Zoomorphology最新文献

Abstract

Trichomycterus bogotensis is one of the three species of fish that inhabit the Colombian Andes. However, several aspects of its basic biology, including its digestive system, are unknown. The morphology and histology of the digestive system are of great importance for understanding a species’ feeding habits and food preferences. Thus, this study aimed to perform a morphological description of the digestive tract of T. bogotensis. The gastrointestinal tract of seven specimens was processed for paraffin histology, high-resolution optical microscopy, and transmission electron microscopy. Anatomically, T. bogotensis exhibits a terminal mouth with villiform teeth, a narrow esophagus, a large and muscular stomach, and a short intestine. Histology and ultrastructure revealed a tissue organization similar to that reported for other Silurids, composed of four layers: mucosal, submucosal, muscular, and serosa. The anatomical and histological characteristics suggest that T. bogotensis is a benthic species with a tendency to carnivory.

In recent years, fluorescence microscopy has revitalized the study of invertebrate comparative morphology. Here we explore the usefulness of combining confocal laser scanning microscopy (CLSM) and cuticular autofluorescence to examine the taxonomically challenging marine planktonic “y-larvae” (Pancrustacea: Facetotecta). To gauge the effectiveness of CLSM with autofluorescence in producing taxonomically useful images, we applied it to seven distinct y-naupliar species or morphospecies that had previously undergone scrutiny by other techniques. The specimens were part of a museum collection of glycerin-jelly slides of exuviae of last-stage y-nauplii, a key instar for studying the taxonomy of y-larvae. For Hansenocaris demodex, the level of detail obtained from a single specimen was comparable to that previously obtained by scanning electron microscopy (SEM). For Hansenocaris aquila, revisiting the original holotype specimen resulted in a dramatic increase in our understanding of the species’ morphology, including taxonomically pivotal information about its spinose labrum and a digitally rotated lateral view. CLSM analyses of the other five specimens, which represented a broad spectrum of y-naupliar morphology, efficiently generated more such information. Novel observations were made concerning putative external rudiments of both the first and second maxillae in late nauplii as well as the extreme dorso-ventral flattening of some naupliar types. CLSM observation of museum slides of naupliar exuviae using cuticular autofluorescence thus shows great promise of becoming an excellent tool for studying the morphology and taxonomy of y-larvae, and we suggest that this technique might also profitably be applied to other forms of larval exuviae.

The ultrastructural spermatozoon organisation of the acanthocolpid digenean Stephanostomum bicoronatum have been described by micrographs of transmission electron microscopy (TEM). Live digeneans were isolated from the digestive tract of the Brown meagre Sciaena umbra (Teleostei: Sciaenidae), obtained from artisanal fishing off the coast of La Chebba (Tunisia Mediterranean Sea). The ultrastructural study reveals that the male gamete of S. bicoronatum is a filamentous cell tapered at both extremities, which present typical characteristics of digenean spermatozoa of the type III, namely two axonemes of the 9 + ‘1’ pattern of trepaxonematan Platyhelminthes, nucleus, one mitochondrion, external ornamentation of the plasma membrane associated with cortical microtubules and located in the posterior part of the anterior region of the sperm cell, two parallel bundles of cortical microtubules, and maximum number of cortical microtubules in the anterior part of the spermatozoon. In addition, the male gamete of S. bicoronatum shows spine-like bodies, a large amount of glycogen granules and a posterior extremity containing only the nucleus. The results are compared and discussed according to the existing data in other digeneans, particularly with those of the family Acanthocolpidae.

Spermatozoa and the male reproductive system (MRS) present great variability, featuring morphological characters that could be used in the taxonomy of different insect groups. Despite their importance, such data are scarce for mosquitoes, and their potential application in taxonomy has been neglected. In this study, we describe the morphology of the MRS and spermatozoa of the mosquito Lutzia bigoti Bellardi, 1862. The MRS consists of a pair of testes, deferent ducts, seminal vesicles, accessory glands, and an ejaculatory duct. The testes have only a single well-compacted follicle. The deferent ducts originate at the base of each testis, with the first portion resembling a goblet, and present an enlargement that forms the seminal vesicles in the posterior region. Subsequently, the ducts merge with the respective ducts of the accessory glands and open into the ejaculatory duct. The spermatozoa of L. bigoti are characterized as filiform and long, measuring around 220 µm, providing a potential distinguishing feature of this species. We hypothesize that the spiral organization of the testes may confer advantages in spermatozoa production. Similar to other mosquitoes, the MRS organization plan of L. bigoti conforms to type B. In addition, we also suggest that Culicinae species possibly share juxtaposed vesicles. This work paved the way for future analyses exploring of reproductive biology of Lutzia, including ultrastructure examinations and taxonomic investigations in the Culicidae family.

The general morphology of the body, including the distribution of putative sensory ciliary cells, was studied using scanning electron microscopy (SEM) in the siboglinid Nereilinum murmanicum Ivanov, 1961 collected from the Barents Sea and at a new, deeper locality in the Greenland Sea outside the known range of this species. The fine features of cuticular structures in N. murmanicum, including the bridle and cuticular plaques from different parts of the body, were described for the first time. Since we have previously shown in the closely related siboglinid Oligobrachia haakonmosbiensis Smirnov, 2000 using SEM and confocal laser scanning microscopy (CLSM) that all epidermal cilia except for the ventral ciliary band belong to sensory cells, we consider all ciliary structures detected in N. murmanicum as sensory. The tentacles, clusters of ciliary cells along the dorsal furrow, areas around the openings of the multicellular glands, papillae, and the ciliary patch located on the cephalic lobe at the base of the tentacles can be regarded as specialized sensory areas. Based on our current knowledge of sensory structures in annelids, a number of assumptions were made about possible functional characteristics of putative sensory structures in siboglinids.

The present study showed a descriptive anatomical study of the parts of the axial skeleton in the ostrich (Struthio camelus) in addition to a morphometric study of each bone. We studied 7 male ostriches aged from 1 to 3 years with an average weight of 120.00 kg. The cranium exhibited two vast orbits supported by a sclerotic ring. Hyoid apparatus was fine delicate horseshoe-shaped and comprised Basihyale, Urohyale, and Cornu branchiale. Cornu branchiale were paired and long rod-shaped, consisting of a proximal bony part Ceratobranchiale and slightly curved distal cartilaginous process, the Epibranchiale located on either side of the hyoid apparatus. The whole vertebral column comprised 54 vertebrae, including 18 cervical vertebrae, 7 separated thoracic vertebrae, a synsacrum, and 9 separated caudal vertebrae. Atlas had a butterfly-shape with a narrow width and large vertebral foramen. Axis had a protruded dens with a rounded tip that arose from the cranial surface of the body for articulation with the Incisura fossae of atlas. Several Pneumatic foramina were found in the cervical vertebrae. The transverse foramen was found in all the cervical vertebrae except atlas. The ribs were nine pairs in number, the sternal ribs extended from the third to the seventh rib while the rest were asternal floating ribs. The sternum was a broad quadrilateral extensive bone, lacking the keel bone. It had dorsally several Pneumatic foramina.

Merodon triangulum Vujić, Radenković & Hurkmans, 2020 is a European endemic hoverfly species belonging to Merodon constans species-group, inside albifrons-lineage. The distribution of this species is known to be mostly central Europe and Balkan peninsula and it has been categorized as Near Threatened in the European IUCN red list of hoverflies; this paper cites the species for the first time in Ukraine (western Ukraine, specifically). In the present study, the preimaginal stages of this species are described and figured using Scanning Electron Microscopy. The material used for the descriptions were larvae collected in Ukraine and Serbia feeding inside underground storage organs of the spring snowflake Leucojum vernum L., 1753. This morphological description constitutes the first one inside the constans species-group, and the sixth description of the albifrons-lineage, in which there is only one species-group left to have at least one species of the preimaginal stages described (i.e., ruficornis species-group). The descriptions were compared with the rest available of the genus, stating the diagnostical characters of the present species and the shared characters inside the lineage. The novel information provided on the trophic interaction between M. triangulum larvae and Leucojum bulbs is stated for the first time and further supports the association of the constans species-group with the underground storage organs of snowflakes and snowdrops (Galantheae) in their role as host plants.

Serpulids are the only polychaetes in which all species secrete calcium carbonate tubes. Some serpulid lineages, such as species in the genus Spirobranchus, possess a second kind of hard-calcified part—the operculum. The tube and operculum microstructure and mineralogy are highly variable among serpulid species, but this type of information is still scarce for some species. Furthermore, comparing the microstructure and mineralogical composition of species from warm and temperate waters helps to determine which are more susceptible to the effects of climate change. Therefore, the aim of this study is to determine and describe the microstructure and mineralogical composition of the tubes and opercula of three Spirobranchus species from warm and temperate waters of the Mexican Pacific. The microstructures of the two hard structures were analyzed with a scanning microscope and complemented by X-ray computed nanotomography; the mineralogy was determined by X-ray diffractometry. The tubes of the three species had two layers—inner and outer—and five microstructures were found in the tubes. Numerous pores cover the operculum of all three species and have an irregularly oriented prismatic (IOP) structure. The tubes of the three species were bimineralic but had different percentages of calcite and aragonite, whereas the opercula were only composed of aragonite. Given the mineralogical characteristics of S. spinosus and because its distribution is only in temperate waters, we may conclude it could probably be the main species negatively affected according to the climate change scenarios predicted for the end of this century.

The tibial organ of Chloropidae and Milichiidae flies is an obscure feature with taxonomic significance. This study provides the first in-depth investigation into the ultrastructure of the hind leg of 11 genera from all Chloropidae subfamilies using a multimodal microscopy approach. The modified dermal tissue associated with the tibial organ indicates glandular function, as evidenced by the presence of secretory vesicles containing non-proteinaceous elements, potentially indicating lipidic secretion. The overall similarity of the tibial organ between Chloropidae and Milichiidae indicates a shared homology. However, the evolutionary history of this structure is still contentious due to limitations in the phylogenetic relationships of both lineages. Moreover, our findings enable future comparative investigations of other Diptera leg organs that possess secretory ability, which could be homologous across schizophoran families, but not necessarily the organs themselves.

A key component of amphibian antipredator strategies is the chemical defenses that make them toxic and/or distasteful, like the cardiotoxic bufadienolides synthesized by the true toads and stored in granular skin glands. The morphology of adult toad glands is well-described, but the ontogenetic timing and distribution of glands during larval stages are poorly understood. A comparative understanding of granular gland development is needed to elucidate the mechanisms underlying the diversification of toad chemical defenses and their ecological roles across lineages and ontogeny. Herein, we analyzed gland morphology before and after metamorphosis of Rhinella horribilis, Incilius melanochlorus, and I. luetkenii. We hypothesized that granular gland development would begin earlier and progress faster in relatively more toxic Rhinella species. Our results showed that the timeline of skin development, the relative dimensions and quantity of structures, and the appearance of protein and mucin content in granular and mucous glands did not vary among Rhinella and Incilius. Furthermore, epidermal mucus and/or giant cells in larval toads may act as sources of chemical defenses prior to gland development. Our findings suggest that gland development is well-conserved among these genera; it is possible that reported differences in toxin profiles are not due to divergent morphogenesis during larval or metamorphic stages, but rather to differences in molecular function or structural differentiation in juveniles or adults. Therefore, complementary studies using integrative techniques such as immunohistochemistry and comparative transcriptomics are needed to uncover the mechanisms responsible for the diversity of chemical defenses found in bufonid toads across development.