RESUMO
Abstract Introduction: Short-term gametes storage is an inexpensive and simple technique that allows the use of the same batch of eggs or sperm at different times, maximizing the application of research protocols and the use of gametes in production. Arbacia dufresnii is a sea urchin species with proven aquaculture potential and already used in the nutraceutical industry. Aging of its gametes is unknown and is a needed information to scale up the production. Objective: Determine the effect of male and female gamete aging on the fertilization success of Arbacia dufresnii. This will allow optimizing the use of gametes after collection decoupling spawning from fertilization. Methods: A. dufresnii individuals were induced to spawn and gametes were kept at 12 ± 1 °C throughout each bioassay. Sperm was separated into two treatments: activated sperm in seawater (AS), and dry sperm (DS). Two bioassays were made: Bioassay 1 evaluated the effect of time on fertility by performing fertilization tests at 0 h, 24 h, 48 h, 72 h, and 96 h after spawning. Bioassay 2 evaluated the contribution of each type of aged gamete on fertility, combining aged gametes (96 h) with fresh gametes (0 h). Results: Bioassay 1: the fertilization success obtained by combining eggs (E) with AS or DS presented important differences. While the fertilization success remained acceptable (greater than 50 %) for up to 72 h using ExDS, it only remained acceptable for up to 48 h using ExAS. Bioassay 2: acceptable fertilization success was found by combining aged E (96 h) with fresh sperm, or aged DS (96 h) with fresh E, but not using aged AS with fresh E. Conclusions: The findings of this work show that fertilization success in A. dufresnii gametes remains relatively unchanged for up to 48 h after spawning when combining ExAS, and for up to 72 h when combining ExDS. However, when combining aged E or aged DS with a fresh gamete, post-collection fertilization can be extended up to 96 h. In this work, the first steps have been taken to understand the conservation time of A. dufresnii gametes with minimum intervention.
Resumen Introducción: El almacenamiento de gametos a corto plazo es una técnica económica y sencilla que permite utilizar el mismo lote de óvulos o espermatozoides en diferentes momentos, maximizando la aplicación de protocolos de investigación y el uso de gametos en la producción. Arbacia dufresnii es una especie con probado potencial acuícola como fuente de gametos para la industria nutracéutica. Sin embargo, se desconoce el envejecimiento de sus gametos y es una información necesaria para escalar la producción. Objetivo: Determinar el efecto del envejecimiento de los gametos masculinos y femeninos en el éxito de la fecundación de Arbacia dufresnii con el fin de optimizar el aprovechamiento de los gametos después de la recolecta desincronizando el desove de la fecundación. Métodos: Se indujo el desove de individuos de A. dufresnii y los gametos se mantuvieron a 12 ± 1 °C durante cada bioensayo. El esperma se separó en dos tratamientos: esperma activado en agua de mar (AS) y esperma seco (DS). Se realizaron dos bioensayos: El Bioensayo 1 evaluó el efecto del tiempo sobre la fertilidad realizando pruebas de fecundación a las 0 h, 24 h, 48 h, 72 h y 96 h después del desove. El bioensayo 2 evaluó la contribución de cada tipo de gameta envejecida (96 h) sobre la fertilidad, combinando gametos envejecidas (96 h) con gametos frescas (0 h). Resultados: Bioensayo 1: el éxito de fecundación obtenido combinando huevos (E) con AS o DS presentó diferencias importantes. Si bien el éxito de la fecundación se mantuvo aceptable (más del 50 %) durante un máximo de 72 h con ExDS, solo permaneció aceptable hasta 48 h con ExAS. Bioensayo 2: se encontró un éxito de fecundación aceptable combinando E envejecidos (96 h) con esperma fresco, o DS envejecido (96 h) con E fresco (0 h), pero no usando AS envejecido con E fresco (0 h). Conclusiones: Los hallazgos de este trabajo muestran que el éxito de la fecundación en los gametos de A. dufresnii permanece relativamente sin cambios hasta 48 h después del desove cuando se combina ExAS, y hasta 72 h cuando se combina ExDS. Sin embargo, cuando se combina E envejecido o DS envejecido con un gameto fresco, el tiempo entre la recolección y la fecundación puede extenderse hasta 96 h. En este trabajo se han dado los primeros pasos para entender el tiempo de conservación de los gametos de A. dufresnii con mínima intervención.
RESUMO
The aim of this study was to analyze the ecological influence of seasonal temperature variations on embryonic development in two species of Majoidea. Leurocyclus tuberculosus and Libinia spinosa. These species inhabit stable populations in the San José Gulf (42°25'41â³S, 64°08'27â³O, Patagonia-Argentina) in a wide depth range and seasonal temperature variations from 8 °C to 18 °C. The influence of seasonal temperatures on embryonic development was examined in ovigerous females of both species, through a bioassay in laboratory conditions at 8 °C, 14 °C, and 18 °C from gastrula to hatching. Additionally, monthly female samplings were conducted for one year, characterizing their spatial depth distribution associated with the seawater temperature in the study area and their ovigerous/non ovigerous condition. Laboratory experimental results showed that duration of incubation increased 67 % in L. tuberculosus and 55% in L. spinosa by a decline in temperature from 18 °C to 8 °C with one diapause period. The embryonic development for the 3 assayed temperatures was divided in five periods. The assayed temperatures did not affect the morphology of the embryo, and its growth during each period did not present significant differences among the different temperatures. Field analysis showed significant differences in the spatial distribution of ovigerous females which were associated to the assessed temperatures along the year. This distribution might modulate the development of embryos leading to two spawnings synchronized with the phyto- and zooplankton peaks in the San José gulf. Finally, ecological and potential impact of ocean warming in these species was also addressed.
Assuntos
Braquiúros/embriologia , Estações do Ano , Temperatura , Distribuição Animal , Animais , Oceano Atlântico , Braquiúros/classificação , Diapausa , Feminino , Especificidade da EspécieRESUMO
Reproductive strategies vary according to season length, individual reproductive traits, and factors associated with the social context such as density and sex ratio of the individuals. The social context predicts the intensity of sexual selection due to its effect on mate choice and intra-sexual competition. Moreover, it exacerbates the costs derived from sexual conflict and allows for the existence of alternative reproductive tactics to counteract such costs. However, these mechanisms are still underexplored in many animal taxa. Majoidea "spider crabs" show a diversity of life history, and behavioral and morphological adaptations for reproduction, which have evolved as an outcome of competition to maximize reproductive success. We aimed to analyze in this study, male reproductive strategies through mating behavior under different social contexts, density of individuals, and males size differences in two species of "spider crabs", Leurocyclus tuberculosus and Libinia spinosa. The experiments were as follows: one female and one male per aquarium (Experiment 1); a female and three males of similar sizes per aquarium (Experiment 2); and a female and three males of distinct sizes per aquarium (Experiment 3). The experiments showed that mating behavior and duration of mate guarding differ between species and among different social contexts. The presence of males with similar or different sizes showed a relevant different behavior, the female copulated with more than one male when males were similar in size (E2), and copulated only with the largest male when males were different in size (E3). In mate guarding, the shape and the use of the chelipeds had an important role: the male of Leurocyclus tuberculosus grasped the female with the chelipeds and did not fight with other males, but the male of Libinia spinosa surrounded the female with the chelipeds and fought with other males. The longest duration of mate guarding was during precopulatory guarding. Precopulatory guarding was present in all the experiments and its duration did not present significant differences among the experiments. However, in both species, the experiments differ in the duration of postcopulatory guarding until spawning. Gonopod morphology revealed important differences between species and are probably associated with sperm competition. The experiments under distinct social contexts linked to the use and shape of the chelipeds and the morphology of the gonopods, could allow to understand the functional significance of the different reproductive strategies.
Assuntos
Braquiúros/fisiologia , Comportamento Sexual Animal/fisiologia , Animais , Braquiúros/anatomia & histologia , Braquiúros/classificação , Feminino , Masculino , Comportamento Social , Especificidade da EspécieRESUMO
A comparative analysis of reproductive effort, fecundity, and egg weight was conducted in two species of spider crabs, Leurocyclus tuberculosus and Libinia spinosa, during one-year period. Ovigerous females were collected from Patagonia-Argentina (42°56'S, 64°21'W) and were measured (CW = carapace width). Each egg brood was weighed, dried and the number of eggs (F = fecundity) counted. Scatterplots of relative fecundity (RF = F/CW) were submitted to regression analyses. Mean F and RF was calculated for each season to assess seasonal variation of reproductive intensity. Mean F was 35,000 eggs in L. tuberculosus and 30,000 eggs in L. spinosa, with these values being intermediate in comparison with other Majoidea. The RF was approximately 18% higher in L. tuberculosus that presented an average dry weight egg 45% less than L. spinosa. Although in both species F showed a positive correlation with CW, less than the 20% of the variation in the number of eggs could be explained by female's size, suggesting there are other factors that influence F. The proportion of body energy devoted to reproduction (reproductive effort), exhibited significant differences between species. In Leurocyclus tuberculosus reproductive activity is significantly different along the 12-month suggesting that the conditions for 'optimal' egg production change throughout the year. In Libinia spinosa mean fecundity did not reveal significant differences over seasons. These results are central in studies of life-history theory and in the development of life history models, as it is directly related to energy allocation and partitioning.
Assuntos
Braquiúros/fisiologia , Animais , Feminino , Óvulo/fisiologia , Reprodução/fisiologiaRESUMO
The embryonic development of the spider crabs Leurocyclus tuberculosus and Libinia spinosa was divided into five periods based on the differentiation of: (I) cleavage, (II) embryonic primordium, III) optic lobes, (IV) optic lobes pigmented and (V) chromatophores presence. Different traits such as spines, setae and telson morphology distinguish the two species from period III until hatching. Egg volume was greater in Leurocyclus tuberculosus than in Libinia spinosa. The duration of each period was different during development. Whereas in Leurocyclus tuberculosus period II (morphogenesis) is the longest, in Libinia spinosa the period IV is the longest. Complete embryonic development at 14'C lasted 36.7 +/- 3.1 days in Leurocyclus tuberculosus and 57.4 +/- 4.4 days in Libinia spinosa.
