Acta Zoologica最新文献

Ciliated and non-ciliated mechanosensory cells in invertebrates have intricate cytoskeletal structures that, combined with microtubules, act as a mechanical link between external stimulus and signal processing. As a result, they can perceive forces like touch, cuticle deformation, gravity and sound. Through the expression of antibodies against serotonin (5-HT), calbindin, inducible nitric oxide synthase (iNOS) and α-smooth muscle actin (αSMA), this research aims to investigate mechanosensory cells in the integument of Lumbricus terrestris (Linnaeus, 1758) in an evolutionary perspective. In the epidermis, we discovered isolated mechanosensory cells that were immunopositive to every antibody examined. Our findings improve the knowledge and the evolution of annelid sensory biology adding new insights on the sensory signal transduction and help to better understand the morpho-structural adaptations of invertebrate skin on an evolutionary scale and to give more taxonomic data for species distinction.

Secondary sexual dimorphism is an interesting and stupendous subject of research study due to the fact that it is a result of sexual selection, mostly attributed to either female mate choice or male–male competition. This study aims to investigate the microscopic characterization of scales and fin rays in several aphaniids (Cyprinodontiformes: Aphaniidae) to find out the possibility of using these structures as secondary sexual dimorphism traits and discuss their taxonomic and evolutionary significance. Herein, the results reveal that (i) male individuals of aphaniid species of the genera Aphanius, Aphaniops and Paraphanius present contact organs in the forms of ctenus-like structure (in posterior margin of the scales) and spicule-like structure (in anal fin rays) that show sexual dimorphism of scales and fins; (ii) number, position, size and shape of contact organs provide taxonomic signal to distinguish members of the genus Aphaniops from two other genera; (iii) females of Aphaniops ginaonis also represent contact organs in scales but fewer than males and (iv) as the sexual dimorphism results from different sexual selection pressures acting on males and females, it provides evolutionary signals.

This study aims to characterize the gonads, folliculogenesis, and spermatogenesis processes of male and female Rhinella bergi through anatomical, histological and morphometric analysis. We worked with specimens previously collected in the spring and summer seasons (2014–2015), in which the gonads were studied based on morphological, histological and morphometric analysis. The reproductive system was analyzed using a stereoscopic microscope and a scanning electron microscope (SEM). Histological preparations were made following the conventional protocol of dehydration, inclusion in paraffin and stained with haematoxylin–eosin, Mallory trichrome and PAS histochemical reactions. The anatomical and morphometric characteristics and the gametogenesis in R. bergi agree with what was proposed for other analyzed species of the Bufonidae family. Females with ovaries with oocytes in different stages of maturity and postovulatory females were found. The males presented continuous spermatogenesis. The results of this work serve as a basis for the characterization of the reproductive cycle in R. bergi and, at the same time, provide background information on the analysis of gametogenic activity. Future investigations will be focused on evaluating the reproductive cycle in this species, both in ovaries and testes as well as Bidder's organ, to compare and correlate with the results obtained in this study.

This is the first study to examine the distribution of a chemokine CXCL14-like peptide in the pituitary and hypothalamus of an avian species, the Japanese quail (Coturnix japonica). We employed immunohistochemical techniques using a specific anti-human CXCL14 antibody. CXCL14-immunoreactive cells were detected in the caudal lobe of the pars distalis. CXCL14-immunoreactive puncta were densely distributed in the external layer and sparsely distributed in the internal layer of the median eminence. CXCL14 staining was absent after pre-absorption of the antibody with recombinant human CXCL14. All CXCL14-immunoreactive cells corresponded to growth hormone (GH)-producing cells in the caudal lobe. In addition, the majority of CXCL14-immunoreactive puncta in the median eminence corresponded to somatostatin-containing fibres. CXCL14 secreted from GH-producing cells and somatostatin-containing fibres may act as an inhibitor of GH release via an autocrine mechanism and neuroendocrine signalling, respectively.

Since the beginning of the 1990s, palaeontologists have been interested in understanding biological processes recorded within the bone microstructure of deinonychosaurian theropods, the group comprising Troodontidae and Dromaeosauridae. Several studies were published on this subject, and the growing database requires the first revision of used terminology and older interpretations. Furthermore, a platform correlating the developmental characters of all investigated taxa is missing. Hence, we lack a perspective to evaluate the potential of deinonychosaurian osteohistology for understanding their evolution and that of their close relatives, including avialans. This study aimed to fill in this gap by offering a comprehensive review of the previous osteohistological investigations published on deinonychosaurians and Archaeopteryx. Four significant evolutionary phenomena are assumed from the investigated deinonychosaurian taxa: (1) it is likely that troodontids evolved general osteohistology closer to basal avialans than to dromaeosaurids, (2) in troodontids, reticular vasculature is correlated to maturation timing, (3) the first growth deceleration occurs later in smaller deinonychosaurs (e.g. Changyuraptor, Sinornithosaurus) than in larger forms (e.g. Buitreraptor), and (4) the growth rate of the deinonychosaurs' hind limbs might be correlated with a specific type of locomotion.

Spinal ganglia and peripheral nerves innervate the regenerating tail and muscles of lizards, which provide new opportunities to probe the mechanisms leading to successful functional recovery following spinal cord injury. The regenerated spinal cord and peripheral nerves were detected using immunohistochemistry in original and regenerating tails of Scincella tsinlingensis. Our results showed that positive PCNA, GFAP and SOX2 cells were observed in the ependymal ducts at 15 and 30 days after the autotomy (dpa), with a small number of immunopositive NSE neurons. GFAP and SOX2 positive cells were primarily localized along the regenerated spinal cord after 45 dpa, and the descending nerve of medulla tissue showed positive NSE. Peripheral axons distributed around the muscle and inside the connective tissue and muscle tissue at 15 dpa. The number of axons decreased after 30 dpa. The peripheral axons was mainly distributed between the connective tissue, muscle group and the muscle and epidermis, presenting a radial distribution centred on the cartilage tube at 120 dpa. MBP myelination labelling of the regenerated tail at 30 dpa revealed that the regenerated axons rapidly myelinated along the rostro-caudal axis. The density of NMJ significantly increased at 120 dpa and 250 dpa. In the second regenerated tails, NMJ density at 250 dpa was still greater than original tails. Overall, these results indicated that neurogenesis was an early event and the ependymal cells were heterogeneous in the regenerated spinal cord of S. tsinlingensis. The regenerated peripheral axons presented a radial distribution centred on the cartilage canal, and the regenerated axons were rapidly myelinated along the rostro-caudal axis. During the process of regeneration, there were a large number of regenerated neuromuscular joints with high density.

Although scorpions have comparatively low regenerative potential, legs and pedipalps are able to regenerate some structures in an often incomplete manner. The most intriguing scorpion appendages are the ventrally located pectines. These organs are equipped with numerous sensilla that scan the substrate for mechanosensory- and chemosensory cues. Due to their ventral position and frequent substrate contact, pectines are vulnerable to traumatic injuries. Pecten malformations have been hypothesized to be the result of incomplete regeneration. To investigate their regeneration capabilities, the pectines of postembryonic stages of Euscorpius italicus (Herbst, 1800) were amputated before the second moult at three different positions. Data on intermoult periods and the number of pectinal teeth were gathered for approximately 2.5 years. The regeneration process on exuviae of up to six moulting events was documented by photographs and confocal laser-scanning microscopy. Regardless of the amputation site, no evidence for regenerative capabilities of pectines in E. italicus could be reported. Thus, incomplete regenerations mentioned in the literature are likely the result of simple wound healing. Depending on habitat complexity, substrate contact time of the pectines seem to differ, which might be interpreted as a trade-off between highest sensory input and the avoidance of traumatic injury of the pectines.

The morphology of the female reproductive system in Cercopis vulnerata, an economically important species, was examined with light and scanning electron microscopy techniques. The female reproductive system of C. vulnerata has two ovaries, each containing 14 telotrophic meroistic ovarioles joined by two lateral oviducts that open in a common oviduct. In this type of ovarioles, the trophocytes within the germarium are transferred to the developing oocytes in the vitellarium via the nutritive cords. The oocytes in the vitellarium have three different development stages: previtello, vitello and choriogenesis. The ovarioles open in the lateral oviduct with a thin canal-shaped pedicel. A pair of lateral oviducts opens distally into the common oviduct. The oviducts are surrounded by a monolayer cubical epithelium with deep folds toward the lumen and a thick muscle layer. A pair of spermatheca and a bursa copulatrix are seen near the common oviduct. Spermatheca has an elongated shape. The bursa copulatrix has an ovoid tube-like structure. No work has been done on the female reproductive system of Cercopidae to date. This study was conducted to fill this gap and forms part of the female reproductive system morphology of this economically important insect.

A group of aquatic Coleoptera specimens was collected from Güvenç Village in the Kahramankazan region of Ankara. Among these specimens was Dryops rufipes (Krynicki, 1832) (Coleoptera: Dryopidae), which is recorded from the Middle Anatolian Region of Turkey for the first time. The egg morphology of D. rufipes is described based on light and scanning electron microscope micrographs. Copulation and oviposition are described.

Analysis of skin development in the Australian lungfish, Neoceratodus forsteri, indicates that keratinocytes form 2 to 3 irregular layers in tadpoles of 2–5 cm in length and are fully stratified (7–12 layers) in juveniles of 16.5–26 cm in length. The epidermis produces mucus and mainly contains intermediate filament keratins of acidic nature but also a minute amount of neutral-basic keratins (pI 7.0–7.3), which is unique among fish. The latter keratins of 60–62 kDa, are generally present in tetrapods but the specific gene structure and amino sequence of acidic, neutral and basic keratins in N. forsteri are presently unknown. No other epidermal proteins are detected although biochemical data suggest the presence of non-keratin proteins, including a basic type (pI 8.0–8.2) of around 32 kDa of molecular weight. The spinulated bony layer of elasmoid scales contains glycoproteins involved in mineralization, such as osteonectin and osteopontin. Also, alkaline phosphatase, involved in calcium precipitation onto the collagen matrix, has been detected in scales of juveniles up to 26 cm in length. The present review concludes that the knowledge of the data derived from epidermal and dermal protein annotation from the recently sequenced genome of this fish species will contribute to address the study on the evolution of tetrapod skin.