an intravenous transfusion of freshly collected, heparinized, whole blood. Three animals survived and currently exhibit no abnormal clinical signs. Two animals died 55 days and 100 days post transfusion. Three animals died 2-22 days post transfusion. Although complications from blood transfusions could not be ruled out, all five animals that died had other health problems that likely contributed to their demise. All eight animals would almost certainly have died without a blood transfusion as they were severely anemic and moribund at the time of presentation. The methods described in this paper may be useful in the treatment of severely anemic elasmobranchs and this is the first report of blood transfusions in clinically abnormal elasmobranchs.

Fish Hematology and Associated Disorders

Fish health is a growing concern as pets, education, and aquaculture evolves. For the veterinary staff, fish handling, diagnostics, medicine, and surgery may require specialized training and equipment in comparison with terrestrial and arboreal animals, simply because of their aquatic nature and diversity. Fish hematology is one diagnostic tool that may not require additional equipment, may be inexpensive, and provide useful information in guiding treatment options. Challenges involving hematology may include handling and restraint, venipuncture, evaluation, and interpretation. In this article, strategies for these challenges are discussed for teleost (bony fish) and elasmobranch (cartilaginous fish) fish types.

Protein and cholesterol electrophoresis of plasma samples from captive cownose ray (Rhinoptera bonasus)

Our study was undertaken to assess the application of semiautomated methods available at the reference laboratory level for the evaluation of plasma protein and cholesterol via electrophoresis in samples from cownose rays ( Rhinoptera bonasus). Three groups of animals were assessed: clinically normal, clinically abnormal, and parasitized with leeches. As reported previously, the albumin band was negligible; the protein electrophoretograms were dominated by a large beta-globulin fraction. While the group of samples from the leech-parasitized rays did not show any large differences, the abnormal group exhibited significantly elevated total solids and cholesterol levels. The latter was related to a significant increase in very low density lipoprotein levels. The results demonstrate the potential application of these laboratory methods in quantitation of plasma proteins and cholesterol fractions in subclass Elasmobranchii.

Serum biochemical reference intervals for free-living Sand Tiger sharks (Carcharias taurus) from east Australian waters

BACKGROUND

Sharks are top-order predators in ocean food chains and the star attractions in aquaria worldwide. Unfortunately, blood biochemistry reference intervals (RI) have been determined for few species.

OBJECTIVE

The study aims to establish serum biochemical RI for free-living Sand Tiger sharks (Carcharias taurus) off eastern Australia.

METHODS

Thirty-seven sharks were captured and their sex, length, weight, reproductive maturity, and health status were recorded. After blood collection, serum analytes were quantified using standard analytical and statistical methods. Reference intervals, means, medians, and 90% confidence intervals were generated. Physiologic data from live and necropsied sharks were used to enhance the study results.

RESULTS

Thirty healthy sharks were included in the study. Albumin could not be detected. With the exception of ALP activity, values were unaffected by sex, length, weight, age, and life-history stage. The means (RI) were: sodium 258 (249-267) mmol/L, potassium 5.0 (4.3-5.7) mmol/L, chloride 242 (227-257) mmol/L, inorganic phosphate 1.8 (1.7-2.0) mmol/L, total calcium 3.9 (3.3-4.4) mmol/L, magnesium 1.9 (1.6-2.2) mmol/L, glucose 2.7 (2.2-3.2) mmol/L, urea 377 (360-394) mmol/L, ALP 20 (8-31) U/L, ALT 3 U/L (no RI), AST 29 (13-45) U/L, CK 42 (5-79) U/L, total protein 30 (24-36) g/L, triglyceride 0.3 (0.1-0.6) mmol/L, cholesterol 1.4 (0.9-2.1) mmol/L, creatinine 32 μmol/L (no RI), total bilirubin 1.5 μmol/L (no RI), and osmolarity 1082 (1027-1136) mmol/L.

CONCLUSIONS

These preliminary RI will assist with the clinical evaluation and treatment of captive and free-living Sand Tiger sharks worldwide. Studies with more animals will increase the precision of upper and lower reference limits.

KUDOA SP. (Myxozoa: Multivalvulida) in skeletal muscle of captive bullnose eagle rays, Myliobatis freminvillei (Rajiformes: Myliobatidae)

Kudoa spp. (Myxozoa: Multivalvulida) are of significant concern in marine and estuarine teleosts because of trophozoites and spores in the skeletal muscle reducing the marketability of wild and cultured fish. Kudoa spp. have rarely been reported from elasmobranchs. Spores of a Kudoa sp. were identified in two captive, mature bullnose eagle rays (Myliobatisfreminvillei) (Rajiformes: Myliobatidae). The male bullnose eagle ray (case 1) showed intractable weight loss, muscle wasting, and hyperkalemia, and was euthanized. The skeletal muscle showed myofiber degeneration, vacuolation, and necrosis, and spores of a Kudoa sp. were present multifocally through the muscle. The female bullnose eagle ray (case 2) had a severe, rapidly progressive, erosive lesion extending through the pectoral fin and was euthanized. Spores of a Kudoa sp. were not found in the lesion but were present in two disparate sections of skeletal muscle. There was no inflammation or degeneration associated with the infected myofibers in case 2. From case 1, morphometrics of 15 spores in histologic section were apical width 6.5-8.0 μm, apical thickness 5.0-7.0 μm, lateral width 5.5-6.5 μm, length 4.5-6.5 μm; the equal-sized polar capsules were spherical, 1.5-2.5 μm in diameter; there was a clear halo 2 μm thick around the spores, considered to be a mucous envelope. Spores from case 2 were indistinguishable from those in case 1. This appears to be the first report of Kudoa sp. in bullnose eagle rays.

Fish hematology and associated disorders

Fish health is a growing concern as pets, education, and aquaculture evolves. For the veterinary staff, fish handling, diagnostics, medicine, and surgery may require specialized training and equipment in comparison with terrestrial and arboreal animals, simply because of their aquatic nature and diversity. Fish hematology is one diagnostic tool that may not require additional equipment, may be inexpensive, and provide useful information in guiding treatment options. Challenges involving hematology may include handling and restraint, venipuncture, evaluation, and interpretation. In this article, strategies for these challenges are discussed for teleost (bony fish) and elasmobranch (cartilaginous fish) fish types.

Experimental infection of yellow stingrays Urobatis jamaicensis with the marine leech Branchellion torpedinis

Infestations of elasmobranchs by the marine leech Branchellion torpedinis can be problematic in aquaria and negatively affect host health. To better characterize the extent and pathogenesis of disease, 12 yellow stingrays Urobatis jamaicensis were infected with 1 or 3 leeches for 14 d. Leeches were associated with anorexia, extensive cutaneous ulceration, decreased host packed cell volume (PCV) and serum total solids (TS), and mortality in 3 rays. Average decrease in host PCV positively correlated with ulcer size and parasite:host ratio. Average decrease in host serum TS positively correlated with parasite:host ratio. Blood chemistry and total white blood cell counts revealed no significant trends. Additional necropsy findings included gill and splenic pallor, pericardial edema, perirenal edema, and decreased hepatocellular lipid deposits. Microscopic evaluation of leeches demonstrated host erythrocytes and proteinaceous fluid within parasite intestines, confirming active blood feeding. Results indicate B. torpedinis has the potential to cause significant disease in elasmobranchs, including death in as few as 5 d, and identifies ulcer size and parasite:host ratio as risk factors for disease. Elucidation of this host-parasite interaction helps characterize host response to parasites and facilitate care of parasitized elasmobranchs in aquarium and wild settings.