The ecological role of bivalve shellfish aquaculture in the estuarine environment: A review with application to oyster and clam culture in West Coast (USA) estuaries

Aquaculture is viewed as a potential mechanism to meet the growing demand for seafood around the world. The future of bivalve shellfish aquaculture in the U.S. hinges on sustainable practices on the part of industry and a more consistent regulatory regime. Bivalve shellfish aquaculture is a recent practice relative to its history in other countries, beginning in the late 1800s along the U.S. West Coast where it is now well established with farm raised product utilizing land-based hatcheries and grow-out directly in numerous estuaries. Bivalve shellfish aquaculture can be viewed as a disturbance which modifies the estuarine system in three ways: 1) changes in material processes — bivalves process food and produce wastes; 2) addition of physical structure — aquaculture introduces the cultured organisms and in some cases a physical anchoring structure; and 3) pulse disturbances like harvest and bed maintenance disturb sediments, remove species in addition to the cultured organisms themselves, and change resource or habitat availability. In U.S. West Coast estuaries, water column and sediment nutrient concentrations are relatively high and influenced by large tidal exchange and proximity to deeper nearshore ocean waters where upwelling controls production during summer months. Bivalves are unlikely to influence material processes except at local bed scales in these systems, although estuary-wide effects could appear as the fraction of cultured area rises or in poorly flushed bays. Bivalve culture clearly modifies estuarine habitat at local community and at landscape scales and effects are most often evaluated against existing structured habitat in the form of submerged aquatic vegetation. Individual activities act as pulse disturbances and the recovery of eelgrass (Zostera marina) to pre-disturbance levels is variable (< 2 to > 5 years). The extent of disturbance depends on the aquaculture practice and the distribution of eelgrass reflects a balance of space competition, pulse disturbance and recovery, and is therefore at dynamic equilibrium on aquaculture beds. Structure provided by aquaculture appears functionally similar to eelgrass for small benthic infauna and mobile epibenthic fauna while use of aquaculture as habitat by larger more mobile invertebrates and fish depends on mobility and varies with life-history stage and taxon being evaluated. Scale seems a very important management consideration and further research at estuarine landscape scales, especially for habitat use by important invertebrates and fish, may prove useful in designing and implementing best management practices. Though local and short term effects from aquaculture are clearly evident in U.S. West Coast estuaries, bivalve aquaculture does not remove area from the estuary or degrade water quality like other anthropogenic influences, and thus has not been implicated in shifts to alternate states or reduced adaptive capacity of the larger ecological system.     

Obstructive struvite ureterolithiasis in 4-month-old intact male Bernese mountain dog

A 4-month-old, 7 kg, intact male, Bernese mountain dog was presented for obstructive struvite ureterolithiasis. Multiple urethroliths, ureteroliths, and urocystoliths were present. Based on an abdominal ultrasound, there was severe left hydronephrosis and hydroureter from distal ureterolith obstruction, just proximal to the vesicoureteral junction. The dog was not azotemic. Successful treatment was accomplished via ventral cystotomy. Bladder wall culture revealed a methicillin-resistant Staphylococcus spp. No predisposing cause was identified. There are no known genetic predispositions in Bernese mountain dogs for struvite urolithiasis. The urinary tract infection resolved with surgical retrieval of the uroliths and antibiotic treatment. The dog remained clinically normal after the cystotomy but developed a subclinical urinary tract infection 4 mo post-operatively.Key clinical message:Urolithiasis is rare in pediatric veterinary patients. To the authors’ knowledge, this is the first report of obstructive ureterolithiasis in a puppy. There is no known genetic predisposition for urolithiasis in Bernese mountain dogs.     

Ronidazole pharmacokinetics after intravenous and oral immediate-release capsule administration in healthy cats

Ronidazole (RDZ) is an effective treatment for feline Tritrichomonas foetus infection, but has produced neurotoxicity in some cats. An understanding of the disposition of RDZ in cats is needed in order to make precise dosing recommendations. Single-dose pharmacokinetics of intravenous (IV) RDZ and immediate-release RDZ capsules were evaluated. A single dose of IV RDZ (mean 9.2mg/kg) and a 95mg immediate-release RDZ capsule (mean 28.2mg/kg) were administered to six healthy cats in a randomized crossover design. Plasma samples were collected for 48 h and assayed for RDZ using high pressure liquid chromatography (HPLC). Systemic absorption of oral RDZ was rapid and complete, with detection in the plasma of all cats by 10 min after dosing and a bioavailability of 99.64 (±16.54)%. The clearance of RDZ following IV administration was 0.82 (±0.07) ml/kg/min. The terminal half-life was 9.80 (±0.35) and 10.50 (±0.82) h after IV and oral administration, respectively, with drug detectable in all cats 48h after both administrations. The high oral bioavailability of RDZ and slow elimination may predispose cats to neurotoxicity with twice-daily administration. Less frequent administration should be considered for further study of effective treatment of T foetus-infected cats.     

Primary ureteral giant cell sarcoma in a Pomeranian

An 8-year-old male neutered Pomeranian dog was presented to the Veterinary Teaching Hospital at Oregon State University for surgical treatment of hydronephrosis of the left kidney and a left cranial abdominal mass. A primary ureteral mass was found during exploratory surgery, and the mass was resected and ureteral anastomosis was performed. Cytologic evaluation of the mass revealed 3 distinct cell populations, including a large number of multinucleated giant cells, a moderate number of thin spindle-shaped cells, and cohesive clusters of transitional epithelial cells. The cytologic diagnosis was giant cell sarcoma. The diagnosis was confirmed by histologic examination, and immunohistochemical staining was performed. The spindle-shaped cells and multinucleated giant cells were both immunoreactive for vimentin and spindle-shaped cells for S-100. Tumor cells did not express wide-spectrum cytokeratin, broad-spectrum muscle actin, smooth muscle actin, sarcomeric actin, desmin, BLA36, Mac 387, synaptophysin, neuron-specific enolase, glial fibrillary acid protein, or von Willebrand factor. These findings are most consistent with an anaplastic sarcoma with giant cells. This is the first case report of a primary ureteral giant cell sarcoma in a dog.     

Correlation between earthworms and plant litter decomposition in a tropical wet forest of Puerto Rico

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1 m and 0.1–0.25 m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the exotic endogeic species Pontoscolex corethrurus Müller; they were more abundant, and had higher biomasses in the upland than in riparian sites of the forest. Plant leaf litter decomposed faster in the upland than riparian sites. We found that earthworm abundance in the upper 0.1 m of the soil profile positively correlated with decomposition rate of plant leaf litter. Ground litter removal had no effect on the abundance or biomass of endogeic earthworms. Our data suggest that earthworms can be used to predict decomposition rates of plant litter in the tropical wet forest, and that the decomposition of aboveground plant litter has little influence on the abundance and biomass of endogeic earthworms.     

Splenic torsion in an alpaca

OBJECTIVE: To describe the clinical signs, diagnostic evaluation and surgical management of an alpaca with splenic torsion. ANIMALS: Six-year-old female alpaca. RESULTS: Splenic torsion and uterine torsion were the inciting cause for persistent abdominal discomfort in this alpaca. Rectal examination, abdominocentesis, and transabdominal ultrasonographic findings were suggestive of a splenic lesion. Surgical management involved splenectomy of a necrotized spleen. CONCLUSIONS: Although rare in occurrence, splenic torsion should be considered as a potential cause of abdominal discomfort in alpacas. Splenectomy is a reasonable and successful method of treatment for a devitalized spleen secondary to splenic torsion in alpacas. CLINICAL RELEVANCE: Splenic torsion causes persistent abdominal discomfort in camelids and may be associated with uterine torsion. Rectal examination, transabdominal ultrasound and abdominocentesis are useful diagnostic tools to differentiate splenic torsion from other causes of abdominal discomfort. Splenectomy is an uncomplicated procedure in camelids and has a favorable prognosis.     

Increased expression of GAPDH protein is not indicative of nitrosative stress or apoptosis in liver of starved rainbow trout (Oncorhynchus mykiss)

Short-term starvation has been linked to in vivo protein degradation in liver of rainbow trout (Oncorhynchus mykiss). However, it is unclear whether this proposed increase in protein degradation is followed by programmed cell death (apoptosis) in liver of starved trout. A preliminary study in our laboratory revealed an isoform of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein that increased 4.5-fold in liver of starved trout. GAPDH is a glycolytic enzyme involved in other cellular functions, including apoptosis. Increased intracellular nitric oxide (NO) promotes nuclear translocation of GAPDH that is associated with increased apoptosis in mammals. If GAPDH protein is associated with apoptosis in rainbow trout, it could potentially be used as a biomarker of cellular stress in liver of teleost fish species. The purpose of this study was to determine whether increased GAPDH protein expression in liver of starved rainbow trout is associated with NO-induced apoptosis. Targeted proteomic analysis using multiple reaction monitoring (MRM) was used to determine the level of GAPDH in nuclear and cytoplasmic fractions and inducible nitric oxide synthase (iNOS) in cell lysates. Dot blot and DNA fragmentation analyses were conducted to evaluate protein S-nitrosylation and apoptosis, respectively. Results showed that cytoplasmic GAPDH was 3.4-fold higher in liver of starved versus fed rainbow trout but could not be detected in nuclear fractions. Starvation significantly reduced hepato-somatic index but had no effect on iNOS protein expression, protein S-nitrosylation, or apoptosis. Our results indicate that starvation promoted significant reduction in liver mass that was not associated with increased apoptosis or NO-induced stress and that greater GAPDH concentration in liver of starved rainbow trout was located primarily in the cytoplasm.     

Vitellogenin in tilapia (Oreochromis mossambicus): Induction of two forms by estradiol,quantification in plasma and characterization in oocyte extract

Two forms of vitellogenin were isolated by DEAE agarose ion-exchange chromatography from plasma of the tilapia, Oreochromis mossambicus. The monomers have apparent molecular masses of 200 and 130 kDa, as indicated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and a total amount of phosphorus of 1.7 and 0.1%, respectively. Antibodies specific to the two forms, designated tVTG-200 and tVTG-130, were generated in rabbits and used to develop enzyme-linked immunosorbent assays (ELISAs) and in Western blot analyses of plasma and oocyte extract. SDS-PAGE of the oocyte extract showed a major protein band at 106.6, minor bands at 26.6, 24.2, and 23.7 kDa, and very faint bands at 83.4 and 17.5 kDa. Western blots of the oocyte extract revealed that the antiserum to tVTG-200 recognized strongly the protein bands at 24.2 and 23.7 kDa, and less strongly the bands at 25.1 and 22.6 kDa, whereas the antiserum to tVTG-130 recognized mainly the protein band at 106.6 kDa. The presence of both VTGs in untreated male tilapia was detected with the ELISAs using relatively high plasma volumes. Their presence in males was confirmed by VTG-like immunoreactive materials eluting from the ion-exchange column at the same positions as tVTG-200 and tVTG-130. The concentrations of the VTGs in males were several orders of magnitude lower than in vitellogenic females. Treatment of male tilapia with estradiol-17β (E₂) induced both VTGs within 24h. After 7 days, tVTG-130 reached a maximum concentration in plasma, whereas tVTG-200 continued to increase. Our findings demonstrate that the two vitellogenins are biochemically distinct, possibly differentially regulated, and made by both sexes.     

Variable variability: difficulties in estimation and consequences for fisheries management

Recent analyses propose that the key regulatory processes in fisheries are stochastic, characterized by increased recruitment variance at low stock sizes (heteroscedasticity). Here, we investigate the consequences of this idea, with the aim of testing its practical relevance to fisheries management. We argue that stock‐recruitment time series are at least one order of magnitude too short to reliably fit heteroscedastic models; indeed, they are typically insufficient even to establish in which direction recruitment variance changes with stock size. Unreliable estimates of heteroscedasticity can have important management implications, depending on the sign of the coefficient of heteroscedasticity. Maximum sustainable yield (MSY) estimates from simple models, which include heteroscedasticity can be volatile, unrealistically high and sometimes non‐existent, as illustrated by an analysis of North Sea cod (Gadus morhua) data. In contrast, for North Sea herring (clupea harengus) data, heteroscedasticity has a negligible effect on MSY estimates. Statistical models are useful to elucidate broad‐scale regulatory processes, but will need to combined with the mechanistic understanding offered by models of population dynamics before being applied in a management setting.