The study of genes involved in sexual differentiation, as Vasa and Sox9, is of great importance, as they serve as specific markers for the germline and the male differentiation pathway, respectively. This study characterized using immunofluorescence the expression of the Vasa and Sox9 genes and laminin during gonadal differentiation in larvae at stages (S) 50, 53, 55, 57 and in 3 months-old urodele amphibian Ambystoma mexicanum. At S50 and S53, laminin delineated the gonad-mesonephros complex and the medullary and cortical regions of the differentiating gonad; Sox9 was detected in somatic cell nuclei and Vasa was expressed in the cytoplasm of germ cells. During gonadal differentiation at S55 and S57, laminin delimited the ovarian cavity and, in the testes, surrounded the testicular cords; Sox9 and Vasa maintained the expression patterns observed at earlier stages. In 3 months-old ovaries, laminin was detected surrounding the follicles, Sox9 expression was absent and Vasa was expressed in the peripheral cytoplasm of oocytes; in the testes, laminin surrounded the testicular cords, Sox9 was expressed in Sertoli cell nuclei and Vasa was detected in spermatogonia. These results suggest that, in A. mexicanum, Sox9 and Vasa are conserved genes that likely perform functions analogous to those observed in other vertebrates.
Morphological information on the digestive and excretory systems of aquatic coleopterans remains extremely limited, despite their importance for understanding morphology and systematic studies. As a predatory aquatic beetle, Aulonogyrus concinnus contributes to natural regulation of pest populations in freshwater ecosystems. This study provides a morphological description of the digestive and excretory systems of A. concinnus using light and scanning electron microscopies. The digestive system consists of a foregut (similar to 2.50 mm), midgut (similar to 1.30 mm), and hindgut (similar to 2.20 mm), with the midgut being the shortest region. The foregut includes the oesophagus, crop, and proventriculus, all lined with a single layer of epithelium, muscle layer and chitinous intima. The oesophagus and crop bear characteristic cuticular spines, while the proventriculus contains four star-shaped plates with brush-like spines. The midgut surface displays 60 finger-shaped gastric caeca, each lined with monolayered epithelial cells with well-developed apical microvilli. Two pairs of Malpighian tubules are found at the junction of the midgut and hindgut and show distinct proximal and distal regions with a single-layered cuboidal epithelium containing secretory granules. The hindgut comprises ileum and rectum, both surrounded by a single layer of epithelium, muscle layer and chitinous intima. These findings fill a significant gap in the literature and provide a morphological basis for future studies on aquatic beetles.
Haematobia irritans exigua (buffalo fly) is a hematophagous ectoparasite of veterinary importance that causes significant stress to cattle, leading to economic losses in livestock production. Detailed knowledge of H. irritans exigua life cycle and its sexual dimorphism is essential for targeted control and integrated pest management. This study characterized the life cycle duration and key morphological, morphometric and wing geometric traits of H. irritans exigua collected from Bargur Hills, Tamil Nadu, India, from Bargur cattle (Bos indicus). The complete life cycle from egg to adult was observed under field conditions, lasting approximately 344-364 h. The classical morphometric analysis revealed statistically significant sexual dimorphism, with male flies possessing greater body length and wing length than female flies (p < 0.001). Geometric morphometric analysis across 15 homologous landmarks showed that the first two principal components captured 86.70% of total shape variance. The Canonical Variate Analysis (Mahalanobis distance = 4.35, Procrustes distance = 0.0339; (p < 0.0001), demonstrated complete group separation (p < 0.0001), primarily driven by localized shape changes at the wing base, distal vein regions and outer margins. The multivariate regression confirmed significant allometric scaling (p < 0.0001). These findings characterize the life cycle of H. irritans exigua and highlight distinct sex-specific wing shape variations, confirming the utility of geometric morphometrics for precise taxonomic identification and sexual dimorphism assessment.
Visual system is of crucial importance for the majority of frogs and toads. The location of retinal specializations and visual acuity are directly related to a species' ecology. However, these aspects of the visual system are poorly studied in Anura. I studied the topography of retinal ganglion cells (GCs) and estimated spatial resolution (SR) in the Dybowski's frog. GCs exhibited a heterogeneous distribution across the retinal surface. Their spatial density (SD) was lowest in the dorsal and ventral periphery (below 4000 cells/mm2). It increased progressively towards the retinal equator, where a moderate visual streak emerged. The greatest GC SD (10,000-10,200 cells/mm2) was found in the temporal retina, close to the equator. The respective zone was identified as area retinae temporalis. The total number of GCs was 308.7 & times; 103 in the smaller retina and 400.5 & times; 103 cells in the larger one. The maximum SR as estimated from eye geometry and GC SD was observed in area retinae temporalis (2.66 and 3.04 cpd in smaller and larger frogs, respectively). The retinal specializations and SR estimates in the Dybowski's frog align with its biology.
The first zoea of two Synalpheus species, namely: S. antillensis and S. cf. townsendi, are herein described. They were also compared with the genus descriptions and with their respective species complexes available in the literature. Morphological information on Synalpheus zoea I exhibits an increase from 19 to 21 species, and it corresponds to 12% of the total number of species. Synalpheus antillensis presented four different morphological characteristics that have helped to identify the species from the Brevicarpus group, whose first larval stage was described. They showed several differences from S. minus and S. brevicarpus and closer morphological similarity with S. ubatuba. Synalpheus cf. townsendi showed three different morphological characteristics that have assumingly contributed to a correct species diagnosis in the Synalpheus townsendi species complex. However, only S. scaphoceris held minimal information about its first zoea. The two herein described larvae had morphological characteristics typical of extended development species: free-swimming larvae often associated with non-eusocial species. Information provided in this study revealed that both larval descriptions provided new information about the morphology of Synalpheus zoea I with extended development species. It also enhanced the knowledge on closely related species and helped better understanding Synalpheus life history.
