Annales des Sciences Naturelles - Zoologie et Biologie Animale最新文献

A conspicuous epidermal thickening at the right ventral side of the anterior end of early larvae of Branchiostoma lanceolatum is described from serial TEM sections. This enigmatic structure is documented in several older studies concerned with other larval structures, but has not been described recently. Its cells show the typical characteristics of mucus-producing cells. Specializations of the basal extracellular matrix and the underlying mesothelium suggest that transport processes into the glandular cells occur. The function of this secretory organ in an ontogenetic stage that is thought to be planktonic is enigmatic. Suggestions of homologies from the literature are briefly discussed.

In this work twenty-four measurable morphological characters of Synisoma mediterranea and Synisoma nadejda were studied. The aim was to determine whether the two species, which are often confused, are really different. Discriminant canonic analysis and generalized distance of Mahalanobis enable us to select four new discriminant morphometric characters. They provide more evidence of differences between the two species.

Comparative study of the epidermis of lepidosaurian reptiles helps us to understand the formation of the shedding complex which determines epidermal shedding. The present ultrastructural study has analyzed the complete sequence of epidermal differentiation in the agamine lizard Physignatus lesueurii from 1 to 80 days post-hatching. Beneath a β-layer 20–40 layers of cells with an α-pattern of keratinization are produced, starting from narrow cells (mesos-like) followed gradually by typical thicker α-cells. At 80 days post-hatching an α-layer is still forming and the first epidermal shedding has still to take place. The differentiation of a shedding complex has been studied on the epidermis at 38 and 64 days of tail regeneration. Beneath the superficial regenerating (wound) epidermis, cells of the clear layer contain a meshwork of coarse and fibrous filaments which appear to turn into large keratohyalin-like granules. This extensive cytoskeleton may determine the progressive hardening of clear cells that function as a template for the formation of the large microornamentations of the underlying layer, a process that might be generalized for the genesis of microornamentations in all lepidosaurian reptiles. The microornamentations in Physignatus have a honey-comb pattern and are produced by the fusion between ‘oberhautchen” and β-cells.

Skeletochronology, used to assess some life history traits in the viviparous African toad, enables us to determine that longevity in natura does not exceed 5 years in females and reaches at least 2 years in males. After sexual maturity, reached at four months, the rate of osteogenesis decreases, as probably does body growth. In this study we discovered a strong endosteal bone resorption in long bone cortices in both males and females. This phenomena only occurs during the first resting period. This period occurs from October (individuals of 5 months old) to March (individuals of 10 months old). During this time toads are underground and their metabolism is thought to be low. The origin of such an endosteal resorption remains more or less unknown.

The freshwater African catfish family Amphiliidae had been reviewed based on the 73 osteological characters with Diplomystidae, † Hypsidoridae, Amblycipitidae, Sisoridae, and Bagridae as out-groups. Because the family position of Leptoglanis (Bagridae/Amphiliidae) is under debate, this genus has been taken as an out-group too. Results of the study indicate that: 1) the Amphiliidae is not a monophyletic group and must now be restricted to the genera Amphilius and Paramphilius; the two subfamilies Amphiliinae and Doumeinae are separated by the sisorids Euchiloglanis (with most of the glyptosternid fishes) and Glyptothorax (with most of the non-glyptosternid fishes); 2) no synapomorphies were found for the subfamily Amphiliinae. 3) The five genera of subfamily Doumeinae constitute a monophyletic group, Andersonia being the sister-group of the four other genera; subfamily Doumeinae + Leptoglanis form the family Doumeidae. The glyptosternids no longer belong to the Sisoridae (family restricted to the non-glyptosternids) and represent the new family Glyptosternidae.

The maximum sagittal curvature of the long bones (humeras, radius, ulna, femur, tibiotarsus and tarsometatarsus) of 45 specimens of birds, belonging to 36 species, was measured and regressed to the corresponding body mass. Mathematical results show a tendency of curvature to scale with strong positive allometry. Within the species studied, those with more characteristic flapping flight tend to show relatively low values of curvature in the wing bones. To check the agreement of the present results with current hypotheses on the origin of long bone curvature, previous results on scaling of myological and cross-sectional parameters in birds are considered. Indirect evidence suggests that curvature tends to increase bone stresses. Hypotheses that consider curvature as a consequence of the mechanical action of muscle allocation and optimization of functional strains are discussed at length. The possible double genetic-epigenetic determinism of the curvature character is evoked.

Temperature-dependent sex determination has been recently characterized for leatherbacks (Dermochelys coriacea) from Playa Grande, on the Pacific coast of Costa Rica. The authors concluded that the pattern of TSD in leatherbacks from Pacific Costal Rica is the same as for leatherbacks from French Guiana, in the Atlantic. However, no statistical tests were performed to validate their conclusion. Here, we use a maximum-likelihood test to look for a possible difference between the populations. We found that the pattern of temperature-dependent sex determination in Atlantic and Pacific leatherbacks was significantly different. The temperature producing 50 % of each sex was not significantly different in both groups, but the range of temperatures producing both sexes was significantly narrower for the French Guiana population. We hypothesize that this difference could reflect a lower genetic polymorphism for temperature-dependent sex determination in this population. A low genetic diversity in the Guiana population compared to the Playa Grande population has been already observed for mitochondrial haplotypes. Our results emphasize the importance of statistical analyses in studies of temperaturedependent sex determination.

Primates exhibit a great variety of arboreal locomotor modes associated with their size and postcranial morphology. The study of sympatric primates is interesting in that it may reveal how primates of different sizes and anatomies move and select for forest structure. This study reports on preliminary data on the locomotion of six non-ateline platyrrhines found in the Yasuni National Park, Napo Province, Ecuador. Pygmy marmosets are confined to the understory using scansorial locomotion and quadrupedalism, preferring large vertical supports. Golden-mantled tamarins, common squirrel monkeys and dusky titis also range in the understory, moving by quadrupedal walk and leap, mainly on small horizontal supports. Monk sakis are found in the main canopy and use quadrupedal walk and less leap on medium-sized horizontal supports. Whitefronted capuchins use the understory and the main canopy equally often, walking quadrupedally and leaping on small and medium-sized oblique supports. In general, smaller species occupy lower strata while larger species tend to spend more time in the upper strata. Small tegulae-bearing monkeys showed the highest proportions of large vertical support use. For all species, leaping was the main gap-crossing mode, though decreasing in proportion with a higher use of the upper forest layers.

Corythomantis greeningi, a casque-headed tree frog, was studied in the field and in captivity. This species belongs to a monotypic genus, and together with other species of anurans, possesses a differentiated head which is flat, very rough and presenting cranial co-ossification with the skin. These are characteristics that are usually associated with phragmotic behaviour which is supposed to have a role in water saving and protection against predators. Observations were focused on the characteristics of the species which make it adapted to life in the Brazilian semi-arid (“caatinga”). Data about the body and external anatomy of the head, integument morphology, life, reproduction, interest for sheltering and defense against desiccation is presented. Finally, it is proposed that adaptation of this species to the dry environment is probably the result of the synergism of a number of different strategies against water loss, including phragmosis.