Controlled reproduction of an important indigenous fish species, Spinibarbus denticulatus (Oshima, 1926), in Southeast Asia

Aquaculture of Spinibarbus denticulatus (Oshima, 1926), a fish species indigenous to North Vietnam and Eastern China, is constrained by lack of fingerlings for stocking ponds and cages. As these fish do not naturally breed in captivity, carp pituitary extract (CPE), luteinizing hormone-releasing hormone analogue (LHRHa) with domperidone (DOM) and human chorionic gonadotropin (HCG) were administered at various doses to induce ovulation. A first set of experiments evaluated the response to LHRHa (30, 40 and 50 μg kg⁻¹) with or without DOM (10 mg kg⁻¹), CPE (20, 30 and 40 mg kg⁻¹) and HCG (3000, 4000 and 5000 IU kg⁻¹). A second set of experiments evaluated the dose response to LHRHa (30, 35, 40 and 50 μg kg⁻¹) primed with 6 mg kg⁻¹ of CPE, and HCG (3000, 3500, 4000, 5000 IU kg⁻¹) primed with 6 mg kg⁻¹ of CPE. The treatment groups were compared with each other and the control (injected with 0.9% saline solution). Only 25% and 50% ovulation resulted when treated with LHRHa at 40 and 50 μg kg⁻¹, whereas 100% ovulation was achieved with an addition of DOM to LHRHa. Both 30 and 40 mg kg⁻¹ CPE induced 100% ovulation. However, HCG (4000 and 5000 IU kg⁻¹) induced ovulation in only 33% of females. When primed with CPE, the minimum dose of LHRHa required was 35 μg kg⁻¹ to achieve 70% ovulation. Priming HCG with CPE also resulted in 100% ovulation, and the minimum effective dose of HCG to induce ovulation was 3500 IU kg⁻¹ with 60% ovulation. Fertilization and hatch rates observed in this study with different hormonal stimulation were high (80–93%). The results indicate that while the use of combined hormone strategy has no apparent advantage over a single hormone strategy, LHRHa+DOM (40 μg kg⁻¹+10.0 mg kg⁻¹) and CPE (30 mg kg⁻¹) are most effective in consistently inducing ovulation and thus can be used for commercial hatchery production of S. denticulatus larvae.     

Characterization of Small-size Egg-bearing Thai ss-strain Rotifers Brachionus rotundiformis and Their First Offspring

This study selected small (100–120 μm) egg-bearing females from a local Thai ss population and characterized their first offspring's life history in an attempt to produce small-size rotifers. Mean lorica length of selected small adult females was 120 ± 6 μm at the time of collection, and this mean length did not increase over their lifetime. While their first offspring life span was only 5.11 ± 0.35 d, the reference population longevity was higher, 9.65 ± 0.4 d. The length of reproductive period of offspring from the small-size egg-bearing female was 2.58 ± 0.38 d, shorter than that of reference population 6.83 ± 0.58 d. Although the rate of egg production was not different between small egg-bearing female and reference population, the total number of eggs produced by the small egg-bearing female's first offspring was lower (4.78 ± 0.60) compared to the reference population (11.83 ± 1.26). The small egg-bearing female's first offspring had a higher egg to lorica length ratio (76.1 ± 1.64%) than the reference population (56.6 ± 1.3%), indicating a relatively high investment in reproduction. The small egg-bearing female's first offspring reached only 125 ± 6 μm in 36 h, and further culture of their offspring over 35 d resulted in a mean offspring size, 163 ± 11 μm, similar to the reference population (159 ± 16 μm). This shows that population mean size reduction is not likely to result from selecting small egg-bearing females within a single generation. The unique reproductive characteristics of small egg-bearing female place it in its own category.     

Plasma indicators of muscle damage in a model of nutritional myopathy in weaner sheep

SUMMARY Subclinical nutritional myopathy was induced in 5-month-old sheep by feeding them a diet low in vitamin E and selenium. Subsequently clinical myopathy was induced by dosing with protected polyunsaturated fatty acids. Plasma activities of creatine kinase (CK), pyruvate kinase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase and aldolase, enzymes of muscle origin, all remained above their reference ranges in clinically affected sheep, but fluctuated widely. Similar fluctuations occurred in subclinically affected animals, resulting in some activities being within the reference ranges and some above, at different times. Plasma malondialdehyde, an indicator of lipid peroxidation, proved of no diagnostic value. Terminal plasma CK activities were significantly correlated with microscopic damage in the vastus lateralis (VL), but not the vastus intermedius (VI) or the tensor fascia lata (TFL) muscles. AST was the most highly correlated with damage in VI and VL. In two clinically affected sheep successfully treated with an oral dose of α-tocopherol actetate all enzymes decreased steadily to within their reference ranges, at rates probably related to their plasma half-lives. These results suggest that measurement of plasma CK activity would be useful in monitoring recovery of treated sheep.     

The effect of the introduction of Nile tilapia (Oreochromis niloticus,L.) on small indigenous fish species (mola,Amblypharyngodon mola,Hamilton; chela,Chela cachius,Hamilton; punti,Puntius sophore,Hamilton)

This is the first controlled experiment to quantify the effect of introduced tilapia on indigenous species. This experiment was conducted in small earthen ponds (100 m²) to assess the impact of mixed‐sex or all‐male Nile tilapia (Oreochromis niloticus) on small indigenous species (SIS) commonly found in south Asia, mola (Amblypharyngodon mola), chela (Chela cachius) and punti (Puntius sophore). Ponds were fertilized, then stocked with 0.56 fish m^?2 of water surface area in the mixed‐sex and all‐male tilapia treatments and 0.42 fish m^?2 in the treatment without tilapia. No additional nutritional inputs were applied after stocking. Treatments were: mixed‐sex tilapia with SIS, mono‐sex male tilapia with SIS and SIS without tilapia (control). All treatments were stocked with 14 fish per species. All species reproduced during the 21‐month culture duration. The number of recruits varied by species, Tilapia reproduced in greater numbers than SIS. Tilapia numbers at harvest were the highest (451 ± 25/100 m²) in the mixed‐sex treatment compared with mola (221 ± 22/100 m²), chela (94 ± 8/100 m²) and punti (100 ± 7/100 m²). The number of mola was higher (399 ± 33/100 m²) in the all‐male tilapia treatment. There was reduction in the number of mola and chela in the treatment containing mixed‐sex tilapia. Gut content analysis combined with water sampling revealed that all fish species fed selectively. Significant interspecies dietary overlap was found between Nile tilapia and SIS and among SIS. Thus, there is potential for tilapia to compete with indigenous fish species when space and other resources are limiting, but a longer duration study with varying level of management is needed to determine how successfully tilapia competes with locally adapted SIS.     

Life expectancy in a birth cohort of Boxers followed up from weaning to 10 years of age

OBJECTIVE: To determine mortality rate over time, risk factors for death, and heritability of life expectancy in Boxers. ANIMALS: 1,733 purebred Boxers born in The Netherlands between January 1994 and March 1995. PROCEDURE: Dogs were followed up from weaning (ie, 49 days of age) to 10 years of age through use of a written questionnaire sent to owners every 6 months. Mortality rate over time, risk factors potentially associated with death, and heritability of life expectancy were examined by use of a proportional hazards model based on the Weibull distribution. RESULTS: stimated mortality rate during the 10-year study period for this birth cohort of Boxers was 45%. The probability of surviving to 5 years of age was 88%; the probability of surviving to 10 years of age was 55%. Estimated effective heritability of life expectancy was 0.076, meaning that in this population, an estimated 76% of the observed variation in life expectancy could be attributed to genetic differences among dogs that were passed from parents to their offspring. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cumulative incidence of death from weaning to 10 years of age among this birth cohort of Boxers was 45%. The estimated heritability of life expectancy suggested that life expectancy can be improved by use of selective breeding.     

Automated observation and analysis of earthworm surface behaviour under experimental habitat quality and availability conditions

Currently, the driving factors of active earthworm dispersal across the soil surface are not sufficiently understood, and distances traversed by individual earthworms have rarely been quantified. Research progress has been hampered by the lack of adequate observation methods as well as fast, objective and quantitative measurements of nocturnal earthworm behaviour.In this work, we report on the potential of a new, automated method using infrared-sensitive webcams and computer image analysis. Nightly surface activities of Lumbricus terrestris L. were monitored quantitatively while manipulating levels of disturbance, burrow availability and congener presence in standard observation units.The automated observation system proved to be simple and inexpensive to build, provided reliable quantitative measures of locomotive behaviour without animal disturbance, and considerably reduced human workload and bias.Waterlogging of the burrow zone stimulated surface activities around and away from the home burrow as compared to habitat disturbance by pesticide application and vibration. However, dispersing earthworms never settled in prefabricated burrows. Surface activity of individuals subjected to waterlogged conditions was influenced by the availability of alternative habitat. Minimal habitat disturbance (vibration) and the presence of conspecific individuals resulted in an increased amount of burrow-anchored, possibly sexually oriented, behaviour, but reciprocal burrow visits and mating were not observed. Pesticide application did not result in dispersal, increased foraging activities or sexual attraction attempts during this short-term study.The presence, extent and mechanisms of the remote assessment of important cues in the surroundings of the home burrow by L. terrestris need further research. Infrared monitoring opens new research avenues of earthworm surface behaviour studies (e.g. density-dependent dispersal, habitat selection, (re)colonization, invasion).     

Tree species selection for land rehabilitation in Ethiopia: from fragmented knowledge to an integrated multi-criteria decision approach

Dryland regions worldwide are increasingly suffering from losses of soil and biodiversity as a consequence of land degradation. Integrated conservation, rehabilitation and community-based management of natural resources are therefore of vital importance. Local planting efforts should focus on species performing a wide range of functions. Too often however, unsuitable tree species are planted when both ecological suitability for the targeted area or preferences of local stakeholders are not properly taken into account during selection. To develop a decision support tool for multi-purpose species selection, first information needs to be pooled on species-specific ranges, characteristics and functions for a set of potentially valuable species. In this study such database has been developed for the highly degraded northern Ethiopian highlands, using a unique combination of information sources, and with particular attention for local ecological knowledge and preferences. A set of candidate tree species and potentially relevant criteria, a flexible input database with species performance scores upon these criteria, and a ready-to-use multi-criteria decision support tool are presented. Two examples of species selection under different scenarios have been worked out in detail, with highest scores obtained for Cordia africana and Dodonaea angustifolia, as well as Eucalyptus spp., Acacia abyssinica, Acacia saligna, Olea europaea and Faidherbia albida. Sensitivity to criteria weights, and reliability and lack of knowledge on particular species attributes remain constraints towards applicability, particularly when many species are jointly evaluated. Nonetheless, the amount and diversity of the knowledge pooled in the presented database is high, covering 91 species and 45 attributes.