RESUMEN
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.
Asunto(s)
Exoesqueleto/fisiología , Fenómenos Biomecánicos/fisiología , Moluscos/fisiología , Exoesqueleto/anatomía & histología , Exoesqueleto/ultraestructura , Animales , Fuerza Compresiva , Ecosistema , ElasticidadRESUMEN
Cuticular hydrocarbons (CHCs) of most terrestrial arthropods primarily serve as a protective barrier against desiccation and infection. Throughout evolution, these compounds have acquired another fundamental function: the exchange of signals during interactions between nestmates. However, even though cuticular hydrocarbons perform a dual function in social insects, little is known about the effect(s) of one function on the other in social insects, and no study has evaluated this relationship in social wasps. Therefore, the present study tests the hypothesis that the level of aggressiveness presented during induced encounters between nestmates of Polybia paulista who were subjected to different conditions temperature is different than between nestmates who remained under the same temperature conditions. If the hypothesis is confirmed, it is likely because the cuticle of the wasps that had been exposed to temperature variation adjusted to these conditions leading them not to recognize the cuticular chemical signature of their colony. To test this hypothesis, workers were exposed to temperature variation in a BOD chamber and then subjected to encounters with workers who were maintained at a constant temperature of 24â. We also used control groups to evaluate the effect of isolation alone among the groups. According to our results, our hypothesis was confirmed, the level of aggressiveness presented between nestmates who were exposed to temperature variation and those who remained at 24â was significantly higher than the levels of aggressiveness presented between nestmates who remained isolated but under constant temperature during the same period, in some cases, it was similar to the aggressiveness presented in encounters between wasps from different colonies. During these encounters, wasps performed alarm behavior, bites, and stings not seen during encounters between wasps that remained under the same temperature, but in isolated groups. The lack of aggressive behavior under isolated conditions indicates that isolation had no effect on chemical recognition signature. These results suggest that temperature variation may have caused some change in the cues that allow recognition between nestmates. On the other hand, these results were not caused by isolation or stress generated by the study design and difference in the CHC profile of workers, as described in the literature, is consistent with our results.(AU)
Asunto(s)
Animales , Avispas/fisiología , Regulación de la Temperatura Corporal/fisiología , Comunicación Animal , Exoesqueleto/fisiologíaRESUMEN
BACKGROUND: In insects, continuous growth requires the periodic replacement of the exoskeleton. Once the remains of the exoskeleton from the previous stage have been shed during ecdysis, the new one is rapidly sclerotized (hardened) and melanized (pigmented), a process collectively known as tanning. The rapid tanning that occurs after ecdysis is critical for insect survival, as it reduces desiccation, and gives the exoskeleton the rigidity needed to support the internal organs and to provide a solid anchor for the muscles. This rapid postecdysial tanning is triggered by the "tanning hormone", bursicon. Since bursicon is released into the hemolymph, it has naturally been assumed that it would act on the epidermal cells to cause the tanning of the overlying exoskeleton. RESULTS: Here we investigated the site of bursicon action in Drosophila by examining the consequences on tanning of disabling the bursicon receptor (encoded by the rickets gene) in different tissues. To our surprise, we found that rapid tanning does not require rickets function in the epidermis but requires it instead in peptidergic neurons of the ventral nervous system (VNS). Although we were unable to identify the signal that is transmitted from the VNS to the epidermis, we show that neurons that express the Drosophila insulin-like peptide ILP7, but not the ILP7 peptide itself, are involved. In addition, we found that some of the bursicon targets involved in melanization are different from those that cause sclerotization. CONCLUSIONS: Our findings show that bursicon does not act directly on the epidermis to cause the tanning of the overlying exoskeleton but instead requires an intermediary messenger produced by peptidergic neurons within the central nervous system. Thus, this work has uncovered an unexpected layer of control in a process that is critical for insect survival, which will significantly alter the direction of future research aimed at understanding how rapid postecdysial tanning occurs.
Asunto(s)
Exoesqueleto/fisiología , Drosophila/fisiología , Hormonas de Insectos/metabolismo , Hormonas de Invertebrados/metabolismo , Animales , Proteínas de Drosophila/metabolismo , Epidermis/fisiología , Femenino , Masculino , Neuropéptidos/metabolismoRESUMEN
At the Ediacaran/Cambrian boundary, ecosystems witnessed an unparalleled biological innovation: the appearance of shelled animals. Here, we report new paleoecological and paleobiological data on Cloudina, which was one of the most abundant shelled animals at the end of the Ediacaran. We report the close association of Cloudina tubes with microbial mat textures as well as organic-rich material, syndepositional calcite and goethite cement between their flanges, thus reinforcing the awareness of metazoan/microorganism interactions at the end of the Ediacaran. The preservation of in situ tubes suggests a great plasticity of substrate utilization, with evidence of different life modes and avoidance behavior. Geochemical analysis revealed walls composed of two secondary laminae and organic sheets. Some walls presented boreholes that are here described as predation marks. Taken together, these data add further information regarding the structuring of shelled animal communities in marine ecosystems.
Asunto(s)
Exoesqueleto/fisiología , Biomineralización/fisiología , Ecosistema , Exoesqueleto/anatomía & histología , Animales , Brasil , Carbonato de Calcio/química , Fósiles , Modelos Biológicos , Espectrometría Raman , Factores de TiempoRESUMEN
Most brachyuran females become receptive during the intermolt period, a condition considered "derived". However, as far as we know, studies testing the existence and function of pheromones in decapods are based on species which have mating linked to molting, a condition considered as "ancestral". For the first time, we studied some physiological and morphological processes involved in Neohelice granulata intermolt female crabs becoming receptive and potentially attracting males. We found that receptive females have mobile vulvae opercula due to a softening process of the cuticle hinge which showed lower calcium levels compared to the hinge of unreceptive females. Local softening of the hinge was stimulated by a low concentration of ecdysone during the intermolt period. A putative pheromone liberated by receptive females to attract males is presumed to be released through the mobile vulvae and not through the urine.
Asunto(s)
Exoesqueleto/fisiología , Braquiuros/fisiología , Ecdisona/fisiología , Muda/fisiología , Conducta Sexual Animal/fisiología , Animales , Femenino , MasculinoRESUMEN
Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH ~ 8.0) and low pH (pH ~ 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers.
Asunto(s)
Exoesqueleto/fisiología , Calcificación Fisiológica , Cadena Alimentaria , Pectinidae/fisiología , Agua de Mar/química , Adaptación Fisiológica , Animales , Chile , Quitina/química , Quitina Sintasa/química , Cambio Climático , Concentración de Iones de Hidrógeno , Océanos y Mares , Consumo de OxígenoRESUMEN
BACKGROUND: Black widow spider (L. tredecimguttatus) has toxic components not only in the venomous glands, but also in other parts of the body and its eggs. It is biologically important to investigate the molecular basis of the egg toxicity. RESULTS: In the present work, an aqueous extract was prepared from the eggs of the spider and characterized using multiple physiological and biochemical strategies. Gel electrophoresis and mass spectrometry demonstrated that the eggs are rich in high-molecular-mass proteins and the peptides below 5 kDa. The lyophilized extract of the eggs had a protein content of 34.22% and was shown to have a strong toxicity towards mammals and insects. When applied at a concentration of 0.25 mg/mL, the extract could completely block the neuromuscular transmission in mouse isolated phrenic nerve-hemidiaphragm preparations within 12.0 ± 1.5 min. Using whole-cell patch-clamp technique, the egg extract was demonstrated to be able to inhibit the voltage-activated Na+, K+ and Ca2+ currents in rat DRG neurons. In addition, the extract displayed activities of multiple hydrolases. Finally, the molecular basis of the egg toxicity was discussed. CONCLUSIONS: The eggs of black widow spiders are rich in proteinous compounds particularly the high-molecular-mass proteins with different types of biological activity The neurotoxic and other active compounds in the eggs are believed to play important roles in the eggs' toxic actions.
Asunto(s)
Proteínas de Artrópodos/toxicidad , Araña Viuda Negra/química , Óvulo/química , Extractos de Tejidos/química , Exoesqueleto/química , Exoesqueleto/fisiología , Animales , Proteínas de Artrópodos/aislamiento & purificación , Canales de Calcio/efectos de los fármacos , Cucarachas/efectos de los fármacos , Ganglios Espinales/efectos de los fármacos , Ratones , Óvulo/fisiología , Nervio Frénico/efectos de los fármacos , Canales de Potasio con Entrada de Voltaje/efectos de los fármacos , Ratas , Extractos de Tejidos/toxicidad , Canales de Sodio Activados por Voltaje/efectos de los fármacosRESUMEN
BACKGROUND: Black widow spider (L. tredecimguttatus) has toxic components not only in the venomous glands, but also in other parts of the body and its eggs. It is biologically important to investigate the molecular basis of the egg toxicity. RESULTS: In the present work, an aqueous extract was prepared from the eggs of the spider and characterized using multiple physiological and biochemical strategies. Gel electrophoresis and mass spectrometry demonstrated that the eggs are rich in high-molecular-mass proteins and the peptides below 5 kDa. The lyophilized extract of the eggs had a protein content of 34.22% and was shown to have a strong toxicity towards mammals and insects. When applied at a concentration of 0.25 mg/mL, the extract could completely block the neuromuscular transmission in mouse isolated phrenic nerve-hemidiaphragm preparations within 12.0 ± 1.5 min. Using whole-cell patch-clamp technique, the egg extract was demonstrated to be able to inhibit the voltage-activated Na+, K+and Ca2+ currents in rat DRG neurons. In addition, the extract displayed activities of multiple hydrolases. Finally, the molecular basis of the egg toxicity was discussed. CONCLUSIONS: The eggs of black widow spiders are rich in proteinous compounds particularly the high-molecular-mass proteins with different types of biological activity The neurotoxic and other active compounds in the eggs are believed to play important roles in the eggs' toxic actions.
Asunto(s)
Animales , Ratones , Ratas , Óvulo/química , Extractos de Tejidos/química , Araña Viuda Negra/química , Proteínas de Artrópodos/toxicidad , Óvulo/fisiología , Nervio Frénico/efectos de los fármacos , Extractos de Tejidos/toxicidad , Canales de Calcio/efectos de los fármacos , Cucarachas/efectos de los fármacos , Canales de Potasio con Entrada de Voltaje/efectos de los fármacos , Exoesqueleto/fisiología , Exoesqueleto/química , Proteínas de Artrópodos/aislamiento & purificación , Canales de Sodio Activados por Voltaje/efectos de los fármacos , Ganglios Espinales/efectos de los fármacosRESUMEN
Most of the shell material in snails is composed of calcium carbonate but the organic shell matrix determines the properties of calcium carbonate crystals. It has been shown that the deposition of calcium carbonate is affected by the ingestion of organic compounds. We hypothesize that organic compounds not synthesized by the snails are important for shell strength and must be obtained from the diet. We tested this idea indirectly by evaluating whether the abundance of the organic matter that snails eat is related to the strength of their shells. We measured shell crushing resistance in the snail Mexipyrgus churinceanus and the abundance of the most common aquatic macrophyte, the water lily Nymphaea ampla, in ten bodies of water in the valley of Cuatro Ciénegas, Mexico. We used stable isotopes to test the assumption that these snails feed on water lily organic matter. We also measured other factors that can affect crushing resistance, such as the density of crushing predators, snail density, water pH, and the concentration of calcium and phosphorus in the water. The isotope analysis suggested that snails assimilate water lily organic matter that is metabolized by sediment bacteria. The variable that best explained the variation in crushing resistance found among sites was the local abundance of water lilies. We propose that the local amount of water lily organic matter provides organic compounds important in shell biomineralization, thus determining crushing resistance. Hence, we propose that a third trophic level could be important in the coevolution of snail defensive traits and predatory structures.