Artículos científicos

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/14821

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Activity of aerial insectivorous bats in two rice fields in the northwestern Llanos of Venezuela
(BioOne Digital Library, 2019-05) Azofeifa Romero, Yara; Estrada-Villegas, Sergio; Mavarez, Jesus; Nassar, Jafet
Abstract. Even though agricultural lands provide abundant food to aerial insectivorous bats (AIB), our understanding of how spatio-temporal factors affect their foraging behavior in these habitats is limited and mostly restricted to temperate regions. In this study, we examined species richness, composition and patterns of activity of AIB in rice fields in the northwestern Llanos of Venezuela. Between 2013 and 2014, we conducted acoustic monitoring of AIB in two rice fields with contrasting forest cover, throughout three phases of the life cycle of this crop (vegetative, reproductive, and ripening), during the dry and rainy season. Out of 108 h recorded, we processed 12,630 files and identified 15 species and 10 sonotypes of AIB from families Molossidae, Mormoopidae, Vespertilionidae, Emballonuridae and Noctilionidae. Molossus molossus and Myotis nigricans showed the highest levels of feeding and general activity across species. The index of general activity (IGA) of AIB was higher above rice fields with more surrounding forest cover, during the dry season and throughout the entire life cycle of the plant. Relative feeding activity (RFA) did not change with respect to forest cover, season or crop phase, but a significant effect of the interaction of these factors was observed on this variable. The response of IGA and RFA to forest cover. season or crop phase was different between M. molossus and M. nigricans and among functional groups. Our results indicate that rice fields in the Venezuelan Llanos can be active feeding grounds for open space and edge-habitat foraging species of insect-feeding bats. Forest patches can promote AIB activity by favoring foraging of 'edge' species above rice fields. Higher general activity of most AIB species during the dry season suggests that rice fields are used more intensively when insect populations decrease in semi-deciduous forest patches around them. Overall, our results suggest that availability of abundant feeding areas to AIB, provided by the rice fields, together with presence of artificial and natural roosts to these bats, could ensure year-round permanence of a rich ensemble of AIB in the rice field-forest landscape in the northwestern Llanos of Venezuela. Some of these species could be the subject of field experiments to test their value in the control of rice's insect pest populations.
Microclimate of developing tubular leaves used as roost sites by bats
(BioOne Digital Library, 2019-05) Pérez - Cárdenas Nathalia; Porras - Brenes, Katherine; Auccacusi-Choque, Leydi V.; Suárez Torres, Joanna Jazmin; Brooks Laverdeza, Rosa María; Chaverri, Gloriana
Abstract. Roosts are critical for the reproduction and survival of bats and many species spend a significant portion of their lives in them; thus, individuals should carefully select sites that reduce predation risk while providing ideal microclimatic conditions. Many studies have determined that bats select warmer and more humid roosts in temperate regions, but few studies have determined if roosts selected by tropical species also provide suitable conditions. In this study we compare temperature and humidity within and outside furled tubular leaves of plants in the order Zingiberales, which are used by several tropical species as roost-sites, to determine if these structures provide microclimatic advantages to bats. We found very small differences between the internal and external temperatures of tubular leaves, and the difference further decreased as leaves developed. However, we found large differences in humidity within the tubular leaf compared to external conditions. which were strongly dependent on a leaf's diameter and genus. The internal humidity was often 20% above the external, particularly when leaves were narrower, and tubular leaves in the genus Heliconia were more humid than those in the genus Calathea. Our findings suggest that. despite being fairly exposed structures, furled tubular leaves provide suitable microclimatic conditions for tropical species.
Serotonin plus spiperone induce ovarian maturation, spawning and potential release of ovarian maturation inducing pheromones in the Pacific white shrimp Litopenaeus vannamei (Penaeidae)
(Elsevier B.V., 2024-09-10) Quesada-Ávila, Isabel; Alfaro-Montoya, Jorge; Umaña-Castro, Rodolfo; Braga, André; Ramírez-Alvarado, Marvin; Ventura, Tomer
Abstract. In this study, we further investigate the hypothesis that serotonin plus spiperone (Ser+Spi) injection induces ovarian maturation and releases ovarian maturation inducing pheromones into the water, thereby stimulating neighboring untreated females. Litopenaeus vannamei females (b.w. = 40.40 ± 5.84 g; n = 120) and males (b.w. = 34.25 ± 4.68 g; n= 90) were divided into three 18-m2 maturation tanks. Each tank contained 40 non-ablated females and 30 males with two treatments per tank. In tank 1, 20 females received a low dose of Ser+Spi (Ser at 25 μg g-1 b.w. and Spi at 2.0 μg g-1 b.w.) along with a control vehicle-injection. In tank 2, 20 females received a high dose of Ser+Spi (Ser at 40 μg g-1 b.w. and Spi at 4.0 μg g-1 b.w.) with the same control vehicle-injection applied to tank 1. In tank 3, unilateral eyestalk ablation (ESA) was performed on 20 females, while 20 control females were maintained non-ablated/injected. The experiment spanned 18 weeks and was divided into three phases. Ovarian maturation was observed in both Ser+Spi-treated and control females, with stages III-IV of maturation occurring one week after injections at both tested doses. Statistical analysis revealed that the average ovarian maturation index (OMI) was significantly higher for the control group in tank 2 (OMI = 0.25), compared to the Ser40+Spi4.0 group. Additionally, control females in tank 1 matured similarly to Ser25+Spi2.0 group (p ≤ 0.05). The control group of tank 3 displayed very low maturation activity (OMI = 0.1). Controls from tanks 1 and 2 exhibited a higher number of mated females and spawning events. These results support the potential of Ser+Spi to induce ovarian maturation and spawning and suggest that Ser+Spi-treated females may release a metabolite into the water that acts as an ovarian maturation inducer for neighboring females.

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