Journal of Morphology最新文献

Some of the most extensively studied phenotypic adaptations in reef fish pertain to trophic diversification. Within the Pomacentridae family, a strong correlation between head morphology and diet has been identified. The relationship between structures involved in food detection (eyes) and capture (mouth) has been demonstrated, prompting the question of whether pharyngeal jaws vary in an integrated manner with the eyes and mouth to detect, capture, and process food according to different trophic guilds. In this study, morphometric analyses were applied to X-rays of the 24 damselfishes of the eastern Pacific. A comprehensive database of dietary items for all species was constructed. The species were grouped according to their diet in trophic groups, which were tested on the morphometric data to determine ecomorphological groups. Six ecomorphological groups were determined: three benthic feeders, one benthopelagic, and two pelagic. Phylogenetic (phy) and nonphylogenetic (n-phy) modulatory analyses were conducted on the entire sample, three broad ecomorphological categories (phy-benthic, pelagic, pelagic–benthopelagic; n-phy, benthic, benthopelagic, pelagic), and the six specific ecomorphological groups (n-phy). Four modularity hypotheses were tested: three modules, the eye (E), mouth (M), and pharyngeal jaws (PJ), and two modules, PJ&E versus M, M&PJ versus E, and M&E versus PJ. Across all groupings, the hypothesis of three distinct modules was most strongly supported, followed by PJ&E versus M, with M&E versus PJ being the least supported. These findings suggest that the eye and mouth are more functionally decoupled than the pharyngeal jaws. It was evident that these structures exhibit a greater decoupling in benthic species than in benthopelagic and pelagic species. Our results indicate that different trophic groups show different levels of decoupling and integration in structures to detect, capture, and process food, and that, despite operating within a relatively narrow range of ecomorphological variation, damselfishes display a remarkable array of ecomorphological combinations.

Supramedullary neurons (SMNs) were described almost 150 years ago as large, unipolar cells whose somata are located on the dorsal aspect of the medulla oblongata and spinal cord in adults of teleost fishes. SMNs are either aligned in a single, median longitudinal row, generally extending over the rostral third of the spinal cord, or clustered over the medulla oblongata and rostral spinal cord. We add to the list of species that have SMNs and provide the first description of a novel distribution of SMNs along most of the spinal cord in the oyster toadfish (Opsanus tau) and sea raven (Hemitripterus americanus). The number of SMNs ranges from 27 in the Atlantic butterfish (Peprilus triacanthus) to 3712 in the oyster toadfish (Opsanus tau), and soma diameter ranges from an average of 23 µm in the Atlantic butterfish to 232 µm in the Southern pufferfish (Sphoeroides nephelus). SMNs could not be identified in 11 species, including seven freshwater fishes. We discuss factors that may affect the presence/absence of SMNs including age, length of time in captivity, and habitat salinity. Proposed functions of SMNs include neurosecretion and mucous secretion, and we suggest approaches that may aid in the discovery of the role of these fascinating neurons.

Lizards represent the closest amniotes to mammals able to regenerate many tissues, therefore are useful models for studies of mammalian regeneration. Tail regeneration occurs by stem cells but tissue dedifferentiation may also be involved. When injury damages numerous tissues they may undergo dedifferentiation (re-programming). This was indicated especially in muscles and connectives of the tail 7–10 days postamputation. The transcriptome of regenerating tail and limb from the lizard Podarcis muralis detected upregulation of spalt-like genes (sall 1–4), known to be involved in re-programming. Here, immunolocalization of the sall4 protein and 5BrdU-labeled cells (proliferating) was conducted. A variable number of 5BrdU and sall4-positive cells are detected among stump connective tissues, injured muscles, and dermis. Labeling for sall4 is cytoplasmic and also nuclear, and it is also noted in cytoplasmic muscle fragments. The latter likely derived from the fragmentation of injured muscles in both tail and limb stumps at 7–16 days postamputation. Occasional, isolated sall4-labeled cells are rarely detected in the blastema, and none in the wound epidermis or regenerating spinal cord and muscles. The present study indicates that cell dedifferentiation occurs during early stages of tail and limb amputation in lizards, contributing with activated stem cells to their regeneration or scarring.

New World Blackbirds (Icteridae) are a diverse group of Neotropical passerines and an important component of the continental radiation of nine-primaried songbirds (Emberizoidea). Icterids and other emberizoids are chiefly omnivorous, but with variable predilection for invertebrates, fruits, and seeds. The icterids also exhibit a peculiar “gaping” behavior, whereby they insert their beaks into soil, fruits or bark and then open them inside the substrate. Cowbirds (Molothrus) stand out among the icterids for not being gapers and, with the exception of the Giant Cowbird, for a marked tendency towards a granivorous diet. To explore the signal of trophic ecology in the lower jaw of icterids and other emberizoids, we applied three-dimensional geometric morphometrics on Microcomputed tomography data and phylogenetic comparative methods. Phylomorphospaces were constructed and possible correlates with diet, gaping, and evolutionary allometry were assessed through phylogenetic ANOVA. Convergence between seed-eater species was also estimated by recently developed measures (Ct1). Results show a significant signal of trophic ecology in the mandible, with seed-eater species occupying a narrow domain of morphospace, partially overwhelming the signal of evolutionary allometry. The cowbird Molothrus ater stands out for clearly diverging from most icterids, showing significant convergence with other seed-eater emberizoids. Mandibular morphology, often neglected in avian ecomorphological studies, is informative of the trophic ecology of these birds.

An enigmatic salamander species Protohynobius puxiongensis was named 25 years ago but since then has been disputed as a genus and species of its own or a species in the genus Pseudohynobius. Here, we provide a detailed anatomical account for P. puxiongensis based on micro-CT scans of five specimens, including one larva, one subadult and three adults. For the first time we reveal anatomical details in the braincase, hyobranchium and the postcranial skeleton. Our comparative study with species of Pseudohynobius and Liua clarified previous disputes over the anatomy of the skull, and confirmed that the internasal bone is an intraspecific variation that is present in several hynobiid species. Our study found that P. puxiongensis possesses fundamental morphological features that distinguish this enigmatic salamander from all species in the genus Pseudohynobius; therefore, the results of our study provide evidence to reject the combination of “Pseudohynobius puxiongensis”, and support Protohynobius as the valid generic name for the species in question for the purpose of the Principle of Priority. The extensive morphological disparities between Protohynobius and Pseudohynobius identified herein combined with their relatively short genetic distances recognized by previous studies indicate that these hynobiids have had a high evolutionary rate that may be associated with the intense orogenies around the eastern edge of the Qinghai-Tibetan Plateau during the Neogene.

Amphibian testes vary in shape, from multilobed in caecilians and salamanders to compact, ovoid organs in anurans. Although these variations have been studied extensively in amphibians, there has been little investigation into the structural, copulatory, and reproductive behavioral consequences of unpaired testes, a character shared among some amphibians, cyclostomates, and some teleosts. We analyzed the morphology and structure of unpaired testes in Pristimantis fetosus and Pristimantis permixtus. We also report a single testis in P. hernandezi. Our results suggest that the testis arrangement in these species results from the hypertrophy and fusion of two testes rather than the loss or reduction of one testis. Furthermore, the occurrence of germ cells at different stages of development suggests that spermatogenesis is similar to that described for vertebrates, with spermatogonia undergoing mitosis to form spermatocytes, which then undergo meiosis to form spermatids. Like other brachycephaloid frogs, Pristimantis with fused testes exhibit direct development and reproduction on land, but they are the only anurans known to undergo testicular fusion. We propose to recognize the occurrence of fused testes as a unique putative synapomorphy for a new species group distributed in the Colombian Andes, which we refer to as the P. hernandezi species group. A comparative survey among vertebrates reveals no apparent variations in testicular organization, sperm development, or copulative and reproductive behavioral characters associated with the fusion of testes, suggesting that its occurrence might not have functional implications for vertebrate testes. The independently evolved occurrence of fused testes in cyclostomates, teleosts, and amphibians raises an exciting perspective on the study of the molecular origin, evolution, and functional significance of testis variation in vertebrate reproduction and biology.

In live specimens of the nemertodermatidan Flagellophora apelti Faubel and Dörjes, 1978, a peculiar organ looking like a fascicle of bristles—and so called a broom organ by its discoverer—occupies the front third or so of the body. The animal can extrude the organ to splay the bristles in a fan-like array, each bristle having an adhesive tip. Described first by light histology as a bundle of flagella, this organ can be seen by transmission electron microscopy to be actually a bundle of exceedingly long necks of glands. Bodies of the glands sat well behind the brain, and the necks reached forward through the brain and folded back to a small bulb where they emerged into a canal. Protrusion of the organ would involve unfolding of the necks, projection of the bulb through a pore at the rostral end of the canal, and eversion of the bulb to form a knob-like point from which the gland necks radiate. Confocal microscopy of specimens stained for F-actin showed the muscles that drive protrusion and retraction and cell junctions that anchor the necks at the bulb, and we propose mechanisms through which these motions can be produced. The animal's rostrum had many other glands besides those of the broom organ, including a set forming a brush-like protruberance immediately ventral to the pore of the broom organ, and it likely plays a role in processing prey captured by the broom. Longitudinal muscles of the ventral body wall were specialized into strong bands that could serve to transfer the prey, then, to a facultative mouth.