Zoology最新文献

Every year, more and more discoveries of photoluminescence in different mammal species are made. The more recent cases thus far have been in duck-billed platypus (Ornithorhyncus anatinus), New World squirrels (Glaucomys spp.) and springhare (Pedetidae). Now we can add another species to the list: the garden dormouse (Eliomys quercinus), an endemic rodent to Europe, currently categorized as Near Threatened (NT) by the IUCN. The fluorescence was described and compared qualitatively in museum specimens, deceased and hibernating animals. The feet and nose of the hibernating dormouse displayed greenish-blue photoluminescence under UV light through a yellow filter, whereas the fur was bright red. The live animal had more vivid red colouring than the museum specimen. The fading and changing of the colour and brightness of photoluminescence was observed in a recently deceased animal and even more strongly in museum specimens.

Shark intestine presents a complicated three-dimensional morphology, characterized by the development of a coiled internal septum. A basic question regarding the intestine is its movement. This lack of knowledge has prevented the testing of the hypothesis on its functional morphology. The present study, to our knowledge, for the first time, visualized the intestinal movement of three captive sharks using an “underwater ultrasound” system. The results indicated that the movement of the shark intestine involved strong twisting. We suspect that this motion is the mechanism that tightens the coiling of the internal septum, enhancing compression of the intestinal lumen. Our data also revealed the presence of active undulatory movement of the internal septum, of which the undulatory wave propagated in the opposite (anal-to-oral) direction. We hypothesize that this motion decreases the flow rate of the digesta and increases absorptive time. These observations indicate that the kinematics of the shark spiral intestine are more complicated than expected based on morphology, and the fluid flow in the intestine is likely highly regulated by intestinal muscular activity.

During tail regeneration in lizards the new corneous layer formed in the regenerating epidermis includes antimicrobial peptides, cystatin and serpins, likely forming an anti-microbial barrier. The present study aims to reveal other proteins potentially contributing to this protective barrier of the epidermis. Using immunohistochemistry we have detected a peptidoglycan-like recognition protein-3 (pglyrp3), an antimicrobial molecule, and an epidermal growth factor receptor kinase 8 l (eps8l), a receptor of EGF (Epidermal Growth Factor) that stimulates epidermal formation. The study shows that the two proteins are mostly accumulated in the forming wound epidermis and in the shedding layer of the regenerating scales. The shedding layer is the intra-epidermal layer that allows the separation of the initial corneous layer from the regenerating epidermis. While presence of pglyrp3 is likely related to the formation of the anti-microbial barrier, the function of the eps8l protein in epidermal regeneration remains unknown. Whether the latter protein is involved in keratinocyte movement within the regenerating epidermis has to be specifically determined in future studies. Together with the antimicrobial peptides cystatin and serpins, previously detected in the wound epidermis and shedding layer, the present study indicates that pglyp3, and potentially eps8l, contribute to protect the new skin and underlying regenerated tissues from the potential microbe invasion.

Functional morphology considers form and function to be intrinsically related. To understand organismal functions, a detailed knowledge of morphological and physiological traits is necessary. Regarding the respiratory system, the combined knowledge about pulmonary morphology and respiratory physiology is fundamental to understand how animals exchange gases and regulate critical functions to sustain metabolic activity. In the present study, the paucicameral lungs of Iguana iguana were analyzed morphometrically through stereological analysis using light and transmission electron images and compared with unicameral and multicameral lungs of six other non-avian reptiles. The morphological data were combined with physiological information to perform a principal component analysis (PCA) and phylogenetic tests of the relationship of the respiratory system. Iguana iguana, Lacerta viridis, and Salvator merianae presented similar pulmonary morphologies and physiologies when compared to Varanus examthematicus, Gekko gecko, Trachemys scripta, and Crocodylus niloticus. The former species showed an elevated respiratory surface area (%A_R), a high diffusion capacity, a low volume of total parenchyma (V_P), a low percentage of parenchyma concerning the lung volume (V_L), and a higher surface/volume ratio of the parenchyma (S_AR/V_P), with high respiratory frequency (f_R) and consequently total ventilation. The total parenchymal surface area (S_A), effective parenchymal surface-to-volume ratio (S_AR/V_P), respiratory surface area (S_AR), and anatomical diffusion factor (ADF) showed a phylogenetic signal, evidence that the morphological traits are more strongly correlated with the species' phylogeny than the physiological traits. In sum, our results indicated that the pulmonary morphology is intrinsically related to physiological traits of the respiratory system. Furthermore, phylogenetic signal tests also indicate that morphological traits are more likely to be evolutionary conserved than physiological traits, suggesting that evolutive physiological adaptations in the respiratory system could happen faster than morphological changes.

The evolutionary transformation of limb morphology to the four-segmented pantograph of therians is among the milestones of mammalian evolution. But, it is still unknown if changes of the mechanical limb function were accompanied by corresponding changes in development and sensorimotor control. The impressive locomotor performance of mammals leaves no doubt about the high integration of pattern formation, neural control and mechanics. But, deviations from normal intra- and interlimb coordination (spatial and temporal) become evident in the presence of perturbations. We induced a perturbation in the development of the neural circuits of the spinal cord of mice (Mus musculus) using a deletion of the Wilms tumor suppressor gene Wt1 in a subpopulation of dI6 interneurons. These interneurons are assumed to participate in the intermuscular coordination within the limb and in left-right-coordination between the limbs. We describe the locomotor kinematics in mice with conditional Wt1 knockout and compare them to mice without Wt1 deletion. Unlike knockout neonates, knockout adult mice do not display severe deviations from normal (=control group) interlimb coordination, but the coordinated protraction and retraction of the limbs is altered. The forelimbs are more affected by deviations from the control than the hindlimbs. This observation appears to reflect a different degree of integration and resistance against the induced perturbation between the limbs. Interestingly, the observed effects are similar to locomotor deficits reported to arise when sensory feedback from proprioceptors or cutaneous receptors is impaired. A putative participation of Wt1 positive dI6 interneurons in sensorimotor integration is therefore considered.

Characterizing the factors that shape variation in brain size in natural populations is crucial to understanding the evolution of brain size in animals. Here, we explore how relative brain size and brain allometry vary with drainage, predation risk and sex in natural populations of the electric knifefish Brachyhypopomus occidentalis. Fish were sampled from high and low predation risk sites within two independent river drainages in eastern and central Panamá. Overall, we observed low variation in brain-body size allometric slopes associated with drainage, predation risk and sex category. However, we observed significant differences in allometric intercepts between predation risk sites. We also found significant differences in relative brain mass associated with drainage, as well as significant differences in absolute brain mass associated with drainage, predation risk and sex category. Our results suggest potential constraints in brain-body allometry across populations of B. occidentalis. However, both drainage and predation risk may be playing a role in brain mass variation among populations. We suggest that variation in brain mass in electric fishes is affected by multiple extrinsic and intrinsic factors, including geography, environmental complexity, social interaction and developmental or functional constraints.

The key role of the skull in food intake and processing implicates its morphology should be to some extent adapted to the functional demands present in different diets, while also showing similarities between those which are closely related. Sigmodontine rodents, with a generalist body plan and broad dietary habits, are an interesting case study to explore these relationships. We used linear morphometrics to assess craniomandibular morphology, and explored its relationship with dietary composition and phylogeny in a sample of sigmodontines from central-eastern Argentina, representative of this subfamily’s morphological and ecological diversity. We took 26 measurements performed on 558 specimens belonging to 22 species, and resorted to bibliographic information for proportion of food items in their diets, dietary categories, and phylogeny. Multivariate statistical analyses revealed a strong evolutionary integration between morphological traits of crania and mandibles, and a conspicuous relationship between them and dietary composition in our study group, independent of phylogeny. Species of larger sizes exhibited more robust skulls and a tendency towards folivorous diets, whereas smaller species had more gracile craniomandibular apparatuses and diets richer in seeds and invertebrates. Additionally, we used the observed patterns to made predictions of dietary categories for the three species of this region with unknown diets, completing the map of feeding ecology of one of the most researched group of sigmodontines and enabling future studies to further explore this topic. The present work contributes to understanding the link between morphology, ecology and phylogeny in small mammals.

Congeneric species often coexist in sympatry using behavioral and morphological adaptations to reduce competition and interspecific interference, but reproductive patterns behind coexistence remain unknown. We analyzed the gonadal morphology and development, reproductive cycle, and population structure of two sympatric congeneric fishes to evaluate the degree of overlap and differentiation of the reproductive biology between species in a Neotropical river. Development of testes and ovaries were similar between species, both showing asynchronous gonadal development, large diameter of gametes and synthesis of mucosubstances by follicle cells to form adhesive eggs. Although the morphometry of germ cells did not present differences, the zona radiata of mature eggs in Hypostomus garmani was markedly thicker than H. francisci, which suggests different spawning habitats. Both species have greater reproductive activity in the rainy season, concomitant with increase in water temperature, however H. garmani initiates and ends its reproduction earlier than H. francisci, indicating a differentiation of reproductive periods. Sexually mature males and females of H. francisci reproduced at a larger mean size then H. garmani. The two congeneric species had a similar abundance and sex ratios in the study area. Results show that although the species exhibited broad overlap of reproductive traits, a spatial and temporal differentiation of the reproductive biology was present. This study contributes to understanding reproductive mechanisms that may facilitate coexistence between congeneric sympatric species.

The freshwater gastropod Latia neritoides is endemic to the streams of New Zealand’s North Island. This species has evolved a unique defence system: it exudes a luminescent mucus thought to deter predators. While the bioluminescence itself has been investigated before, the underlying gland system has remained unstudied and relevant information to understand the defence system has been missing till now. For the release of the glowing mucus of L. neritoides two places of origin were assumed: the lateral foot area or the mantel cavity. In this study the focus was on the first suggestion. To gain insight into the defence system, morphological as well as histochemical analyses were performed involving all secretory gland types in the sub-epithelial foot layer. The results were compared with the foot gland system of Neritina sp., a snail living in a comparable habitat, but using a different survival strategy. The gland types of the two gastropods were compared and their mucus types were investigated. Seven subepithelial gland cell types can be distinguished in the foot region of L. neritoides. Neritina sp., in contrast, has six gland cell types of which three laterally located ones are epithelial. Both species show a pedal gland in the anterior foot region. A striking difference between the species are two prominent subepithelial gland cell types (L1l/L2l) in the lateral foot area of L. neritoides, which are missing in Neritina sp. These gland cells are distributed throughout the entire lateral foot area of L. neritoides and make up about 85% of the mucus gland cells in this area. Defence mucus and trail mucus of L. neritoides show different specificities in lectin staining, but are not equally represented in the gland cell types. Yet, based on the huge size and high density of L1l and L2L, we envision a role for these gland types in the defence system.

The red-legged partridge (Alectoris rufa) is a medium-sized galliform endemic to southwestern Europe. In the easternmost part of the species’ range, the population inhabiting Elba Island (Tuscan Archipelago National Park, Italy) is of undisputed conservation value. While we found nuclear and maternal DNA introgression with the exotic chukar partridge (A. chukar) in previous studies based on microsatellite DNA (n = 25) and two mitochondrial markers (n = 103), respectively, we disclosed a limited or null admixture in a few Elban partridges (n = 4) in a recent genomic investigation relying on 168,675 Single Nucleotide Polymorphisms (SNPs). We herein carried out an extended microsatellite DNA survey including additional 65 samples (total, 90) and six loci (total, 11) to determine both spatial structure and genetic integrity of local A. rufa. A sharp divergence between the subpopulations inhabiting the two sides of the island was disclosed, and the microsatellites indicated that all Elban partridges were not admixed with the chukar, thus fully reflecting the picture inferred using SNPs. We hypothesized that the spreading of chukar genes was constrained by negative selection, with the persistence of only the maternal lineage being indicative of thermal adaptation. The two subpopulations should be treated as distinct Management Units, and an envisaged plan to secure a stock onto nearby Pianosa Island could not only warrant endurance of the Elban population but also establish a source of valuable founders for the ex-situ management of the species in Italy. Our study exemplifies how a suitable samples/loci combination is the key to solve wildlife issues dealing with introgression.