Zoomorphology最新文献

Abstract

In all vertebrates, reproductive strategies are achieved by modulation of the neuroendocrine system in a similar manner and with minor variations among the different classes. Most of the available information on amphibian testicular cycles derive from anurans, and among these, water frogs have been extensively studied in terms of reproductive mechanisms and sex steroid correlation. Adiponectin (AdipoQ) and its receptors—AdipoR1 and AdipoR2—are essential for most of the normal testicular and sperm functions. In this study, the identification of AdipoQ and its two receptors was carried out by immunohistochemistry in the testis of adult males of Pelophylax bergeri. The AdipoQ system was observed in the frog spermatogenic cysts, in both germinal and Sertoli cells, as well as in the rete testis. AdipoQ and AdipoR1 were localized in germ-line cells, from spermatogonia to round spermatids, while AdipoR2 was detected in the elongated spermatids, spermatozoa, and Sertoli cells. AdipoR1 was also observed in the intratesticular canals of the rete testis. This preliminary study shows the AdipoQ system’s presence in the anurans’ testis. The results obtained could be a starting point for future functional studies aimed at defining the physiological role of the AdipoQ system in frog testicular functions.

Abstract

The study reveals a lack of histomorphogenesis in New Zealand white rabbit teeth. The teeth development was examined through sequential histological segments in 24 rabbits from prenatal ages (E19, E21, E23, E25, and E28), neonates (E30), and postnatal age (1 week and 2 weeks); (three animal specimens at each age stage). Rabbit teeth first appeared at 19 days of prenatal life (E19) as an ectodermal epithelial thickening on each side of the mouth opening. At E21, the bud of upper incisor tooth appeared as an epithelial bud, which composed of many condensed epithelium cells, was simply identified from the larger with less condensed vestibular lamina, and was surrounded by mesenchymal connective tissue while the lower incisor took the cap stage. At (E23), tooth regular construction is formed from enamel, dentine, and pulp cavity. Peg incisor appearance (supplementary and assistant incisors) is visible at the lingual surface of the upper major incisor. Teeth prenatal development went through successive stages like initiation, bud, cap, late bell, maturation, and crown stages. The first initiation phase of tooth formation was seen as ectodermal epithelial cell collection at (E19). Bud stage saw on upper incisor tooth, while in cap structure in lower incisor teeth at (E19). A cap-formed tooth is composed of the enamel organ and fundamentally dense mesenchymal tissue. Enamel organs are segmented into three distinct layers: the external tooth enamel epithelial, the internal tooth enamel epithelial, and finally the stellate reticular layer. The cement layer covered teeth all around on enamel on both the labial and lingual sides while not contacting the dentine on the lateral side, forming enamel space. Teeth develop consistently all through life; they have expanded enamel thickness; they are diphyodont teeth; they have two continuous dentitions; they are deciduous and perpetual, with long crown teeth and an open root.

Abstract

Mylodon darwinii is an extinct terrestrial species of sloth with a wide fossil record in South America, the record of the skin and hairs found from "La Cueva del Milodón", Chile. More than a century after the first studies on its hair, we aimed to redescribe the morphological characteristics of the hairs of M. darwinii by applying modern protocols of trichology and microscopy. Hair patterns were also compared with those of two other extinct species of sloths available in the literature. Hairs from mummified specimen housed in Museo de La Plata (Argentina) were analyzed through light and scanning electron microscopy to identify their cuticular and medullary patterns. Guard hairs lack medulla and have a wavy cuticle with irregular scale orientation, while underhairs have an amorphous cuticle pattern and no medulla. Hence, the former ones help in the diagnosis of the hair morphology of the species, while the latter ones do not. Differences found in the final product of each microscopy technique are discussed and should be considered in future research. The outcomes presented herein are a step further toward the understanding of evolutionary processes within Xenarthra, providing important data for such a poorly studied group that has only been recorded in Central and South America.

Representatives of Eunicida have the most complex jaw apparatus among the Annelida group. The general morphology of their jaws is well studied and is important both for the classification of recent species and for the evolutionary interpretation of extant–extinct eunicidan relationships. The fine structure of the jaws can be useful as an additional trait to external morphology that allows to clear up the evolutionary relationships within the group. However, the ultrastructural data remain absent for the Lumbrineridae and Hartmaniellidae, which are also the only families with symmetrognathous jaws. In the present study, we describe the fine structure of the jaws of Scoletoma fragilis from the Lumbrineridae family. More than 40 S. fragilis specimens, from juvenile to adult, were studied with different morphological approaches, concentrating on electron microscopy. We have distinguished three stages of jaw structure, depending on the worm size: juvenile, subadult, and adult jaws. The juvenile jaws had the simplest structure, consisting of only scleroproteins. The adult ones had a more complex and multilayered structure that varied in different areas of the jaw apparatus. The subadult jaws exhibited the intermediate fine structure between juvenile and adult ones that raises the question of continuous growth possibility, which is also discussed in the article. Whereas juvenile and massive jaws share the same pattern as the other eunicidan families studied to date, the most interesting finding was the new, undescribed type of jaw structure found in the elastic elements of adult maxillary apparatus. It is characterized by heterogeneous sclerotization with a lack of mineralization.

Abstract

Calceoli are putative sensory organs which are known in limnic, marine, and subterranean amphipods for almost 200 years. Despite an otherwise comprehensive understanding of the sensory organs of crustaceans, we still have not unambiguously understood their function. Since calceoli are mainly found on the antennae of male animals, previous studies suggested a chemosensory function mainly related to reproduction. Here, we use a combination of light and electron microscopic techniques to examine the calceoli of Gammarus locusta (Linnaeus 1758) and Oediceroides calmani (Walker 1906), to provide an overview over these structures, and in addition reveal nervous tissue in close proximity to the calceoli. The calceoli of both species are cuticular structures and consist of proximal and distal elements, a stalk and a receptacle that connects both regions. The two studied calceoli differ in the structure of their proximal and distal element, as well as in their receptacle. This study provides new insight into the functional morphology of the antenna and calceolus. Histological sections through the antennae and the calceoli indicate that the calceoli might possess a mechanosensory function.

The three-dimensional morphologies of insects, such as spines and horns, have recently garnered attention as an effective system for elucidating the processes underlying dramatic changes in external morphology. Adult leaf beetles of Dactylispa Weise 1897 exhibit sharp spines on their pronotum and elytra, while their pupae lack such features. In order to obtain foundational data for future investigations into the developmental mechanisms governing spine formation, this study assessed variations in spine numbers across ten body regions and in spine size across three body regions in adults of Dactylispa higoniae (Lewis in Ann Mag Nat Hist (Ser. 6) 17:329–343, 1896. https://doi.org/10.1080/00222939608680376) and D. issikii (Chûjô in Bull Umeno Entomol Lab 6:5–13, 1938). As a result, the degree of variation in spine numbers and size was variable among body regions even within single species. However, the number of spines on the pronotal front margin in D. higoniae and the elytral interval 4 in D. issikii was stable. The spine numbers of these two species did not exhibit significant differences between the right and left sides of the body and was not likely to be influenced by sex or elytral length. Furthermore, we observed pronotal and elytral spines that formed inside the pupal cuticle of late-stage pupae of these two species. Our observations suggested neither pronotal nor elytral spines exhibit a formation pattern resembling concentric folded structures, as seen in beetle horns.

Abstract

Despite amphibians having the least number of families in comparison with other vertebrate classes, the digenean parasites within these host species are largely predominant. To date, no investigation has been conducted on the digenean fauna of frogs in western Iran. The helminths occurrence and morphological description of this study were analyzed for the first time. A total of 54 Levant water frogs, Pelophylax bedriagae, (n = 53), and a long-legged wood frog, Rana macronemis, (n = 1) were examined. Frogs harbor in total four digenean parasites. Three taxa were characterized based on morphological features as Gorgodera cf. asiatica, G. varsoniensis, and Pleurogenoides sp. within P. bedriagae, while Haematoloechus sp. was only found in R. macronemis. Pleurogenoides sp. exhibited a moderate prevalence (23%) and intensity (7.3 ± 6.3). Gorgodera cf. asictica can be distinguished from congeners based on the body and sucker size, the ovary and testes shape, and in G. varsoviensis by having lobulated caeca and transversely elongated testes. In addition, Pleurogenoides sp. mainly differs from all its congeners by the form of its body, genital apparatus shape and Y-shaped excretory vesicles. With regard to helminths in amphibians, the existing body of literature is extensive and complex. To accurately determine the species boundaries, both morphological and molecular data are needed. We report two new records of these parasites from the region.

The Trichogaster fasciata (Bloch and Schneider, 1801) is a small, indigenous, tropical labyrinth perch of Osphronemidae family with a great value in the ornamental fish industry and biological experiment. Morphological descriptors of the sagitta otolith are used as an important tool in fish taxonomy and fish biology. Detailed morphological and morphometrical characteristics of almost all visible descriptors of sagitta otolith in different body length groups of T. fasciata are described. The sagitta contains a heterosulcoid, ‘J”-shaped, ostio-caudal sulcus with a distinct rostrum and orthorostrum patch. Different morphostructural development in the ortho-rostrum patch is directly proportional to the total length. The caudal fork is well-developed and its growth is directly proportional to the total length. The marginal sculptures of the sagittae comprised numerous scallops, whose shape and size are considerably changed with the increment of the total length. The Kruskal–Wallis H test revealed that some sagitta descriptors display important changes in different body length groups of T. fasciata. About nineteen sagitta descriptors among the studied structures display a significant developmental relationship to the increment of the total length and they might be used as an important predictor to evaluate the fish size. Different shape indices of the sagitta and the sulcus are analyzed, some of which have a significant relationship to the total length. These shape indices and the sagitta predictors might be useful in stock separation of the T. fasciata. The characteristics of the sagitta descriptors of T. fasciata are compared with the available data of other Anabantiformes fishes.

Abstract

Tachinidae is a large family of flies, but studies on its antennal morphology and ultrastructure are still scarce. Thus, the male and female antennae of Neoeuantha aucta (Wiedmann) were studied using scanning electron microscopy. The three antennal segments are densely covered with microtrichia, with postpedicel being the one that carries the greatest diversity of sensilla. In total, eight types of sensillar structures were observed: trichoid, basiconic (three subtypes), coeloconic, chaetic, setiferous plaques, and pedicellar button. The s. trichoid and s. basiconic have a porous wall, indicating a chemoreceptor function. A central pore was found in the pedicellar button, possibly with mechanoreceptor and chemoreceptor function. Another highlight is the numerous sensory pits covered by microtrichia in the postpedicel, housing only one type of sensilla each. Our results were compared with those available for Tachinidae and other families of dipterans, mainly those of Calyptratae, and provide the basis for future investigations in sensory functions related to the behavior of parasitoid flies, as well as for studies of comparative morphology.

Abstract

The study aimed to provide a detailed anatomical description of the forelimb of the capybara using gross anatomy, radiography images, and three-dimensional reconstruction. Four adult animals were used for macroscopic dissections, one for the acquisition of radiographic images and reconstructions, and one specimen for bone descriptions. The results showed the anatomical details of the scapula with a developed hamate process and the absence of a clavicle. Radius and ulna do not fuse. The hand has five metacarpal bones, and the first digit is rudimentary. The proximal row of the carpal comprises the intermedioradial, ulnar, and accessory carpal bones, and the distal row comprises four carpal bones. The muscles present a general pattern similar to other groups of domestic animals; however, the absence of the accessory head of the triceps brachii muscle has been demonstrated. The resulting images provided excellent detail of the main anatomical structures of the capybara’s thoracic limb. The illustrations in the present study are a valuable reference for the interpretation of normal and pathological imaging studies in the species in the present study.