Redundancy and compensation in axon guidance: genetic analysis of the Drosophila Ptp10D/Ptp4E receptor tyrosine phosphatase subfamily

Background: Drosophila has six receptor protein tyrosine phosphatases (RPTPs), five of which are expressed primarily in neurons. Mutations in all five affect axon guidance, either alone or in combination. Highly penetrant CNS and motor axon guidance alterations are usually observed only when specific combinations of two or more RPTPs are removed. Here, we examine the sixth RPTP, Ptp4E, which is broadly expressed. Results: Ptp4E and Ptp10D are closely related Type III RPTPs. Non-drosophilid insect species have only one Type III RPTP, which is closest to Ptp10D. We found that Ptp4E mutants are viable and fertile. We then examined Ptp4E Ptp10D double mutants. These die before the larval stage, and have a mild CNS phenotype in which the outer longitudinal 1D4 bundle is frayed. Ptp10D Ptp69D double mutants have a strong CNS phenotype in which 1D4 axons abnormally cross the midline and the outer and middle longitudinal bundles are fused to the inner bundle. To examine if Ptp4E also exhibits synthetic phenotypes in combination with Ptp69D, we made Ptp4E Ptp69D double mutants and Ptp4E Ptp10D Ptp69D triple mutants. No phenotype was observed in the double mutant. The triple mutant phenotype differs from the Ptp10D Ptp69D phenotype in two ways. First, the longitudinal tracts appear more normal than in the double mutant; two or three bundles are observed, although they are disorganized and fused. Second, axons labelled by the SemaIIB-tMyc marker often cross in the wrong commissure. We also examined motor axon guidance, and found that no phenotypes are observed in any Ptp4E double mutant combination. However, triple mutants in which Ptp4E Ptp10D was combined with Ptp69D or Ptp52F exhibited stronger phenotypes than the corresponding Ptp10D double mutants. Conclusions: Type III RPTPs are required for viability in Drosophila, since Ptp4E Ptp10D double mutants die before the larval stage. Unlike Ptp10D, Ptp4E appears to be a relatively minor player in the control of axon guidance. Strong phenotypes are only observed in triple mutants in which both Type III RPTPs are eliminated together with Ptp69D or Ptp52F. Our results allow us to construct a complete genetic interaction matrix for all six of the RPTPs

Nile Tilapia “Oreochromis niloticus” Farming in Fresh and Geothermal Waters in Tunisia: A Comparative Study

This work aims to compare the farming of Nile Tilapia Oreochromis niloticus in fresh and geothermal waters through monitoring the specie’s zootechnical parameters: growth, mortality and feed conversion rate. For geothermal water rearing, fish was placed in cages in Bechima Station, in southern Tunisia, while Smati Reservoir, in the center of the country was used for fresh water. The spawners were first adapted to geothermal waters in Bechima experimental station. Then, the broodstock phase lasted 60 days and allowed the obtainment of 1–2 g larvae. Fertility was important and varied between 451 and 1589 larvae/female, which is associated with the females’ total weight (F = 1.6 W2.1). In the pre-growing phase, the comparison of fry growth rates (weight 1.3 g) in the geothermal and freshwaters showed a small variation with recorded rates slightly in favor of fish bred in fresh water. During 50 days within the breeding phase, fish weight achieved in freshwater was more important reaching 12.7 g (TCJ = 0.228 g /day compared to 10.51 g (TCJ = 0.184 g/day) recorded in geothermal waters. Similarly, during the fattening phase, the weights gained after 30days demonstrated better growth rates for tilapia cultured in freshwater (up to 60 g) in contrast to that bred in geothermal water (35–40 g)

Contribution au suivi de la population nicheuse du faucon crecerellette (Falco naumanni) à l'Aqueduc de Zaghouan (Tunisie)

Le faucon crécerellette (Falco naumanni) est une espèce globalement menacée. Nous avons étudié la dynamique de la population de Zaghouan (Tunisie). Nos résultats suggèrent que le nombre des couples nicheuses à l'Aqueduc diminue significativement d'une année à une autre. Ce résultat serait du à la destruction ou la modification des habitats du fait des travaux de restauration de l'Aqueduc. La protection et la restauration des habitats et des sites de reproduction en particulier ainsi que l'aménagement des sites de nidification constituent les principales mesures proposés pour la conservation de l'espèce en Tunisie.The Lesser Kestrel (Falco naumanni) is a globally threatened species.We studied the population dynamics of nesting Lesser Kestrels at the aqueduct of Zaghouan (Tunisia). Our results suggest that the number of nesting pairs at this site has decreased significantly from year to year. This is primarily due to destruction or modification of nest sites during restoration of the aqueduct. The protection and the restoration of their habitat, especially of breeding sites, as well as the installation of additional nesting sites, constitute the principal conservation measures proposed for this species in Tunisia. Ostrich 2007, 78(2): 401–40

Optimization of fishing for stock enhancement of Rutilis rutilus and Scardinius erythropththalmus in forage fish-deficient Tunisian reservoirs

International audienc

Characterization of fish assemblages and population structureof freshwater fish in two Tunisian reservoirs: implicationsfor fishery management

International audienceTo monitor and assess the state of Tunisian freshwater fisheries, two surveys were undertaken at Ghezala and Lahjar reservoirs. Samples were taken in April and May 2013, a period when the fish catchability is high. The selected reservoirs have different surface areas and bathymetries. Using multi-mesh gill nets (EN 14575 amended) designed for sampling fish in lakes, standard fishing methods were applied to estimate species composition, abundance, biomass, and size distribution. Four species were caught in the two reservoirs: barbel, mullet, pike-perch, and roach. Fish abundance showed significant change according to sampling sites, depth strata, and the different mesh sizes used. From the reservoir to the tributary, it was concluded that fish biomass distribution was governed by depth and was most abundant in the upper water layers. Species size distribution differed significantly between the two reservoirs, exceeding the length at first maturity. Species composition and abundance were greater in Lahjar reservoir than in Ghezala. Both reservoirs require support actions to improve fish productivit