Journal of Morphology最新文献

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.

The maxillofacial region is one of the most complex areas in the vertebrate body plan. The homology of the upper jaw bones remain controversial, both between mammals and nonmammalian amniotes and among humans and other mammals, leading to various hypotheses on how this region evolved from ancestral amniotes to humans. As a key mammalian model, the mouse (Mus musculus) is vital for unraveling the evolution and development of the maxillofacial region experimentally. However, limited detailed morphological descriptions of murine cranial development hinder the extrapolation of findings to other species, including humans. Here, we describe the development of the murine face, including the nerves, skeletons, and vasculatures from the pharyngula (9.0 days post-coitum [dpc]) to the late fetal period (18.5 dpc) based on three-dimensional reconstructions of histological sections. The present results confirm that the morphology of the pharyngula stages and developmental process of chondrocranium of mice is highly conserved when compared to nonmammalian tetrapods and humans. We also propose that the Os incisivum, the rostralmost bone in the mammalian upper jaw, consists of septomaxillary and palatine components, supporting our previous hypothesis that the ancestral premaxilla was entirely lost in mammals. The present descriptive study of mice strengthen the anatomical correspondence between mouse and human faces and offers a solid framework for comparative craniofacial studies across vertebrates.

Silphopsyllus desmanae, a species of the small subfamily Platypsyllinae of Leiodidae, lives in the fur of the semiaquatic Russian desman, and is apparently adapted to this highly specialized life style. Even though the morphology of adults of the species was described almost 70 years ago, we re-examined it with modern methods and documented its external and internal features in detail, and discuss them with respect to phylogeny and function. Our analyses of morphological data place Leptinillus as the sister group of the remaining genera of Platypsyllinae, and Leptinus as the sister group of Silphopsyllus + Platypsyllus. Platypsyllinae are supported by many putative autapomorphies: supraantennal ridges directed mesad but not extending beyond the antennal insertions and not forming a transverse ridge; tentorium without connected laminatentoria anterior to the tentorial bridge; submentum subrectangular; labrum about as wide as the maxillary-labial complex; elongate and posteriorly projecting lateral lobes of the mentum; antennomeres lacking periarticular gutters (and Hamann's organs); cervical sclerites absent; precoxal prosternal region distinctly longer than the coxal rests; mesocoxal cavities situated closer to the body midline than to the lateral mesothoracic margins; metanepisterna fused with the metaventrite; metascutum laterally overlapping the meso- and metapleural regions; procoxae subglobose or only slightly elongate; mesocoxae subglobose. Platypsyllinae are most likely the sister group of Coloninae + Cholevinae. Eight unique apomorphies differentiating Platypsyllus from all the remaining Platypsyllinae are mainly adaptations for living in the fur of beavers. Silphopsyllus is much less adapted to life on a semiaquatic host than Platypsyllus.

In mammals the fila olfactoria, fascicles of axons coursing from sensory neurons in the olfactory epithelium to the glomeruli of the olfactory bulb, not only have a topographic projection pattern but also serve as routes for cerebrospinal fluid (CSF) drainage from around the brain. Les is known about the fila olfactoria in nonmammalian taxa. This work explores the fila olfactoria of the American alligator (Alligator mississippiensis) using a combination of gross dissection, histology, Diffusible Iodine-based contrast-enhanced computed tomography, latex corrosion casting, and India ink tracers. In Crocodylians, as in other nonmammalian vertebrates, the fila olfactoria courses through a foramen in the nasal capsule rather than an ethmoidal cribriform plate. In Alligator this foramen is filled by dense connective tissue; prominent perineural spaces extend through the connective tissue, effectively making it perforate like the cribriform plate. Latex or India ink introduced into the cranial CSF pass through the dense connective to reach the submucosa of the olfactory epithelium, suggesting that Crocodylians have the same cranial CSF drainage pattern as mammals. In Alligator, the fila olfactoria is asymmetric, with more fascicles entering the ventral and lateral surfaces of the olfactory bulb than the dorsal or medial surfaces. If individual fascicles of the fila olfactoria are traced in Alligator, a clear topographic projection emerges; with medial and lateral polarity maintained between olfactory epithelium and olfactory bulb, and a rostral-caudal polarity projecting as dorsal-ventral on the olfactory bulb.