Plasticity and regeneration of gonads in the annelid Pristina leidyi

International audienceGonads are specialized gamete-producing structures that, despite their functional importance, are generated by diverse mechanisms across groups of animals and can be among the most plastic organs of the body. Annelids, the segmented worms, are a group in which gonads have been documented to be plastic and to be able to regenerate, but little is known about what factors influence gonad development or how these structures regenerate. In this study, we aimed to identify factors that influence the presence and size of gonads and to investigate gonad regeneration in the small asexually reproducing annelid, Pristina leidyi.We found that gonad presence and size in asexual adult P. leidyi are highly variable across individuals and identified several factors that influence these structures. An extrinsic factor, food availability, and two intrinsic factors, individual age and parental age, strongly influence the presence and size of gonads in P. leidyi. We also found that following head amputation in this species, gonads can develop by morphallactic regeneration in previously non-gonadal segments. We also identified a sexually mature individual from our laboratory culture that demonstrates that, although our laboratory strain reproduces only asexually, it retains the potential to become fully sexual.Our findings demonstrate that gonads in P. leidyi display high phenotypic plasticity and flexibility with respect to their presence, their size, and the segments in which they can form. Considering our findings along with relevant data from other species, we find that, as a group, clitellate annelids can form gonads in at least four different contexts: post-starvation refeeding, fission, morphallactic regeneration, and epimorphic regeneration. This group is thus particularly useful for investigating the mechanisms involved in gonad formation and the evolution of post-embryonic phenotypic plasticity

Fine taxonomic sampling of nervous systems within Naididae (Annelida: Clitellata) reveals evolutionary lability and revised homologies of annelid neural components

Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Introduction: An important goal for understanding how animals have evolved is to reconstruct the ancestral features and evolution of the nervous system. Many inferences about nervous system evolution are weak because of sparse taxonomic sampling and deep phylogenetic distances among species compared. Increasing sampling within clades can strengthen inferences by revealing which features are conserved and which are variable within them. Among the Annelida, the segmented worms, the Clitellata are typically considered as having a largely conserved neural architecture, though this view is based on limited sampling. Results: To gain better understanding of nervous system evolution within Clitellata, we used immunohistochemistry and confocal laser scanning microscopy to describe the nervous system architecture of 12 species of the basally branching family Naididae. Although we found considerable similarity in the nervous system architecture of naidids and that of other clitellate groups, our study identified a number of features that are variable within this family, including some that are variable even among relatively closely related species. Variable features include the position of the brain, the number of ciliary sense organs, the presence of septate ventral nerve cord ganglia, the distribution of serotonergic cells in the brain and ventral ganglia, and the number of peripheral segmental nerves. Conclusions: Our analysis of patterns of serotonin immunoreactive perikarya in the central nervous system indicates that segmental units are not structurally homogeneous, and preliminary homology assessments suggest that whole sets of serotonin immunoreactive cells have been gained and lost across the Clitellata. We also found that the relative position of neuroectodermal and mesodermal segmental components is surprisingly evolutionarily labile; in turn, this revealed that scoring segmental nerves by their position relative to segmental ganglia rather than to segmental septa clarifies their homologies across Annelida. We conclude that fine taxonomic sampling in comparative studies aimed at elucidating the evolution of morphological diversity is fundamental for proper assessment of trait variability.https://doi.org/10.1186/s12983-015-0100-

Delayed differentiation of epidermal cells walls can underlie pedomorphosis in plants: the case of pedomorphic petals in the hummingbird-pollinated Caiophora hibiscifolia (Loasaceae, subfam. Loasoideae) species

Understanding the relationship between macroevolutionary diversity and variation in organism development is an important goal of evolutionary biology. Variation in the morphology of several plant and animal lineages is attributed to pedomorphosis, a case of heterochrony, where an ancestral juvenile shape is retained in an adult descendant. Pedomorphosis facilitated morphological adaptation in different plant lineages, but its cellular and molecular basis needs further exploration. Plant development differs from animal development in that cells are enclosed by cell walls and do not migrate. Moreover, in many plant lineages, the differentiated epidermis of leaves, and leaf-derived structures, such as petals, limits organ growth. We, therefore, proposed that pedomorphosis in leaves, and in leaf-derived structures, results from delayed differentiation of epidermal cells with respect to reproductive maturity. This idea was explored for petal evolution, given the importance of corolla morphology for angiosperm reproductive success

Long-term time-lapse live imaging reveals extensive cell migration during annelid regeneration

Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Background: Time-lapse imaging has proven highly valuable for studying development, yielding data of much finer resolution than traditional “still-shot” studies and allowing direct examination of tissue and cell dynamics. A major challenge for time-lapse imaging of animals is keeping specimens immobile yet healthy for extended periods of time. Although this is often feasible for embryos, the difficulty of immobilizing typically motile juvenile and adult stages remains a persistent obstacle to time-lapse imaging of post-embryonic development. Results: Here we describe a new method for long-duration time-lapse imaging of adults of the small freshwater annelid Pristina leidyi and use this method to investigate its regenerative processes. Specimens are immobilized with tetrodotoxin, resulting in irreversible paralysis yet apparently normal regeneration, and mounted in agarose surrounded by culture water or halocarbon oil, to prevent dehydration but allowing gas exchange. Using this method, worms can be imaged continuously and at high spatial-temporal resolution for up to 5 days, spanning the entire regeneration process. We performed a fine-scale analysis of regeneration growth rate and characterized cell migration dynamics during early regeneration. Our studies reveal the migration of several putative cell types, including one strongly resembling published descriptions of annelid neoblasts, a cell type suggested to be migratory based on “still-shot” studies and long hypothesized to be linked to regenerative success in annelids. Conclusions: Combining neurotoxin-based paralysis, live mounting techniques and a starvation-tolerant study system has allowed us to obtain the most extensive high-resolution longitudinal recordings of full anterior and posterior regeneration in an invertebrate, and to detect and characterize several cell types undergoing extensive migration during this process. We expect the tetrodotoxin paralysis and time-lapse imaging methods presented here to be broadly useful in studying other animals and of particular value for studying post-embryonic development.https://doi.org/10.1186/s12861-016-0104-

Sampling multiple life stages significantly increases estimates of marine biodiversity

Biodiversity assessments are critical for setting conservation priorities, understanding ecosystem function and establishing a baseline to monitor change. Surveys of marine biodiversity that rely almost entirely on sampling adult organisms underestimate diversity because they tend to be limited to habitat types and individuals that can be easily surveyed. Many marine animals have planktonic larvae that can be sampled from the water column at shallow depths. This life stage often is overlooked in surveys but can be used to relatively rapidly document diversity, especially for the many species that are rare or live cryptically as adults. Using DNA barcode data from samples of nemertean worms collected in three biogeographical regions—Northeastern Pacific, the Caribbean Sea and Eastern Tropical Pacific—we found that most species were collected as either benthic adults or planktonic larvae but seldom in both stages. Randomization tests show that this deficit of operational taxonomic units collected as both adults and larvae is extremely unlikely if larvae and adults were drawn from the same pool of species. This effect persists even in well-studied faunas. These results suggest that sampling planktonic larvae offers access to a different subset of species and thus significantly increases estimates of biodiversity compared to sampling adults alone. Spanish abstract is available in the electronic supplementary material.Fil: Maslakova, Svetlana A.. University of Oregon; Estados UnidosFil: Ellison, Christina I.. University of Oregon; Estados UnidosFil: Hiebert, Terra C.. University of Oregon; Estados UnidosFil: Conable, Frances. University of Oregon; Estados UnidosFil: Heapy, Maureen C.. University of Oregon; Estados UnidosFil: Venera Pontón, Dagoberto E.. Smithsonian Tropical Research Institute; PanamáFil: Norenburg, Jon L.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Schwartz, Megan L.. University of Washington; Estados UnidosFil: Boyle, Michael J.. Smithsonian Tropical Research Institute; PanamáFil: Driskell, Amy C.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Macdonald, Kenneth S.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Zattara, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Collin, Rachel. Smithsonian Tropical Research Institute; Panam

Chromosome-Level Assembly and Annotation of the Genome of the Endangered Giant Patagonian Bumble Bee Bombus dahlbomii

This article describes a genome assembly and annotation for Bombus dahlbomii, the giant Patagonian bumble bee. DNA from a single, haploid male collected in Argentina was used for PacBio (HiFi) sequencing, and Hi-C technology was then used to map chromatin contacts. Using Juicer and manual curation, the genome was scaffolded into 18 main pseudomolecules, representing a high-quality, near chromosome-level assembly. The sequenced genome size is estimated at 265 Mb. The genome was annotated based on RNA sequencing data of another male from Argentina, and BRAKER3 produced 15,767 annotated genes. The genome and annotation show high completeness, with >95% BUSCO scores for both the genome and annotated genes (based on conserved genes from Hymenoptera). This genome provides a valuable resource for studying the biology of this iconic and endangered species, as well as for understanding the impacts of its decline and designing strategies for its preservation.This article is published as Lican Martínez, Eduardo E Zattara, Marina P Arbetman, Carolina L Morales, Rick E Masonbrink, Andrew J Severin, Marcelo A Aizen, Amy L Toth, Chromosome-Level Assembly and Annotation of the Genome of the Endangered Giant Patagonian Bumble Bee Bombus dahlbomii, Genome Biology and Evolution, Volume 16, Issue 7, July 2024, evae146, https://doi.org/10.1093/gbe/evae146. © The Author(s) 2024. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited

Composition, distribution and trophic relationships of the fish fauna of the Negro river, Patagonia Argentina

La provincia ictiogeográfica Patagónica se caracteriza por una llamativa pobreza de especies. El río Negro es el curso de agua más importante de esta región y a pesar de sus dimensiones e importancia socioeconómica su fauna íctica ha sido poco estudiada. Este trabajo describe algunos aspectos biogeográficos y características ecológicas de su ictiofauna. Se muestrearon estacionalmente cinco sitios a lo largo del río, por medio de redes de enmalle, pesca eléctrica, redes de arrastre costero y atarraya. Se analizó la composición y distribución de peces y se estudió la dieta para determinar los roles tróficos y los niveles de competencia y de piscivoría. Se capturaron ejemplares de 13 especies: siete de origen nativo y seis exóticas, de las cuales se destaca la novedosa presencia de la coridora (Corydoras paleatus) y la carpa común (Cyprinus carpio), ampliando su distribución austral. Las especies más importantes fueron las nativas pejerrey patagónico (Odontesthes hatcheri), perca bocona (Percychthis colhuapiensis), perca de boca chica (P. trucha) y madrecita (Jenynsia multidentata). Los índices ecológicos indican que el curso inferior es diferente al resto del río presentando una dominancia de pejerrey patagónico y madrecita. En este sector se observó una mayor importancia de especies exóticas. Se encontraron ocho grupos tróficos, existencia de solapamientos en las dietas entre componentes nativos y exóticos, y evidencia de piscivoría importante entre las especies. La presencia y distribución de los peces en el río Negro está fuertemente influenciada por fenómenos de antropocoria accidental o intencional. Es necesario desarrollar estudios que analicen el impacto generado por las introducciones y la evolución de las relaciones entre los componentes nativos y exóticos, teniendo en cuenta que la trucha arco iris y la carpa común han influido negativamente en otros lugares del mundo.The Patagonic ictiogeographic region is characterized by a low species diversity. Despite that the Negro river is the most important water body in the region, both in terms of the size of its drainage basin and of its socioeconomic importance, its fish fauna has scarcely been studied. The present paper addresses biogeographic and ecological characteristics related to its fish. Gill net gangs, electro fishing and beach seine nets were used to sample seasonally five stations along the river. Fish fauna composition and distribution were analyzed throughout different ecological indexes. Diet composition was also analyzed to establish trophic roles, competition and piscivory. We caught seven native and six exotic species; two of them (Corydoras paleatus and Cyprinus carpio) represent a widening of their austral distribution. The natives Odontesthes hatcheri, Percychthis colhuapiensis, P. trucha and Jenynsia multidentata were more important in terms of numbers in catches. Ecological indexes show that the lower part of the Negro river differs from the rest of the river with higher numbers of O. hatchery and J. multidentata. Eight trophic groups were found as well as evidence of diet overlapping and considerable piscivory. Presence and distribution of fish in the Negro river is strongly influenced by introduction by men, either accidentally or intentionally. Impacts by introduced species need to be addressed, specially in terms of emerging processes between native and exotic fish, taking into special consideration the negative impacts that the rainbow trout and the carp have already had in different parts of the world

Monitoreo de visitas florales mediante el Conteo Cronometrado de Visitantes Florales (FIT Count)

El Conteo Cronometrado de Visitantes Florales (de aquí en adelante denominado como FIT Count) es un sencillo protocolo de ciencia ciudadana que tiene como objetivo colectar datos sobre eventos de visita en flores por una amplia gama de polinizadores, incluyendo abejorros, abejas sin aguijón, abejas melíferas, moscas y picaflores. Cada FIT Count está estandarizado a una duración de 10 minutos y se realiza en un parche floral determinado, usando un cuadrante de 50 x 50 cm. Dado que la polinización depende de las interacciones de los insectos (u otros visitantes florales) con las flores, es importante para un programa de ciencia ciudadana de largo plazo el poder evaluar cómo estas interacciones cambian en el tiempo y el espacio. El protocolo FIT Count nos permite afrontar este desafío mediante la obtención de datos de abundancia de visitantes florales en distintos hábitats y lugares. ¡También ofrece una excelente oportunidad de aprendizaje y de acercar a las personas a los polinizadores y las flores, dado que cualquier persona puede participar!Fil: Carvell, Claire. UK Centre for Ecology & Hydrology; Reino UnidoFil: Chiazzese, Jim. UK Centre for Ecology & Hydrology; Reino UnidoFil: Zattara, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Fontúrbel, Francisco E.. Pontificia Universidad Católica de Valparaíso; ChileFil: Muschett Rivera, Giselle. Instituto de Ecologia y Biodiversidad; ChileFil: Pirani Ghilardi Lopes, Natalia. Universidad Federal Do Abc; BrasilFil: Miranda Soares, Filipi. Universidade de Sao Paulo; Brasi

Gene content evolution in the arthropods

Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genome evolution to be addressed, even across hyper-diverse taxa within arthropods. Using 76 whole genome sequences representing 21 orders spanning more than 500 million years of arthropod evolution, we document changes in gene and protein domain content and provide temporal and phylogenetic context for interpreting these innovations. We identify many novel gene families that arose early in the evolution of arthropods and during the diversification of insects into modern orders. We reveal unexpected variation in patterns of DNA methylation across arthropods and examples of gene family and protein domain evolution coincident with the appearance of notable phenotypic and physiological adaptations such as flight, metamorphosis, sociality, and chemoperception. These analyses demonstrate how large-scale comparative genomics can provide broad new insights into the genotype to phenotype map and generate testable hypotheses about the evolution of animal diversity