Cannibalistic Behavior Research Articles

Aurantiochytrium dietary supplements reduce intra-cohort cannibalism among orange-spotted groupers (Epinephelus coioides) by modulating brain 5-HT and serum cortisol

Aurantiochytrium strain BL10 is rich in highly unsaturated fatty acids (HUFAs), particularly docosahexaenoic acid (DHA). Previous research has shown that adding 2% of dry BL10 powder to increase the DHA content of feed for orange-spotted grouper (Epinephelus coioides) does not benefit growth but can significantly reduce size discrepancies between individuals and thereby potentially decrease the chance of cannibalism.To understand whether a 2% BL10 supplement can really reduce the cannibalism rates of E. coioides, whether increasing the BL10 dosage can reduce the cannibalism rates of E. coioides even further, and how the BL10 supplements affect cannibalistic behavior, we produced four isonitrogenous and isolipidic experimental diets dosed with different weight percentages (0, 2, 4, 6%) BL10 meal and fed it to E. coioides fingerlings (total length 3.8 ± 0.3 cm) for two weeks. During the feeding period, cannibalism in the experiment groups were observed. After the feeding period, we analyzed the brain fatty acid composition, brain 5-hydroxytryptamine (5-HT) levels, and serum cortisol levels in the experiment groups and used regression analysis to examine the relationships among these biochemical variants and cannibalism rates.The results indicate that 2–6% BL10 supplements, particularly 2% BL10 supplement, could significantly reduce the cannibalism rates of E. coioides. The BL10 supplements increased the proportions and contents of HUFAs in the brains of E. coioides, increased brain 5-HT levels, and reduced serum cortisol levels. The results of univariate linear regression indicated that the serum cortisol level exhibited a significant negative correlation with brain HUFA content, particularly arachidonic acid (ArA). Whereas, brain 5-HT was positively correlated with the ratio of n-3/n-6 fatty acids in the brain. Subsequent multivariate linear regression demonstrated that cannibalism is affected by serum cortisol, brain 5-HT levels and their interaction. Our results provide new insight into the physiological regulation mechanisms behind the cannibalistic behavior of teleost and provide a feasible solution at the same time.

Cannibalism and Habitat Selection of Cultured Chinese Mitten Crab: Effects of Submerged Aquatic Vegetation with Different Nutritional and Refuge Values

We examined the food preference of Chinese mitten crabs, Eriocheir sinensis (H. Milne Edwards, 1853), under food shortage, habitat choice in the presence of predators, and cannibalistic behavior by comparing their response to the popular culture plant Elodea nuttallii and the structurally more complex Myriophyllum verticillatum L. in a series of mesocosm experiments. Mitten crabs were found to consume and thus reduce the biomass of Elodea, whereas no negative impact on Myriophyllum biomass was recorded. In the absence of adult crabs, juveniles preferred to settle in Elodea habitats (appearance frequency among the plants: 64.2 ± 5.9%) but selected for Myriophyllum instead when adult crabs were present (appearance frequency among the plants: 59.5 ± 4.9%). The mortality rate of mitten crabs in the absence of plant shelter was higher under food shortage, primarily due to cannibalism. The proportion of molting crabs dying in the structurally more complex Myriophyllum habitats was significantly lower than in the less complex Elodea habitats, indicating that Myriophyllum provides better protection from cannibalistic behavior, likely due to its structurally more complex canopy. Stable isotope analyses of crab samples revealed a trophic shift in both δ13C and δ15N (Δδ13C: 2.2–4.0‰; Δδ15N: 1.5–2.8‰) during the experimental period. Significant positive correlations between body mass and δ13C and δ15N were recorded, suggesting that cannibalistic feeding might further increase crab growth and lead to ontogenetic increases in trophic position with increasing size. Our study overall demonstrates that a combination of submerged aquatic vegetation functioning as a highly suitable food with other less palatable plant species acting as efficient refuges against predators may be the optimal method of plant stocking in mitten crab aquacultures to ensure both high crab growth and a high survival rate.

Indirect effects of climate change altered the cannibalistic behaviour of shell-drilling gastropods in Antarctica during the Eocene.

The fossil record from Seymour Island, Antarctic Peninsula, provides a record of biotic response to the onset of global climatic cooling during the Eocene. Using drilling traces—small, round holes preserved on prey shells—we examined the effect of a cooling pulse 41 Ma on the cannibalistic behaviour of predatory naticid gastropods. We predicted that cannibalistic attacks would decline in response to the cooling climate, reflecting reduced activity levels, energy requirements and constraints on the chemically aided drilling process of the naticids. Surprisingly, however, cannibalism frequencies did not change. This counterintuitive result is best explained by a sharp reduction in durophagous (shell-crushing) predation in shallow-benthic communities in Antarctica that also occurred as the climate cooled. Reduced durophagous predation may have created a less-risky environment for foraging naticids, stimulating cannibalistic behaviour. The change in the top-down control exerted by shell-crushing predators on naticids may have counteracted the direct, negative effects of declining temperatures on the predatory performance of naticids. Our results suggest that the long-term consequences of climate change cannot be predicted solely from its direct effects on predation, because the temperature can have large indirect effects on consumer–resource interactions, especially where risk-effects dominate.

Cannibalism associated with artificial wounds on the bodies of Reticulitermes speratus workers and soldiers (Isoptera: Rhinotermitidae)

We investigated the cannibalism and its association with cannibalistic grooming in Reticulitermes speratus (Kolbe), first by observing workers’ cannibalistic behavior against workers artificially wounded on different body parts. Almost all the wounded thoraces and abdomina were eaten, while in some of the abdomen-wounded individuals, nestmates’ cannibalism extended from the abdomen to the thorax, and thorax was cannibalistically attacked in all the abdomen-wounded individuals. In thorax-wounded individuals cannibalistic damage mostly extended from the thorax to the abdomen to a lesser degree. In the assessments of the frequencies and durations of the cannibalistic groomings toward different body parts, the wounded individuals, upon being groomed, occasionally exhibited vibrational behavior, and its frequencies upon the groomings toward wounded body parts were significantly higher than those toward non-wounded body parts. Vibration significantly reduced the duration of cannibalistic grooming on the wounded head and abdomen, while it reduced the grooming frequency and did not reduce the duration of grooming on wounded thorax. These results suggest that the vibration serves as a vital sign or death-negative factor in death recognition. A feeding experiment with workers’ cuticular hydrocarbon extract showed that it did not promote cannibalistic behavior. A feeding experiment with filter papers impregnated with different body part extracts showed that all the extracts exhibited phagostimulant activity, with workers’ body extracts resulting in significantly higher quantity of consumption than in soldiers’ except abdomen. Further assay revealed a stronger activity of labial gland compared to the labial gland-removed thorax, suggesting the key role of labial gland in cannibalism.

Filial Cannibalism by Male Fish as an Infanticide to Restart Courtship by Self-Regulating Androgen Levels

Parental care is costly for animal parents [1-3], who often desert, abort, or kill their offspring and sometimes even eat them-so-called filial cannibalism [1,4]. A primary adaptive hypothesis for filial cannibalism centers on the expected nutritional benefits from eating offspring (the energy-based [EB] hypothesis [5-7]). However, many empirical studies are inconsistent with the EB hypothesis [8, 9]. One notable case is total filial cannibalism observed in some fishes. The caregiving males of these species eat all eggs and restart reproduction when tending a small number of eggs, as predicted by the EB hypothesis; but, this is puzzling because they can potentially court females even while tending eggs and increase the eggs by additional matings. Here we show that brood termination known as total filial cannibalism in blenniid fish Rhabdoblennius nitidus males is an endocrinological necessity to restart courtship behavior for subsequent mating. Males exhibit androgen-dependent brood cycling, and they are normally incapable of exhibiting courtships during the parental phase [10]. Egg manipulation experiments demonstrated that egg presence in the nest is a key stimulus regulating male androgen levels; they cannot restart courtship until removing all eggs. Furthermore, surprisingly, eggs were sometimes spit out without being consumed, and the occurrence of cannibalization and removal of all eggs was not associated with male condition. These results strongly suggest that the egg cannibalistic and removal behaviors that have been regarded as total filial cannibalism in this species are infanticide or embryocide rather than cannibalism, which serve to increase the males' androgen levels.

Mass spider silk production through targeted gene replacement in Bombyx mori

Spider silk is one of the best natural fibers and has superior mechanical properties. However, the large-scale harvesting of spider silk by rearing spiders is not feasible, due to their territorial and cannibalistic behaviors. The silkworm, Bombyx mori, has been the most well known silk producer for thousands of years and has been considered an ideal bioreactor for producing exogenous proteins, including spider silk. Previous attempts using transposon-mediated transgenic silkworms to produce spider silk could not achieve efficient yields, due to variable promoter activities and endogenous silk fibroin protein expression. Here, we report a massive spider silk production system in B. mori by using transcription activator-like effector nuclease-mediated homology-directed repair to replace the silkworm fibroin heavy chain gene (FibH) with the major ampullate spidroin-1 gene (MaSp1) in the spider Nephila clavipes We successfully replaced the ∼16-kb endogenous FibH gene with a 1.6-kb MaSp1 gene fused with a 1.1-kb partial FibH sequence and achieved up to 35.2% chimeric MaSp1 protein amounts in transformed cocoon shells. The presence of the MaSp1 peptide significantly changed the mechanical characteristics of the silk fiber, especially the extensibility. Our study provides a native promoter-driven, highly efficient system for expressing the heterologous spider silk gene instead of the transposon-based, random insertion of the spider gene into the silkworm genome. Targeted MaSp1 integration into silkworm silk glands provides a paradigm for the large-scale production of spider silk protein with genetically modified silkworms, and this approach will shed light on developing new biomaterials.

Hormonal modulation of cannibalistic behaviors in mosquito (Culex pipiens) larvae

Cannibalism has been observed occasionally in a limited number of different animal species, but the underlying mechanisms that foster this behavior are mostly unknown. Here we show that mosquito (Culex pipiens) larvae show this behavior towards conspecifics under certain conditions. Cannibalism was only observed in 4th instar larvae and only in response to starvation. Well fed animals never showed any cannibalistic behavior. Starvation induced cannibalism of Culex 4th instar was predominantly directed towards 3rd instars rather than to 1st or 2nd instar larvae. Specific mandibular structures of these larvae enable this cannibalistic behavior. We could show that treatment with the biogenic amine octopamine, which is known to be involved in the control of starvation and aggression, increased the rate of cannibalism of food-deprived 4th instar larvae significantly. Incubation with the octopamine receptor antagonist phentolamine suppressed this cannibalistic behavior. Moreover, octopamine not only increased the rate of cannibalism, it also induced a shift towards smaller prey. A role of octopamine in this starvation induced behavior was further supported by direct measurements of the total content of this important neuroactive compound. Taken together, we could show that 4th instar mosquito larvae showed cannibalistic behavior after starvation and that this behavior apparently depends on octopamine.

Cannibalistic behavior of aphidophagous coccinellid, Hippodamia variegata (Goeze, 1777) (Coleoptera: Coccinellidae)

The variegated lady beetle, Hippodamia variegata (Goeze, 1777) is widely distributed in different agroecosystems of Turkey. Cannibalism, intraspecific predation, where individuals of the same species feed upon each other, is a common phenomenon in most aphidophagous coccinellids including H. variegata. We investigated the cannibalistic behavior of various growth stages of H. variegata in the presence and absence of Acyrthosiphon pisum Harris, 1776 under laboratory conditions . The results for cannibalism of eggs and larvae by adults revealed that eggs and younger larvae were more vulnerable to cannibalism. Notably, egg cannibalism by adults was found to be higher even at high prey abundance. Whereas, larval cannibalism was found significantly lower. Cannibalism of eggs by larvae and within the larvae showed that older larvae consumed significantly higher number of eggs and younger larvae in the absence of A. pisum indicating that cannibalism was mainly influenced by scarcity of prey. However, all the larval instars, especially 4 th and 3 rd instars, also consumed a substantial number of eggs even in the presence of prey. Cannibalism within the same stage/age larvae showed a successive increase with the successive larval stage showing minimum cannibalism by 1 st instar larvae and maximum by 4 th instar larvae. The study found that scarcity of prey leads to cannibalism in H. variegata and that egg cannibalism occurs even at high prey densities.

Embryonic, larval and juvenile development of the longfin batfish, Platax teira (Forsskål, 1775) under controlled conditions with special regard to mitigate cannibalism for larviculture

Longfin batfish Platax teira is one of the most important finfish species in Asian aquaculture. However, knowledge on early ontogeny and reproduction of this species in captivity are scarce and incomplete. In this study, the embryonic, larval and juvenile development of P. teira are described and illustrated for the first time. The effect of temperature (27, 30 and 33 °C) on hatching rate, yolk-sac volume and oil globule volume was demonstrated. Cannibalism control via aeration adjustment for the enhancement of larval survival was also examined. Fertilized eggs were spherical, buoyant and had a diameter of 1.29 ± 0.05 mm (mean ± SD). Embryonic development lasted 16 h at 26.2 °C. Newly hatched larvae were 2.81 ± 0.24 mm in total length (LT) with 24 myomeres and had an oil globule in the ventroposterior area of the yolk sac. Early larvae had xanthophores appeared all over the body, except for the tip of the notochord. Larvae completed yolk absorption within 3 days post hatching (dph) at 3.41 ± 0.11 mm LT. Larvae were fed initially on rotifers Brachionus ibericus, followed by Artemia nauplii and finally weaned onto an artificial diet. From 8 dph, the larger larvae (over 4 mm LT) began to exhibit cannibalistic behaviour. Transformation of larvae to the juvenile stage was completed at 23.80 ± 1.98 mm LT, all fins had the adult complement of rays and spines. A statistical model: Y = 2.4968e0.0786x, where Y is mean LT (mm) and X represents dph, explained 96.45% of variation in growth (P < 0.001, R2 = 0.9645). The hatching rate, yolk-sac volume and oil globule volume of newly hatched larvae were significantly (P < 0.05) decreased when the incubation temperature increased. Only 2–6% of embryos hatched at 33 °C, while the hatching rate was 63 ± 6% at 27 °C. Larvae reared in aeration rate of 300 mL min−1 attained the highest survival rate at 70.00 ± 7.20%, but remained significantly (P < 0.05) lower in cannibalism: 24.44 ± 4.16% compared with 66.67 ± 5.44% in 20 mL min−1. These results indicate that the optimal incubation temperature recommended is approximately at 27 °C, and aeration at 300 mL min −1 could enhance larval survival by reducing cannibalism.

Gender-specific differences in cannibalism between a laboratory strain and a field strain of a predatory mite

Many phytoseiid species, including Phytoseiulus persimilis, are known to engage in cannibalism when food is scarce and when there is no possibility to disperse. In nature adult females of P. persimilis are known to disperse when prey is locally depleted. Males, in contrast, are expected to stay and wait for potential mates to mature. During this phase, males can obtain food by cannibalizing. Therefore, we hypothesize that male P. persimilis exhibit a higher tendency to cannibalize than females. Because rearing conditions in the laboratory usually prevent dispersal, prolonged culturing may also affect cannibalistic behavior. We hypothesize that this should especially affect cannibalism by females, because they consume far more food. We tested these hypotheses by comparing males and females from two strains, one of which had been in culture for over 20 years, whereas the other was recently collected from the field. It is known that this predator can discriminate between kin and non-kin and prefers cannibalizing the latter, hence to construct lines with high relatedness we created isofemale lines of these two original strains. We subsequently tested to what extent the adult females and males of the original strains and the isofemale lines cannibalized conspecific larvae from the same strain/line in a closed system. Relatedness with the victims did not affect cannibalistic behavior, but males engaged more often in cannibalism than females, and females of the laboratory strain engaged more in cannibalism than those of the field strain, both in agreement with our ideas. We hypothesize that the difference in cannibalism between the two genders will increase when they have the alternative to disperse.

Opportunistic random searcher versus intentional search image user

We consider two types of optimal foragers: a random searcher and a search image user. A search image user can find its desired prey with higher and undesired prey with lower probability than a random searcher. Our model considers the density-dependent travelling time and the time duration of reproduction (oviposition). In the framework of optimal foraging theory for one predator–two prey systems, we find that there are ranges of prey densities in which the search image user has a higher net energy intake, and there are other ranges of prey densities in which the random searcher has higher net energy intake. The damsel bug Nabis pseudoferus Remane (Hemiptera: Nabidae) is a generalist predator rather than an omnivore. This species has a wide range of arthropod prey (predominantly insects and mites). Several aspects of the biology of this species have been studied, especially its cannibalistic behaviour, which is a quite important feature because N. pseudoferus is often used as a biological control agent against lepidopteran pests in greenhouse crops. Experimentally, we found that Nabis is a search image user in the above sense.

An insight into the cannibalistic behavior of giant cell granulomas of the jaws.

Background:Cellular cannibalism is defined as a large cell engulfing a smaller one within its cytoplasm. It is predominantly a feature of aggressive malignancies but has recently been demonstrated in giant cell (GC) lesions such as GC tumor of tendon sheath, central GC granuloma (CGCG) and peripheral GC granuloma (PGCG).Aim:The aim of the study is to assess the cannibalistic GCs in CGCG and PGCG and correlate with aggressiveness of the lesion.Settings and Design:Archival data of histopathologically confirmed cases of CGCG (n = 40) and PGCG (n = 25) were studied in the Department of Oral Pathology, Maulana Azad Institute of Dental Sciences.Materials and Methods:Quantification of cannibalistic cells was performed using H&E stain on microscopic sections. One hundred GCs were examined in each slide, and the number of cannibalistic cells was expressed in percentage.Results:GC cannibalism was observed in all cases. The mean number of cannibalistic GCs in CGCG was 44.67 which was significantly higher (P = 0.028) than PGCG (mean 28.04). In aggressive (n = 18) CGCG, the mean number of cannibalistic GCs was 51.27 which was significantly higher (P = 0.019) than cannibalistic GCs in nonaggressive (n = 22) CGCG (mean 39.27). No significant difference was observed between the number of cannibalistic cells in recurrent (mean = 52.9) and nonrecurrent (mean = 49.2) cases of CGCG (P > 0.05). Two of the nine cases treated initially by steroid showed fewer and smaller cannibalistic GCs with vesicular nuclei.Conclusion:There was a clear distinction in the mean cannibalistic count between aggressive and nonaggressive CGCG. Hence, the aggressiveness of the lesion could be assessed following which appropriate treatment modality can be constituted.

Spider silk foam coating of fabric

Abstract Silks are well known natural fibers used for textile applications and have got for the first time available upon sericulture of silkworms (Bombyx mori) several thousand years ago in China. In contrast to silkworm silk, spider silks offer better mechanical properties such as higher tensile strength and much better toughness, but natural spider silk is less accessible due to the cannibalistic behavior of spiders prohibiting large scale farming, and therefore has not been employed in textile industry yet. In this study, a biotechnologically produced spider silk protein was introduced as a new material for textile applications in form of foam coating material. The spider silk foam coating was developed to increase the abrasion behavior of natural and polymeric furniture textiles. Modern textiles are high-tech materials and optimized concerning yarn design and fabric weave to fit a wide range of applications. Often hydrofluorocarbons based coatings are used to enhance textile performances. Upon coating with sustainable spider silk, yarn fraying was significantly reduced lowering the tendency to form knots and loops. Further, the textile abrasion resistance, analyzed by pilling tests, was improved significantly (17–200%) for all tested types of fabrics, in particular long term strain pilling was minimized.

Both feather peckers and victims are more asymmetrical than control hens

Feather pecking is the major welfare issue facing the egg farming industry worldwide. Previous research has found a relationship between cannibalistic behaviour, fluctuating asymmetry of bilateral traits (FA) and body weight in laying hens. As cannibalism is linked to severe feather pecking, it could be suggested that a relationship between feather pecking, FA and body weight also exists. The purpose of this study was to analyse the association between feather pecking behaviour and a) FA, b) body weight and c) comb size in laying hens. Sixty-four laying hens were categorised as feather peckers, victims or control hens based on weekly performance of feather pecking behaviour from age 0–23 weeks and plumage condition at age 23 weeks. After culling at 23 weeks of age, the lengths of ulna, tarsus and middle toe as well as the widths of tarsus and hock were measured twice in each side. Each trait was tested for repeatability, directional asymmetry and antisymmetry. Only the three lengths were considered appropriate for analyses of composite and single-trait FA. Control hens displayed less composite FA (P=0.0005) and less FA of ulna (P=0.0001) than feather peckers and victims. Tarsus asymmetry differed between all categories with victims displaying most, control hens least and feather peckers intermediate levels of asymmetry (P<0.0001). Victims were also lighter in body weight compared to control hens and feather peckers (P=0.043). No difference was found in comb size between the three categories (P=0.1). The results suggest that feather peckers and victims were exposed to similar levels of negative experiences, causing developmental instability, whereas control hens were less negatively affected than both feather peckers and victims during early life.

Using incentives to address cannibalization

In a decentralized multi-product firm, different products within the firm sometimes compete with one another for the same customers. This paper proposes managing such cannibalistic behavior with incentives. Designing the appropriate incentives requires detailed information on how the sales of one product impact the profitability of other products. As this paper shows, the only additional information required is the second choice preferences of buyers. Drawing on successful development by General Motors, this paper shows how this information can be collected and used to develop cannibalization incentives. While developed for the automotive industry, this approach is applicable across industries.

Cannibalism: Do risks of fighting and reprisal reduce predatory rates?

Cannibalism is a common phenomenon among insects. It has raised considerable interest both from a theoretical perspective and because of its importance in population dynamics in natural ecosystems. It could also play an important role from an applied perspective, especially when using predatory species in biological control programmes. The present paper aims to study the cannibalistic behaviour of Nabis pseudoferus Remane and the functional response of adult females. In a non-choice experiment, adult females showed clear acceptance of immature conspecifics as prey, with relatively high mortality values (51.89 ± 2.69%). These values were lower than those occurring for heterospecific prey, Spodoptera exigua Hübner, under the same conditions (80.00 ± 2.82%). However, the main result was that the rate of predation on heterospecific prey was reduced to 59.09 ± 7.08% in the presence of conspecific prey. The prey-capture behaviour of adult females differed when they hunted conspecific versus heterospecific prey. This was shown in the average handling time, which was 23.3 ± 3.3 min in the first case (conspecific) versus 16.6 ± 2.5 min in the second (heterospecific). Furthermore, the values increased in the former case and declined in the latter according to the order in which the prey were captured. The difference in handling time was not significant when adjusting the adult female functional response to conspecific nymphs. We argue that these results likely indicate risk aversion and a fear of reprisal among conspecifics.

Adopt, ignore, or kill? Male poison frogs adjust parental decisions according to their territorial status

Systematic infanticide of unrelated young has been reported in several animal taxa. Particular attention has been given to carnivores and primates, where infanticide is a sexually selected strategy of males to gain increased access to female mating partners. Cannibals must ensure avoiding their own offspring and targeting only unrelated young. Therefore, decision rules are needed to mediate parental and cannibalistic behaviour. Here we show experimentally that male poison frogs adjust their parental responses – care or infanticide – towards unrelated clutches according to their territorial status. Male frogs followed the simple rule ‘care for any clutch’ inside their territory, but immediately switched to cannibalism when establishing a new territory. This demonstrates that simple cognitive rules can mediate complex behaviours such as parental care, and that care and cannibalism are antagonistically linked. Non-parental infanticide is mediated by territorial cues and presumably serves to prevent misdirected care in this poison frog. Our results thus prompt a re-consideration of evolutionary and causal aspects of parental decision making, by suggesting that selective infanticide of unrelated young may generally become adaptive when the risks and costs of misdirected care are high.

Ecosystem structure and trophic dynamics of an exploited ecosystem of Bay of Bengal, Sundarban Estuary, India

A trophic structure model for commercial fisheries of Sundarban Estuary in the northern Bay of Bengal (BoB) is developed using the mass balance modeling software Ecopath (Version 6.4.10992.0). In this model, we simulated 15 functional groups spread across an area of 17,049 km2. The mean trophic level of the present study area is 2.716. The ecotrophic efficiency of the present studied ecosystem is in the range of 0.424 of medium demersals and 0.961 of medium pelagics. Penaeid prawn, small pelagics, and medium pelagics are the most exploited groups of this ecosystem. The coastal northern BoB food web is mainly detritivorous and planktivorous; phytoplankton and detritus positively affected almost all the functional groups, and top predators are essentially absent in the system. The zooplankton and benthos have negative impacts on themselves because of cannibalistic behavior. The average catch per net primary production, i.e. the gross efficiency of the system is around 0.001. The system is low trophic and efficient. Proper ecosystem-based management practice can improve the efficiency of this overexploited ecosystem.

Feeding Propensity and Cannibalism of Micraspis Discolor (Fab.) to Different Prey Species (Aphis craccivora and Nilaparbata lugens) under Laboratory

Feeding propensity and cannibalism of Micraspis discolor (Fab.) to different prey species (bean aphids and brown plant hopper ) was studied in the laboratory of the Department of Entomology, Bangladesh Agricultural University, Mymensingh, during January, 2007 to April, 2007. It was found that the highest pre-oviposition period was to 5.6±0.54 days when BPH were used and this period was lowest, 4.6±0.54 days using bean aphid. The oviposition period was maximum 40.20±1.78 days using bean aphid and minimum 29.00± 2.00 days were found using BPH. Maximum number of eggs 216.00±16.58 was laid when fed on bean aphid. The hatching percent was highest 88.71% using bean aphid and hatching percent was lowest 85.34% when fed on BPH. Incubation period varied from 2.40±0.54 to 3.80±0.44 days using different foods. However, the larvae passed through four larval instars and highest larval period was 10.00 ± 0.70 when BPH were used as food and lowest was 8.40 days feeding on bean aphid. Pupal period was 3.00±0.00 &amp; 3.80±0.44 days when bean aphid &amp; BPH were supplied as food. The average longevity of female was 38.60±3.78 and 31.40±2.96 days and that of male was 32.00±2.91 &amp; 26.00±0.91 days when feeding on bean aphid and BPH respectively. It was significant at 1% level. The sex ratio of male and female was found (0.78:1.00) using different foods and these were not significant at 1% level. By this experiment, It was observed that feeding propensity of Micraspis discolor to different prey species during the total life cycle was as follows: bean aphid &gt; BPH. It was also found that M. discolor had cannibalistic behavior and this was significant at 1% level.J. Environ. Sci. &amp; Natural Resources, 9(1): 81-85 2016

Intra-instar larval cannibalism in Anopheles gambiae (s.s.) and Anopheles stephensi (Diptera: Culicidae).

BackgroundCannibalism has been observed in a wide range of animal taxa and its importance in persistence and stability of populations has been documented. In anopheline malaria vectors the inter-instar cannibalism between fourth- and first-instar larvae (L4-L1) has been shown in several species, while intra-instar cannibalism remains poorly investigated. In this study we tested the occurrence of intra-instar cannibalism within larvae of second-, third- and fourth-instar (L2, L3 and L4) of Anopheles gambiae (s.s.) and An. stephensi. Experiments were set up under laboratory conditions and the effects of larval density, duration of the contact period among larvae and the presence of an older larva (i.e. a potential cannibal of bigger size) on cannibalism rate were analysed. Cannibalism was assessed by computing the number of missing larvae after 24 and 48 h from the beginning of the experiments and further documented by records with a GoPro videocamera.ResultsIntra-instar cannibalism was observed in all larval instars of both species with higher frequency in An. gambiae (s.s.) than in An. stephensi. In both species the total number of cannibalistic events increased from 0–24 to 0–48 h. The density affected the cannibalism rate, but its effect was related to the larval instar and to the presence of older larvae. Interestingly, the lower cannibalism rate between L4 larvae was observed at the highest density and the cannibalism rate between L3 larvae decreased when one L4 was added.ConclusionsThe present study provides experimental evidence of intra-instar cannibalism in the malaria vectors An. gambiae (s.s.) and An. stephensi and highlights the possible occurrence of complex interactions between all larval instars potentially present in the breeding sites. We hypothesize that the high density and the presence of a potential cannibal of bigger size could affect the readiness to attack conspecifics, resulting into low risk larval behavior and lower cannibalism rate. The understanding of cannibalistic behavior and the factors affecting it is of utmost importance for malaria vectors, as nutrition during larval development can strongly affect the fitness of adult female mosquitoes and ultimately their vector ability.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1850-5) contains supplementary material, which is available to authorized users.