Acta Zoologica最新文献

Hymenoepimecis wasps (Hymenoptera: Ichneumonidae) are ectoparasitoids of spiders that modify the hosts’ behaviour by inducing changes in webs. Variations in the male reproductive tract contribute to enhancing our understanding of the reproductive behaviour of these insects. This study describes the morphology of the male reproductive tract of Hymenoepimecis bicolor (Brullé, 1846) using light microscope. The male reproductive tract of H. bicolor consists of a pair of testes, each containing a single follicle, two vasa deferentia, one ejaculatory duct and two accessory glands. The testis follicle has cysts at various stages of spermatogenesis, indicating ongoing sperm cell development and maturation. The vasa deferentia are elongated, with a coiled distal portion, whereas the proximal regions are laterally associated with a pair of accessory glands. The wall of the vasa deferentia has simple cuboidal epithelium. The accessory glands had a simple columnar epithelium with the lumen filled with heterogeneous content. The seminal vesicle is absent. The similarity in the anatomy and histology of the male reproductive tract of H. bicolor with other Hymenoptera suggests that the parasitoid behaviour does not result in significant alteration to their reproductive organs, indicating that the reproductive tract is conserved in Hymenoptera, regardless of their behaviours.

Regeneration varies largely among metazoans. Aside molecular processes, this epiphenomenon depends on the biological complexity and evolutive history of each species during the adaptation to their specific environment. While most species adapted to marine or freshwater conditions can extensively regenerate, those adapted to terrestrial conditions and parasitism lost the ability to regenerate. They are mainly represented from ascelmintes evolving eutely and numerous arthropods and amniotes. High regeneration can only occur in water-adapted species and requires high tissue hydration, indirect development through metamorphosis and often also presence of asexual propagation. Metamorphosis allows the anatomical-physiological transformation of a larva in an adult through an initial destructive phase followed by a constructive (regenerative) phase. Invertebrates and vertebrates that possess genomes including metamorphic genes can re-utilize in part or largely similar genes for the regeneration of lost organs. I submit that during land adaptation in both invertebrates and vertebrates the initial larval stages and metamorphosis were lost or altered as some key genes, including those for telomerases, could no longer be expressed in the dry environment. Consequently, also the initial regenerative ability was lost while other epiphenomena were gained, including complex immunity and behaviour but also an evident process of ageing.

Skin structure of the slow worm lizard Anguis fragilis (Anguidae, Sauria, Reptilia) with emphasis on the epidermal micro-ornamentation in relation to the animal movements (Acta Zoologica, Stockholm). The structure of the skin and superficial micro-ornamentation in the slow worm Anguis fragilis, a limbless lizard with a fossorial activity, was examined using histology, immunofluorescence, scanning and transmission electron microscopy. The scales, with a triangular to trapezoidal shape, are very overlapped and interlocked to form a smooth surface and are reinforced by osteoderms. The epidermis shows a thin Oberhautchen layer merged with a thicker beta-layer that contains corneous beta-proteins. The SEM survey detects a smooth surface made of tile-like patterned Oberhautchen cells with irregular perimeters that form an interlocking surface. Disk-like sensory organs of 15–20 μm diameter are observed only on the head scales, the first to sense the environment and contact the ground. Numerous Oberhautchen denticles, namely corneous thorns of about 0.2–0.3 μm, adorn the caudally directed perimeter of Oberhautchen cells in the ventral scales of the trunk and tail. This microstructure may determine gripping and increased friction with the substrate during the lateral undulating and forward movements of the slow worm. TEM observations reveal sparse short serrated protrusions of Oberhautchen cells that are largely merged with the underlying beta-cells. Altogether, the scale surface of the slow worm efficiently suites this limbless lizard to its environment and lifestyle.

Shrimp fisheries and culture are important food sources worldwide. Central East Pacific fisheries are mainly supported by four species: Penaeus brevirostris, P. californiensis, P. stylirostris and P. vannamei. However, the same shrimp fishery practices, management strategies and closures are applied to these four species despite their differences in life history and reproductive periods. Most molecular studies have focused on the cultured species P. vannamei, while knowledge for the rest of the species is scarce. Therefore, this study sought to examine the transcriptomes of these four shrimp species from the Mexican Pacific at different maturity stages. A total of 165 unigenes were found to be reproduction-related in the four shrimp species. The genes with the highest overall expression levels were associated with ribosomes, transcription and methyltransferase pathways. Moreover, the reproduction-related genes with the highest expression values were polehole protein and ovarian peritrophin. The major expression similarities were primarily among pre-vitellogenic and vitellogenic females within each species, and secondly among the species P. brevirostris and P. californiensis and the species P. vannamei and P. stylirostris. Although these four species might share a geographical location or niche, the expression of reproduction related-genes at different gonadal maturity stages exhibited species-specific variations.

Fertilized bird eggs are an alternative model to conventional animal testing. In recent studies, a preclinical imaging model based on large ostrich eggs was introduced in a clinical research centre using imaging systems designed for humans, thus bypassing the need for dedicated small animal imaging systems. Ostrich eggs are only laid during the season with increased daylength, which limits its year-round availability. The current study focuses on large emu eggs instead of ostrich eggs and aims at investigating its suitability for preclinical imaging research. Physiological development of emu embryos was observed by serial weightings and serial CT scans until developmental day (DD) 46. Differences between fertilized a non-fertilized eggs were analysed. In fertilized eggs, the embryo was identified on CT scans as early as DD 13. As expected, CT scans showed continuous embryonal development and growth over time, comparable to ostriches. Neither the eggs' volume and weight nor the weight loss nor the radiodensity provided significant differences between fertilized and non-fertilized eggs. Despite inferior incubation success in emus compared to ostriches, suitability of emu eggs for artificial incubation and subsequent research was confirmed. Hence, emu eggs represent an alternative model for preclinical imaging and allow a year-round use for research purposes if combined with ostrich eggs.

Investigating the ontogeny of threatened freshwater fishes is vital for designing future conservation actions that will increase the potential of species' persistence. This study provides a detailed description of the early life stages of a threatened freshwater fish species, the Evrotas minnow Pelasgus laconicus, which occupies aquatic ecosystems with extreme seasonal hydrological variation. The study of the embryonic and juvenile stages was conducted in vivo using light microscopy from eggs obtained from acclimatized wild spawners at 20 ± 1°C. Fertilized eggs were spherical and transparent with a mean diameter of 1.24 ± 0.06 mm and the average length of free embryos at hatching was 3.85 mm NL (notochord length). The main morphological changes observed are related to the absorption of the yolk, the increase and distribution of the melanophores and the sequential development of the fins. In conclusion, the Evrotas minnow was identified as a multiple spawner, exhibiting a protracted reproductive period (March to August), a particularly short egg-hatching period (5–6 days), a short free embryo stage and a rapid onset of exogenous feeding (2 days). The conservation implications of our study, such as safety stock creation, population reintroduction, conservation of fish refugia and breeding habitats and beaver dam analogues, are discussed.

Walking is a locomotion mode in which animals move over the ground using their appendages. Walking is observed in both terrestrial and aquatic animals, but the morphology and diversity of appendages in the latter group have been less extensively studied. The present paper reports on the “adhesive areas,” which may represent morphological and physiological adaptations for stable aquatic walking, in the paintpot cuttlefish, Ascarosepion tullbergi. This animal employs arm IV as a forelimb and an ambulatory flap as a hindlimb for walking, resulting in a gait-like manner of movement. The structure of the adhesive area is exclusively located on the ventral skin surface of arm IV and the ambulatory flap, which are in contact with the ground during walking. The “adhesive areas” are characterized by a dense population of adhesive mucus-secreting cells and the development of numerous wrinkles on the surface. These features may enhance the gripping and sticking capacity of the ground-contact area, thus improving walking stability. The use of adhesive areas for walking is a unique feature of A. tullbergi, as other cuttlefish with adhesive areas primarily use them for attaching to substrata in strong currents. Our results contribute to the understanding of the locomotion strategy of cuttlefish.

Capturing data on the life of fossorial vertebrates is difficult since access to the subterranean environment is made unfeasible by its density and opacity. Collecting specimens is only possible through excavation work, causing damage or even death to the specimens. Due to the obstacles of in situ studies, the scarce information comes from reports obtained indirectly, mainly through specimens preserved in museums. Considering the adaptations to fossoriality, investments in studying these groups could be very enlightening since they would contribute enormously to the knowledge of the evolutionary strategies developed throughout the colonisation of the subterranean world. Amphisbaena alba is the species of Amphisbaenia with the broadest geographic distribution in the world. It occupies virtually all countries in South America except for Chile and southern Argentina. This study, carried out over the last 36 years, aims to provide data on the biology and behaviour of A. alba in captivity and in the field. Our main objective is to provide subsidies to expand the knowledge of the life history of this species and, by extension, of amphisbaenians in general.