Behavioural determinants of distribution and survival in early stages of walleye pollock, Theragra chalcogrammai a synthesis of experimental studies

This review summarizes results of an extensive series of laboratory studies on the behavioural responses of early life stages of walleye pollock, Theragra chakogramma to key environmental factors including light, temperature, gravity, turbulence, food availability and predator presence. Experiments focused on vertical distribution of egg through 0-age stages, and social interactions of age-0 juveniles. Key factors were modified either singly or in concert to determine their direct and indirect influence on fish behaviour. The observed results suggest that the behaviour of individual fish depends on the integration of a continually changing hierarchy of both intrinsic and extrinsic factors, with the relative importance of a specific factor varying with ontogeny and over time and space. The broad range of responses displayed by early life stages suggests that behaviour plays an important role in determining the consequences of environmental variability on walleye pollock populations. In general, results from our laboratory experiments are consistent with patterns observed in field studies, supporting the efficacy of using experimental behavioural research to define some of the underlying mechanisms controlling distribution and survival in the field, and eventual recruitment to adult populations.     

The enhancement of resistance of the American eel, Anguilla rostrata Le Sueur, to a pathogenic bacterium, Aeromonas hydrophila, by an extract of the tunicate, Ecteinascidia turbinata

Abstract. Extracts of the tunicate Ecteinascidia turbinate were used in preventing Aeromono hydrophila infection in the American eel, Anguilla rostrata. Intraperitoneal injection of the extract 2 days after bacterial challenge was shown to increase dramatically eel phagocytic activity and resistance to disease. Intravenous injection of the extract 2 days post-bacterial injection was shown to increase antibody titres. This study helps to substantiate the possible use of E. turbinata extract in treating eel diseases. The exact nature of its protective effect will be dependent on the time and route of its delivery.     

Serological variability in Xanthomonas albilineans, causal agent of leaf scald disease of sugarcane

The serological characteristics of 215 strains of Xanthomonas albilineans from 28 locations throughout the world were investigated. Three serovars were identified by using three sera prepared against strains from different locations. The same variation among strains was observed with different serological assays: immunofluorescence. dot-blot enzyme immunoassay and agglutination. Serovar I is the largest group and consists of strains from various geographic locations such as Australia. USA (Florida), Guadeloupe. India. Mauritius. Réunion and including South Africa. Serovar II contains only strains from Africa: Burkina Faso. Cameroon. Kenya. Ivory Coast. Serovar III is the smallest group and contains strains from Caribbean islands (Guadeloupe. Saint Kitts. Martinique). Oceania (Fiji) and Asia (Sri Lanka). This serological variability should be considered when serological techniques are applied for the diagnosis of leaf-scald disease of sugarcane.     

Besnoitiosis in a miniature donkey

A 1-year-old male miniature donkey ( Equus asinus ) from a herd of eight was presented with a 9-month history of pruritic dermatitis, lethargy and anorexia. Physical examination revealed diffuse lichenification and scales involving the skin of the face, head and dorsum from the neck to the pelvis. The main histological alteration within the superficial and deep dermis was the presence of multiple large, spherical, thick walled, protozoal Besnoitia cysts. In addition, the inflammatory response consisted of a moderate, superficial and deep perivascular, mixed mononuclear cell infiltrate, with epidermal hyperplasia and compact orthokeratosis. Based upon the large size of the protozoal cysts and the ultrastructural features of the bradyzoites contained therein (conoid, polar ring, rhoptries, micronemes and microtubules), a diagnosis of cutaneous besnoitiosis was established. Treatment with trimethoprim-sulphamethoxazole resulted in significant clinical improvement. To our knowledge, this is the first reported case of besnoitiosis in a miniature donkey in North America.