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1.
J Exp Biol ; 225(10)2022 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-35638557

RESUMO

Even though mollusks' capacity to repair shell damage is usually studied in response to a single event, their shells have to defend them against predatory and environmental threats throughout their potentially multi-decadal life. We measured whether and how mollusks respond to chronic mechanical stress. Once a week for 7 months, we compressed whole live California mussels (Mytilus californianus) for 15 cycles at ∼55% of their predicted one-time breaking force, a treatment known to cause fatigue damage in shells. We found mussels repaired their shells. Shells of experimentally stressed mussels were just as strong at the end of the experiment as those of control mussels that had not been experimentally loaded, and they were more heavily patched internally. Additionally, stressed shells differed in morphology; they were heavier and thicker at the end of the experiment than control shells but they had increased less in width, resulting in a flatter, less domed shape. Finally, the chronic mechanical stress and repair came at a cost, with stressed mussels having higher mortality and less soft tissue than the control group. Although associated with significant cost, mussels' ability to maintain repair in response to ongoing mechanical stress may be vital to their survival in harsh and predator-filled environments.


Assuntos
Exoesqueleto , Mytilus , Exoesqueleto/anatomia & histologia , Animais , Mytilus/fisiologia , Comportamento Predatório , Estresse Mecânico
2.
Gene ; 823: 146367, 2022 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-35202732

RESUMO

To understand the molecular responses of Pinctada fucata with different shell colors to salinity stress, we used transcriptome sequencing on the mantle of P. fucata with a black shell and red shell color under the salinity of 20, 35, and 50. The 414 and 2371 differentially expressed genes (DEGs) in P. fucata with a black shell under low- or high-salt stress, while there were 588 and 3009 DEGs in P. fucata with a red shell. KEGG pathway enrichment analysis showed that, under low salt stress, the DEGs of P. fucata with the black shell were significantly enriched in pathways MAPK signaling pathway, protein processing in endoplasmic reticulum, vitamin B6 metabolism, longevity regulating pathway-multiple species, estrogen signaling pathway and antigen processing and presentation, the DEGs of P. fucata with a red shell were significantly enriched in pathways vitamin B6 metabolism. Under high salt stress, the DEGs of P. fucata with a red shell were significantly enriched in pathways arginine biosynthesis. 11 DEGs were randomly selected for quantitative real-time PCR, and the results were consistent with the RNA-seq. In addition, under high salt stress, DEGs were enriched into some pathways related to osmotic regulation and immune defense of P. fucata with black shell and red shell, such as Glycolysis / Gluconeogenesis, AMPK signaling pathway, Beta-Alanine metabolism, Glycine, serine and threonine metabolism, MAPK signaling pathway and Phagosome. The study showed that high salt stress had a greater influence on P. fucata with two shell colors, and P. fucata with a black shell made a positive immune defense response. Our results will improve to further understand the salt tolerance mechanism of P. fucata with different shell colors.


Assuntos
Perfilação da Expressão Gênica/veterinária , Redes Reguladoras de Genes , Pinctada/anatomia & histologia , Exoesqueleto/anatomia & histologia , Exoesqueleto/química , Animais , Cor , Regulação da Expressão Gênica , Pinctada/genética , RNA-Seq , Estresse Salino
3.
Sci Rep ; 12(1): 710, 2022 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-35027596

RESUMO

Mollusks have developed a broad diversity of shelled structures to protect against challenges imposed by biological interactions(e.g., predation) and constraints (e.g., [Formula: see text]-induced ocean acidification and wave-forces). Although the study of shell biomechanical properties with nacreous microstructure has provided understanding about the role of shell integrity and functionality on mollusk performance and survival, there are no studies, to our knowledge, that delve into the variability of these properties during the mollusk ontogeny, between both shells of bivalves or across the shell length. In this study, using as a model the intertidal mussel Perumytilus purpuratus to obtain, for the first time, the mechanical properties of its shells with nacreous microstructure; we perform uniaxial compression tests oriented in three orthogonal axes corresponding to the orthotropic directions of the shell material behavior (thickness, longitudinal, and transversal). Thus, we evaluated whether the shell material's stress and strain strength and elastic modulus showed differences in mechanical behavior in mussels of different sizes, between valves, and across the shell length. Our results showed that the biomechanical properties of the material building the P. purpuratus shells are symmetrical in both valves and homogeneous across the shell length. However, uniaxial compression tests performed across the shell thickness showed that biomechanical performance depends on the shell size (aging); and that mechanical properties such as the elastic modulus, maximum stress, and strain become degraded during ontogeny. SEM observations evidenced that compression induced a tortuous fracture with a delamination effect on the aragonite mineralogical structure of the shell. Findings suggest that P. purpuratus may become vulnerable to durophagous predators and wave forces in older stages, with implications in mussel beds ecology and biodiversity of intertidal habitats.


Assuntos
Exoesqueleto/fisiologia , Fenômenos Biomecânicos/fisiologia , Moluscos/fisiologia , Exoesqueleto/anatomia & histologia , Exoesqueleto/ultraestrutura , Animais , Força Compressiva , Ecossistema , Elasticidade
4.
Nat Commun ; 12(1): 5383, 2021 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-34508091

RESUMO

The function-optimized properties of biominerals arise from the hierarchical organization of primary building blocks. Alteration of properties in response to environmental stresses generally involves time-intensive processes of resorption and reprecipitation of mineral in the underlying organic scaffold. Here, we report that the load-bearing shells of the brachiopod Discinisca tenuis are an exception to this process. These shells can dynamically modulate their mechanical properties in response to a change in environment, switching from hard and stiff when dry to malleable when hydrated within minutes. Using ptychographic X-ray tomography, electron microscopy and spectroscopy, we describe their hierarchical structure and composition as a function of hydration to understand the structural motifs that generate this adaptability. Key is a complementary set of structural modifications, starting with the swelling of an organic matrix on the micron level via nanocrystal reorganization and ending in an intercalation process on the molecular level in response to hydration.


Assuntos
Adaptação Fisiológica , Exoesqueleto/fisiologia , Invertebrados/fisiologia , Estado de Hidratação do Organismo/fisiologia , Exoesqueleto/anatomia & histologia , Exoesqueleto/ultraestrutura , Animais , Invertebrados/anatomia & histologia , Invertebrados/ultraestrutura , Microscopia Eletrônica
5.
Sci Rep ; 11(1): 17114, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429487

RESUMO

Assessing the taxonomic importance of the suture line in shelled cephalopods is a key to better understanding the diversity of this group in Earth history. Because fossils are subject to taphonomic artifacts, an in-depth knowledge of well-preserved modern organisms is needed as an important reference. Here, we examine the suture line morphology of all known species of the modern cephalopods Nautilus and Allonautilus. We applied computed tomography and geometric morphometrics to quantify the suture line morphology as well as the conch geometry and septal spacing. Results reveal that the suture line and conch geometry are useful in distinguishing species, while septal spacing is less useful. We also constructed cluster trees to illustrate the similarity among species. The tree based on conch geometry in middle ontogeny is nearly congruent with those previously reconstructed based on molecular data. In addition, different geographical populations of the same species of Nautilus separate out in this tree. This suggests that genetically distinct (i.e., geographically isolated) populations of Nautilus can also be distinguished using conch geometry. Our results are applicable to closely related fossil cephalopods (nautilids), but may not apply to more distantly related forms (ammonoids).


Assuntos
Exoesqueleto/anatomia & histologia , Nautilus/classificação , Filogenia , Animais , Fósseis/anatomia & histologia , Nautilus/anatomia & histologia
6.
Proc Natl Acad Sci U S A ; 118(25)2021 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-34140412

RESUMO

Biological systems have a remarkable capability of synthesizing multifunctional materials that are adapted for specific physiological and ecological needs. When exploring structure-function relationships related to multifunctionality in nature, it can be a challenging task to address performance synergies, trade-offs, and the relative importance of different functions in biological materials, which, in turn, can hinder our ability to successfully develop their synthetic bioinspired counterparts. Here, we investigate such relationships between the mechanical and optical properties in a multifunctional biological material found in the highly protective yet conspicuously colored exoskeleton of the flower beetle, Torynorrhina flammea Combining experimental, computational, and theoretical approaches, we demonstrate that a micropillar-reinforced photonic multilayer in the beetle's exoskeleton simultaneously enhances mechanical robustness and optical appearance, giving rise to optical damage tolerance. Compared with plain multilayer structures, stiffer vertical micropillars increase stiffness and elastic recovery, restrain the formation of shear bands, and enhance delamination resistance. The micropillars also scatter the reflected light at larger polar angles, enhancing the first optical diffraction order, which makes the reflected color visible from a wider range of viewing angles. The synergistic effect of the improved angular reflectivity and damage localization capability contributes to the optical damage tolerance. Our systematic structural analysis of T. flammea's different color polymorphs and parametric optical and mechanical modeling further suggest that the beetle's microarchitecture is optimized toward maximizing the first-order optical diffraction rather than its mechanical stiffness. These findings shed light on material-level design strategies utilized in biological systems for achieving multifunctionality and could thus inform bioinspired material innovations.


Assuntos
Exoesqueleto/anatomia & histologia , Exoesqueleto/fisiologia , Besouros/anatomia & histologia , Besouros/fisiologia , Flores/parasitologia , Fenômenos Ópticos , Animais , Fenômenos Biomecânicos , Modelos Biológicos , Fótons , Pigmentação , Espalhamento de Radiação
7.
Zootaxa ; 4981(3): 469480, 2021 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-34186710

RESUMO

Continued sampling of the latest Eocene to earliest Oligocene Gries Ranch Formation in Lewis County, Washington State, has yielded new heterobranch microgastropod species. Orbitestella kieli sp. nov., is the third fossil species of this genus and family Orbitestellidae from western North America. Two new species of Ammonicera, A. rolani sp. nov. and A. danieli sp. nov., are together only the second fossil record of this genus and the family Omalogyridae from the northeastern Pacific Ocean. New specimens of two previously recorded species, O. palaiopacifica Squires Goedert and A. benhami Squires Goedert, from early Eocene rocks of the Crescent Formation provide new data regarding shell morphology. The fossil record of both Ammonicera and Orbitestella in western North America is restricted to early Eocene to earliest Oligocene age rocks in Washington State.


Assuntos
Fósseis , Gastrópodes , Exoesqueleto/anatomia & histologia , Animais , Gastrópodes/anatomia & histologia , Gastrópodes/classificação , Especificidade da Espécie , Washington
8.
Sci Rep ; 11(1): 8196, 2021 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-33854121

RESUMO

The New Zealand green-lipped mussel aquaculture industry is largely dependent on the supply of young mussels that wash up on Ninety Mile Beach (so-called Kaitaia spat), which are collected and trucked to aquaculture farms. The locations of source populations of Kaitaia spat are unknown and this lack of knowledge represents a major problem because spat supply may be irregular. We combined genotypic (microsatellite) and phenotypic (shell geochemistry) data in a geospatial framework to determine if this new approach can help identify source populations of mussels collected from two spat-collecting and four non-spat-collecting sites further south. Genetic analyses resolved differentiated clusters (mostly three clusters), but no obvious source populations. Shell geochemistry analyses resolved six differentiated clusters, as did the combined genotypic and phenotypic data. Analyses revealed high levels of spatial and temporal variability in the geochemistry signal. Whilst we have not been able to identify the source site(s) of Kaitaia spat our analyses indicate that geospatial testing using combined genotypic and phenotypic data is a powerful approach. Next steps should employ analyses of single nucleotide polymorphism markers with shell geochemistry and in conjunction with high resolution physical oceanographic modelling to resolve the longstanding question of the origin of Kaitaia spat.


Assuntos
Exoesqueleto/anatomia & histologia , Bivalves/genética , Polimorfismo de Nucleotídeo Único , Ração Animal , Exoesqueleto/crescimento & desenvolvimento , Animais , Aquicultura , Variação Biológica da População , Bivalves/anatomia & histologia , Bivalves/crescimento & desenvolvimento , Genótipo , Nova Zelândia
9.
Sci Rep ; 11(1): 5720, 2021 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-33707514

RESUMO

Sympatric coexistence of recently diverged species raises the question of barriers restricting the gene flow between them. Reproductive isolation may be implemented at several levels, and the weakening of some, e.g. premating, barriers may require the strengthening of the others, e.g. postcopulatory ones. We analysed mating patterns and shell size of mates in recently diverged closely related species of the subgenus Littorina Neritrema (Littorinidae, Caenogastropoda) in order to assess the role of premating reproductive barriers between them. We compared mating frequencies observed in the wild with those expected based on relative densities using partial canonical correspondence analysis. We introduced the fidelity index (FI) to estimate the relative accuracy of mating with conspecific females and precopulatory isolation index (IPC) to characterize the strength of premating barriers. The species under study, with the exception of L. arcana, clearly demonstrated preferential mating with conspecifics. According to FI and IPC, L. fabalis and L. compressa appeared reliably isolated from their closest relatives within Neritrema. Individuals of these two species tend to be smaller than those of the others, highlighting the importance of shell size changes in gastropod species divergence. L. arcana males were often found in pairs with L. saxatilis females, and no interspecific size differences were revealed in this sibling species pair. We discuss the lack of discriminative mate choice in the sympatric populations of L. arcana and L. saxatilis, and possible additional mechanisms restricting gene flow between them.


Assuntos
Comportamento Sexual Animal/fisiologia , Caramujos/fisiologia , Simpatria/fisiologia , Exoesqueleto/anatomia & histologia , Animais , Análise por Conglomerados , Copulação/fisiologia , Masculino , Tamanho do Órgão , Isolamento Reprodutivo , Especificidade da Espécie
10.
PLoS One ; 16(2): e0242208, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33591987

RESUMO

A fossil oyster bed (Ostrea edulis) was recently encountered offshore Helgoland (German Bight). Oysters are important filter feeders in marine environments and their habitat structure supports a large associated biodiversity. The European flat oyster Ostrea edulis has historically occurred in vast populations in the North Sea, but declined massively in the early 20th century. The ecological restoration of Ostrea habitats is a current focal point in the North Sea. To better understand the mechanisms that caused the local collapse of the oyster population, this study investigated the size structure, weight, and age of the shells, along with the spatial dimensions, seafloor properties, and environmental context of the oyster bed. The results show that the demise of the population occurred around 700 CE, ruling out excessive harvest as a driver of decline. Synchronicity of increased geomorphological activity of rivers and concurrent major land use changes in early medieval Europe suggest that increased sedimentation was a viable stressor that reduced the performance of the oysters. The shells provided no indication of a demographically poor state of the oyster bed prior to its demise, but manifested evidence of the wide-spread occurrence of the boring sponge Cliona sp. Our study challenges the assumption of a stable preindustrial state of the European flat oyster in the North Sea, and we conclude that the long-term variability of environmental conditions needs to be addressed to benchmark success criteria for the restoration of O. edulis.


Assuntos
Ecossistema , Fósseis , Ostrea , Exoesqueleto/anatomia & histologia , Animais , Biodiversidade , Espécies em Perigo de Extinção , Fósseis/anatomia & histologia , Mar do Norte , Ostrea/anatomia & histologia , Densidade Demográfica
11.
Arthropod Struct Dev ; 61: 101025, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33508710

RESUMO

Snapping shrimp (Alpheidae) are decapod crustaceans named for the snapping claws with which they produce cavitation bubbles. Snapping shrimp use the shock waves released by collapsing cavitation bubbles as weapons. Along with their distinctive claws, snapping shrimp have orbital hoods, extensions of their carapace that cover their heads and eyes. Snapping shrimp view the world through their orbital hoods, so we asked if the surfaces of the orbital hoods of the snapping shrimp Alpheus heterochaelis have features that minimize the scattering of light. Using SEM, we found that surface features, primarily microbial epibionts, covered less space on the surfaces of the orbital hoods of A. heterochaelis (∼18%) than they do elsewhere on the carapace (∼50%). Next, we asked if these surface features influence aerophobicity. By measuring the contact angles of air bubbles, we found the orbital hoods of A. heterochaelis are less aerophobic than other regions of the carapace. Surfaces that are less aerophobic are more likely to have cavitation bubbles adhere to them and are more likely to have shock waves cause new cavitation bubbles to nucleate upon them. Computational modeling indicates the orbital hoods of A. heterochaelis face a functional trade-off: fewer surface features, such as less extensive communities of microbial epibionts, may minimize the scattering of light at the cost of making the adhesion and nucleation of cavitation bubbles more likely.


Assuntos
Decápodes , Visão Ocular , Exoesqueleto/anatomia & histologia , Animais , Decápodes/anatomia & histologia , Decápodes/fisiologia , Visão Ocular/fisiologia
12.
Sci Rep ; 11(1): 2523, 2021 01 28.
Artigo em Inglês | MEDLINE | ID: mdl-33510331

RESUMO

Many parasites and hosts are embroiled in an on-going arms race that affects the evolution of each participant. One such battle is between parasitic nematodes and terrestrial gastropods which have co-evolved for 90-130 MY. Recently, snails have been shown to encase and kill invading nematodes using their shell as a defence mechanism. However, there is remarkably little known about this process in terms of understanding where, when and how nematodes are fixed within the shell. Also there has never been any attempt to observe this process using methods other than light microscopy. Therefore, we used micro CT scanning of a Cepaea nemoralis shell (a common host for nematodes) to 3D visualise encased nematode parasites and quantify morphological parameters. By taking this approach future studies could use micro CT scanning of fossil shells in conchology collections to understand nematode/snail co-evolution.


Assuntos
Exoesqueleto/anatomia & histologia , Imageamento Tridimensional , Caramujos/anatomia & histologia , Microtomografia por Raio-X , Exoesqueleto/ultraestrutura , Animais , Evolução Biológica
13.
Curr Opin Genet Dev ; 69: 1-5, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33388521

RESUMO

Recent technical innovations are revealing surprising patterns in mollusc shell pigmentation, such as an unexpectedly modest role for melanins and rapid divergences in the mix of pigments used to achieve similar colour patterns. The elucidation of the molecular genetic basis of shell pigmentation has been slow, probably because of the high genome complexity of gastropods and bivalves. Recent work within the old field of evolutionary ecology of shell pigmentation allows a greater role for the analysis of large-geographic-scale patterns (sometimes employing citizen-science data), as well as experimental field studies. However, the field remains dominated by land snails as model organisms, while colour pattern evolution in marine gastropods and bivalves, particularly those not exposed to visual predators, remains mysterious.


Assuntos
Evolução Biológica , Bivalves/anatomia & histologia , Gastrópodes/anatomia & histologia , Pigmentação/genética , Exoesqueleto/anatomia & histologia , Animais , Bivalves/genética , Cor , Ecologia , Gastrópodes/genética , Fenótipo
14.
Sci Rep ; 11(1): 1017, 2021 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-33441712

RESUMO

The beetle horn primordium is a complex and compactly folded epithelial sheet located beneath the larval cuticle. Only by unfolding the primordium can the complete 3D shape of the horn appear, suggesting that the morphology of beetle horns is encoded in the primordial folding pattern. To decipher the folding pattern, we developed a method to manipulate the primordial local folding on a computer and clarified the contribution of the folding of each primordium region to transformation. We found that the three major morphological changes (branching of distal tips, proximodistal elongation, and angular change) were caused by the folding of different regions, and that the folding mechanism also differs according to the region. The computational methods we used are applicable to the morphological study of other exoskeletal animals.


Assuntos
Exoesqueleto/anatomia & histologia , Besouros/anatomia & histologia , Algoritmos , Exoesqueleto/crescimento & desenvolvimento , Animais , Padronização Corporal , Besouros/crescimento & desenvolvimento , Simulação por Computador , Cornos/anatomia & histologia , Cornos/crescimento & desenvolvimento , Processamento de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/estatística & dados numéricos , Imageamento Tridimensional/métodos , Imageamento Tridimensional/estatística & dados numéricos , Modelos Biológicos , Microtomografia por Raio-X
15.
J Evol Biol ; 34(1): 224-240, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33150701

RESUMO

Pteropods, a group of holoplanktonic gastropods, are regarded as bioindicators of the effects of ocean acidification on open ocean ecosystems, because their thin aragonitic shells are susceptible to dissolution. While there have been recent efforts to address their capacity for physiological acclimation, it is also important to gain predictive understanding of their ability to adapt to future ocean conditions. However, little is known about the levels of genetic variation and large-scale population structuring of pteropods, key characteristics enabling local adaptation. We examined the spatial distribution of genetic diversity in the mitochondrial cytochrome c oxidase I (COI) and nuclear 28S gene fragments, as well as shell shape variation, across a latitudinal transect in the Atlantic Ocean (35°N-36°S) for the pteropod Limacina bulimoides. We observed high levels of genetic variability (COI π = 0.034, 28S π = 0.0021) and strong spatial structuring (COI ΦST  = 0.230, 28S ΦST  = 0.255) across this transect. Based on the congruence of mitochondrial and nuclear differentiation, as well as differences in shell shape, we identified a primary dispersal barrier in the southern Atlantic subtropical gyre (15-18°S). This barrier is maintained despite the presence of expatriates, a gyral current system, and in the absence of any distinct oceanographic gradients in this region, suggesting that reproductive isolation between these populations must be strong. A secondary dispersal barrier supported only by 28S pairwise ΦST comparisons was identified in the equatorial upwelling region (between 15°N and 4°S), which is concordant with barriers observed in other zooplankton species. Both oceanic dispersal barriers were congruent with regions of low abundance reported for a similar basin-scale transect that was sampled 2 years later. Our finding supports the hypothesis that low abundance indicates areas of suboptimal habitat that result in barriers to gene flow in widely distributed zooplankton species. Such species may in fact consist of several populations or (sub)species that are adapted to local environmental conditions, limiting their potential for adaptive responses to ocean changes. Future analyses of genome-wide diversity in pteropods could provide further insight into the strength, formation and maintenance of oceanic dispersal barriers.


Assuntos
Distribuição Animal , Gastrópodes/genética , Zooplâncton , Exoesqueleto/anatomia & histologia , Animais , Gastrópodes/anatomia & histologia , Oceanos e Mares , Fenótipo
16.
J Evol Biol ; 34(1): 193-207, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33108001

RESUMO

Littorina saxatilis is becoming a model system for understanding the genomic basis of ecological speciation. The parallel formation of crab-adapted ecotypes that exhibit partial reproductive isolation from wave-adapted ecotypes has enabled genomic investigation of conspicuous shell traits. Recent genomic studies suggest that chromosomal rearrangements may enable ecotype divergence by reducing gene flow. However, the genomic architecture of traits that are divergent between ecotypes remains poorly understood. Here, we use 11,504 single nucleotide polymorphism (SNP) markers called using the recently released L. saxatilis genome to genotype 462 crab ecotype, wave ecotype and phenotypically intermediate Spanish L. saxatilis individuals with scored phenotypes. We used redundancy analysis to study the genetic architecture of loci associated with shell shape, shape corrected for size, shell size and shell ornamentation, and to compare levels of co-association among different traits. We discovered 341 SNPs associated with shell traits. Loci associated with trait divergence between ecotypes were often located inside putative chromosomal rearrangements recently characterized in Swedish L. saxatilis. In contrast, we found that shell shape corrected for size varied primarily by geographic site rather than by ecotype and showed little association with these putative rearrangements. We conclude that genomic regions of elevated divergence inside putative rearrangements were associated with divergence of L. saxatilis ecotypes along steep environmental axes-consistent with models of adaptation with gene flow-but were not associated with divergence among the three geographical sites. Our findings support predictions from models indicating the importance of genomic regions of reduced recombination allowing co-association of loci during ecological speciation with ongoing gene flow.


Assuntos
Cromossomos , Ecótipo , Especiação Genética , Caramujos/genética , Exoesqueleto/anatomia & histologia , Animais , Fluxo Gênico , Polimorfismo de Nucleotídeo Único , Caramujos/anatomia & histologia
17.
Proc Natl Acad Sci U S A ; 118(3)2021 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-33323482

RESUMO

One of the most conserved traits in the evolution of biomineralizing organisms is the taxon-specific selection of skeletal minerals. All modern scleractinian corals are thought to produce skeletons exclusively of the calcium-carbonate polymorph aragonite. Despite strong fluctuations in ocean chemistry (notably the Mg/Ca ratio), this feature is believed to be conserved throughout the coral fossil record, spanning more than 240 million years. Only one example, the Cretaceous scleractinian coral Coelosmilia (ca. 70 to 65 Ma), is thought to have produced a calcitic skeleton. Here, we report that the modern asymbiotic scleractinian coral Paraconotrochus antarcticus living in the Southern Ocean forms a two-component carbonate skeleton, with an inner structure made of high-Mg calcite and an outer structure composed of aragonite. P. antarcticus and Cretaceous Coelosmilia skeletons share a unique microstructure indicating a close phylogenetic relationship, consistent with the early divergence of P. antarcticus within the Vacatina (i.e., Robusta) clade, estimated to have occurred in the Mesozoic (ca. 116 Mya). Scleractinian corals thus join the group of marine organisms capable of forming bimineralic structures, which requires a highly controlled biomineralization mechanism; this capability dates back at least 100 My. Due to its relatively prolonged isolation, the Southern Ocean stands out as a repository for extant marine organisms with ancient traits.


Assuntos
Exoesqueleto/metabolismo , Antozoários/metabolismo , Calcificação Fisiológica/genética , Carbonato de Cálcio/metabolismo , Exoesqueleto/anatomia & histologia , Exoesqueleto/química , Animais , Antozoários/anatomia & histologia , Antozoários/classificação , Antozoários/genética , Evolução Biológica , Carbonato de Cálcio/química , Fósseis , Filogenia
18.
Mol Phylogenet Evol ; 155: 107014, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33217577

RESUMO

A coiled shell is the most evident feature of the typical Bauplan of a gastropod mollusc. However, at least 54 families independently evolved an apparently simplified shell morphology: the limpet. Species with this largely uncoiled, depressed shell morphology occur in almost every aquatic habitat and are associated to a number of different lifestyles and diets. The marine gastropod family Capulidae includes 18 recognised genera, the large majority of which are coiled, but with a number of limpet-like species. Capulid shell plasticity is also associated to a broad range of feeding ecologies, from obligate suspension feeders to kleptoparasites. To investigate the evolution of the limpet-like shell in the family Capulidae we performed an ancestral state reconstruction analysis on a time-calibrated phylogenetic tree (COI, 16S, and ITS2) including 16 species representing a good deal of its morphological diversity. Our results identified at least three capulid lineages that independently evolved limpet-like shells, suggesting that a recurrent limpetization process characterizes this family. One of the limpet-like genera was undescribed and was here named Cryocapulus n. gen. We suggest that capulids evolved from a coiled suspension feeder lineage and that the shift to kleptoparasitism, which occurred in the family ancestor, may have represented a strategy to save energy through the exploitation of the water current produced by the host. Probably the major drivers of shell evolution in capulids are related to their ecology, most of them being kleptoparasites, include the shape and the kind of host substrate, and lead to the repeated acquisition of a limpet-like shape.


Assuntos
Gastrópodes/fisiologia , Interações Hospedeiro-Parasita , Parasitos/fisiologia , Exoesqueleto/anatomia & histologia , Animais , Calibragem , Filogenia , Processos Estocásticos , Fatores de Tempo
19.
J Morphol ; 282(2): 173-184, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33111991

RESUMO

Variations in the number and arrangement of scutes often are used for species identification in hard-shelled sea turtles. Despite the conserved nature of scute arrangements, anomalous arrangements have been noted in the literature for over a century, with anomalies linked to sub-optimal environmental conditions in the nest during development. Long-held assumptions suggest that anomalous scute arrangements are indicative of underlying physiological or morphological anomalies, with presumed long-term survival costs to the individual. Here, we examined a 25-year photo database of two species of sea turtle (Caretta caretta and Chelonia mydas) captured incidentally and non-selectively on the eastern coast of Florida. Our results suggest that C. mydas is substantially more variable with respect to the arrangement of carapacial scutes, while C. caretta had a relatively higher proportion of individuals with anomalous plastron scute arrangements. We also show evidence that (a) the forms and patterns of anomalous scutes are stable throughout growth; (b) there is limited evidence for selection against non-modal arrangements in the size classes that were examined; and (c) that their frequency has remained stable in juvenile cohorts from 1994 until present. These findings indicate that there may not be a survival cost associated with anomalous scute arrangements once the turtles reach juvenile size classes, and that variation in scute arrangements within populations is relatively common.


Assuntos
Exoesqueleto/anatomia & histologia , Tartarugas/anatomia & histologia , Animais , Bases de Dados como Assunto , Florida , Tamanho do Órgão
20.
Sci Rep ; 10(1): 19425, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33173119

RESUMO

Bivalves protect themselves from predators using both mechanical and behavioral defenses. While their shells serve as mechanical armor, bivalve shells also enable evasive behaviors such as swimming and burrowing. Therefore, bivalve shell shape is a critical determinant of how successfully an organism can defend against attack. Shape is believed to be related to shell strength with bivalve shell shapes converging on a select few morphologies that correlate with life mode and motility. In this study, mathematical modeling and 3D printing were used to analyze the protective function of different shell shapes against vertebrate shell-crushing predators. Considering what life modes different shapes permit and analyzing the strength of these shapes in compression provides insight to evolutionary and ecological tradeoffs with respect to mechanical and behavioral defenses. These empirical tests are the first of their kind to isolate the influence of bivalve shell shape on strength and quantitatively demonstrate that shell strength is derived from multiple shape parameters. The findings of this theoretical study are consistent with examples of shell shapes that allow escape behaviors being mechanically weaker than those which do not. Additionally, shell elongation from the umbo, a metric often overlooked, is shown to have significant effects on shell strength.


Assuntos
Exoesqueleto/anatomia & histologia , Exoesqueleto/fisiologia , Bivalves/anatomia & histologia , Bivalves/fisiologia , Animais , Evolução Biológica , Modelos Teóricos , Impressão Tridimensional
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