Journal of Morphology最新文献

Information detection affects physiological performance and behaviour and is vital to survival and fitness. Despite the recognised importance of sensory adaptations in information acquisition and manipulation, many forms of sensory variation—from within individuals to between species—remain underexplored. To better understand the role of information in evolution, it is important to examine sensory variation as part of a cohesive framework of sensory diversity. Using the decapod claw, a structure well-recognised for its morphological variation, we investigated sensory diversity at the intraspecific level by assessing heterochely and sexual dimorphism in the chelar morphologies of Pagurus bernhardus hermit crabs. We employed a novel methodology using scanning electron microscopy (SEM) to assess moulted chelar tissue from both the major and minor claws. The shape, size, and sensillation (i.e., the distribution and abundance of sensilla) of both chelipeds were examined by geometric morphometric landmark analysis (GMLA), generalised Procrustes analysis (GPA), and linear mixed effects models. Hermit crabs exhibited heterochely and sexual dimorphism in both gross and sensory chelar morphologies. Sexual dimorphism was greater in the sensory morphology of the major claw, suggesting sex-based sensory specialisations, likely due to differences in mating roles and behaviours. In contrast, the minor claw's sensory morphology lacked sexual dimorphism, suggesting the sensory role of this appendage is equally important for both sexes. Our results highlight sensory variation as a fundamental aspect of functional morphology and emphasise the need to consider sexual dimorphism and body asymmetry in information acquisition. These findings contribute to a broader framework for studying sensory diversity, underscoring the importance of integrating sensory morphology, function, and ecology to fully understand the evolutionary implications of sensory specialisations.

We present, for the first time, the suction feeding behavior of the tadpole of Dendropsophus cerradensis (Hylidae, Dendropsophini), along with a detailed description of its external morphology, buccopharyngeal cavity, and musculoskeletal system. The tadpole exhibits a depressed body, anteriorly positioned nostrils, a modified oral disc (completely covered by external folds), and a low tail, resembling other members of the D. microcephalus group. The buccopharyngeal cavity is reduced in features, with internal nares positioned at an acute angle and covered by prenarial papillae, exclusive for this species. Muscle insertion patterns are generally consistent with other Dendropsophini tadpoles, except for the insertion of the m. levator mandibulae longus profundus on Meckel's cartilage. The feeding behavior is characterized by the use of an oral tube that protrudes exclusively during predation. This mechanism may be associated with robust mandibular and hyoid musculature, as well as a modified cranial structure—including a unique suprarostral element, quadrangular muscular processes, robust ceratohyals, and a reduced branchial basket in the hyobranchial skeleton—which enables fast suction movements. This study presents a previously unknown aspect of the protractile oral tube and feeding behavior of the D. microcephalus group, providing new insights into the morphology and feeding behavior of the group.

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.