Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.129
Filtrar
1.
Genome Biol Evol ; 11(11): 3144-3157, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31621849

RESUMO

Since its initial publication in 2002, the genome of Ciona intestinalis type A (Ciona robusta), the first genome sequence of an invertebrate chordate, has provided a valuable resource for a wide range of biological studies, including developmental biology, evolutionary biology, and neuroscience. The genome assembly was updated in 2008, and it included 68% of the sequence information in 14 pairs of chromosomes. However, a more contiguous genome is required for analyses of higher order genomic structure and of chromosomal evolution. Here, we provide a new genome assembly for an inbred line of this animal, constructed with short and long sequencing reads and Hi-C data. In this latest assembly, over 95% of the 123 Mb of sequence data was included in the chromosomes. Short sequencing reads predicted a genome size of 114-120 Mb; therefore, it is likely that the current assembly contains almost the entire genome, although this estimate of genome size was smaller than previous estimates. Remapping of the Hi-C data onto the new assembly revealed a large inversion in the genome of the inbred line. Moreover, a comparison of this genome assembly with that of Ciona savignyi, a different species in the same genus, revealed many chromosomal inversions between these two Ciona species, suggesting that such inversions have occurred frequently and have contributed to chromosomal evolution of Ciona species. Thus, the present assembly greatly improves an essential resource for genome-wide studies of ascidians.


Assuntos
Inversão Cromossômica , Ciona intestinalis/genética , Evolução Molecular , Animais , Cordados não Vertebrados , Genoma , Filogenia
2.
Proc Natl Acad Sci U S A ; 116(26): 12925-12932, 2019 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-31189599

RESUMO

A defining feature of chordates is the unique presence of a dorsal hollow neural tube that forms by internalization of the ectodermal neural plate specified via inhibition of BMP signaling during gastrulation. While BMP controls dorsoventral (DV) patterning across diverse bilaterians, the BMP-active side is ventral in chordates and dorsal in many other bilaterians. How this phylum-specific DV inversion occurs and whether it is coupled to the emergence of the dorsal neural plate are unknown. Here we explore these questions by investigating an indirect-developing enteropneust from the hemichordate phylum, which together with echinoderms form a sister group of the chordates. We found that in the hemichordate larva, BMP signaling is required for DV patterning and is sufficient to repress neurogenesis. We also found that transient overactivation of BMP signaling during gastrulation concomitantly blocked mouth formation and centralized the nervous system to the ventral ectoderm in both hemichordate and sea urchin larvae. Moreover, this mouthless, neurogenic ventral ectoderm displayed a medial-to-lateral organization similar to that of the chordate neural plate. Thus, indirect-developing deuterostomes use BMP signaling in DV and neural patterning, and an elevated BMP level during gastrulation drives pronounced morphological changes reminiscent of a DV inversion. These findings provide a mechanistic basis to support the hypothesis that an inverse chordate body plan emerged from an indirect-developing ancestor by tinkering with BMP signaling.


Assuntos
Evolução Biológica , Padronização Corporal/fisiologia , Proteínas Morfogenéticas Ósseas/fisiologia , Cordados não Vertebrados/embriologia , Gastrulação/fisiologia , Animais , Embrião não Mamífero , Regulação da Expressão Gênica no Desenvolvimento , Larva/crescimento & desenvolvimento , Sistema Nervoso/embriologia , Filogenia , Ouriços-do-Mar/embriologia
3.
Artigo em Inglês | MEDLINE | ID: mdl-31136851

RESUMO

Thyroid hormones (THs) are the only iodine-containing hormones that play fundamental roles in chordates and non-chordates. The chemical nature, mode of action and the synthesis of THs are well established in mammals and other vertebrates. Although thyroid-like hormones have been detected in protostomes and non-chordate deuterostomes, TH signaling is poorly understood as compared to vertebrates, particularly in protostomes. Therefore, the central objective of this article is to review TH system components and TH-induced effects in non-vertebrate chordates, non-chordate deuterostomes and protostomes based on available genomes and functional information. To accomplish this task, we integrate here the available knowledge on the THs signaling across non-vertebrate chordates, non-chordate deuterostomes and protostomes by considering studies encompassing TH system components and physiological actions of THs. We also address the possible interactions of thyroid disrupting chemicals and their effects in protostomes and non-chordate deuterostomes. Finally, the perspectives on current and future challenges are discussed.


Assuntos
Hormônios de Invertebrado/metabolismo , Invertebrados/efeitos dos fármacos , Invertebrados/fisiologia , Hormônios Tireóideos/metabolismo , Animais , Evolução Biológica , Cordados não Vertebrados/efeitos dos fármacos , Cordados não Vertebrados/metabolismo , Cordados não Vertebrados/fisiologia , Disruptores Endócrinos/toxicidade , Enzimas/metabolismo , Invertebrados/metabolismo , Metamorfose Biológica , Transdução de Sinais
4.
Proc Natl Acad Sci U S A ; 116(17): 8403-8408, 2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-30967509

RESUMO

The trunk is a key feature of the bilaterian body plan. Despite spectacular morphological diversity in bilaterian trunk anatomies, most insights into trunk development are from segmented taxa, namely arthropods and chordates. Mechanisms of posterior axis elongation (PAE) and segmentation are tightly coupled in arthropods and vertebrates, making it challenging to differentiate between the underlying developmental mechanisms specific to each process. Investigating trunk elongation in unsegmented animals facilitates examination of mechanisms specific to PAE and provides a different perspective for testing hypotheses of bilaterian trunk evolution. Here we investigate the developmental roles of canonical Wnt and Notch signaling in the hemichordate Saccoglossus kowalevskii and reveal that both pathways play key roles in PAE immediately following the completion of gastrulation. Furthermore, our functional analysis of the role of Brachyury is supportive of a Wnt-Brachyury feedback loop during PAE in S. kowalevskii, establishing this key regulatory interaction as an ancestral feature of deuterostomes. Together, our results provide valuable data for testing hypotheses of bilaterian trunk evolution.


Assuntos
Padronização Corporal , Cordados não Vertebrados , Regulação da Expressão Gênica no Desenvolvimento , Animais , Padronização Corporal/genética , Padronização Corporal/fisiologia , Cordados não Vertebrados/embriologia , Cordados não Vertebrados/genética , Cordados não Vertebrados/crescimento & desenvolvimento , Cordados não Vertebrados/fisiologia , Embrião não Mamífero/embriologia , Embrião não Mamífero/fisiologia , Desenvolvimento Embrionário/genética , Desenvolvimento Embrionário/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/genética , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Receptores Notch/genética , Receptores Notch/fisiologia , Via de Sinalização Wnt/genética , Via de Sinalização Wnt/fisiologia
5.
Nat Commun ; 10(1): 1366, 2019 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-30911013

RESUMO

Deuterostomes are a morphologically disparate clade, encompassing the chordates (including vertebrates), the hemichordates (the vermiform enteropneusts and the colonial tube-dwelling pterobranchs) and the echinoderms (including starfish). Although deuterostomes are considered monophyletic, the inter-relationships between the three clades remain highly contentious. Here we report, Yanjiahella biscarpa, a bilaterally symmetrical, solitary metazoan from the early Cambrian (Fortunian) of China with a characteristic echinoderm-like plated theca, a muscular stalk reminiscent of the hemichordates and a pair of feeding appendages. Our phylogenetic analysis indicates that Y. biscarpa is a stem-echinoderm and not only is this species the oldest and most basal echinoderm, but it also predates all known hemichordates, and is among the earliest deuterostomes. This taxon confirms that echinoderms acquired plating before pentaradial symmetry and that their history is rooted in bilateral forms. Yanjiahella biscarpa shares morphological similarities with both enteropneusts and echinoderms, indicating that the enteropneust body plan is ancestral within hemichordates.


Assuntos
Equinodermos/anatomia & histologia , Fósseis/anatomia & histologia , Filogenia , Animais , Evolução Biológica , China , Cordados não Vertebrados/anatomia & histologia , Cordados não Vertebrados/classificação , Cordados não Vertebrados/fisiologia , Equinodermos/classificação , Equinodermos/fisiologia , Fósseis/história , Sedimentos Geológicos/análise , História Antiga
6.
Artigo em Inglês | MEDLINE | ID: mdl-30902582

RESUMO

Previously, we demonstrated that the animal aspartate racemase (AspR) gene has evolved from the serine racemase (SerR) gene by acquisition of three consecutive serine residues (Ser155-Ser156-Ser157) involved in the strong AspR activity, and this event has occurred independently and frequently during animal evolution. In the present study, we cloned and characterized two mammalian SerR homologous genes from the hemichordate acorn worm (Saccoglossus kowalevskii). The enzymes have been identified as an AspR and an aspartate/glutamate racemase (Asp/GluR) on the basis of their kinetic parameters. The S. kowalevskii Asp/GluR shows comparable substrate affinity and high catalytic efficiency (kcat/Km) for both aspartate and glutamate and is the first reported enzyme from animals that can synthesize d-glutamate. Amino acid sequence alignment analysis and site-directed mutagenesis studies have revealed that the amino acid residue at position 156, which is serine in AspR and alanine in Asp/GluR, is associated with binding and recognition of glutamate and aspartate. Phylogenetic analysis suggests that the S. kowalevskii AspR gene has evolved from the SerR gene after the divergence of hemichordata and vertebrate lineages by acquisition of the three serine residues at position 155 to 157 as in the case of other animal AspR genes. Furthermore, the S. kowalevskii Asp/GluR gene is the result of AspR gene duplication and several amino acid substitutions including that of the 156th serine residue with alanine. The fact that SerR has acquired substrate specificity towards aspartate or glutamate raises the possibility that synthesis of other d-amino acids is carried out by enzymes evolved from SerR.


Assuntos
Isomerases de Aminoácido , Cordados não Vertebrados , Filogenia , Isomerases de Aminoácido/genética , Isomerases de Aminoácido/metabolismo , Sequência de Aminoácidos , Animais , Ácido Aspártico/economia , Ácido Aspártico/metabolismo , Cordados não Vertebrados/enzimologia , Cordados não Vertebrados/genética , Clonagem Molecular
7.
Dev Growth Differ ; 61(2): 158-165, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30561008

RESUMO

The origin of the notochord is a central issue in chordate evolution. This study examined the development of the acorn worm pygochord, a putative homologue of the notochord. Because the pygochord differentiates only after metamorphosis, the developmental was followed process by inducing regeneration after artificial amputation in Ptychodera flava. It was found that although the regeneration of the posterior part of the body did not proceed via formation of an obvious regeneration bud, pygochord regeneration was observed within a few weeks, possibly via trans-differentiation of endoderm cells. The expression of the fibrillary collagen gene (Fcol) and elav in the pygochord during regeneration was detected. This indicates that pygochord cells are not part of gut epithelial cells, but that they differentiated as a distinct cell type. Our gene expression analyses do not provide supporting evidence for the homology between the pygochord and notochord, but rather favored the convergent evolution between them.


Assuntos
Evolução Biológica , Cordados não Vertebrados/crescimento & desenvolvimento , Notocorda/embriologia , Regeneração , Animais , Diferenciação Celular , Cordados não Vertebrados/citologia , Notocorda/citologia
8.
Dev Biol ; 445(1): 8-15, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30412702

RESUMO

Hemichordates are a phylum of marine invertebrate deuterostomes that are closely related to chordates, and represent one of the most promising models to provide insights into early deuterostome evolution. The genome of the hemichordate, Saccoglossus kowalevskii, reveals an extensive set of non-coding elements conserved across all three deuterostome phyla. Functional characterization and cross-phyla comparisons of these putative regulatory elements will enable a better understanding of enhancer evolution, and subsequently how changes in gene regulation give rise to morphological innovation. Here, we describe an efficient method of transgenesis for the characterization of non-coding elements in S. kowalevskii. We first test the capacity of an I-SceI transgenesis system to drive ubiquitous or regionalized gene expression, and to label specific cell types. Finally, we identified a minimal promoter that can be used to test the capacity of putative enhancers in S. kowalevskii. This work demonstrates that this I-SceI transgenesis technique, when coupled with an understanding of chromatin accessibility, can be a powerful tool for studying how evolutionary changes in gene regulatory mechanisms contributed to the diversification of body plans in deuterostomes.


Assuntos
Animais Geneticamente Modificados/genética , Técnicas de Transferência de Genes/instrumentação , Poliquetos/genética , Animais , Evolução Biológica , Cordados/genética , Cordados não Vertebrados/genética , Evolução Molecular , Técnicas de Transferência de Genes/veterinária , Genoma , Invertebrados
9.
J Dermatolog Treat ; 29(6): 606-616, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29409374

RESUMO

PURPOSE: Aims of this study is to evaluate the therapeutic effects and toxicity of Se-loaded cellulose film originated from Styela clava tunic (SeSCTF) on cutaneous wounds during diabetic conditions. MATERIALS AND METHODS: Alterations in skin regeneration, angiogenesis and toxicity were examined using streptozotocine (STZ)-induced diabetic Sprague Dawley® (SD) rats with surgical skin wounds after application of SeSCTF for 12 days. RESULTS: SCTF showed high tensile strength (1.64 MPa), low elongation (28.59%), low water vapor transmission rate (WVTR) and outstanding porous structure. Although SeSCTF application did not induce any significant alterations in glucose concentration or toxicity, wound morphology was rapidly recovered in the SeSCTF treated group relative to the gauze (GZ) and SCTF treated group. Moreover, recovery of re-epithelization, wound contraction and number of blood vessel was observed in SeSCTF treated groups when compared with all other groups. Furthermore, the SeSCTF treated group showed complete recovery of key protein expressions of the downstream signaling pathway of vascular endothelial growth factor (VEGF), angiopoietin-2/1 (Ang-2/1), the signaling pathway of insulin receptors and anti-oxidative status. CONCLUSIONS: Overall, the results of this study suggest that SeSCTF accelerates the healing process of cutaneous wounds in STZ-induced diabetic SD rats through stimulation of angiogenesis and the glucose receptor signaling pathway.


Assuntos
Bandagens , Celulose/química , Cordados não Vertebrados/metabolismo , Selênio/química , Animais , Antioxidantes/metabolismo , Diabetes Mellitus Experimental/induzido quimicamente , Diabetes Mellitus Experimental/patologia , Masculino , Malondialdeído/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor de Insulina/metabolismo , Regeneração/efeitos dos fármacos , Selênio/farmacologia , Transdução de Sinais/efeitos dos fármacos , Pele/patologia , Estreptozocina , Resistência à Tração , Cicatrização/efeitos dos fármacos
10.
Dokl Biol Sci ; 483(1): 228-230, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30603944

RESUMO

Histological examination of a specimen of a deep-sea enteropneusts that belongs to a yet undescribed species (Torquaratoridae gen. sp.) revealed numerous trunk coelomoducts. They open into the genital wing coelom as a typical funnels; short ducts communicate with environment through pores located on the outer side of the genital wings. Total number of coelomoducts in a specimen is estimated at several thousand. Trunk coelomoducts have not been found earlier in any member of the phylum. We believe that the release of the male gonad products occurs through coelomoducts of Torquaratoridae gen. sp.


Assuntos
Estruturas Animais/anatomia & histologia , Cordados não Vertebrados/anatomia & histologia , Cordados não Vertebrados/classificação , Animais , Masculino
11.
Curr Biol ; 27(1): 87-95, 2017 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-27939313

RESUMO

Many animals are indirect developers with distinct larval and adult body plans [1]. The molecular basis of differences between larval and adult forms is often poorly understood, adding a level of uncertainty to comparative developmental studies that use data from both indirect and direct developers. Here we compare the larval and adult body plans of an indirect developing hemichordate, Schizocardium californicum [2]. We describe the expression of 27 transcription factors with conserved roles in deuterostome ectodermal anteroposterior (AP) patterning in developing embryos, tornaria larvae, and post-metamorphic juveniles and show that the tornaria larva of S. californicum is transcriptionally similar to a truncated version of the adult. The larval ectoderm has an anterior molecular signature, while most of the trunk, defined by the expression of hox1-7, is absent. Posterior ectodermal activation of Hox is initiated in the late larva prior to metamorphosis, in preparation for the transition to the adult form, in which the AP axis converges on a molecular architecture similar to that of the direct developing hemichordate Saccoglossus kowalevskii. These results identify a molecular correlate of a major difference in body plan between hemichordate larval and adult forms and confirm the hypothesis that deuterostome larvae are "swimming heads" [3]. This will allow future comparative studies with hemichordates to take into account molecular differences caused by early life history evolution within the phylum. Additionally, comparisons with other phyla suggest that a delay in trunk development is a feature of indirect development shared across distantly related phyla.


Assuntos
Cordados não Vertebrados/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Genes Homeobox , Morfogênese , Animais , Evolução Biológica , Padronização Corporal , Cordados não Vertebrados/genética , Larva/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
12.
Zootaxa ; 4208(6): zootaxa.4208.6.2, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-28006796

RESUMO

Gothograptus? meganassa Rickards & Palmer, 2002 is assigned to a new genus Semigothograptus. New, well preserved material from the dubius/nassa Biozone (upper Homerian, Silurian) of the Bartoszyce IG-1 drill core Poland is described. This provides a new phylogenetic perspective on the evolution of post-lundgreni Event retiolitines. Semigothograptus meganassa is considered to be a descendant of Gothograptus nassa, although one of the most significant differences between these forms is the position of the nema, and narrow finite tubarium ending in an appendix in G. nassa. S. meganassa possesses looping meshes of the ancora umbrella recognised in Gothograptus, Papiliograptus, and Baculograptus and shares the common characters of all stratigraphical younger retiolitines. It is recognised that the S. meganassa is known from four terrains: Avalonia, Baltica, Bohemia, and Saxo-Thuringia. Analysis of the genicular hoods of nassa type, characteristic of Gothograptus nassa, Gothograptus kozlowskii, Semigothograptus meganassa, and Neogothograptus eximinassa, demonstrates their unique, solid bandage construction.


Assuntos
Cordados não Vertebrados/anatomia & histologia , Cordados não Vertebrados/classificação , Fósseis/anatomia & histologia , Animais , Evolução Biológica , Polônia
13.
PLoS One ; 11(10): e0162564, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27701429

RESUMO

Phylum Hemichordata, composed of worm-like Enteropneusta and colonial Pterobranchia, has been reported to only contain about 100 species. However, recent studies of hemichordate phylogeny and taxonomy suggest the species number has been largely underestimated. One issue is that species must be described by experts, and historically few taxonomists have studied this group of marine invertebrates. Despite this previous lack of coverage, interest in hemichordates has piqued in the past couple of decades, as they are critical to understanding the evolution of chordates-as acorn worms likely resemble the deuterostome ancestor more closely than any other extant animal. This review provides an overview of our current knowledge of hemichordates, focusing specifically on their global biodiversity, geographic distribution, and taxonomy. Using information available in the World Register of Marine Species and published literature, we assembled a list of 130 described, extant species. The majority (83%) of these species are enteropneusts, and more taxonomic descriptions are forthcoming. Ptychoderidae contained the greatest number of species (41 species), closely followed by Harrimaniidae (40 species), of the recognized hemichordate families. Hemichordates are found throughout the world's oceans, with the highest reported numbers by regions with marine labs and diligent taxonomic efforts (e.g. North Pacific and North Atlantic). Pterobranchs are abundant in Antarctica, but have also been found at lower latitudes. We consider this a baseline report and expect new species of Hemichordata will continue to be discovered and described as new marine habitats are characterized and explored.


Assuntos
Biodiversidade , Cordados não Vertebrados , Animais , Organismos Aquáticos , Cordados não Vertebrados/anatomia & histologia , Cordados não Vertebrados/classificação , Cordados não Vertebrados/genética , Geografia , Filogenia
14.
PLoS One ; 11(10): e0163808, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27732626

RESUMO

Three benthic megafaunal species (i.e. sablefish Anoplopoma fimbria; pacific hagfish Eptatretus stoutii and a group of juvenile crabs) were tested for diel behavioral patterns at the methane hydrates site of Barkley Canyon (890 m depth), off Vancouver Island (BC, Canada). Fluctuations of animal counts in linear video-transects conducted with the Internet Operated Deep-Sea Crawler "Wally" in June, July and December of 2013, were used as proxy of population activity rhythms. Count time series and environmental parameters were analyzed under the hypothesis that the environmental conditioning of activity rhythms depends on the life habits of particular species (i.e. movement type and trophic level). Non-linear least squares modeling of biological time series revealed significant diel periods for sablefish in summer and for hagfish and crabs in December. Combined cross-correlation and redundancy (RDA) analyses showed strong relationships among environmental fluctuations and detected megafauna. In particular, sablefish presence during summer months was related to flow magnitude, while the activity of pacific hagfish and juvenile crabs in December correlated with change in chemical parameters (i.e. chlorophyll and oxygen concentrations, respectively). Waveform analyses of animal counts and environmental variables confirmed the phase delay during the 24 h cycle. The timing of detection of sablefish occurred under low flow velocities, a possible behavioral adaptation to the general hypoxic conditions. The proposed effect of chlorophyll concentrations on hagfish counts highlights the potential role of phytodetritus as an alternative food source for this opportunistic feeder. The juvenile crabs seemed to display a cryptic behavior, possibly to avoid predation, though this was suppressed when oxygen levels were at a minimum. Our results highlight the potential advantages such mobile observation platforms offer in multiparametric deep-sea monitoring in terms of both spatial and temporal resolution and add to the vastly understudied field of diel rhythms of deep-sea megafauna.


Assuntos
Cordados não Vertebrados/fisiologia , Animais , Braquiúros/fisiologia , Canadá , Feiticeiras (Peixe)/fisiologia , Estações do Ano
16.
J Biochem ; 160(6): 369-379, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27493210

RESUMO

Paramyosin is a myosin-binding protein characteristic of invertebrate animals, while troponin is a Ca2+-dependent regulator of muscle contraction. Both proteins are widely distributed in protostomes, while in deuterostomes, their distribution is limited; namely, presence of paramyosin and absence of troponin are common features in echinoderm muscles, while muscles of chordates contain troponin but lack paramyosin. In this study, we examined the muscle of a hemichordate, acorn worm, to clarify whether this animal is like echinoderms or like the other deuterostome animals. We found a 100-kDa protein in the smooth muscle of acorn worm. This protein was identified with paramyosin, since the purified protein formed paracrystals with a constant axial periodicity in the presence of divalent cations as paramyosin of other animals, showed ability to interact with myosin and shared common antigenicity with echinoderm paramyosin. On the other hand, troponin band was not detected in isolated thin filaments, and the filaments increased myosin-ATPase activity in a Ca2+-independent manner. The results indicate that troponin is lacking in thin filaments of acorn worm muscle just as in those of echinoderms. The muscle of hemichordate acorn worm is quite similar to echinoderm muscles, but different from chordate muscles.


Assuntos
Cordados não Vertebrados , Músculo Liso/metabolismo , Tropomiosina , Animais , Cordados não Vertebrados/genética , Cordados não Vertebrados/metabolismo , Tropomiosina/genética , Tropomiosina/metabolismo
17.
BMC Biol ; 14: 56, 2016 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-27383414

RESUMO

BACKGROUND: The combination of a meager fossil record of vermiform enteropneusts and their disparity with the tubicolous pterobranchs renders early hemichordate evolution conjectural. The middle Cambrian Oesia disjuncta from the Burgess Shale has been compared to annelids, tunicates and chaetognaths, but on the basis of abundant new material is now identified as a primitive hemichordate. RESULTS: Notable features include a facultative tubicolous habit, a posterior grasping structure and an extensive pharynx. These characters, along with the spirally arranged openings in the associated organic tube (previously assigned to the green alga Margaretia), confirm Oesia as a tiered suspension feeder. CONCLUSIONS: Increasing predation pressure was probably one of the main causes of a transition to the infauna. In crown group enteropneusts this was accompanied by a loss of the tube and reduction in gill bars, with a corresponding shift to deposit feeding. The posterior grasping structure may represent an ancestral precursor to the pterobranch stolon, so facilitating their colonial lifestyle. The focus on suspension feeding as a primary mode of life amongst the basal hemichordates adds further evidence to the hypothesis that suspension feeding is the ancestral state for the major clade Deuterostomia.


Assuntos
Cordados não Vertebrados/classificação , Fósseis , Animais , Evolução Biológica , Cordados não Vertebrados/anatomia & histologia , Brânquias/anatomia & histologia , Filogenia
19.
J Exp Zool B Mol Dev Evol ; 326(1): 47-60, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26663879

RESUMO

The indirect-developing enteropneust acorn worm Ptychodera flava has been used as a hemichordate model system for studying the developmental evolution of deuterostome body plans and the origins of chordate characteristics. However, research progress has been hindered by the limited accessibility of its embryonic materials and metamorphosing larvae. In this study, we identified an abundant population of P. flava in Penghu, Taiwan, and examined the feasibility of using this animal for developmental studies. Through histological examination, we established that the reproductive season of this population is between September and December, with a peak breeding period in October and November. In addition, we have developed new procedures that can induce P. flava spawning at any time of the day during the breeding season, with a higher successful rate than that achieved using a previously published method. Moreover, the culturing system we developed enables rearing of P. flava larvae through various planktonic stages and eventual metamorphosis into benthic juveniles, all under laboratory conditions. We anticipate that the animal resources and new technical procedures reported here will further facilitate the use of P. flava as a model organism for evolutionary and developmental biology research.


Assuntos
Cordados não Vertebrados/fisiologia , Metamorfose Biológica , Animais , Aquicultura , Cordados não Vertebrados/crescimento & desenvolvimento , Larva/crescimento & desenvolvimento , Larva/fisiologia , Estágios do Ciclo de Vida , Reprodução , Estações do Ano , Taiwan
20.
Rev Biol Trop ; 64(3): 1311-31, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29462547

RESUMO

Reports on the abundances and on metal concentrations in intertidal estuarine invertebrates from the Eastern Tropical Pacific are rare. Thus, the objectives of this report are to make accessible data on the abundances (1984-1987, 49 dates; 2013, 12 dates) of sipunculans, brachiopods and hemichordates from a sand-mud flat; and on trace metals (1996, 2000) and abundances (2015, 3 dates) of sipunculans and brachiopods at a sand flat in the Gulf of Nicoya estuary (10o N-85o W). Cores (17.7 cm2) were collected at the sand-mud flat, and quadrats (0.2 m2) at the sand flat. The flats contrasted in their sand (65 % vs 90 %) and silt+clay (31.5 % vs 5.6 %) contents. At the sand-mud flat (1984-87: 1.83 m2) the sipunculans were represented by 13 individuals, the brachiopods by 129 and the acorn worms by 185, with estimated maximum densities of: 5.7, 29, and 40 ind./m2, respectively. Trace metal (Fe, Mn, Ni, Cr, Cd, Zn, and Pb) analysis (Atomic Absorption Spectrometry) were conducted in specimens of Sipunculus nudus (Sipuncula) and Glottidia audebarti (Brachiopoda). Maximum mean concentrations in S. nudus were: For non-depurated worms, Fe (16.0 mg/g dw) > Mn (165 µg/g dw) > Zn (81 µg/g dw) > Cu (26 µg/g dw) > Cr (11 µg/g dw) > Ni (10.4 µg/g dw) > Pb (9.3 µg/g dw) > Cd (1.2 µg/g dw). For 72 hour depurated worms: Fe (5.0 mg/g dw) > Mn (61 µg/g dw) > Zn (39 µg/g dw) > Cu (24 µg/g dw) > Ni (8.4 µg/g dw) > Pb (2.7 µg/g dw) > Cd (0.62 µg/g dw). For G. audebarti: Fe (1.6 mg/g dw-soft parts) > Zn (123.5 µg/g dw-soft parts) > Cu (31.4 µg/g dw-pedicles) > Pb (21.0 µg/g dw-shells) > Cd (5.2 µg/g dw-soft parts) > Cr (4.7 µg/g dw-shells). For sediments; Fe (46 mg/g dw) > Mn (41.3 µg/g dw) > Zn (63 µg/g dw) > Cu (36.2 µg/g dw) > Cr (31.5 µg/g dw) > Pb (21.1 µg/g dw) > Ni (16.1 µg/g dw) > Cd (1.1 µg/g dw). These concentrations were expected for a nonindustrialized estuary. At the sand flat (Area sampled: 10.6 m2 ) 76 individuals of G. audebarti, 112 of G. albida, and 366 of S. nudus were collected in 2015, with estimated maximum densities of: 7.1, 10.5, and 31 ind./m2, respectively. Densities of G. audebarti and G. albida were relatively low, while those of S. nudus were relatively high when compared with other reports. The shell lenght of G. audebarti ranged from 9.0 mm to 38.0 mm and from 6.0 mm to 29.0 mm for G. albida. These ranges were within those found for these lingulides elsewhere. The mean length of S. nudus was 41 mm and the maximum weight was 1.6 g, which are small. No brachiopods were found at the sand-mud flat in 2013, nor enteropneusts at the sand flat in 2015. G. audebarti had a relatively stable presence, while G. albida almost vanished from the samples at the end of 2015. The spatial distributions of the three invertebrates were found aggregated at both intertidal flats. Strong ENSO warming events during 1983 and 2015, and red tides in 1985 may have influenced the abundances.


Assuntos
Cordados não Vertebrados/fisiologia , Estuários , Invertebrados/fisiologia , Metais/análise , Nematoides/fisiologia , Distribuição Animal , Animais , Costa Rica , Monitoramento Ambiental/métodos , Sedimentos Geológicos , Oceano Pacífico , Densidade Demográfica , Valores de Referência , Estações do Ano , Água do Mar/química , Análise Espaço-Temporal , Especificidade da Espécie , Espectrofotometria Atômica , Poluentes Químicos da Água/análise
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA