We comparatively examined the trunk musculature and prezygapophyseal angle of mid-trunk vertebra in eight urodele species with different locomotive modes (aquatic Siren intermedia, Amphiuma tridactylum, Necturus maculosus and Andrias japonicus; semi-aquatic Cynops pyrrhogaster, Cynops ensicauda; and terrestrial Hynobius nigrescens, Hynobius lichenatus and Ambystoma tigrinum). We found that the more terrestrial species were characterized by larger dorsal and abdominal muscle weight ratios compared with those of the more aquatic species, whereas muscle ratios of the lateral hypaxial musculature were larger in the more aquatic species. The lateral hypaxial muscles were thicker in the more aquatic species, whereas the M. rectus abdominis was more differentiated in the more terrestrial species. Our results suggest that larger lateral hypaxial muscles function for lateral bending during underwater locomotion in aquatic species. Larger dorsalis and abdominal muscles facilitate resistance against sagittal extension of the trunk, stabilization and support of the ventral contour line against gravity in terrestrial species. The more aquatic species possessed a more horizontal prezygapophyseal angle for more flexible lateral locomotion. In contrast, the more terrestrial species have an increasingly vertical prezygapophyseal angle to provide stronger column support against gravity. Thus, we conclude trunk structure in urodeles differs clearly according to their locomotive modes.
Trunk musculature in Urodela species varies by habitat. In this study, trunk musculature was examined in five species of adult salamanders representing three different habitats: aquatic species, Amphiuma tridactylum and Necturus maculosus; semi-aquatic species, Cynops pyrrhogaster; terrestrial species, Hynobius nigrescens and Ambystoma tigrinum. More terrestrial species have heavier dorsal and ventral trunk muscles than more aquatic forms. By contrast, the lateral hypaxial musculature was stronger in more aquatic species. The number of layers of lateral hypaxial musculature varied among Urodela species and did not clearly correlate with their habitats. The M. rectus abdominis was separated from the lateral hypaxial musculature in both terrestrial and semi-aquatic species. In aquatic species, M. rectus abdominis was not separated from lateral hypaxial musculature. Lateral hypaxial musculature differed in thickness among species and was relatively thinner in terrestrial species. In more terrestrial species, dorsal muscles may be used for stabilization and ventral flexing against gravity. Ventral muscle may be used in preventing dorsally concave curvature of the trunk by dorsal muscles and by weight. The lengthy trunk supported by limbs needs muscular forces along the ventral contour line in more terrestrial species. And, the locomotion on well-developed limbs seems to lead to a decrease of the lateral hypaxial musculature.
Today, the necessity of marine education is being stated. Especially raising awareness about biodiversity is important in marine education. Museums not only house exhibits but also have the function of storing specimens. They hold specimens not available to the public daily that can be used for educational and research purposes. Samples of creatures that are difficult to keep and of unusual organisms are often stored in museums. Also, since immersion specimens do not move, they are suitable for observation. The forms of fish are especially diverse. Observations of fish of various forms facilitate the understanding of fish morphology and awareness of biodiversity. Therefore, we conducted a marine biology course using museum fish specimens. In that course, in order to encourage learners' activeness, we implemented quizzes and organized sessions with story nature. Before the lecture, the awareness of the morphology of the fish was low. The lecture was able to make the diversity of fish form understanding. Learners actively attended, observed and deepened their understanding. Also, we were able to tell learners about the function of the museum. It was found that the use of museum specimens is beneficial for observing precious biological specimens.
The need for marine education has increased in Japan, and recently, many marine education programs have emerged. Fishes are very popular with children; however, children are not familiar with cephalopods. There is little opportunity for children to observe marine life from the perspective of functional morphology; hence, we offered a lecture about the functional morphology of cephalopods. The lecture incorporated a presentation and the opportunity to observe body forms. During the observation, we used suckers and arms of squid and octopus. Squid and octopus have tentacles with different types of suckers. The morphology of the suckers is related to their function and ecology. The questionnaire we administered to evaluate the lecture revealed that it was varied for both children and parents, and helped them to understand the morphology of cephalopods.
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