Stage specific feeding attributes and mobilization of nutrients in Mexican beetle,Zygogramma bicolorata Pallister on Parthenium hysterophorus L.

Parthenium hysterophorus L. (Asteraceae) is a toxic weed of agricultural farms, pastures and wastelands with a pan-tropical distribution. The weed causes a reduction in crop production of agricultural fields and severe health problems in humans. The Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) is among the most promising candidates for the weed biocontrol. However, no previous study has evaluated assimilation of nutrients in this beetle. In the present study, feeding attributes and assimilation of nutrients by larvae of Z. bicolorata were assessed on the weed. Results revealed that the first larval instars of Z. bicolorata exhibited lowest consumption rates, and accumulated minimum concentrations of glucose, proteins and triglycerides in their body. They showed compensatory feeding, and displayed highest food utilization efficiencies and developmental rates. In contrast, the fourth larval instars exhibited higher food consumption rates and conversion efficiencies, but displayed lowest developmental rates. Accumulation of food reserves was also recorded maximum for the fourth larval instars. Overall, the findings may aid current mass-rearing efforts for Z. bicolorata in laboratories, but field trials are still needed to strengthen the present findings.     

Size-based intraspecific variations along altitudinal gradient and follow of Bergmann’s rule in Parthenium beetle,Zygogramma bicolorata Pallister

Body size in insects is coupled with numerous physiological, life-history and ecological traits. Its variation along temperature gradient is widely studied. However, information regarding variations in body size of insects along altitudinal gradient is limited. Present study was designed considering hypothesis that there would be an increase in body size of Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) with increasing altitude and decreasing in temperature. To achieve the objectives, beetles were collected from three eco-climatic zones of NEPAL [Kathmandu (1400 mts, 24 °C; warm temperate zone), Chitwan (415 mts, 25 °C; upper tropical/sub-tropical zone), and Mahendranagar (229 mts, 34 °C; humid subtropical zone)], and one of INDIA [Varanasi (81 mts, 36 °C; humid subtropical zone)] for their morphometric analysis (body length and body biomass). Results revealed that the size of beetles in all eco-climatic zones increased with increasing altitude and decreasing temperature. While adults of Kathmandu were largest, followed by Chitwan and Mahendranagar, but those of Varanasi were smallest in size. The sex ratio was female-biased in Kathmandu and Varanasi, but was male-biased in Chitwan and Mahendranagar. Irrespective of temperature and altitude, females were larger than males in all eco-climatic zones. Our results affirmed our hypothesis and were in compliance with Bergmann’s rule. The findings may be helpful in understanding phenotypic plasticity and distribution pattern of Z. bicolorata adults in Indian sub-continent under global climate change scenario.     

Host range and risk assessment of Zygogramma bicolorata,a defoliating agent released in South Africa for the biological control of Parthenium hysterophorus

Parthenium hysterophorus (parthenium) is a weed of international importance and is spreading rapidly in sub-Saharan Africa. Consequently, it has been targeted for biocontrol in South Africa since 2003. Based on precedents elsewhere in the world, the defoliating beetle Zygogramma bicolorata was prioritised as a candidate agent. Although no-choice tests, involving some 48 test plant species, indicated a significant preference for parthenium, significantly reduced feeding and oviposition was recorded on some species. Multiple-choice tests resolved many of these non-target results; however, Helianthus annuus (sunflower) was still selected for oviposition and feeding. Of the 12 sunflower cultivars tested, four were selected for oviposition, while two were selected for oviposition and feeding. These six cultivars were then subjected to larval development trials, together with three native and two weed species (in the Asteraceae). These trials showed high levels of complete development on parthenium, significantly reduced development on sunflower cultivars, and partial development on only one of the weed species. Finally, a risk assessment was conducted on the six sunflower cultivars to quantify Z. bicolorata feeding and reproductive performance. Feeding risk calculations revealed these cultivars to have an extremely low risk (<0.2%) of supporting Z. bicolorata feeding and development. Similarly, reproductive risk calculations showed a very low risk (<0.16%) of supporting viable Z. bicolorata populations. These data are supported by findings from both the native (Mexico) and introduced ranges (Australia, India) of Z. bicolorata, where it has never been recorded as a pest of sunflower. These considerations were accepted by the regulatory authorities and in August 2013, Z. bicolorata became the second insect agent to be released in South Africa for the biocontrol of parthenium.     

Enhancing bio-suppression of Parthenium hysterophorus L.: Diapause in Zygogramma bicolorata Pallister and its manipulation through insulin-like peptides (ILPs)

In-depth investigations on diapause behaviour of Z. bicolorata revealed that the adults entered diapause at any time from August to December and that the number peaked (42.00%) during the last half of November. The percentage of adults entering diapause increased with a decrease in day length. Weight of diapausing adults was significantly higher than weight of non-diapausing adults. The percentage of adults undergoing diapause at 30 °C was significantly lower than those undergoing diapause at 15 and 25 °C. The percentage of adults burrowing increased with increasing moisture. In silty soil and soil with high organic matter, 46.7% and 49.2% of adults entered diapause, respectively, whereas in sandy soil, only 23.5% of adults entered diapause. When newly emerged beetles were exposed to 5 μg of human insulin 30/70, a significantly lower percentage of treated adults underwent diapause compared to untreated adults under both feeding and no feeding conditions. Insulin treatment also influenced the emergence period from diapause (93.92 ± 1.73 days), percent emergence (81 ± 1.54%) and fecundity/month (512.7 ± 25.38 eggs) of Z. bicolorata in treated adults as compared to untreated adults (109.05 ± 2.2, 74.00 ± 1.82 and 438.3 ± 19.33 eggs, respectively). However, there was no significant impact of insulin on adult longevity. These findings are of great utility in the biological suppression of Parthenium as it will enhance the effectiveness of this beetle through manipulation of diapause.     

Semiochemical footprints of the predaceous coccinellid beetle,Menochilus sexmaculatus,deter Zygogramma bicolorata (Coleoptera: Chrysomelidae) from feeding on Parthenium

Present study assessed if semiochemical cues left by an aphidophagous beetle, M. sexmaculatus influenced foraging behaviour of a phytophagous beetle, Z. bicolorata on noxious weed, P. hysterophorus. The lower predation attributes of Z. bicolorata in presence of M. sexmaculatus semiochemical footprints confirms they interfere with weed biological control.     

Does Zygogramma bicolorata Pallister really affects the growth,density and reproductive performance of Parthenium hysterophorus L?

Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) is a satisfactory potential candidate for controlling Parthenium hysterophorus L. The study was conducted in order to evaluate the bio-control potential of Z. bicolorata to satisfactory reduced the density of parthenium weed in natural field conditions. Therefore, beetles were released in the twelve study sites @ 12 adults and/or larvae/m² in their respective sites on 5th, 10th, 15th and 20th day after initial field releases. Observations were made on defoliation by the beetle, perthenium plant height, plant biomass, leaf injury rating and soil seed reservoir. Present study showed that field releases of Z. bicolorata considerably lowering down the parthenium density at all treated sites. At larval release sites by the 60th day of observation a complete defoliation was noted, however at adult release sites it took 80 days for complete defoliation. Moreover, significantly higher number of developmental stages i.e. eggs, larvae and adults were noted in the adults released sites than to larval released sites and the controls. It was also noted that plant height and its density, flowers & leaves production, biomass of parthenium plant and seed reservoir in soil was negatively affected in treated sites as compared to untreated sites. Thus, we have concluded that adults can be utilized in biocontrol program because population build-up was greater in those sites where adults were released.     

Benefits of polyandry in Parthenium beetle,Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae)

The influence of polyandry on the reproductive performance of females and on offspring fitness in Zygogramma bicolorata Pallister was investigated using four experimental treatments, viz. (A) monandrous, limited mating, (B) monandrous, unlimited mating, (C) polyandrous, no-choice limited mating, and (D) polyandrous, mate choice unlimited mating. Polyandrous females had higher reproductive performance than monandrous ones. Monandrous females subjected to unlimited matings had higher egg viability than those subjected to limited matings, but fecundity did not differ significantly. In polyandrous females, the freedom to choose mates did not affect reproductive performance. However, offspring of polyandrous females allowed mate choice developed fastest and had the highest survival at 25, 27, and 30 °C. Thus, polyandry in Z. bicolorata appears to provide both direct (material) and indirect (genetic) benefits resulting in better reproductive performance and increased adaptability of the offspring to counter environmental stresses. The present study not only adds to the knowledge of reproductive biology of Z. bicolorata but it could also be of economic value as it may help in the mass rearing of Z. bicolorata and in the management of Parthenium hysterophorus.     

Impact of defoliation by the biocontrol agentZygogramma bicolorataon the weed Partheniumhysterophorus in Australia

The leaf-feeding beetle Zygogrammabicolorata Pallister was introduced from Mexico intoAustralia in 1980 as a biocontrol agent for the weedParthenium hysterophorus L. (Asteraceae). Z. bicolorata became abundant in 1990, and since 1992there has been regular outbreaks resulting in thedefoliation of the weed in central Queensland. In thisstudy we evaluated the impact of defoliation by Z. bicolorata on P. hysterophorus from 1996 to1998. Z. bicolorata caused 91–100% defoliationresulting in reductions in weed density by 32–93%,plant height by 18–65%, plant biomass by 55–89%,flower production by 75–100%, soil seed-bank by13–86% and seedling emergence in the following seasonby 73–90%. At sites with continued outbreaks ofZ. bicolorata, it is expected that the existing soilseed-bank will be minimised, resulting in reduceddensity of parthenium in 6 to 7 years.     

Host range evaluation of the leaf-feeding beetle,Zygogramma bicolorata and the stem-boring weevil,Listronotus setosipennis demonstrates their suitability for biological control of the invasive weed,Parthenium hysterophorus in Ethiopia

The invasive weed, parthenium (Parthenium hysterophorus L.) (Asteraceae: tribe Heliantheae), damages agriculture, adversely impacts biodiversity and is hazardous to human and animal health in Ethiopia. The host range of two natural enemies, a leaf-feeding beetle, Zygogramma bicolorata (Coleoptera: Chrysomelidae) and a stem-boring weevil, Listronotus setosipennis (Coleoptera: Curculionidae) was evaluated for biological control of the weed in Ethiopia. The specificity of Z. bicolorata and L. setosipennis was assessed against 29 and 31 non-target plant species, respectively. The host range of Z. bicolorata and L. setosipennis was first assessed using no-choice tests to examine their oviposition and feeding response on non-target plants. Although oviposition by Z. bicolorata occurred on six non-target species in four Asteraceae species in no-choice tests, it was significantly lower than on parthenium and no larvae developed. Zygogramma bicolorata nibbled the leaves of one of the five niger seed (Guizotia abyssinica L. – an oil seed crop closely related to parthenium) cultivars tested, but feeding and oviposition were significantly less than on parthenium. Furthermore, choice tests indicated that Z. bicolorata did not oviposit nor feed on G. abyssinica when parthenium was present. In no-choice tests, L. setosipennis did not oviposit on any of the non-target species assessed. Mean oviposition on parthenium was 39.0?±?3.4 eggs per plant whereas no eggs were laid on any of the 31 species tested. Based on these and other host range tests, permission was obtained to field release Z. bicolorata and L. setosipennis in Ethiopia.     

Activity enhancement of Zygogramma bicolorata,a biocontrol agent of Parthenium hysterophorus,by temperature regulated diapause aversion

Diapause is a unique strategy of dormancy in insects to avoid unfavourable conditions. The exotic beetle Zygogramma bicolorata, is an effective biological control agent of Parthenium hysterophorus in India, Adults diapause in soil during December to May. As a result, there is delay in its effectiveness on the plant that reaches to flowering and seed production by the time the beetle is able to build up its population after emerging from diapause. Therefore, a study was conducted to explore possibilities of diapause aversion by temperature regulation. Results indicated that exposure of newly emerged adults to heat treatment of 35°C and to low temperature of 10°C could reduce diapause in Z. bicolorata. The low temperature can also be used as a medium for the storage of the mass reared beetles for a long time without having negative effect on their longevity and fecundity.     

沿海拔梯度的表型可塑性影响银胶菊叶甲的取食效率和发育(英文)

【目的】本研究旨在弄清楚生态气候因子是否影响尼泊尔银胶菊Parthenium hysterophorus盛产区中银胶菊叶甲Zygogramma bicolorata成虫后代的形态学测量参数和基础生物学。【方法】 从尼泊尔Kathmandu (24℃, 海拔1 400 m, 温带气候), Chitwan (25℃, 海拔415 m, 热带或亚热带气候)和Mahendranagar (34℃, 海拔229 m, 湿润 亚热带气候)地区采集银胶菊叶甲成虫,在最适室内条件下评估各生态气候区中其F₁代4龄幼虫和雌成虫的取食特征。我们假定在自由取食和最适非生物条件下饲养的后代将不会受到食物和气温的间接影响,不管亲本属于哪一生态气候区,后代利用食物的能力一致。【结果】然而,我们发现,尽管在最适条件下饲养,银胶菊叶甲后代的体型和取食特征与其亲本相似。体型大的亲本(来自Kathmandu地区),其后代体型也大,但是其食物利用效率比体型小的亲本(来自Chitwan 和Mahendranagar地区)所产后代小。这3个生态气候区中,与幼虫相比正在发育的雌成虫均表现出体重增加而食物利用效率降低。【结论】这些发现说明,食物和最适非生物条件的间接影响可能不影响银胶菊叶甲后代的表型可塑性,后代的体型和取食特征与亲本相似。发生的可遗传的变化可能是由于种内的遗传多样性。我们期望这些发现有助于理解气候变化背景下银胶菊叶甲成虫的表型可塑性、分布格局和取食行为。     

Aboveground activity rhythm in Arctic black-capped marmot (Marmota camtschatica bungei Katschenko 1901) under polar day conditions

Daily aboveground activity of wild black-capped marmots of Yakutia (Marmota camtschatica bungei) was recorded under ‘polar day’ conditions at 71°56’ N and 127°19’ E (north of the Polar Circle). From the beginning of May until the end of August, the sun was permanently above or close to the horizon. However under this condition of continuous lighting, the aboveground activity of these arctic hibernating mammals was periodic. Onset and end of activity showed marked changes throughout the seasons. Activity time increased strongly from hibernation emergence until the end of July and then decreased slowly until onset of hibernation. Below daily mean temperatures of 5 °C, activity started when the sun was 35° above the horizon, and ended when it dropped below 28°. When daily mean temperatures were above 5 °C, activity onset was synchronised with a solar altitude around 17–18° and activity ended at 10°. Activity onset was more precise relative to the solar altitude than the end of activity. This may be explained by late feeding bouts, following a midday thermal stress. In absence of rapid natural light-dark (LD) transitions that occur at civil twilight, our results suggest that the activity pattern of black-capped marmots may be synchronised by the light cycle through the solar altitude and ambient temperature.     

Effects of temperature and adult nutrition on the development of Acanthoscelides macrophthalmus,a natural enemy of an invasive tree,Leucaena leucocephala

Leucaena leucocephala (Lam.) de Wit (Fabales: Fabaceae; leucaena) is an exceptionally invasive weed in South-East Asia (due to its long flowering period and excessive seed output) causing considerable economic losses in Taiwan. A seed predator originating from Central America and inadvertently introduced to South-East Asia, Acanthoscelides macrophthalmus (Schaeffer) (Coleoptera: Chrysomelidae: Bruchinae), is considered to be a potential augmentative biocontrol agent to check the spread of leucaena. To evaluate the feasibility of using A. macrophthalmus for biological control we investigated its development under six constant temperatures (15–35 °C). The relationship between temperature and developmental rate was evaluated using three developmental models of which the Brière model was the best fit for the empirical data. The lower developmental threshold (T₀), estimated by linear regression, was 12.8 °C. The thermal constant was 632.8 degree-days (DD) for total development (egg to adult emergence). The proportion of females was highest and lowest at the extreme temperatures, 15 °C (100%) and 31 °C (36.4%), respectively. Given the compatibility between its bionomic parameters (the optimal temperature for development and highest proportion of females) and the local daily average temperatures in Taiwan, augmentative annual releases of beetles to restrict the spread of L. leucocephala appear to be a promising solution. Given the finding that the adult of A. macrophthalmus can effectively elongate its life span and increase its population densities by feeding on nutrient supplements in the field (e.g., saccharose), we infer that A. macrophthalmus can be used effectively for restricting the expansion of L. leucocephala in an integrated control program.     

Stressor interactions in freshwater habitats: Effects of cold water exposure and food limitation on early‐life growth and upper thermal tolerance in white sturgeon,Acipenser transmontanus

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Pattern of ant diversity in Korea: An empirical test of Rapoport's altitudinal rule

Two diversity patterns (hump-shaped and monotonic decrease) frequently occur along altitude or latitude gradients. We examined whether patterns of ant species richness along altitudes in South Korea can be described by these patterns and whether ranges of ant species follow Rapoport's altitudinal rule. Ants on 12 high mountains (> 1100 m) throughout South Korea (from 33° N to 38° N) were surveyed using pitfall traps at intervals of 200–300 m altitude. The temperatures at the sampling sites were determined from digital climate maps. Ant species richness decreased monotonically along the altitudinal gradient and increased along the temperature gradient. However, species richness of cold-adapted species (highland species) showed a hump-shaped pattern along altitude and temperature gradients. The altitude and temperature ranges of ant species followed Rapoport's rule. Sampling site temperature ranges were significantly correlated with coldness. Therefore, Rapoport's rule can be explained by high cold-tolerance of species inhabiting high altitudes or latitudes.     

Thermophilic response post feeding in Pleurodema nebulosum (Anura: Leptodactylidae) from Monte desert,Argentina.

We studied the thermophilic response to feeding of a typical desert adapted anuran from the Monte Desert. Our aim was to evaluate thermal changes in the selected body temperature of adult frogs of Pleurodema nebulosum, and measure the intestinal passage time, and food digestion. Our results show that after feeding, they selected higher micro-environmental temperatures ~ + 2 °C than frogs that remained starved. Pleurodema nebulosum would present a postprandial thermophilic response. The time of retention of food in the digestive tract was thermo-dependent, being lower in those individuals who were incubated at high temperatures (25 °C) compared to those subjected to lower temperatures (20 °C). Although we did not detect effects of temperature on digestive efficiency, the mass of faecal material indicates an increase at temperatures closer to the selected ones, suggesting that the defecation rate is influenced by temperature. Laiuoperinae frogs are characterized by explosive breeding behavior and fast growing rate. The digestive efficiency is essential for acquiring energy necessary for growth, reproduction and refuge-seeking, among others. In this framework, the differential selection of temperatures between moments of fasting and feeding allows the frogs to maintain a high digestive efficiency, maximizing the absorption of nutrients.     

Modeling analysis on sporulation capacity,storage and infectivity of the aphid-specific pathogen Conidiobolus obscurus (Entomophthoromycota: Entomophthorales)

Entomophthorales are important natural enemies against agroforestry pests. Conidiobolus obscurus in this order, a common obligate aphid pathogen, possesses features of rapid growth in vitro and ease to mass production. This study sought to evaluate the potential of C. obscurus in aphid biocontrol, by modeling analyzing on the sporulation capacity and storage of its alginate formulation and infectivity to Myzus persicae. The C. obscurus mycelia-entrapping alginate pellets discharges 0.12–18.26 × 10⁴ conidia per pellet at 4−32 °C. The optimal temperature for the fungal sporulation was computed as 23.3 °C. Each pellet could sporulated for 7 d, releasing 22.3-fold more conidia than a cadaver at 24 °C. Moreover, it had longevity of 8 mo at 4 °C, with half decline time of 2.3 mo. The infectivity of C. obscurus was assessed by multi-concentration bioassays at 10−28 °C and 8−16 h light per d. The median lethal concentration (LC₅₀) at each temperature-photoperiod regime was computed based on the morality-concentration trend. The LC₅₀ values reached the lowest one of 15 conidia per mm² at 28 °C and 16:8 L:D cycles. The total results suggest that C. obscurus mycelia-inclusive alginate pellets meet the requirement of aphid biocontrol in the high-temperature surroundings of 24–28 °C.     

Effect of chronic low body temperature on feeding and gut passage in a plethodontid salamander

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Lethal and sublethal effect of heat shock on Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

Temperature is an important abiotic environmental factor, and is responsible for various kinds of behavioral and physiological changes in living organisms. Induced heat shock is associated with feeding behaviour, reproduction and reactive oxygen species (ROS) generation that causes oxidative damage. In this experiment, we examined the lethal and sublethal effects of heat shock on reproduction, feeding behaviour and antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD) and peroxidases (POD) in P. solenopsis. Results showed that males were highly susceptible to heat shock treatments than females, as LTemp₅₀ values were 43.8 °C for males and 45.11 °C for females. Heat shock events non-significantly affected the fecundity in female only treated adults and significantly affected the both sexes heat treated adults, it increased the xylem feeding duration, percentage of xylem feeding adults and reduce the phloem feeding duration and percentage of phloem feeding adults. Similarly it alter the antioxidant enzymes activities, an increase of CAT, SOD and POD activities were noticed in response to highest intensity of heat shock while a reduction of CAT and SOD activity were noticed in response to lowest intensity of heat shock compared to control (30 °C). These results suggest that heat shock may result in loss of body water and induce oxidative stress in P. solenopsis. However, antioxidant enzymes play a significant role in overcoming the oxidative damage.