Influence of dietary protein level on growth performance and body composition of juvenile blackspot seabream, Pagellus bogaraveo(Brunnich, 1768)

Blackspot seabream Pagellus bogaraveo is a potential candidate species for southern European aquaculture. A 12‐week feeding trial was then conducted to evaluate the effect of dietary protein level on growth performance, body composition and feed use efficiency of blackspot seabream juveniles (22·7 g each). Five isolipidic diets (12·5%) with graded levels of protein (20, 30, 40, 50 and 60%) were hand‐distributed, twice a day, to duplicate groups of fish (120 fish per tank), until satiation. Growth (DGC), survival and feed utilization (FCR) were recorded through monthly sampling. Growth performance was significantly affected by dietary protein level ( P  < 0·05), and fish fed at the 50% protein level exhibited the highest final body mass. Feed conversion ratio decreased with increasing levels of dietary protein, fish fed 60% protein being the most efficient. No significant differences were found in whole body composition among treatments ( P > 0·05). Financed by FCT (Project POCTI/CVT/39239/2001, PhD Grant SFRH‐BD‐14068–2003)     

Native Colonizing Species and Degraded Land Restoration in La Gran Sabana, Venezuela

We evaluated the ecological and reproductive characteristics of plant species occurring in severely disturbed areas that were revegetated with exotic grasses. We identified those species with the best combination of attributes that increase their probability of success in degraded lands. Fifteen degraded areas were studied in two different bioclimatic regions, a high premontane humid bioclimate and a low premontane humid bioclimate. The frequency of native colonizing species and the presence of arbuscular mycorrhizal colonization in their roots were evaluated. The sexual and breeding system, pollination mode, fruit set, and dispersal syndrome of ten of the most frequent colonizing species were also studied. The floristic survey of the colonizing species revealed a similarity to the reported flora of the treeless savannas that are dominant in the region. Bioclimatic conditions prevailing in the degraded lands seem to be an important factor for the presence of colonizing species and for species richness. All colonizing species studied were mycorrhizal, and for this reason the restoration program in these degraded areas should take mycorrhizae into account, reintroducing them or manipulating the soils to increase the mycorrhizal inoculum. We suggest Scleria cyperina and Trachypogon plumosus to start or promote the natural succession in the degraded areas from La Gran Sabana. Because their frequency is high and their reproductive system is less dependent on biotic factors, these species stand out in the studied areas.     

Morphometry of the sexual forms of Acromyrmex subterraneus brunneus Forel, 1911 (Hym., Formicidae) in queenright and queenless laboratory colonies

Abstract:  A morphometric study was performed on the sexual forms of Acromyrmex subterraneus brunneus in colonies kept under laboratory conditions. The males studied were obtained from queenright and queenless colonies, i.e. they were produced by either the queen or the workers. Cluster analysis revealed a wide distribution in the size of the sexual forms produced in queenless colonies compared with queenright colonies, and that some of the worker-produced males were significantly smaller than those produced in queenright colonies. However, we found no indication that the males produced in queenless colonies are unable to mate, as smaller and larger males had identical genitalia that varied only in size, and therefore probably represent an alternative route of reproduction in this species.     

Physical resistance as a criterion in the selection of foraging material by Acromyrmex subterraneus brunneus Forel, 1911 (Hym., Formicidae)

Abstract:  Leaf-cutting ants forage on a wide variety of plant species using the physical and chemical characteristics of the plants as a selection criterion. In order to determine the influence of the physical factor on the selection of foraging material, inert materials such as floral sponge, polystyrene, plastic and clay, which possess different degrees of physical resistance to cutting, were offered simultaneously to five Acromyrmex subterraneus brunneus colonies, and assessed 12 and 24 h after foraging. No substrate selectivity was observed during foraging. Physical resistance was used as a decision criterion for the incorporation or return of the foraged material. This fact suggests the existence of a second time of selection of the foraged material inside the colony during cultivation of the symbiontic fungus.