Journal of Morphology最新文献

Investigating the developmental patterns of extinct species provides valuable insights into their anatomy, biology and ecomorphological adaptations. Research on the ontogeny of non-mammaliaform cynodonts has offered significant contributions to our understanding of these aspects. Here, we aim to describe and discuss the intraspecific and ontogenetic variation of the skull of the Brazilian traversodontid Siriusgnathus niemeyerorum (Candelária Sequence, Upper Triassic). We evaluated an ontogenetic series of the species through qualitative comparison and allometric analyses using cranial measures. Our findings reveal several trends during skull growth, including a relative increase in rostrum length, a relative decrease in orbit size, and changes in the zygomatic arch and temporal fenestra proportions. These patterns, when analyzed in the context of the adductor musculature, may be correlated with changes in feeding behaviour, similar to those described for the gomphodontosuchine Exaeretodon argentinus. We also report changes in cranial ornamentation, bone fusion, and suture complexity throughout ontogeny. Overall, this study provides a greater understanding of the cranial ontogenetic patterns of S. niemeyerorum, contributing to the knowledge of its intraspecific variation. The possible ecological implications of these findings highlight the importance of ontogenetic studies for elucidating the biology of extinct taxa.

Larvae of the black soldier fly, Hermetia illucens, are currently intensively studied, owing to their potential importance in various fields such as waste bioconversion, forensic entomology, and food supply for humans and life stock. Despite the increased attention, a detailed anatomical documentation of the larvae using modern methods is lacking, and even statements on the number of larval stages are contradictory. Misinterpretations of the ontogeny of this species have led to frequent erroneous identifications of the last larval instar as pupa. Consequently, many studies with a focus on larval morphology have neglected the last larval stage. In this contribution, we describe and document morphological changes of the larval head throughout the postembryonic development, with emphasis on the transition between the last two instars. This is characterized by a crucial behavioral shift from a feeding stage to a stage of increased vagility. We show that different cephalic structures undergo major changes, especially the mandibulo-maxillary complex and the digestive tract, and associated muscles. Our measurements of the body length and the length of the head capsule tentatively confirm that the larval development of H. illucens passes through seven instars.

Shark skin is covered in denticles that provide texture important for hydrodynamic function. In bony fishes, both skin texture and function are modified by mucus that covers the outermost layer of the skin and scales. Despite the similar potential for mucus to change skin texture and function in shark skin, little is known about the occurrence and effect of external mucus in sharks. Specifically, we do not know where mucus is present along the shark body or how mucus alters surface texture, which could alter denticle function. To fill these gaps, we obtained individuals of Mustelus canis (dusky smooth-hound shark) and used gel-based profilometry to quantify the texture of the three-dimensional surface at eight body regions under two conditions: (1) a live anesthetized condition with mucus and (2) a condition after mucus was removed during preservation. We discovered that mucus covers and obscures the denticles on the dorsal fin and tail trailing edge tips; as a result, these regions were smoother and had a different surface texture than the preserved condition at the same region. Specifically, five parameters were significantly changed by mucus in these regions: roughness, skew, kurtosis, developed interfacial area ratio, and exposed area of the denticles. Notably, mucus did not change surface texture at any of the other body regions. Both the tips of the dorsal fin and tail are regions where flow separates and vortices are shed, so these results could indicate that mucus is modifying the boundary layer flow. Our results demonstrate that shark skin mucus is secreted selectively in particular body regions and that it can drastically change the surface texture when present. These findings suggest a need to both explore the morphology and properties of shark mucus and to consider mucus in studies of shark skin hydrodynamics.

This study investigates the coevolution of male attachment devices and female elytral morphology in coccinellid beetles, focusing on the sexual dimorphism of claws and adhesive pads. We analyzed 11 species from different tribes with different feeding regime, examining the structure of male and female attachment organs (claws and hairy pads) in relation to the surface structure of female elytra. Our findings show that disco-setae, which enhance adhesion during mating, are present only in males of some species and are localized on the hairy pads of their legs. These setae exhibit morphological adaptations based on the surface structure of female elytra, with larger discoid setal tips in species with smooth elytra and smaller tips in those with hairy elytra. Additionally, male beetles with hairy elytra possess dimorphic claws, which enhance attachment efficiency compared to species with smooth elytra, where claw dimorphism is less pronounced. Our results reveal that sexual dimorphism in hairy pads is more pronounced in larger species, where claw dimorphism is absent, while in smaller species, claw dimorphism alone suffices for effective attachment. These findings contribute to a deeper understanding of the evolutionary dynamics shaping attachment adaptations in Coccinellidae, with implications for reproductive strategies, pest management, and ecological interactions in this diverse beetle family.

Geometric morphometry is effective in distinguishing bivalve species and populations, including the economically and environmentally important Mediterranean mussel, Mytilus galloprovincialis. Although widely distributed, shell shape variation in M. galloprovincialis along the eastern Adriatic Sea has been infrequently studied. Farming practices and environmental conditions may affect the development of shell shape, as has been reported in the Mytilus genus from numerous locations globally. Building on earlier genetic analyses of mussels collected along a natural environmental gradient, this study aimed to identify shell landmark differentiation between wild and cultured populations and among northern, middle, and southern populations of the eastern Adriatic Sea using a geometric morphometric approach. Samples from 12 sites in Croatia, Montenegro, and Albania, including 4 aquaculture farms, were examined for variation in 9 internal shell landmarks. Wild populations exhibited a more extended posterior adductor muscle scar and a more elongated shape compared to farmed populations. Mussels from low salinity environments in the north and south exhibited an elongated shell shape compared to high salinity environments. Southern populations exhibited an extended posterior adductor muscle scar, along with an elongation of the lateral ligament and ventral umbo orientation that caused a concave shape of the ventral shell border compared to northern populations. The differences in environmental conditions in the Adriatic Sea, such as reduced salinity in Boka Kotorska Bay (Montenegro) in the south and Limski Bay (Croatia) in the north, likely play a role in influencing the variability of shell landmarks. These results may be applied to farming practices so that high-quality spat are collected from source sites with environmental conditions that match the farm site to which the spat are transferred. Overall, these results provide valuable insight into how M. galloprovincialis shell landmarks respond to environmental variation at large (hundreds of kilometres) spatial scale.

Eviota and Sueviota are two genera of cryptobenthic fishes of the family Gobiidae commonly known as dwarfgobies, that collectively contain 142 species. Despite thorough descriptions of the variation of their external morphology, little is known about variations on their skeleton. Combining traditional clearing-and-staining technique with computed scanning microtomography, we examined five species of Sueviota and 40 species of Eviota, representing the two major monophyletic groups in the latter genus, the “branched clade” and “unbranched clade,” named for their pectoral ray morphology. The purpose of this study was to provide generalized descriptions for both genera and highlight potentially phylogenetically informative characters that will aid in future classification of this diverse assemblage of fishes. The posterior portion of the mesethmoid was found to be unossified in eight species of Eviota from the unbranched clade. Twenty-five vertebrae (vs. 26 vertebrae) are present only in species of the unbranched clade of Eviota, and it is considered another potential synapomorphy for this clade. Direct contact between the retroarticular and the anterior edge of the interopercle without the retroarticular-interopercle ligament occurs in all species of Eviota and Sueviota, being interpreted as a potential synapomorphy grouping these two genera. The posterior edge of the interopercle is notched in all species of Eviota and Sueviota, as well as in the closely related genera Bryaninops, Pleurosicya, and Paragobiodon. In species of Sueviota and the branched clade of Eviota, the notch is deep, and there is an additional posteroventral process, forming a wrench-like posterior edge of the interopercle. This wrench-shaped interopercle is a potential synapomorphy, grouping Sueviota with representatives of the branched clade of Eviota. Individual and ontogenetic variations are discussed, including an assessment of the characters previously proposed for characterizing the branched and unbranched clades of Eviota.