Acta Zoologica最新文献

Determination of sex on the base of external morphological features is very difficult in most birds. However, molecular sex identification methods can be used for sexing of these so-called monomorphic bird species. This study analysed the sexual dimorphism of radiographic morphometric features in rock pigeons whose sexes were determined by the molecular sex identification method. Body weights and 21 radiographic measurements of 43 rock pigeons (18 males and 25 females) were taken. Among cranium measurements, the skull width value was statistically significant in terms of gender (p < .01). Length of carpometacarpus (p < .001) was the most statistically significant measurement of the thoracic limb skeleton, and length of tarsometatarsus (p < .01) was the most statistically significant measurement in the pelvic limb. The body weight showed a positive correlation with all measurements. It was observed that 81.4% of the samples were classified correctly with the measurements used in the discriminant analysis. With this study's results, it can be concluded that sex determination in rock pigeons can also be made by radiographic morphometric methods. In addition, more measurements can be obtained with radiographic images compared to external morphometry.

The optical light microscopy and scanning electron microscopy techniques have proven to play a key and noteworthy role in the advancement of morphological studies in general, and in investigating fish scale morphology in particular. These techniques have illustrated several hidden architectural structures in scales that contribute effectively to fish identification and classification. The scale morphological and topological characters such as type, size, shape, lateral surface, focus position, circuli appearance, radii type, lepidonts, and posterior and anterior margin shapes were obtained using macro- and microscopic analysis in six body regions for three size classes of Garra sharq, a cyprinid endemic fish of the Arabian Peninsula. The general scale type in the studied G. sharq species was a basal elasmoid cycloid and a sectioned type. As a protective structure, the scales display several specific characteristics including firm attachment to the fish body, overlapping, and thin structure with a high surface area and high strength. These characteristics improve scale resistance to penetration, increase protection against mechanical injury and microbial infection, enhance scale flexibility, reduce fish weight (reduce friction drag), and increase scale transparency. The scales demonstrate plasticity in focus shape, size, and position in the six fish body parts and fish size groups. The examined scales displayed narrow or wide grooves (radii) in three types including primary, secondary, and tertiary present in all four scale fields (anterior, posterior, and laterals), thus a tetra-sectioned type that is almost specific to the genus Garra. This characteristic also increases scale flexibility. The rostral margin of scales was characterized by the presence of waved and striate types. The lepidont shape and size varied being blunt, flat, pointed, tiny, sharp, short, and long. Some of these scale characters and their morphologies could be used as an alternative tool for identification, classification, and phylogenetic interpretation among the different freshwater fish species and genera.

This study gives a comprehensive description of eyelids movement in little owl and discusses the impact of some surrounding conditions in their kinetic performance. The present study used the video's recording technique to record the kinetic activity of eyelids, besides the anatomical and histological studies of the eyelid's structure. The fundamental eyelid movements can be uniquely and reliably characterized by their anatomical relationship that was confirmed via video recording for their kinetic activity. The levator palpebrae muscle is considered a main generating motor for the upper eyelid; in the little owl, this muscle splits into multiple directions and is distinguished from the levator palpebrae superioris (Lps) and the levator anguli oculi (Lao) muscle. That anatomical pattern of insertion increases the movement of the upper lid. On the other side, the contraction of depressor palpebrae inferioris (Dpi) muscle and the active upward forces of levator palpebrae muscle help in increasing the opening of the eye's fissure. However, the closure process is produced from the passive downward forces and relaxation of the levator palpebrae superioris (Lps), levator anguli oculi (Lao), and depressor palpebrae inferioris muscle, as well as the contraction of retractor anguli oculi lateralis (Raol) and medialis (Raom) muscle. The present results also recorded that nictitating membrane's (Nm) movement is reversely proportionate to the level of kinetic of other eyelids. The mobility of Nm in little owl occurs under the effect of artificial external stress. These anatomical data and sequence video recordings have confirmed that the upper eyelid moves more compared to other eyelids. The authors also suggest that the mobility of eyelids may get stimulated through external pressure force of some surrounding structure like the periorbital sheet. Also, the histological study exhibited that the structure of two eyelids is very similar in the little owl and the variability is showing in the number of cell layers that forms their epithelium of skin and palpebral surfaces, the distribution of pigment granules, and degree of keratinization on their surface. That variability in the histological characters of eyelids may counteract the abrasive forces occurring during the opening and closing processes.

Studying sexual dimorphism facilitates better understanding of the general intersexual divergence of the same species and gives insights into the impact of selective forces on each sex. The sexual dimorphism in anuran external morphology or limb muscles has been well studied in reproductive context, but less so outside the breeding season. Herein, the intersexual differences in 12 external morphological characteristics, 11 forelimb and 12 hindlimb muscles of Hylarana guentheri during non-breeding season were investigated. We found that the males possessed significantly greater head width and tympanum diameter, while the females had significantly larger body size and head length; there was no sexual differences in the examined limb muscles, except for the mass of flexor carpi radialis. The larger body size means greater fertility for the females, and the longer head may be related to the allometry and reduce resource competition. For the males, the wider head is likely correlated with prey size and male–male competition, and also, the larger tympanum and heavier flexor carpi radialis probably aid the productive success. This study provides the comprehensive morphological accounts about the sexual differences of H. guentheri during non-breeding season, which will contribute to clarify the sex-specific resource allocation and reproductive strategies of anurans.

Myzostomida are putatively nested within the errant Annelida and exhibit a unique morphology. The latter fact might possibly be related to their long host-dependent radiation. Hence, an incomplete segmentation, lack of prominent sensory structures in adults and a dorso-ventrally flattened body are just some examples. Although numerous investigations of the nervous system exist for myzostomids, detailed ultrastructural as well as histological examinations of neuronal structures are lacking so far. Therefore, we investigate the nervous system of Myzostoma cirriferum Leuckart, 1836 using a comparative approach including paraffin histology, serial semi-thin sections, immunohistochemistry and ultrastructural investigations. Our analyses reveal a lack of complexity within the anterior-most neuronal condensation (herein called brain) of adult specimens. Hence, prominent tracts or glomeruli are absent, and a glial layer surrounding the brain or radial-like glial cells are lacking. Nevertheless, the ultrastructure of the ventral nervous system is comparable to other Errantia. Therefore, our investigations hint towards a reduction of neuronal complexity in Myzostomida. Additionally, an ontogenetic simplification seems plausible, although further investigations are necessary to verify such a hypothesis. A simplification of neuronal structures due to a drastic change in lifestyle was so far mainly observed for basally branching annelid clades.

Review. The regenerating tail of lizard transits through a tumour-like stage represented by the regenerative blastema. Acta Zoologica (Stockolm). Molecular studies on lizard tail regeneration indicate that the blastema stage is a tumour-like outgrowth capable of self-regulate to produce a new tail. Various oncogenes and tumour suppressors are expressed, and their proteins are localized in specific regions of the growing blastema. SnoRNAs are exclusively overexpressed in the tail blastema suggesting changes in ribosome translation efficiency in blastema cells, like in cancer. Blastema cells secrete high levels of hyaluronate and adopt an anaerobic metabolism (Warburg effect). These studies indicate that the lizard blastema represents a unique case among terrestrial vertebrates of physiological tumour remission. Mesenchymal cells and fibroblasts forming the blastema are turned within 1–2 months into a functional organ, the tail. In vitro studies on isolated mesenchymal cells from the regenerative blastema shows that these cells do not undergo contact inhibition but continue proliferation after confluence, and contain nestin, vimentin and K17. After 2–3 weeks they stratify into 5–7 layers forming a pellicle of loose connective tissue. Future molecular studies on genes and proteins that allow the control of growth in the lizard blastema may help to determine how lizards turn a tumour into a new organ with numerous differentiated and functional tissues, providing clues on cancer growth regulation.

Reproductive traits are critically important for understanding how organisms adapt to their respective environments. In this study, we provide information on relative litter mass (RLM) and other litter and neonate related characters of nine female Plestiodon lynxe captured in the field. We also recorded seven body dimensions in 16 neonates and 15 two-month juveniles, and on the basis of these dimensions we compared the body shape of these two age classes to detect changes in the proportions of body parts. The average litter size (4.55) is larger than that found in other viviparous species of Plestiodon, but smaller than those of congeneric oviparous species of similar size. However, the average body size of newborns (25.49 mm) is similar to that of other oviparous and viviparous species of Plestiodon. The average RLM was relatively high (0.36). The relative size of the head and limbs becomes proportionally smaller, whereas the axilla-groin length becomes proportionally larger in the first 2 months of life. We suggest that these changes are related to changes in locomotion and microhabitat use.

The abdominal and pregenital segments and genitalia were studied in males of Zaphne barbiventris (Zetterstedt, 1845) and Delia fabricii (Holmgren, 1872) (Anthomyiidae). The examined species are very similar in the structure of the sclerites and muscles of their terminal segments. Differences between Delia Robineau-Desvoidy, 1830 and Zaphne Robineau-Desvoidy, 1830 were found only in the structure of the pregenital segments and their muscles. Delia has well-developed and well-identified tergite VI, while tergite VI of Zaphne is fused in syntergosternite VI + VII + VIII as indicated by the insertion of muscles of ITM 5 running from tergite V. Within members of the muscoid grade, the skeleton and musculature of male terminalia of the Anthomyiidae were similar to that in the subfamily Azeliinae of the Muscidae and the Scathophagidae. The complete set of phallapodeme muscles, as well as the complete set of muscles of the pregenital sclerites and the position of cercal muscles M 26, has shown that the Anthomyiidae have more plesiomorphic character states than other members of the muscoid grade. Descriptions and figures of the terminal sclerites and muscles of Zaphne barbiventris are provided.

The scale morphology of pleuronectiforms in the Gulf of Oman remains insufficiently known. This study used light microscopy and morphological analysis to examine scale variation across the flank of four Tonguefishes species; Cynoglossus arel, C. bilineatus, C. lingua, and C. puncticeps. Scales were extracted from six flank regions, three on the eyed and blind sides, respectively. The most differentiated species was C. arel, which showed significant differences in four size variables in five regions. In Cynoglossus arel and C. lingua, the scales of the eyed side were ctenoid, and those scales from the blind side were cycloid; C. puncticeps have ctenoid scales on both flank sides and C. bilineatus has cycloid scales on both sides. All species' scales on the blind side have fewer ctenial spines (except in C. bilineatus). This study indicated that scale morphology demonstrated considerable variation among the flank regions of the examined species. As a result, the scales from the head and the trunk regions of the eyed side and the scales from the head region of the blind side have a good power of species separation in this family.

The distribution of orexin-A and orexin-B immunoreactivity was examined in the pituitaries of the white-spotted conger (Conger myriaster) and the Japanese eel (Anguilla japonica) using immunohistochemical techniques. Orexin-A-immunoreactive puncta were dispersed in the pars nervosa of the neurointermediate lobe, and a part of these puncta were immuno-positive for galanin. In contrast, orexin-B immunoreactive cells were observed in the proximal part of the pars distalis, and these cells were immuno-positive for luteinizing hormone. Considering the present results and previous findings, orexin-A and orexin-B may modulate the secretion of α-melanocyte-stimulating hormone and growth hormone, respectively, and participate in the regulation of energy homeostasis.