Perinatal hypoxia induces subsequent retinal degeneration in the offspring of ovoviviparous fish, Xiphophorous maculates

OBJECTIVE: This experiment evaluated the perinatal hypoxic effect on the retina of offspring of the ovoviviparous fish. ANIMAL STUDIED: The ovoviviparous fish Xiphophorous maculates was used for the experiment. PROCEDURE: The mothers were kept in a hypoxic environment of 3.5% oxygen for 6 h, starting 30 h before hatching. Subsequently, the retinae of the offspring were fixed, sectioned at 6 microm and evaluated microscopically from the age of 1 to 35 days. RESULTS: Degeneration of the outer nuclear layer of the retina was noted on the 3rd day and severe retinal degeneration was observed on the 35th day. Immunocytochemistry confirmed apoptosis by TUNEL reaction. There was no difference in neovascularization, as revealed by vascular endothelial growth factor, between controls (group 1) and hypoxic fish (group 2). CONCLUSIONS: Perinatal hypoxia could have long-lasting effects on the central nervous system in some species.     

Utilization of wastewater-grown zooplankton: Nutritional quality of zooplankton and performance of silver perch Bidyanus bidyanus (Mitchell 1838) (Teraponidae) fed on wastewater-grown zooplankton

Zooplankton grow in the last stage of water purification at the Werribee Sewage Treatment Lagoons (WSTL) and the resource is huge and unutilized. Daphnia carinata and Moina australiensis are the dominant species at the WSTL. The protein content of D. carinata and M. australiensis was 54.80% and 64.80%, respectively. Analysis of zooplankton showed that both essential and nonessential amino acids were present at a level that was higher than control diet. Silver perch fed on D. carinata exhibited better growth, better food conversion ratio (FCR), protein efficiency ratio (PER) and apparent net protein utilization (ANPU), which were not significantly different from the control diet ( P  > 0.05). Heavy metals concentrations were at very low levels in fish fed on wastewater-grown zooplankton.     

Pond culture of snakehead in Hong Kong: a case study of an economic solution to common resources

This article records the trade practice and culture cycle of Ophiocephalus maculatus (snakeheads) as adopted by a fish farm at Ngau Tam Mei, the New Territories, Hong Kong. This farm is one of the few remaining local enterprises that have the skills to spawn this labyrinth fish. Documentation is timely not only because there has been great demand for the transfer of culture technology (spawning) to China, but also because the species may become extinct with the demise of the culture business through urbanization. The discussion throws light on the effectiveness and limitations of the institutions of private rights as a means of conserving common resources.     

Lethal doses of ammonia on the late-stage larvae of Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), (Decapoda: Grapsidae) reared in the laboratory

Four successive life stages (zoea-III, zoea-IV, zoea-V and megalopa) of the Chinese mitten-handed crab, Eriocheir sinensis (H. Milne-Edwards), were exposed to ammonia in a series of short-term bioassays with the static-renewal method at 22°C, pH 8.0 and 25%o salinity. The greatest sensitivity was observed in the zoea-III stage. The 24-h LC₅₀ values for zoea-III, zoea-IV, zoea-V and megalopa were 32.8, 73.1, 84.0 and 90.1 mg L^?1 for NH₃+ NH₄⁺, and 1.11, 2.36, 2.77 and 3.18 mg L^?1 for NH₃, respectively. The 72-h LC₅₀ values for zoea-III, zoea-IV and zoea-V were 11.9, 23.6 and 38.2 mg L^?1 for NH₃+ NH₄⁺, and 0.40, 0.76 and 1.26 mg L^?1 for NH₃, respectively. The 96-h LC₅₀ values for megalopa were 37.3 mg L^?1 for NH₃+ NH₄⁺ and 1.31 mg L^?1 for NH₃. It was found that ammonia tolerance increased with larval development from zoea-III to megalopa, especially from zoea-III to zoea-IV and from zoea-IV to zoea-V. A comparison of safe levels of ammonia among the different life stages indicated that all stages were significantly different with respect to safe levels of ammonia (P < 0.05) except zoea-V and megalopa, which had the highest safe levels. In general, both the larvae and juveniles of E. sinensis are less resistant to ammonia than those of other crustacean species studied so far.     

Macroalgal meadow habitats support fish and fisheries in diverse tropical seascapes

Canopy‐forming macroalgae can construct extensive meadow habitats in tropical seascapes occupied by fishes that span a diversity of taxa, life‐history stages and ecological roles. Our synthesis assessed whether these tropical macroalgal habitats have unique fish assemblages, provide fish nurseries and support local fisheries. We also applied a meta‐analysis of independent surveys across 23 tropical reef locations in 11 countries to examine how macroalgal canopy condition is related to the abundance of macroalgal‐associated fishes. Over 627 fish species were documented in tropical macroalgal meadows, with 218 of these taxa exhibiting higher local abundance within this habitat (cf. nearby coral reef) during at least one life‐history stage. Major overlap (40%–43%) in local fish species richness among macroalgal and seagrass or coral reef habitats suggest macroalgal meadows may provide an important habitat refuge. Moreover, the prominence of juvenile fishes suggests macroalgal meadows facilitate the triphasic life cycle of many fishes occupying diverse tropical seascapes. Correlations between macroalgal canopy structure and juvenile abundance suggests macroalgal habitat condition can influence levels of replenishment in tropical fish populations, including the majority of macroalgal‐associated fishes that are targeted by commercial, subsistence or recreational fisheries. While many macroalgal‐associated fishery species are of minor commercial value, their local importance for food and livelihood security can be substantial (e.g. up to 60% of landings in Kenyan reef fisheries). Given that macroalgal canopy condition can vary substantially with sea temperature, there is a high likelihood that climate change will impact macroalgal‐associated fish and fisheries.     

Who benefits from international tourism in small Pacific islands? Value capture in the hotel industry in Hawaii

There is a consensus among small Pacific islands that the extent to which they benefit from international tourism largely depends on how much of the value created by tourism remains in the local economy. This study examines how the value created in the hotel industry is distributed among the key stakeholders in a small Pacific island context. We used aggregated income statements of full-service and limited-service hotels from the STR Inc., a hotel industry data company, to calculate the value distribution among the key stakeholders in the hotel industry of a small Pacific island. We found that labour and owners captured most of the value created, whereas hotel management companies and franchisors captured a small share of the value. Our results suggest that tourism workers' ability to take united action and hence to negotiate higher wages will result in higher value capture by local labour and less value leaking out of the local economy. Our results also reveal that foreign ownership in the hotel industry is the single largest cause of economic leakages. The study has several implications for the tourism-based growth policies in small Pacific islands.     

Congenital porto-systemic shunts in sixteen dogs and three cats

Congenital porto-systemic shunts in sixteen dogs and three cats are described. A major symptom was hepato-encephalopathy. In most cases diagnosis was based on elevated venous ammonia levels, abnormal ammonia tolerance and results of operative mesenteric portography. Clinical signs, laboratory findings, results of portography, and pathologic findings in the liver and the central nervous system are described. A diagnostic schedule is proposed to aid in recognition of this syndrome.     

The effect of increased atmospheric carbon dioxide concentration on emissions of nitrous oxide, carbon dioxide and methane from a wheat field in a semi-arid environment in northern China

There are no reports on the effects of elevated carbon dioxide [CO₂] on the fluxes of N₂O, CO₂ and CH₄ from semi-arid wheat cropping systems. These three soil gas fluxes were measured using closed chambers under ambient (420 ± 18 μmol mol⁻¹) and elevated (565 ± 37 μmol mol⁻¹) at the Free-Air Carbon dioxide Enrichment experimental facility in northern China. Measurements were made over five weeks on a wheat crop (Triticum aestivum L. cv. Zhongmai 175). Elevated [CO₂] increased N₂O and CO₂ emission from soil by 60% and 15%, respectively, but had no significant effect on CH₄ flux. There was no significant interaction between [CO₂] and N application rate on these gas fluxes, probably because soil N was not limiting. At least 22% increase in C storage is required to offset the observed increase in greenhouse gas emissions under elevated [CO₂].     

IMPROVING CONSPICUITY OF THE CANINE GASTROINTESTINAL WALL USING DUAL PHASE CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY: A RETROSPECTIVE CROSS‐SECTIONAL STUDY

Gastrointestinal (GI) disease is a common clinical complaint in small animal patients; computed tomography (CT) examinations enable a global overview of the GI tract and associated structures. Previously, the GI wall has been reportedly identified from serosa to mucosa in 77% of standard postcontrast CT studies and wall layers seen in ultrasound have not been distinguished. Inconsistent strong contrast enhancement of the inner layer of the GI mucosal surface was noted on dual phase CT studies acquired in our institution, which increased the visibility of the GI tract and disease processes. The aim of this retrospective, observational, cross‐sectional study was to determine the optimal portal vein attenuation for maximizing GI wall conspicuity using dual phase contrast‐enhanced CT. Patients with abdominal CT for a non‐GI related disease were included. In a pilot study, 175 GI segments from 35 CT studies were graded for presence of mucosal surface enhancement (MSE). The strongest mucosal surface enhancement grade correlated with portal vein attenuation of 43–150 HU; this value was used as inclusion criterion in the main study. A total of 441 GI segments were evaluated in 42 CT studies postcontrast for GI wall conspicuity. The GI wall was conspicuous in 56.7% precontrast, 84.5% at 30s, and 77.3% late postcontrast; 4.7% of segments were removed due to motion blur. At 30 s distinct mucosal surface enhancement was seen in the small intestine and gastric mucosal surface enhancement was poor. Findings supported the use of dual phase contrast‐enhanced CT for improving conspicuity of the GI wall.