RESUMO

The global average temperature will increase by up to 5.7 °C, under high greenhouse gas emissions, consequently increasing the frequency of heatwaves, according to recent IPCC forecasts. These especially impacts ectotherms, such as insects, which are the most susceptible animals to changes in environmental temperature, affecting their physiology and reproduction. Thus, we investigated the effects of a 96-h exposure to constant temperatures (CT: 27, 30.5, 34, 39, 41, or 43 °C) and fluctuating temperatures (FT: 27/34 °C, 12/12 h) on the survival, metabolic rate, and oviposition of the female cricket Gryllus (Gryllus) assimilis (Orthoptera: Gryllidae). Mortality, body mass and water content of females and males were quantified and compared. It was found that CT27, CT34 and FT27/34 do not cause mortality in females of G. (G.) assimilis. CT30.5 (average temperature between 27 and 34), despite causing mortality of 5.0 ± 3.5%, do not differ from CT27, CT34 or FT27/34. CT39 causes a mortality of 8.3 ± 5.5%. Estimated lethal temperature for 50% of the population of females (LT50Temp) is 40 °C, and 43 °C promotes 100% mortality in 96 h. Comparing mortality between sexes, females present higher LT50Temp and thermotolerance than males. In addition, FT27/34 and CT34 do not differ in the metabolic rate, but both have higher values than CT27. CT34 strongly reduces oviposition in females, however FT27/34 does not. We suggest that CT34 reduces oviposition in females in two ways: by affecting the endocrine system related to egg production, or by causing behavioral egg retention, as a strategy to survive thermal stress. Moreover, females had a higher wet body mass and present a lower average weight loss than males. In conclusion, despite females present a higher mortality at temperatures above 39 °C, they are more thermotolerant than males. Furthermore, CT34 is detrimental to the oviposition of G. (G.) assimilis.

Assuntos

Gryllidae , Termotolerância , Masculino , Animais , Feminino , Temperatura , Gryllidae/fisiologia , Oviposição , Reprodução

RESUMO

Ectotherms, such as insects, are susceptible to climate changes because their body temperature is not physiologically regulated. Forecasts indicate a worldwide temperature rise of 1.4-6 °C by 2100, and an increase in heatwave frequency is expected. This study investigated the effects of constant temperatures (CT; 27, 34, 39, 40 and 41 °C) and fluctuating temperature (FT; 27/34 °C: 12/12 h) on the survival, metabolic rate, locomotor activity, gas exchange pattern, heat loss and water content of the male Jamaican field cricket, Gryllus assimilis (Fabricius, 1775) (Orthoptera: Gryllidae). It was found that 39 °C was the estimated lethal temperature for 50% of the population and that 41 °C was considered the thermal limit, causing 100% mortality in 96 h. Furthermore, FT caused slightly higher mortality (8.9 ± 3.8%) than CT27 (0%) and CT34 (1.43 ± 1.43%). FT caused a greater increase in the metabolic rate and locomotor activity than CT27. It was found that G. assimilis males had a continuous gas exchange as a standard at CT27; however, CT34 changed the gas exchange pattern from continuous to cyclic in 27% of crickets. FT decreased heat loss in crickets more than CT34; however, no significant differences were found in locomotor activity and metabolic rate. In addition, no significant differences between CT27, CT34 and FT were observed in terms of water content, thus suggesting no difference in water loss. Thus, it is suggested that FT, despite involving a modest warming, increased the climate sensitivity of G. assimilis males and led to a change in their optimum temperature, pushing it beyond its usual thermal limits. However, higher mortality in FT compared to CT27 (control) and CT34 must be interpreted with caution. In addition, the risk of higher mortality of G. assimilis males is predicted, especially in South America, where this cricket is widely distributed.

Assuntos

Gryllidae , Animais , Mudança Climática , Jamaica , Masculino , Temperatura , Água

RESUMO

Physiological trade-offs among expensive fitness-related traits, such as reproduction and immunity, are common in life histories of animals. An immune challenge can have different effects on female reproduction mediated by resource allocation and acquisition. In this study, employing a widely used method to challenge the insect immune system (nylon implant), we assessed the effects of mounting a chronic immune response simulating three successive immune assaults on survival and reproduction of mated females of Gryllus assimilis. We also verified feeding behavior following an implantation, which can be important in explaining trade-off dynamics in terms of energy acquisition. For this, three experimental groups were designed (Control, Sham, and Implant) with oviposition rates, egg morphometry, and nymph vigour observed over 3 weeks, at which ovarian mass and unlaid eggs were quantified from remaining individuals. The results showed that chronic implants were detrimental to female survival and reproduction throughout the experiments; Surgical Sham had no effect on survival compared to the control, but did on reproductive aspects such as oviposition rates and hatchling vigour. These negative effects on reproduction in Sham disappeared in the last experimental week, but still strong in the implanted females. Such immune challenge affected the feeding behavior of implanted females by reducing food consumption compared to control after infection, which is probably explained by illness-induced anorexia that takes place to maximize the immune system performance as a part of sickness behavior, exacerbating the adverse effects observed on reproduction (i.e., fewer and smaller eggs, and low vigour of nymphs) and survival.

Assuntos

Gryllidae , Animais , Comportamento Alimentar , Feminino , Gryllidae/fisiologia , Insetos , Ninfa , Fenótipo , Reprodução/fisiologia

RESUMO

Carbon nanotubes (CNTs) have been increasingly more prevalent due to their use in product technology owing to their exceptional electrical and thermal conductivity and tensile strength because of their nanostructure and strength of the bonds among carbon atoms. The potential increase of CNTs in the environment is a concern, and studies to assess the toxic effects of these nanomaterials (NMs) are needed. However, so far, most of the studies are focused on aquatic species and much less is understood about the effects of NM in terrestrial organisms. This investigation used a functionalized multi-walled carbon nanotube (f-MWCNT) and the Jamaican cricket Gryllus assimilis to assess the effects of this NM. Cricket nymphs were injected with f-MWCNT suspension-at three different concentrations. The insecticide Fipronil was used as a positive control. Survival was monitored, and histological analysis was made in the brains. Pyknotic cells were quantified in two brain regions, a neurosecretory called Pars intercerebralis (PI), and an associative region called mushroom body (MB). No mortality was observed in any f-MWCNT concentration tested. A significant increase in pyknotic cells was observed as sub-lethal effect for the intermediate concentration of f-MWCNT, at PI, while any significant change was observed at the Kenyon cells of the MB. These results are discussed in the context of agglomeration and dispersion of the f-MWCNT at different concentrations, and availability of the f-MWCNT on the circulatory system, as well as the natural decay of pyknotic cells with time and different patterns of adult cricket neurogenesis. Our results showed that f-MWCNT had negative effects in the neurosecretory region of the brain.

Assuntos

Gryllidae , Nanotubos de Carbono , Animais , Encéfalo , Jamaica , Nanotubos de Carbono/toxicidade

RESUMO

The effects of reproduction are variable among insects, as well as the time of mate. In animals, a trade-off is usually observed between reproduction and self-maintenance, mostly in females because of egg producing costs. In the present investigation, manifestations of aging and senescence at population and cellular levels were studied associated with the mating opportunities. The main goal of this study was to evaluate the effect of mating on lifespan and also on the physiological aging in adult Jamaican field cricket females, Gryllus assimilis (Fabricius, 1775). Three experimental groups were set: virgin, normal-mated (14 days old), and late-mated (30 days old) insects. Lifespan, age-specific mortality rate, number of eggs laid, and in situ amount of the age-pigment neurolipofuscin were quantified. Results showed a trade-off between reproductive females and lifespan, with the strongest effects found in late-mated. Age-specific mortality showed a faster increase for late-mated females from 35 to 50 days old, followed by normal-mated females (35 to 60 days old). Virgins had the lowest age-specific mortality of all, increasing just from 65 to 73 days old. Normal-mated had the highest number of eggs laid, followed by late-mated and virgins, respectively. Neurolipofuscin accumulation rate was similar among groups, which was reflected in similar physiological rate of aging. Results indicate that reproductive status did affect the life-history of these field cricket females.

Assuntos

Envelhecimento , Gryllidae , Animais , Feminino , Gryllidae/fisiologia , Longevidade , Óvulo , Reprodução

RESUMO

Natural diet of Neohelice granulata in two salt marshes of Lagoa dos Patos, RS were studied. Sampling was performed seasonally and crabs were captured by hand by three persons during one hour, fixed in formaldehyde (4 percent) during 24 h, transferred to alcohol (70 percent). Each foregut was weighed and repletion level was determined. Differences between sexes in the frequencies of occurrence of items were tested by χ2test. A total of 452 guts were analyzed. Quali-quantitative analyses were calculated following the method of relative frequency occurrence and relative frequency of the points. At both sites, for both sexes and in all seasons, the main food items were sediment, Spartina sp. and plant detritus. The highest values of mean repletion index were estimated for the spring and summer. Analysing both salt marshes, in different seasons significant shifts in the natural diet of Neohelice granulata was not observed throughout the period of study.

RESUMO

Decapod crustaceans show proliferation of the nerve cells in the olfactory lobe throughout their lives. However, the regulation of this process is still poorly understood, since it may vary with endogenous and exogenous factors. The objective of the present investigation was to quantify the proliferation of nerve cells and number of nerve cells with ecdysone receptors in the clusters of the central olfactory system in Neohelice granulata, according to moult stages and in different seasons (summer and winter). Three injections of bromodeoxyuridine (BrdU) were administered to the crabs. Brains were sectioned by microtome and fixed on slides for immunohistochemistry with anti-BrdU and anti-EcR antibodies. The proliferation of nerve cells was higher in winter than in summer, probably because in winter the crabs do not breed and the premoult and postmoult periods are longer. Crabs in postmoult exhibited more BrdU-labelled cells than crabs in premoult or intermoult in winter, because of a greater number of mitoses related to an increase in body size and addition of olfactory receptor neurons. The number of EcR-labelled cells was higher in premoult than in postmoult or intermoult in winter. The proliferation of nerve cells is regulated seasonally and according to moult stages.

Assuntos

Braquiúros , Proliferação de Células , Muda/fisiologia , Neurônios/citologia , Receptores de Esteroides/metabolismo , Estações do Ano , Animais , Contagem de Células , Sistema Nervoso Central/citologia , Sistema Nervoso Central/fisiologia , Ecdisona/metabolismo , Ecdisona/fisiologia , Gânglios dos Invertebrados/citologia , Gânglios dos Invertebrados/metabolismo , Neurônios/metabolismo , Condutos Olfatórios/citologia , Condutos Olfatórios/metabolismo

RESUMO

Growth hormone (GH) excess causes an increment in the metabolic rate and in reactive oxygen species generation, which accelerate the ageing process in mammals. Considering that there is no information on this subject in fish, the aim of the present study was to evaluate the excess GH effect on senescence in a zebrafish (Danio rerio) transgenic model. In order to reach this objective, we analyzed the phenotype of spinal curvature and expression of genes related to the anti-oxidant defense system and myogenesis in muscle of 8 and 30 months old GH-transgenic males. Gene expression analyses revealed that both superoxide dismutase isoforms were down-regulated only in 30 months old animals, while glutamate cysteine ligase was down-regulated in GH-transgenic zebrafish. Acceleration of the spinal curvature and a reduction in the expression of miogenin at both ages and MyoD in the old fish were also observed. Although neurolipofuscin accumulation was not significant in GH-transgenic zebrafish, the estimation of maximum longevity based on the von Bertalanffy growth function was significantly lower in this group. The results obtained here indicate that GH overexpression reduces the transcription of anti-oxidant defense system and myogenesis-related genes, which probably accelerates senescence in the zebrafish transgenic model used.

Assuntos

Glutamato-Cisteína Ligase/genética , Hormônio do Crescimento/metabolismo , Desenvolvimento Muscular/genética , Curvaturas da Coluna Vertebral/metabolismo , Superóxido Dismutase/genética , Peixe-Zebra/metabolismo , Envelhecimento/fisiologia , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Antioxidantes/metabolismo , Carpas/genética , Amplificação de Genes , Regulação da Expressão Gênica no Desenvolvimento , Glutationa/genética , Glutationa/metabolismo , Gráficos de Crescimento , Hormônio do Crescimento/genética , Hormônio do Crescimento/fisiologia , Peroxidação de Lipídeos/genética , Lipofuscina , Masculino , Músculo Esquelético/metabolismo , Fenótipo , Reação em Cadeia da Polimerase , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Mensageiro/metabolismo , Radiografia , Curvaturas da Coluna Vertebral/diagnóstico por imagem , Peixe-Zebra/genética

RESUMO

Kalliapseudes schubartii (Crustacea: Tanaidacea) é um invertebrado tubícola que habita fundos moles de regiões estuarinas e que distribui-se ao longo da costa sudeste e sul do Brasil e na costa uruguaia. Este tanaidaceo é comedor de depósitos e filtrador, e é presa de vários consumidores secundários. Taxas de mortalidade sazonal foram examinadas através de amostras feitas durante um ano num local da região estuarina da Lagoa dos Patos. Os resultados não demonstraram diferenças significativas entre as taxas de mortalidade nas diferentes estações do ano, o que sugere que populações de K. schubartii são fortemente predadas ao longo de todo o ano e que a premissa de maior mortalidade no verão/outono pode não ser correta em fundos de águas rasas não vegetados.