RESUMO
Sea spiders (Pycnogonida) are marine chelicerates. Current pycnogonid phylogeny based on molecular data remains uncertain and contradicts traditional morphological perspectives. To resolve this conflict, understanding their inner anatomy is crucial. The reproductive system of sea spiders shows promise as a source of phylogenetic signal, yet our knowledge in this area is limited. This study presents the first description of the whole female reproductive system of a sea spider at the ultrastructural level. We suggest a more detailed functional regionalization of the ovary based on the ovarian wall ultrastructure and distribution of oocyte developmental stages. Meiosis begins in the germarium, and oocytes progress to the vitellarium through a transportational zone. Vitellogenic oocytes extend through the vitellarium wall, connected with it by a stalk - specialized cells. Balbiani bodies are present in early vitellogenic oocytes but dissipate later. The formation of the vitelline envelope, yolk, and fertilization envelope involves functionally diverse RER vesicles. The study also identifies a reproductive sinus as a separate haemocoel compartment that may enhance nutrient concentration near vitellogenic oocytes. Additionally, oviduct and gonopore glands are described in the female of P. femoratum, although their specific functions and prevalence in other sea spider species remain unclear.
Assuntos
Microscopia Eletrônica de Transmissão , Animais , Feminino , Genitália Feminina/ultraestrutura , Genitália Feminina/anatomia & histologia , Genitália Feminina/crescimento & desenvolvimento , Oócitos/ultraestrutura , Microscopia Eletrônica de Varredura , Ovário/ultraestrutura , Ovário/anatomia & histologia , Ovário/crescimento & desenvolvimentoRESUMO
Abstract This study describes and illustrates the biodiversity of macroinvertebrates associated to Sargassum and Dictyota seaweed habitats in the Alcatrazes archipelago, the largest Marine Protected Area (MPA) in the state of São Paulo, southeast Brazil. Assemblages were sampled during the summers of 2018, 2019 and 2020 and winter of 2018 at two sites on the main island. Macroalgae containing the associated fauna were collected at approximately 10 meters deep, with six samples at each site and in each sampling campaign. Sargassum fronds prevailed during summer collections, whilst were absent in the winter campaigns, when Dictyota was the most frequent seaweed. Among invertebrates, 32 species were exclusively found on summer months, associated to Sargassum beds, while 12 species were only registered on winter collection, in association with Dictyota. In total, 91 species were identified, belonging to 60 families, 19 orders, 7 classes and 3 phyla, including Arthropoda (Malacostraca and Pycnogonida), Mollusca (Gastropoda, Bivalvia and Polyplacophora), and Echinodermata (Ophiuroidea and Echinoidea). Among the 91 species found, 73 species are new records for the Alcatrazes archipelago marine area, thus revealing the expressive invertebrate biodiversity living in association with macroalgae beds in that area, which has still been little explored. No significant difference in species diversity was found between the two sites of Alcatrazes. In addition, few specimens of two invasive species were found: Perna perna (Mollusca: Bivalvia) and Ophiothela mirabilis (Echinodermata: Ophiuroidea), which underscores the importance of monitoring different habitats within MPAs to check for possible changes in the fauna over the years. As far as our knowledge, this is the first illustrated inventory of the seaweed-associated macroinvertebrate fauna within the Alcatrazes Archipelago, one of the largest MPAs in the Brazilian coast; besides unravelling its notorious biodiversity, this can act as a reference for future monitoring of local coastal diversity.
Resumo Este estudo descreve e ilustra a biodiversidade de macroinvertebrados associados a habitats de macroalgas pardas marinhas dos gêneros Sargassum e Dictyota no Arquipélago de Alcatrazes, a maior Área Marinha Protegida (AMP) do estado de São Paulo, sudeste do Brasil. As assembleias foram amostradas durante os verões de 2018, 2019 e 2020 e no inverno de 2018 em dois locais na ilha principal. As macroalgas contendo a fauna associada foram coletadas a aproximadamente 10 metros de profundidade, com seis amostras em cada local e em cada campanha amostral. Frondes de Sargassum predominaram nas coletas de verão, enquanto estiveram ausentes nas campanhas de inverno, quando Dictyota foram predominantes. Entre os invertebrados, 32 espécies foram encontradas exclusivamente nos meses de verão, associadas aos bancos de Sargassum, enquanto 12 espécies foram registradas apenas na coleta de inverno, em associação com Dictyota. No total, foram identificadas 91 espécies, pertencentes a 60 famílias, 19 ordens, 7 classes e 3 filos, incluindo Arthropoda (Malacostraca e Pycnogonida), Mollusca (Gastropoda, Bivalvia e Polyplacophora) e Echinodermata (Ophiuroidea e Echinoidea). Das 91 espécies encontradas, 73 espécies são novos registos para a área marinha do arquipélago de Alcatrazes, revelando assim a expressiva biodiversidade de invertebrados que vivem em associação com bancos de macroalgas naquela área ainda pouco explorada. Nenhuma diferença significativa de diversidade de espécies foi encontrada entre os dois locais de Alcatrazes. Além disso, foram encontrados poucos exemplares de duas espécies invasoras: Perna perna (Mollusca: Bivalvia) e Ophiothela mirabilis (Echinodermata: Ophiuroidea), o que ressalta a importância do monitoramento de diferentes habitats dentro das AMPs para verificar possíveis alterações na fauna ao longo dos anos. Até onde sabemos, este é o primeiro inventário ilustrado da fauna de macroinvertebrados associados a algas marinhas no Arquipélago de Alcatrazes, uma das maiores AMPs da costa brasileira; além de desvendar a sua notória biodiversidade, pode servir de referência para futuro monitoramento da diversidade costeira local.
RESUMO
Regeneration is widespread across all animal taxa, but patterns of its distribution and key factors determining regeneration capabilities stay enigmatic. A comparative approach could shed light on the problem, but its efficacy is limited by the fact that data is only available on a few species from derived taxa. Pycnogonida are nested basally within the Chelicerata. They can shed and replace their walking legs and have a high regeneration capacity. In this work, we carried careful observation on leg appendotomy and regeneration processes in a sea spider under laboratory settings. The limb structure and in vivo observation reveal autotomy as the most likely appendotomy mechanism. High regeneration capabilities were ascertained: an anatomically normal but small leg appeared in a single molting cycle and the full functionality regained in 2-3 cycles. Wound closure after appendotomy in N. brevirostre primarily relies on hemolymph coagulation, which apparently differs from both xiphosurans and crustaceans. Regeneration is provided by proliferation in the leg cutpiece. Regenerative morphogenesis resembles the normal ontogenetic morphogenesis of a walking leg, but accelerated. Unlike in most arthropods, in N. brevirostre, regeneration does not necessarily correspond to the molting cycle, inferring a plesiomorphic state.
Assuntos
Artrópodes , Animais , Extremidades , Morfogênese , RegeneraçãoRESUMO
Regenerative abilities and their evolution in the different animal lineages have fascinated generations of biologists. While some taxa are capable of restoring entire individuals from small body fragments, others can regrow only specific structures or lack structural regeneration completely. In contrast to many other protostomes, including the segmented annelids, molting animals (Ecdysozoa) are commonly considered incapable of primary body axis regeneration, which has been hypothesized to be linked to the evolution of their protective cuticular exoskeleton. This holds also for the extraordinarily diverse, segmented arthropods. Contradicting this long-standing paradigm, we here show that immatures of the sea spider Pycnogonum litorale reestablish the posterior body pole after transverse amputation and can regrow almost complete segments and the terminal body region, including the hindgut, anus, and musculature. Depending on the amputation level, normal phenotypes or hypomeric six-legged forms develop. Remarkably, also the hypomeric animals regain reproductive functionality by ectopic formation of gonoducts and gonopores. The discovery of such complex regenerative patterns in an extant arthropod challenges the hitherto widely assumed evolutionary loss of axial regeneration during ecdysozoan evolution. Rather, the branching of sea spiders at the base of Chelicerata and their likely ancestral anamorphic development suggests that the arthropod stem species may have featured similar regenerative capabilities. Accordingly, our results provide an incentive for renewed comparative regeneration studies across ecdysozoans, with the aim to resolve whether this trait was potentially even inherited from the protostome ancestor.
Assuntos
Anelídeos , Artrópodes , Animais , Muda , Filogenia , Artrópodes/genética , RegeneraçãoRESUMO
A new genus of Callipallenidae, Agnathia, is established to accommodate two new species of pycnogonid from southern Australia; A. aria and A. chuki. Both new species are represented by adult and sub-adult forms. Gravid females and ovigerous and larvigerous males are represented. Postembryonic growth stages are recorded and briefly discussed. The presence of six-segmented ovigers in males of one species, as opposed to the usual ten segments in both sexes, is recorded. Genera that share morphological relationships are discussed and a key to these genera is provided. The genera Bradypallene, Pycnopallene and Safropallene are reassessed and reassigned to family incertae sedis.
Assuntos
Artrópodes , Animais , Artrópodes/classificação , Artrópodes/fisiologia , Feminino , Masculino , Austrália do SulRESUMO
Sea spiders (Class Pycnogonida Latreille, 1810) are chelicerate arthropods, with an extraordinarily reduced body armed with eight to twelve elongated legs. A literature review of taxonomic and ecological studies of pycnogonids from Mexico identified 49 nominal species (~3.6% out of 1,335 species described worldwide). This low species richness is likely caused by limited taxonomic research and intermittent sampling and research efforts initially carried out by foreign scientists (1893-1996) and later by Mexican scientists. The present study investigates the latitudinal gradient of species richness of the pycnogonids associated with nine marine docks located between Cabo San Lucas (22°53'N) and Santa Rosalía (26°58'N) along the west coast of the Gulf of California, 22°53'N Mexico and provides a detailed morphological re-description of each nominal species using light and scanning electron microscopy. Nine nominal pycnogonid species and one unidentified species in the genus Tanystylum were collected and identified from the biological samples collected between 2011-2017. The highest pycnogonid species richness was recorded at Bahía de La Paz (seven species, 24°14'N) and the lowest species richness at Cabo San Lucas (one species) without an evident latitudinal species richness gradient. Anoplodactylus californicus Hall, 1912 and Ammothella spinifera Cole, 1904 were the most abundant species (52% of the total number of individuals). Tanystylum occidentale (Cole, 1904) and Nymphon apheles Child, 1979 were new geographical records for Mexico and Ammothella symbia Child, 1979 and A. californicus were new records for Baja California Sur state. Adding these new geographical records of pycnogonids increased the species richness previously recorded at Baja California Sur from 20 to 24 nominal species and for Mexico, the species richness increased from 49 to 51 nominal species.
Assuntos
Artrópodes , Animais , California , Geografia , MéxicoRESUMO
Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and 3 nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.
Assuntos
Artrópodes/genética , Filogenia , Animais , Feminino , Genoma , MasculinoRESUMO
Sea spiders (Pycnogonida) are a small group of arthropods, sister to other chelicerates. They have an unusual adult bauplan, oligosegmented larvae, and a protracted postembryonic development. Pycnogonum litorale (Strøm, 1762) is an uncommonly long-lived sea spider with a distinctive protonymphon and adult anatomy. Although it was described ~250 years ago, little is known about its internal organization and development. We examined the anamorphic and early epimorphic development of this species using histology, light microscopy, and SEM, and provide the first comprehensive anatomical study of its many instars. Postembryonic development of P. litorale includes transformations typical of pycnogonids: reorganization of the larval organs (digestive, nervous, secretory), formation of the abdomen, trunk segments (+ appendages), primary body cavity and reproductive system. Specific traits include the accelerated articulation of the walking legs, formation of the subesophageal and posterior synganglia, and the system of twin midgut diverticula. In addition, P. litorale simultaneously lose the spinning apparatus and all larval appendages. We found that developmental changes occur in synchrony with changes in ecology and food sources. The transition from the anamorphic to the epimorphic period in particular is marked by considerable anatomical and lifestyle shifts. HIGHLIGHTS: Postembryonic development of P. litorale includes numerous anamorphic and epimorphic stages. The instars acquire abdomen, trunk segments, body cavity, and gonads, while losing all larval appendages. Developmental changes are synchronized with changes in lifestyle and food sources.
Assuntos
Artrópodes/anatomia & histologia , Artrópodes/crescimento & desenvolvimento , Crescimento e Desenvolvimento , Animais , Artrópodes/ultraestrutura , Feminino , Larva/anatomia & histologia , Larva/ultraestrutura , Masculino , Reprodução/fisiologiaRESUMO
Ten intertidal sea spider (Pycnogonida) species from five families - Pycnogonidae (1 species), Ammotheidae (3 species), Callipallenidae (3 species), Phoxichilidiidae (2 species) and Endeidae (1 species) - are reported in the present study. Out of these ten species, four are first records from Pakistan, including a new species, Achelia karachiensis sp. nov. Intertidal zoanthid colonies have been found to provide shelter and food to a large and diverse Pycnogonid population at Sandspit and the Buleji, Karachi coast. This study highlights the significance of the intertidal fauna of pycnogonids of these areas and contributes to our understanding of the species diversity from the Karachi coast.
Assuntos
Antozoários , Artrópodes , Animais , PaquistãoRESUMO
We report the discovery of a new species of the genus Pycnogonum Brünnich, 1764 found in the shallow waters of Green Island, Taiwan. Pycnogonum (Nulloviger) granulatum sp. nov. is characterized by the presence of the granular integument, a dorsal tubercle on the proboscis, the transverse ridges on the dorsal surface of the trunk, and the spines on the ventral surface of the tibia, tarsus, and propodus having cleft tips. Because the male gonopores are present and ovigers are absent, the present species belongs to the subgenus Nulloviger. The present species has been compared with P. (N.) moolenbeeki Stock, 1992, P. (N.) lobipes Stock, 1991, P. (N.) tuberculatum Clark, 1963, P. nodulosum Döhrn, 1881, and P. spatium Takahashi, Dick Mawatari, 2007. Among the congeners, P. spatium is geographically the closest congener, of which type locality is Amami Island, Japan. The holotype of P. spatium was loaned from Hokkaido University Museum (ICHUM) and re-examined. To determine the exact gender of the holotype of P. spatium, additional investigations of the coxal pellicula and gonopores are required.
Assuntos
Artrópodes , Animais , Ilhas , Masculino , TaiwanRESUMO
Sea spiders (Pycnogonida) constitute a group of marine benthic arthropods that has a particularly high species diversity in the Southern Ocean. The "longitarsal" group of the sea spider family Colossendeidae is especially abundant in this region. However, this group also includes some representatives from other oceans, which raises the question where the group originates from. Therefore, we here investigated the phylogeny of the group with a hybrid enrichment approach that yielded a dataset of 1607 genes and over one million base pairs. We obtained a well-resolved phylogeny of the group, which is mostly consistent with morphological data. The data support an Antarctic origin of the longitarsal Colossendeidae and multiple dispersal events to other regions, which occurred at different timescales. This scenario is consistent with evidence found in other groups of marine invertebrates and highlights the role of the Southern Ocean as a source for non-Antarctic biota, especially of the deep sea. Our results suggest an initially slow rate of diversification followed by a more rapid radiation possibly correlated with the mid-Miocene cooling of Antarctica, similar to what is found in other taxa.
Assuntos
Organismos Aquáticos/classificação , Organismos Aquáticos/genética , Artrópodes/classificação , Artrópodes/genética , Filogenia , Animais , Regiões Antárticas , Teorema de Bayes , Funções Verossimilhança , Oceanos e Mares , FilogeografiaRESUMO
This is the first record of the genus Sericosura from the "Duanqiao" hydrothermal field on the Southwestern Indian Ridge. Collected material included two juvenile specimens temporarily assigned to S. bamberi and S. heteroscela respectively, and one male specimen with dimorphic legs here proposed as a new species, S. duanqiaoensis sp. nov. The discovery suggests potential connectivity among the hydrothermal vents of the Atlantic, Indian and Southern Oceans, expecting obtaining more specimens for further evolutionary studies to clarify the relationships of these hydrothermal vents.
Assuntos
Artrópodes , Fontes Hidrotermais , Animais , Masculino , Oceanos e MaresRESUMO
Five species of epibenthic pycnogonids collected on the giant lion´s-paw scallop Nodipecten subnodosus are recorded. A new species of Eurycyde, Eurycyde bamberi, is described. Of the 19 species known in this genus; the new species is closest to Eurycyde hispida Kroyer, 1844 but differs from it in the absence of plumose spines and the shapes of the lateral process, first coxa, and ocular tubercle. The new species represents the third member of Eurycyde from the eastern Pacific in addition to Eurycyde spinosa Hilton, 1916 and Eurycyde clitellaria Stock, 1955. Besides Eurycyde bamberi, the following species were collected: Nymphopsis duodorsospinosa Hilton, 1942c; Callipallene californiensis (Hall, 1913); Nymphon lituus Child, 1979; and Pycnogonum rickettsi Schmitt, 1934. Pycnogonum rickettsi is recorded for first time from Mexican waters, as is Nymphon lituus from the western coast of Baja California Peninsula. Each of these four species are re-described and re-illustrated in order to fill in existing gaps in the literature of the region.
RESUMO
Assessing the enormous diversity of Southern Ocean benthic species and their evolutionary histories is a central task in the era of global climate change. Based on mitochondrial markers, it was recently suggested that the circumpolar giant sea spider Colossendeis megalonyx comprises a complex of at least six cryptic species with mostly small and non-overlapping distribution ranges. Here, we expand the sampling to include over 500 mitochondrial COI sequences of specimens from around the Antarctic. Using multiple species delimitation approaches, the number of distinct mitochondrial OTUs increased from six to 15-20 with our larger dataset. In contrast to earlier studies, many of these clades show almost circumpolar distributions. Additionally, analysis of the nuclear internal transcribed spacer region for a subset of these specimens showed incongruence between nuclear and mitochondrial results. These mito-nuclear discordances suggest that several of the divergent mitochondrial lineages can hybridize and should not be interpreted as cryptic species. Our results suggest survival of C. megalonyx during Pleistocene glaciations in multiple refugia, some of them probably located on the Antarctic shelf, and emphasize the importance of multi-gene datasets to detect the presence of cryptic species, rather than their inference based on mitochondrial data alone.
RESUMO
A new species of pycnogonid collected by the Chinese research vessel, R/V HY IV, during deep sea cruises to the South China Sea in 2013, is described. The new species, Hemichela nanhaiensis, obtained from more than 1300 m depth, is distinguished from the other two species in the genus by the characters of the chela dactylus with 12 denticulations on the inner margin and by the presence of taller tubercles on the lateral processes.
RESUMO
A new species of pycnogonid collected by the Chinese research vessel R/V Dayangyihao during cruises to the Southwest Indian Ridge in 2008 and 2009 is recorded. The new species, Austrodecus bamberi, is placed into the tristanense-section by the characters of 4-articled ovigers and present auxiliary claws and is distinguished from other species in this section by the number and length of tubercles on the first coxae.
RESUMO
The Pycnogonida from Uruguayan waters are scarcely known, and their reports are markedly discontinuous. In this paper, several individuals of two previously unrecorded Pycnogonids at the shallow rocky subtidal and lower intertidal fringes of Cerro Verde (Rocha, Uruguay) are reported. The specimens were assigned to Pycnogonum pamphorum Marcus, 1940 and Anoplodactylus petiolatus (Kroyer, 1844). This is the first record of these species on the Uruguayan coast and the southernmost record of P. pamphorum, previously recorded only in Santos, Brazil (type locality).
Pouco se conhece da fauna dos Pycnogonida de águas Uruguaias, e seus registros são marcadamente descontínuos. Neste trabalho, são reportados vários indivíduos de dois picnogonídeos não registrados previamente, nas faixas rochosas submareal rasa e bordas intermareais baixas de Cerro Verde (Rocha, Uruguai). Os espécimes foram atribuídos às espécies Pycnogonum pamphorum Marcus, 1940 e Anoplodactylus petiolatus (Kroyer, 1844). Este é o primeiro registro dessas duas espécies para a costa Uruguaia e constitui o registro mais austral para P. Pamphorum, conhecido previamente somente em Santos, Brasil (localidade tipo).