Follicle cell processes (FCP) are actin‐based, tube‐like structures that connect the developing oocyte to the follicle cells throughout oogenesis. They were first described in Selachians (sharks) ...where their suggested roles were facilitating the transport of metabolites to the developing oocyte and providing structural support to the large egg cells of sharks, an early stage in the evolution of viviparity. Subsequent studies found that FCP are absent in Rajiformes (skates), suggesting that FCP may have been novel structures specific to the sharks. Here, FCP in Hydrolagus colliei, a Chimaeriform, were described. The FCP of H. colliei differ morphologically from those previously described in sharks, but as they also contain actin, they presumably play similar roles provisioning the developing oocyte and providing structural support. The presence of FCP in the order Chimaeriformes suggests that their origin predates the split of the elasmobranchs and the holocephalans.
Little is known about the genetic basis of convergent traits that originate repeatedly over broad taxonomic scales. The myogenic electric organ has evolved six times in fishes to produce electric ...fields used in communication, navigation, predation, or defense. We have examined the genomic basis of the convergent anatomical and physiological origins of these organs by assembling the genome of the electric eel (Electrophorus electricus) and sequencing electric organ and skeletal muscle transcriptomes from three lineages that have independently evolved electric organs. Our results indicate that, despite millions of years of evolution and large differences in the morphology of electric organ cells, independent lineages have leveraged similar transcription factors and developmental and cellular pathways in the evolution of electric organs.
Skates are cartilaginous fish whose body plan features enlarged wing-like pectoral fins, enabling them to thrive in benthic environments
. However, the molecular underpinnings of this unique trait ...remain unclear. Here we investigate the origin of this phenotypic innovation by developing the little skate Leucoraja erinacea as a genomically enabled model. Analysis of a high-quality chromosome-scale genome sequence for the little skate shows that it preserves many ancestral jawed vertebrate features compared with other sequenced genomes, including numerous ancient microchromosomes. Combining genome comparisons with extensive regulatory datasets in developing fins-including gene expression, chromatin occupancy and three-dimensional conformation-we find skate-specific genomic rearrangements that alter the three-dimensional regulatory landscape of genes that are involved in the planar cell polarity pathway. Functional inhibition of planar cell polarity signalling resulted in a reduction in anterior fin size, confirming that this pathway is a major contributor to batoid fin morphology. We also identified a fin-specific enhancer that interacts with several hoxa genes, consistent with the redeployment of hox gene expression in anterior pectoral fins, and confirmed its potential to activate transcription in the anterior fin using zebrafish reporter assays. Our findings underscore the central role of genome reorganization and regulatory variation in the evolution of phenotypes, shedding light on the molecular origin of an enigmatic trait.
The use of local wisdom as learning resources has been widely known to be able to create meaningful learning. The purposes of this study were to 1) produce module based on freshwater fish anatomy as ...local wisdom in Ngebel Lake, Ponorogo and 2) find the quality of the module produced. The Research and Development (R&D) was designed based on the Thiagarajan model which consisted of defining, designing, developing, and disseminating stages. The data were collected using interview guidelines, validation sheets, and students’ response questionnaire. The validation results of the media, material, and language experts showed that the module was very valid with the percentages were 86.5%, 88.2%, and 85.3% respectively. In addition, the student responses reached 87.9% (very good). In conclusion, the fish anatomy learning module based on local wisdom is appropriate to be used as learning resource.
The use of local wisdom as learning resources has been widely known to be able to create meaningful learning. The purposes of this study were to 1) produce module based on freshwater fish anatomy as ...local wisdom in Ngebel Lake, Ponorogo and 2) find the quality of the module produced. The Research and Development (R&D) was designed based on the Thiagarajan model which consisted of defining, designing, developing, and disseminating stages. The data were collected using interview guidelines, validation sheets, and students’ response questionnaire. The validation results of the media, material, and language experts showed that the module was very valid with the percentages were 86.5%, 88.2%, and 85.3% respectively. In addition, the student responses reached 87.9% (very good). In conclusion, the fish anatomy learning module based on local wisdom is appropriate to be used as learning resource.
An integrative approach by the congruence of genetics, morphology and ecological niche modelling (ENM) was used to delimit a new species of Hypanus (Rafinesque, 1818), a recently resurrected genus of ...marine stingrays comprising eight species, five of which occur in the western Atlantic. The species with the widest distribution, Hypanus americanus (Hildebrand and Schroeder, 1928), from the northeastern coast of the United States to southeastern Brazil, was demonstrated to be paraphyletic based on protein‐coding mitochondrial genome analyses. This data set also indicates that the genetic distance between the new species Hypanus berthalutzae sp. nov. and its three closely related species (H. americanus, H. longus and H. rudis) varies from 0.82% to 3.14%. In addition, Bayesian Analysis of Population Similarity using the mitochondrial gene mt‐nd2 supports the separation of H. berthalutzae sp. nov. (southwestern Atlantic) from its sister species H. rudis (eastern Atlantic). Similarly, morphological and morphometric analyses corroborated four morphotypes within the H. americanus species group and indicated the ventral caudal fold height and length and interspiracular and interorbital lengths as useful measurements to distinguish among them. Claspers of adult males also exhibit morphological differences among species. The ENM agreed with molecular and morphological analyses and delimits the distribution of H. berthalutzae sp. nov. to shallow areas close to shore along the Brazilian coast, from the mouth of the Amazon River to São Paulo State, including the northeastern oceanic islands, suggesting that the great outflow of fresh water and sediments and the Mid‐Atlantic Ridge might act as barriers. The integration of these data to describe a new species provides information relevant to their conservation status, because all species of the H. americanus species group are under the “data‐deficient” status.
The endoskeleton of elasmobranchs (sharks and rays) is comprised largely of unmineralized cartilage, differing fundamentally from the bony skeletons of other vertebrates. Elasmobranch skeletons are ...further distinguished by a tessellated surface mineralization, a layer of minute, polygonal, mineralized tiles called tesserae. This ‘tessellation’ has defined the elasmobranch group for more than 400 million years, yet the limited data on development and ultrastructure of elasmobranch skeletons (e.g. how tesserae change in shape and mineral density with age) have restricted our abilities to develop hypotheses for tessellated cartilage growth. Using high‐resolution, two‐dimensional and three‐dimensional materials and structural characterization techniques, we investigate an ontogenetic series of tessellated cartilage from round stingray Urobatis halleri, allowing us to define a series of distinct phases for skeletal mineralization and previously unrecognized features of tesseral anatomy. We show that the distinct tiled morphology of elasmobranch calcified cartilage is established early in U. halleri development, with tesserae forming first in histotroph embryos as isolated, globular islets of mineralized tissue. By the sub‐adult stage, tesserae have increased in size and grown into contact with one another. The intertesseral contact results in the formation of more geometric (straight‐edged) tesseral shapes and the development of two important features of tesseral anatomy, which we describe here for the first time. The first, the intertesseral joint, where neighboring tesserae abut without appreciable overlapping or interlocking, is far more complex than previously realized, comprised of a convoluted bearing surface surrounded by areas of fibrous attachment. The second, tesseral spokes, are lamellated, high‐mineral density features radiating outward, like spokes on a wheel, from the center of each tessera to its joints with its neighbors, likely acting as structural reinforcements of the articulations between tesserae. As tesserae increase in size during ontogeny, spokes are lengthened via the addition of new lamellae, resulting in a visually striking mineralization pattern in the larger tesserae of older adult skeletons when viewed with scanning electron microscopy (SEM) in backscatter mode. Backscatter SEM also revealed that the cell lacunae in the center of larger tesserae are often filled with high mineral density material, suggesting that when intratesseral cells die, cell‐regulated inhibition of mineralization is interrupted. Many of the defining ultrastructural details we describe relate to local variation in tissue mineral density and support previously proposed accretive growth mechanisms for tesserae. High‐resolution micro‐computed tomography data indicate that some tesseral anatomical features we describe for U. halleri are common among species of all major elasmobranch groups despite large variation in tesseral shape and size. We discuss hypotheses about how these features develop, and compare them with other vertebrate skeletal tissue types and their growth mechanisms.
A new species of Okamejei is described based on two adult males collected from deep waters in the South China Sea. The new species, Okamejei picta sp. nov., is readily distinguished from most other ...congeners in having densely scattered black spots on dorsal disc. Okamejei hollandi and O. mengae is quite similar to the new species by their spot patterns on dorsal disc, but the new species differs from the former by a combination of characters: a yellowish brown dorsal surface densely covered with small, circular to irregular-shaped black spots; blotches on dorsal disc indistinct; posterior ocellus absent; ventral disc white; disc length 45.0-47.7% TL; distance between cloaca to caudal-fin tip 53.6-55.1% TL; trunk centra 31; total basal radials 73-76, morphology of clasper terminal skeleton, and lacking component funnel at the clasper end.
Highlights • The active electrosense uses multiple topographic maps of the receptor array. • Different cellular and circuit properties of the maps shape spatiotemporal tuning. • The tuning properties ...of the maps can be linked to specific behavioral tasks. • Topography is lost at the level of the pallium. • Nevertheless, descending projections from the pallium shape the activity of midbrain maps.
Distributing learning across multiple layers has proven extremely powerful in artificial neural networks. However, little is known about how multi-layer learning is implemented in the brain. Here, we ...provide an account of learning across multiple processing layers in the electrosensory lobe (ELL) of mormyrid fish and report how it solves problems well known from machine learning. Because the ELL operates and learns continuously, it must reconcile learning and signaling functions without switching its mode of operation. We show that this is accomplished through a functional compartmentalization within intermediate layer neurons in which inputs driving learning differentially affect dendritic and axonal spikes. We also find that connectivity based on learning rather than sensory response selectivity assures that plasticity at synapses onto intermediate-layer neurons is matched to the requirements of output neurons. The mechanisms we uncover have relevance to learning in the cerebellum, hippocampus, and cerebral cortex, as well as in artificial systems.
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•Biological solutions to general problems in multi-layer learning are shown•Intermediate layer function requires compartmentalization of learning and signaling•Circuit organization based on learning solves the credit assignment problem
Using a cerebellum-like structure in an electric fish as a model system for investigating mechanisms of learning in multi-layer networks, Muller et al. observed that functional compartmentalization within individual neurons allows synaptic plasticity at an intermediate processing layer to adaptively shape network output.
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