Acta Zoologica最新文献

The order Zeiformes comprises a small order of predominantly deep-sea fishes. However, little information is available on their morphology, such as squamation. Therefore, in the present study, we analysed and described the squamation pattern and scale morphology of five species of Zeiformes occurring on the Brazilian coast: Allocyttus verrucosus, Grammicolepis brachiusculus, Xenolepidichthys dalgleishi, Zenion hololepis and Zenopsis conchifer. Our analysis revealed greater morphological diversity than previously reported for this order. All species, except the scaleless Zenopsis conchifer, presented cycloid scales of spinoid subtype. Grammicolepis and Zenion presented exclusively scales of the spinoid subtype, whereas both Allocyttus and Xenolepidichthys also displayed true cycloid subtype. A. verrucosus is characterised by two distinct groups of scales of different sizes that form scale clusters. G. brachiusculus and X. dalgleishi presented a unique vertically elongated scale covering most of the body. Small bony plates were observed at the dorsal- and anal-fin bases of G. brachiusculus, X. dalgleishi and Z. hololepis. The variation observed is putatively useful for the systematics of the order.

In this study, the live cell imaging microscopy of an old word cyprinodontiform fish, the Shirini toothcarp Esmaeilius shirini during its embryogenesis, is described and illustrated for the first time through the detailed morphological description and chronology of the events of all developmental stages (from fertilization to hatching). External fertilization of transparent, spherical, sticky and macrolecithal eggs bearing adhesive filaments with an average diameter of 0.83–1 mm is the first step in the ontogenesis of E. shirini. Embryogenesis continued with a process of meroblastic cleavage (approximately 2 and half h post-fertilization, hpf), formation of blastula (blastulation), gastrula (gastrulation), neurulation, somatogenesis, organ formation (organogenesis) and pre-hatching. The development continued with hatching (a stage between the embryonic and larval periods) at approximately 131 haf (at 24 ± 1°C). The new larvae were about 3.9–5.8 mm in length with distinct fin rays and pigmentation on the head, body and fins. Basic data from this study can be used in forthcoming investigations on the reproduction processes, breeding, behaviour and conservation of E. shirini. Fish development comprises an integrated, ordered and well-mapped sequence of early life-history events controlled by intrinsic and extrinsic factors. Knowledge of fish developmental stages during embryogenesis/ontogeny is essential for a better understanding of their biology, breeding criteria, phylogenetic relationships, dietary requirements, conservation plans, environmental requirements and ecological preferences.

Cnidarians are the first phylum of metazoans to exhibit a functional mucus layer. In evolution, mucous cells perform the classical secretory function of mucus and act as sentinels for external insults, particularly in mammals. However, this topic has not been much analysed in the lower metazoans. This study aims to investigate the role of mucous cells in Actinia equina (Anthozoa, Hexacorallia) (Linnaeus, 1758) by using confocal microscopy and bioinformatics. The results show colocalization of Toll-like receptor 2 (TLR2) and Mucin2 (MUC2) on these cells, suggesting a crosstalk between defence response and mucus secretion in cnidarians. Furthermore, the presence of TLR2 on the surface of mucous cells suggests their involvement in host defence responses, as occurs in vertebrates. Moreover, through in silico analysis, we confirmed the presence of orthologous genes for the tested antibodies, providing additional evidence to support our results from an evolutionary perspective. These data suggest that mucous cells play a defensive role throughout evolution, helping us understand how these cells have developed and adapted across phylogenesis. This information also provides new insights into the defensive strategies of invertebrates and clarifies their evolutionary history.

Aberrations in the otolith can harmfully influence the imperative actions of the fish species. The chief drive of the current investigation is to describe the deformities in the otoliths of the European eel Anguilla anguilla. Out of 76 Anguilla anguilla individuals collected from Bafa Lake in Western Anatolia, Türkiye, four female specimens exhibited abnormal otoliths. Scanning electron microscope was used to determine the deformed otoliths examined. The outcomes of the abnormality analyses in A. anguilla otoliths, deformities were noticed such as numerous prominence structures and bumps of different sizes on the surface of the otolith produced by buildup of the different crystal structures in some parts of the otolith. These deformities were found in the left and/or right otoliths of the female individuals of different total lengths. The percentage of individuals with abnormal otoliths of A. anguilla is calculated as 5.3%. The current study presents for the first-time abnormal otolith information on left and right otoliths in female A. anguilla. Deformities in the otoliths of European eels are believed to result from a combination of genetic predisposition and stress caused by various environmental factors, such as water pollution, changes in salinity, temperature fluctuations and nutritional imbalances.

Widely distributed Species in different geological and ecological environments often exhibit great intraspecific diversity. Aphaniops stoliczkanus (Day, 1872) is an endemic species of Middle East occurring over a vast geographic range in different basins. This species has been observed in freshwater, brackish water and hot sulphur springs; therefore, its populations are known to exhibit considerable morphological variation. In the present study, we have investigated the poorly studied populations of A. stoliczkanus of the Hormuz and Makran basins of Iran in terms of otolith morphology and morphometrics. According to the results, these populations can be divided into two distinct groups including east and west of the Strait of Hormuz. Our results also provide evidence that there is a relationship between otolith morphology and the environment, serving as environmental factors that may influence the formation of specific regions in the otolith shape. Despite the remarkable morphological similarities among otoliths in geographically close populations of Charak and Chiruyeh, our data purposed that geographically these populations have different dorsal tip shapes in their otolith. In comparison to the data from other studies, the otoliths of Qeshm Island appear to resemble the overall shape of otolith found in Oman very closely. However, it is believed that Qeshm Island population was separated from the Hormuz basin populations during the Holocene Sea level rise. Also, the outcomes of this study provide insights into the potential role of environmental factors in shaping intraspecific diversity and the migration patterns of this species within the Persian Gulf.

This is the first study investigating the aberrant otolith morphology in the Lessepsian lizardfish Saurida lessepsianus in the Aegean Sea, Turkey. A Leica Emspira 3 digital microscope was used to determine the aberrant otoliths examined. Two female specimens measuring 230 and 274 mm in total length (TL) were examined and showed an aberrant otolith on both sides of their head. These deformities might have been instigated by the impacts of changing water factors related to diverse pollutants in the Aegean Sea. Characteristics of otolith deformities are of immeasurable significance for aquatic habitats and other otolith studies.

Fish, first jawed vertebrate group appearing in evolution, have immune system similar to those of mammals. These early animals' innate and adaptive immune systems are completely developed, having head kidney and thymus as primary, spleen and mucosa associated lymphoid tissue as secondary immune organs. The adaptive immunity performs key role in defence against recurring infections and elimination of fish pathogens with the help of its memory cells, T-cell-receptors and immunoglobulins. Epidermal secretions including antibacterial peptides, lysozymes, lectins, complement and C-reactive proteins which function in disruption of antigens, phagocytosis, inflammatory response and mending of tissue injury play a significant role as elements of fish immune system. Fish, however, have greater innate immunity than humans do. Estrogens play crucial role in immunomodulation through nuclear oestrogen receptors, which are found in majority of immune cells and lymphoid organs in fish. There is mounting proof that xenoestrogens, that can attach as agonists to oestrogen receptors, pose significant ecotoxicological risk by disrupting the defence mechanism in fish. Though less potent than natural oestrogen, they can bioaccumulate to finally reach a substantial dose. This review's objective is to give an overview of the fish defence system, its estrogenic regulation and estrogenic-endocrine disruption.

The killifish genus Aphaniops consists of nine species distributed in Eastern Africa and the Middle East. However, distinguishing these species from each other based on morphological traits is challenging. Here we investigate the utility of otoliths (sagittae) in distinguishing between A. dispar, A. ginaonis, A. hormuzensis, A. kruppi and A. stoliczkanus. Our approach is based on otoliths from 89 specimens and involves (1) otolith morphometrics, following prior recommendations, (2) shape analysis of otolith contours based on discrete wavelet transformation—a novel method in killifish otolith research—and comparative statistical analyses. Both methods reveal significant interspecific variation in the otolith regions of the rostrum, antirostrum and excisura. While method (1) effectively discriminates most species, method (2) struggles to differentiate A. hormuzensis, A. stoliczkanus and A. kruppi. Additionally, both methods encounter challenges in correctly classifying A. hormuzensis due to the high otolith variability of this species in our sample. Possible factors accounting for their variability are environmental fluctuations at the sampled hot sulphuric spring (Khurgo) and potential introgressive hybridization. We conclude that otolith morphometry is a valuable tool for Aphaniops species identification. Furthermore, we found that the distinctiveness of species-specific otolith traits increases with the divergence age of the species.

Calcareous skeletal structures are common among different invertebrate groups, including Porifera, Cnidaria, Platyhelminthes, Mollusca, and Echinodermata. They appear externally as shells, plates, or scales, or internally as subepidermal spicules. Although typically formed outside of the cells, in one class of gastropod molluscs, the Heterobranchia, subepidermal and intracellular spicules are found—a rare case, at least for the molluscs. This type of spicules is present in several phylogenetically distant groups of heterobranch molluscs (Rhodopemorpha, Acochlidimorpha, and Nudibranchia), each different in terms of morphology and autecology. This raises questions about the origin and homology of subepidermal spicules in heterobranch molluscs. To answer these questions, understanding the process of spicule formation is crucial. This is impeded by insufficient data on the fine structure of the subepidermal spicules and adjacent epithelia. To address this problem, we carried out a comprehensive morphological study of subepidermal spicules and the body wall in one species of Acochlidimorpha. We revealed variations in the cellular composition of the epidermis, musculature organization, and spicules' arrangement, which most likely reflect the different functional roles of the spicule complex within Heterobranchia representatives. However, the obtained data are insufficient to answer the question of the origin of spicules and their homology within Heterobranchia.

The present study reports the formation of claws in lizards and their cornification. From a flat epidermis with lose mesenchyme, the skin forms undulations that become symmetric domes and later asymmetric for the elongation of their proximal part that gives rise to the outer scale surface. At the tip of digits claws develop in association with a mesenchyme that surrounds the cartilage of the last phalange. Beta-cells of claws appear 2–3 embryonic stages before those of scales formed in other body regions, including digital scales. The epidermis of the developing claw initially forms 3–4 embryonic layers under which elongated beta-cells accumulate long bundles of corneous material, immunopositive for CBPs. Claw beta-keratinocytes incorporate tritiated proline and accumulate numerous, oriented corneous bundles that rapidly occupy the entire cell. The bundles are electron-dense under transmission electron microscopy, suggesting that, in association to CBPs, other proteins are synthesized and increase the mechanical resistance of claws. Immunolabelling for cysteine-rich IFKs, HA and HB, shows that these keratins co-localize with CBPs only in claws but are low to absent in digital scales and adhesive setae. This indicates that the hardness of claws mainly depends from the association between these different proteins rich in glycine and cysteine.