Rate Of Cannibalism Research Articles

Impact of dietary restriction on development, mating, and reproduction in the natural predator Pardosa pseudoannulata.

Dietary restriction-influenced biological performance is found in many animal species. Pardosa pseudoannulata is a dominant spider species in agricultural fields and is important for controlling pests. In this study, three groups - a control group (CK group), a re-feeding group (RF group), and a dietary restriction group (RT group) - were used to explore development, mating, reproduction, and the expression levels of Vg (vitellogenin) and VgR (vitellogenin receptor) genes in the spider. The findings indicated that when subjected to dietary restriction, the carapace size, weight of the spiderlings, and weight of the adults exhibited a decrease. Furthermore, the preoviposition period and egg stage were observed to be prolonged, while the number of spiderlings decreased. It was also observed that re-feeding reduced cannibalism rates and extended the preoviposition period. Dietary restriction also affected the expression of the Vg-3 gene in the spider. These results will contribute to the understanding of the impact of dietary restriction in predators of pest control, as well as provide a theoretical foundation for the artificial rearing and utilisation of the dominant spider in the field.

Does female control and male mating system predict courtship investment and mating outcomes? A comparative study in five widow spider species (genus Latrodectus) tested under similar laboratory conditions

BackgroundMale courtship investment may evolve in response to the male’s expectation of future mating opportunities or the degree of female control during mating interactions. We used a comparative approach to test this hypotheses by assessing the courtship and mating behaviors of five widow spider species (genus Latrodectus) under common laboratory conditions. We predicted male investment in courtship would be higher in species where males mate only once because of high cannibalism rates (monogyny, L. geometricus, L. hasselti, L. mirabilis), compared to species with rare cannibalism (L. mactans, L. hesperus) in which males should reserve energy for future mating opportunities. Increased male investment, measured as courtship duration, might also evolve with increased female control over mating outcomes if females prefer longer courtships. We tested this by assessing the frequency of copulations, timing of sexual cannibalism, and the degree of female-biased size dimorphism, which is expected to be negatively correlated with the energetic cost of rebuffing male mating attempts.ResultsCopulation frequency was consistently lower in species with extreme female-skewed size dimorphism, and where sexual cannibalism was more prevalent, suggesting the importance of female control for mating outcomes. We confirmed significant interspecific variation in average courtship duration, but contrary to predictions, it was not predicted by male mating system, and there was no consistent link between courtship duration and sexual size dimorphism.ConclusionWe show that the degree of sexual dimorphism is not only correlated with sexual cannibalism, but also with mating success since restriction of male copulation frequency by female Latrodectus affects paternity. However, predictions about male mating system or female control affecting courtship duration were not supported. We propose that the form of female control over mating and cannibalism, and male responses, might be more informative for understanding the evolution of courtship duration. For example, male tactics to avoid female aggression may drive lower courtship duration in species like L. mirabilis. Nonetheless, our results differ from inferences based on published studies of each species in isolation, illuminating the need for standardized data collection for behavioural comparative studies.

Cannibalism facilitated by parasite infection induces dispersal in a semi-aquatic insect.

Parasites are known to have direct effects on host dispersal ability and motivation. Yet, parasites have a variety of impacts on host populations, including shaping predation and cannibalism rates, and therefore may also have indirect effects on host dispersal; these indirect pathways have not been studied. We tested the hypothesis that parasites influence host dispersal through effects on cannibalism using backswimmers (Notonecta undulata) and Hydrachnidia freshwater mites. Mite parasitism impedes swimming in backswimmers, which we found increased their vulnerability to cannibalism. We imposed a manipulation that varied cannibalism rates across experimental populations consisting of a mix of backswimmers with and without simulated parasites. Using simulated parasites allowed us to examine the effects of cannibalism without introducing infection risk. We found that the odds of dispersal for infected backswimmers increased by 2.25× with every 10% increase in the risk of being cannibalized, and the odds of dispersal for healthy backswimmers increased by 2.34× for every additional infected backswimmer they consumed. Our results suggest that cannibalism was used as an energy source for dispersal for healthy individuals, while the risk of being eaten motivated dispersal in infected individuals. These results elucidate the complex ways that parasites impact host populations and strengthen our understanding of host-parasite interactions, including host and parasite population stability and spread. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'.

Unobserved mortality occurs early in larval walleye (Sander vitreus) aquaculture

One of the most persistent challenges in walleye larviculture is the high rate of unobserved mortality occurring within the first 30 days post-hatch. Walleye larviculture is characterized by high mortality rates, but oftentimes, only a fraction of the total mortality in walleye larviculture is observed. Unobserved mortality is frequently attributed to a high rate of cannibalism, but decomposition of larvae and other factors may also be important contributors. Unobserved mortality can make walleye larviculture especially challenging as accurately estimating daily feed rations and forecasting larval production rely on accurate counts of surviving fish. Despite the importance of unobserved mortality, there is little empirical evidence available that assesses the temporal occurrence and causes of unobserved mortality in walleye larviculture. This study assessed when unobserved mortality occurs during walleye larviculture by examining survival at three timepoints (8, 15, and 30 days post-stocking). Tanks were cleaned daily and dead fry were enumerated to account for observed mortality. At the end of each treatment period, the tanks were drained, all remaining fry were enumerated, and the unobserved mortality rate was calculated. While observed mortality trended higher as trial duration increased, unobserved mortality did not increase significantly from the 8-day treatment suggesting that the bulk of unobserved mortality occurs during the first 8 days of walleye larviculture.

Natural breeding performance in different saline water pens, crablets rearing and cannibalism in juvenile phase of mangrove mud crab (Scylla olivacea) in earthen mangrove pens

The current study focused on natural breeding techniques using locally available mud crab broods during breeding season. The breeding trial was tested in artificially created earthen pens that designed with mangrove plants and salt tolerance grass. Mature brood crabs were collected from local rivers and equally distributed in 20 L black color plastic containers in three different salinities (T1 = 24ppt, T2 = 26ppt, and T3 = 28ppt) and covered with black cloth. The river salinity was 26ppt during breeding season that is considered as control(T2), and treatment T1 and T3 were prepared artificially mixing with water and sea salt respectively. Broods are reared in containers until hatching and zoea was transferred to earthen pens immediately after hatching. Zoea were reared in earthen pens until turns to crablet(0.027 ± 0.005 g). The broods as well as crablet were identified through molecular barcoding and confirmed species as Scylla olivicea. Besides, morphometric characters like weight(126.22 ± 0.19 g), carapace length(6.36 ± 0.08 cm), carapace width(9.08 ± 0.08 cm), carapace color(brownish to brownish green), Anterolateral margin and teeth (3.79 ± 0.05 cm), abdomen length(3.04 ± 0.02 cm), hand (5.50 ± 0.03 cm), carpus(2.54 ± 0.04), antenna (2.69 ± 0.07), frontal margin(2.90 ± 0.07 cm), dactylus(3.13 ± 0.06 cm), thoracic sternites(4.17 ± 0.10), merus(4.16 ± 0.11 cm) etc. are also assessed during the experiment. The hatching rate, survival %, incubation period and other parameters are significantly different among the treatments. The highest hatching rate was observed in T2(91.34 ± 4.61 %) and lowest was in T1(57.98 ± 1.38) whereas the highest survival rate was recorded in T2(10.53 ± 1.56) and lowest observed in T1(2.87 ± 0.68). The order of incubation was T1(12.3 days)>T3(11 days)>T2(8.67days) observed during experiment. The cannibalism rate was also estimated in this experiment and observed cannibalism rate was 71.20 ± 2.08. Natural mud crab breeding is easy and can be applicable in fields at low cost with significant survival rate.

Herbicide changes the role of body condition in mating interactions of a wolf spider but courtship is primarily affected by female immunity

AbstractAnimals that live in human‐impacted landscapes experience an onslaught of novel stimuli that may interfere with natural communication pathways. During mating, this interference may alter the criteria deployed to assess potential mates as males and females find they must shift their focus and emphasize alternative sensory modalities. The wolf spider, Tigrosa helluo (Araneae, Lycosidae) is common in agricultural fields where commercial formulations of herbicides with glyphosate as the active ingredient are regularly applied. With the development of genetically resistant crops, glyphosate‐based herbicides have become among the most widely used and heavily applied agricultural chemicals in the world. In a laboratory experiment, we explored the effects of this herbicide on male—female interactions during courtship, mating, and sexual cannibalism. We expected that it might impact assessment such that there was a shift in the features that were important to the outcome of mating interactions. When herbicide was present, female body condition, an indication of recent feeding success, became important to mating success. This result was, in part, due to higher rates of sexual cannibalism in parings of males and females with low body condition values. The leg raises and pedipalp waves that males perform in courtship were not affected by herbicide nor were they related to mating success but, across all treatments, they were negatively correlated with lytic activity of females as measured just prior to pairing. This result indicates that males detected this aspect of the female's physiology and that a strong immune response made the female less attractive, possibly because it indicated a current or recent infection. Taken together, these results verify that a common herbicide shifts mating criteria used by an agribiont spider and, separate from the herbicide, the immune status of females affects the reactions of courting males.

Evaluation of the Digestibility of Diets Containing Soy Okara in Clarias gariepinus (Burchell, 1822) Fries Raised in a Controlled Environment in Benin

Aims: To evaluate the digestibility of diets containing soy okara in Clarias gariepinus fries. Study Design: Random complete block design. Place and Duration of Study: Laboratory of Hydrology and Wetland Research, Faculty of Sciences and technics, University of Abomey-calavi, between June 2019 and July 2019. Methodology: Four diets containing different levels of soy okara (0%, 10%, 20% and 30%) respectively noted T0, T1, T2 and T3 were tested. Twelve 40L tanks were randomly distributed into 04 batches with 03 repetitions for each of the 04 diets. The fries with an initial average weight of 10.47 +/- 2g were fed ad libitum three times a day (8 A.M., 12 P.M., 4 P.M.) for 30 days. Survival rate, cannibalism rate, average daily gain, specific growth rate, weight-length relationship, condition factor, consumption index, ingested protein, protein efficiency coefficient and digestive utilization coefficients were measured. Results: The specific growth rates (SGR) ranged between 2.25 +/- 0.165 and 2.58 +/- 0.115 with the best rate for the treatment containing 0% soy okara. The consumption index varied from 1.18 +/- 0.009 to 1.41 +/- 0.132 with the best index for the T3 treatment. Furthermore, the mortality rates were 0% for treatments containing 20% and 30% soy okara. The results indicate that it is possible to incorporate up to 30% soybean okara into the diet of Clarias gariepinus fry without hindering their zootechnical performance. The digestive protein utilization coefficients of the diets were calculated and are 95.12; 88.47; 92.21 and 90.37 for diets containing 0%, 10%, 20% and 30% soy okara respectively. Conclusion: The results demonstrate that among the different diets tested, treatment T2, containing 20% soy okara, proved to be the most favorable in terms of zootechnical performance. These results suggest that T2 treatment can be considered as a promising option for feeding Clarias gariepinus fries.

Effects of weaning time, light regime, and stocking density on growth, condition, survival, and cannibalism rates in northern pike (Esox lucius L.) larvae and early juveniles under intensive culture

In this study, three separate experiments were conducted to optimize the intensive larviculture of pike (Esox lucius L.) under different weaning times, light regimes, and stocking densities. In the first experiment, larvae were fed sequential combinations of live feed (LF), co-feeding with dry starter (DS), and only DS feed for 18 days as follows: 9 days LF followed by 3 days co-feeding and 5 days DS (group A); 6 days LF followed by 3 days co-feeding and 9 days DS (group B); 3 days LF followed by 3 days co-feeding and 12 days DS (group C); and DS alone for 18 days (group D). Fish fed LF had significantly higher growth rates than those fed a dry diet (p< 0.05). Extending the feeding period on LF resulted in a significantly higher growth rate (24.6% d−1), variability (13.5%), and heterogeneity (299.5% d−1) than fish fed a DS. In the second experiment, the effect of the light regime was assessed at eight different levels (L0:D24; L24:D0; L16:D8; L4:D4:L4:D4:L4:D4; L8:D4:L8:D4; L12:D12; L8:D16; and L4:D8:L4:D8). The growth and survival of the larvae increased with increasing light period. Groups exposed to complete light (L24:D0) and 16 h of light (L16:D8) exhibited significantly higher weight gain and specific growth rate (SGR, %) than the other groups. The highest survival was observed in fish reared with complete light (68.5 ± 4.5%) and an L8:D4:L8:D4 light regime (61.4 ± 5.2%). All larvae maintained under L0:D24 died during the experiment. The third experiment tested the effect of the fish density within four experimental groups: 10 ind L−1, 20 ind L−1, 40 ind L−1, and 80 ind L−1. Fish at densities of 20 and 40 ind L−1 had significantly higher weight gain and SGR (%) than those in the other groups. The highest survival was in fish reared with 20 ind L−1 density (72.5 ± 8.5%). Fish at densities of 10 and 80 ind L−1 showed significantly higher cannibalism rates than those in the other groups. These results indicated that weaning time, photoperiod, and stocking density play significant roles in early pike larval performance.

Efek warna cahaya terhadap tingkah laku dan kanibalisme pada benih ikan kerapu cantang (Epinephelus fuscoguttatus lanceolatus)

This research was experimental in nature which was carried out by observing the response and behavior of cantang grouper to the color of the light. The research was carried out by spreading food in containers with different colored lights. From the food spread in containers with different lights, we can see the response and behavior shown by the cantang grouper to each color of light. Apart from that, research was also carried out to determine the level of cannibalism and mortality rates in each container with different lights. This research is using experimental method. The research design used was a Completely Randomized Design (CRD), with 4 treatments and 3 replications using blue, yellow-green and no light. The research was carried out by measuring water quality 3 times a day, starting in the morning, afternoon and evening for 14 days of research. The conclusion of the research is that outside its natural habitat the best response and behavior is when living in a blue treatment container (treatment A). It is thought that in blue light the cantang grouper feels like it is in its natural habitat. Apart from that, blue light also reduces the level of cannibalism in cantang grouper fish compared to green and yellow light, and no light.
 
 Keywords: Light, cantang grouper, cannibalism, mortality, behavior.

The habitat quality paradox: loss of riparian forest cover leads to decreased risk of parasitism and improved body condition in an imperiled amphibian.

Amphibian declines are a global phenomenon but responses of populations to specific threats are often context dependent and mediated by individual physiological condition. Habitat degradation due to reduced riparian forest cover and parasitism are two threats facing the hellbender salamander (Cryptobranchus alleganiensis), but their potential to interact in nature remains largely unexplored. We investigated associations between forest cover, parasitic infection and physiology of hellbenders to test the hypotheses that physiological condition responds to infection and/or habitat degradation. We sampled 17 stream reaches in southwest Virginia, USA, on a year-round basis from 2013 to 2016 and recorded 841 captures of 405 unique hellbenders. At each capture we documented prevalence of two blood-associated parasites (a leech and trypanosome) and quantified up to three physiological condition indices (body condition, hematocrit, white blood cell [WBC] differentials). We used generalized linear mixed models to describe spatiotemporal variation in parasitic infection and each condition index. In general, living in the most heavily forested stream reaches, where hellbender density was highest, was associated with the greatest risk of parasitism, elevated neutrophil-to-lymphocyte (N:L) ratios and eosinophils, slightly lower hematocrit and lower mean body condition in hellbenders. All condition indices fluctuated temporally in a manner consistent with seasonal variation in hellbender metabolic demands and breeding phenology and were associated with land use during at least part of the year. Paradoxically, relatively low levels of forest cover appeared to confer a potential advantage to individuals in the form of release from parasites and improved body condition. Despite improved body condition, individuals from less forested areas failed to exhibit fluctuating body condition in response to spawning, which was typical in hellbenders from more forested habitats. We postulate this lack of fluctuation could be due to reduced conspecific competition or reproductive investment and/or high rates of filial cannibalism in response to declining forest cover.

Effects of Water Temperature and Salinity on the Growth and Survival of Hybrid Pufferfish Larvae (Takifugu obscurus♀ X T. rubripes♂)

Takifugu genus pufferfish are popular in East Asian countries such as Korea, Japan, and China, but they are avoided as aquaculture species due to slow growth, high cannibalism rates, and susceptibility to diseases. Hybridization is considered one of the most important and efficient breeding methods for aquatic animals, and recent studies have been conducted on hybridization. This study compared optimal water temperature and salinity ranges for hybrid pufferfish by examining three water temperature conditions (15, 20, and 25°C) and five salinity conditions (0, 3, 10, 25, and 33 psu). The hatching rates of hybrid pufferfish embryos were 65.3%, 63.5%, and 67.7% at 0, 3, and 10 psu, respectively, while all embryos died at 25 and 33 psu. Hybrid pufferfish larvae had the highest survival rates at 20°C, and growth rates increased with rising water temperatures. In the salinity experiment, survival rates were 86.0%, 85.0%, 88.0%, and 88.5% at 3 psu, 10 psu, 25 psu, and 33 psu conditions, respectively, with the highest growth observed at 25 psu conditions. Hybrid pufferfish embryos showed good survival in freshwater, but all died in seawater. However, larvae showed good survival and growth in seawater, while all died in freshwater. Therefore, rearing hybrid pufferfish embryos seem suitable at salinities of 10 psu or lower, and increased resistance to salinity was observed in hybrid pufferfish after hatching, indicating that rearing under various salinity conditions ranging from 3 to 33 psu may be feasible.

Intraguild predation and cannibalism between two co-occurring ladybird species (Coccinella septempunctata and Menochilus sexmaculatus): A fight for supremacy

<p><em>Coccinella septempunctata</em> L. (<em>C7</em>) and <em>Menochilus sexmaculatus</em> (Fabricius)<em> (Ms) </em>are aphidophagous ladybirds (Coleoptera: Coccinellidae), which dominates the ladybird fauna of Oriental region. Since these species co-occur and are highly predaceous on various aphids, it was hypothesized that in the scarcity or absence of aphids, i.e., extraguild prey, one ladybird species will start attacking and killing the other one, which will endanger their co-occurrence. Thus, we aim to determine, which ladybirds’ larvae will subdue the other; their attack rates (rate at which a superior individual attacks the inferior one), escape rates (rate at which an inferior individual escapes from the attack of superior one) and predation rates (rate at which a superior individual eats the inferior one) were investigated, as they indulged in cannibalism and intraguild predation. Larvae of <em>C7</em> were slightly bigger and heavier than those of <em>Ms</em>, thereby they gained a slight competitive advantage. This enabled <em>C7 </em>a better attacker and an escapist when confronted with larvae of <em>Ms</em> in a predatory guild, which resulted in lesser larval mortality due to intraguild predation by <em>Ms </em>larvae. However, <em>C7 </em>successfully preyed upon the larvae of <em>Ms. </em>The highest rate of cannibalism and intraguild predation was executed by <em>C7 </em>which made it a potent cannibal and an intraguild predator. Despite being outplayed by <em>C7</em>, the inferior <em>Ms</em> larvae didn’t suffer much loss during the intraguild combat due to their armoured morphological features in the form of spines and rough texture. This is the reason why <em>Ms</em> still exists as the second most commonly occurring ladybird in the field.</p>

GROWTH PERFORMANCE OF CLARIAS GARIEPINUS (BURCHELL, 1822) REARED IN GLASS AQUARIA UNDER DIFFERENT LIGHT CONDITIONS

Growth performance of Clarias gariepinus (Burchell, 1822) reared in glass aquaria under different light conditions was studied from hatching to 75 days post hatching (dph). The objective was to generate baseline data/information on artificial seed production of catfish under different rearing conditions. Eggs of C. gariepinus were hatched at three photoperiods in complete darkness (DD), full illumination (LL) and control 12 h dark and 12 h light (normal) growth conditions. African catfish showed higher survival rates in the dark conditions than in the light conditions. The larvae also showed significantly increased cannibalistic behavior under light condition. Highest survival rate (92.8%) was observed for C. gariepinus that grew under darker condition. The higher activity of C. gariepinus under dark conditions resulted in reduced rates of cannibalism and higher rates of survival than light conditions. The sequence of development and ossification was faster in dark group by a day than in the light and by two days in the control group, whereas light group faster by a day compared to the control group. Some of the organ development and appearance completed within an hour gap and it was difficult to look sequential ontogeny on dark growth conditions. Dark growth conditions may be recommended as a best, effective technique for intensification of production of C. gariepinus, as it improves catfish survival rates.

Growth and survival rate of blue swimming crab enlargement in the south coast of Pamekasan, Madura Island

Indonesia has fishery commodities favoured by the world market, especially blue swimming crab fisheries. Fishing activities that continue to increase have caused the blue swimming crab population in nature tend to decrease. Therefore, it is necessary to develop aquaculture in ponds and coastal waters. However, blue swimming crab enlargement has technological constraints that have yet to be widely known by the wider community. The study aimed to determine the survival rate of blue swimming crabs in coastal waters using ponds conducted in Pamekasan, East Java. The parameters measured were the width of the blue swimming crab’s carapace using a ruler and the growth of the blue swimming crab’s weight using a digital scale. The experimental results on blue swimming crabs obtained an absolute growth of 9.8 cm and a survival rate of 3.96%. The high rate of cannibalism in blue swimming crabs can indicate the cause of the low survival rate of blue swimming crabs. This research is expected to increase the choice of blue swimming crab enlargement to reduce the pressure of catches and be another alternative to reduce the level of blue swimming crab fishing in nature.

Evaluation of cannibalism during hatchery rearing of tiger muskellunge crosses

AbstractObjectiveJuvenile tiger muskellunge (Northern Pike Esox lucius × Muskellunge E. masquinongy) are cannibalistic, which can lead to a substantial reduction in yields within an intensive culture environment. Utah hatcheries have traditionally raised the female Northern Pike × male Muskellunge cross, and hatchery managers are reluctant to raise the female Muskellunge × male Northern Pike due to a perceived difference (increase) in cannibalism rates when rearing this cross.MethodsWe raised both crosses in replicated microcosms to evaluate the differential cannibalism between them. All rearing conditions were consistent among treatments and replicates. We evaluated weekly cannibalism using generalized linear regression models.ResultAfter 6 weeks, we found that the female Muskellunge × male Northern Pike cross offspring were significantly more cannibalistic than juveniles from the female Northern Pike × male Muskellunge cross, with total cannibalism across the 6‐week period estimated at 27% and 5.6%, respectively.ConclusionWe documented a previously unreported difference in tiger muskellunge cross cannibalism rates. Choosing the female Northern Pike × male Muskellunge cross could substantially increase survival of juvenile tiger muskellunge in aquaculture facilities.

Year-Round Spawning, Filial Cannibalism, and Embryonic and Larval Development of the Coral Reef Fish Orchid Dottyback, Pseudochromis fridmani

Aquaculture of marine ornamental fish could potentially reduce the fishing pressure on wild stocks by the global aquarium trade, but its expansion is often constrained by the limited understanding on the biology and early life history of candidate species. The orchid dottyback Pseudochromis fridmani is a valuable and popular marine ornamental fish, but scientific reports on its baseline biology, especially the egg filial cannibalistic behaviour, are scarce. The present study documented key aspects of reproductive biology and early ontogeny of P. fridmani in captivity, including reproductive behaviour, patterns of spawning and filial cannibalism throughout a 12-month period by seven pairs of brood fish, as well as the embryonic and larval development. The results showed that the captive spawning of the broodstock pairs generally occurred every 5–11 days, most commonly every 6–8 days, throughout a year. Despite feeding the brood fish to satiation throughout the data collection period, the average monthly rate of egg filial cannibalism reached 55 ± 37%, but the cannibalism frequency appeared to be pair-specific. The egg incubation duration was approximately 96 h at 27 ± 1 °C, and the development of embryos from cleavage, blastula, gastrula, and segmentation to the pharyngula stage is herein described in detail. The newly hatched P. fridmani larvae possessed important structures and organs for first feeding, including pigmented eyes, developed jaws, and a straight-tube gut. The 0 to 14 days post-hatching (DPH) period appeared to be an important larval stage, as P. fridmani larvae were observed to complete major changes in morphology, gut development, and phototactic behaviour by 14 DPH. Under the culture conditions of this study, the earliest transition to the juvenile stage was observed on 31 DPH, and the majority of fish became juveniles by 56 DPH. The results of this study inform baseline aquaculture production protocols and direct future research, particularly to reduce filial cannibalism through broodstock management and to improve larval culture through supporting the early ontogenetic development of P. fridmani. Additionally, these findings form a foundation for further studying the biology and ecology of P. fridmani in the wild.

COMBINED IMPACT OF CANNIBALISM AND ALLEE EFFECT ON THE DYNAMICS OF A PREY–PREDATOR MODEL

In ecological environment, Allee effect is one of the important factors which cause significant changes to the system dynamics. In this paper, using the theory of dynamical systems, we analyze a variation of a standard cannibalistic two-dimensional prey–predator model with Holling type-II functional response in the presence of both weak and strong Allee effects. We have analyzed the impact of strong and weak Allee effects on the dynamics of a cannibalistic system, knowing the dynamics of the cannibalistic model without Allee effect. We have deduced that in the presence of cannibalism, both strong and weak Allee effects generate bistability between equilibrium points. For strong Allee effect, bistability occurs between trivial equilibrium point and predator-free equilibrium point as well as between trivial and coexistence equilibrium points. But for weak Allee effect, bistability occurs only between coexistence equilibrium points. We also pointed out that the cannibalistic system without Allee effect exhibits tristability among the trivial equilibrium point, coexistence equilibrium point having low prey concentration and coexistence equilibrium point having comparatively high prey concentration. But in the presence of strong Allee effect, cannibalistic system experiences tristability among trivial and two other stable coexistence equilibrium points. By a comprehensive bifurcation analysis, we have observed that Allee effect enriches both the local and global dynamics of the system. Here, we have reported all possible codimension-one and codimension-two bifurcations extensively by choosing cannibalism, Allee effect and predator natural death rate as the bifurcation parameters. In the analysis of bifurcations, we have explored the existence of transcritical bifurcation, saddle-node bifurcation, Hopf bifurcation, Bogdanov–Takens bifurcation and Bautin bifurcation. Our analytical findings are validated through exhaustive numerical simulations. Finally, we have reported a comparative study between the impacts of strong and weak Allee effects on the dynamics of the cannibalistic system.

A Binary Black Widow Optimization Algorithm for Addressing the Cell Formation Problem Involving Alternative Routes and Machine Reliability

The Cell Formation Problem (CFP) involves the clustering of machines to enhance productivity and capitalize on various benefits. This study addresses a variant of the problem where alternative routes and machine reliability are included, which we call a Generalized Cell Formation Problem with Machine Reliability (GCFP-MR). This problem is known to be NP-Hard, and finding efficient solutions is of utmost importance. Metaheuristics have been recognized as effective optimization techniques due to their adaptability and ability to generate high-quality solutions in a short time. Since BWO was originally designed for continuous optimization problems, its adaptation involves binarization. Accordingly, our proposal focuses on adapting the Black Widow Optimization (BWO) metaheuristic to tackle GCFP-MR, leading to a new approach named Binary Black Widow Optimization (B-BWO). We compare our proposal in two ways. Firstly, it is benchmarked against a previous Clonal Selection Algorithm approach. Secondly, we evaluate B-BWO with various parameter configurations. The experimental results indicate that the best configuration of parameters includes a population size (Pop) set to 100, and the number of iterations (Maxiter) defined as 75. Procreating Rate (PR) is set at 0.8, Cannibalism Rate (CR) is set at 0.4, and the Mutation Rate (PM) is also set at 0.4. Significantly, the proposed B-BWO outperforms the state-of-the-art literature’s best result, achieving a noteworthy improvement of 1.40%. This finding reveals the efficacy of B-BWO in solving GCFP-MR and its potential to produce superior solutions compared to alternative methods.

Sibling cannibalism in the false widow spider is dependent on spiderling density and the reliable availability of fresh prey

AbstractAdult female spiders lay batches of eggs in silken egg sacs, and after hatching, the spiderlings live for transient periods in their mother's web before dispersing. Sibling cannibalism is frequently observed among spiderlings of many species under conditions of food deprivation. Here, we conducted assays in small Petri dishes with different densities of newly hatched (second instar) spiderlings of the false widow spider, Steatoda grossa, using a split‐clutch design. Prey (freshly killed fruit flies) availability was manipulated both numerically and temporally. Offspring from 10 different females were separated as siblings into densities of two, four, or eight spiderlings per Petri dish and these were provided with either 0 flies (starvation control), two flies, four flies, or eight flies that were replenished weekly or every 3 weeks. A further control was conducted with solitary spiderlings in Petri dishes deprived of flies. The number of surviving spiderlings per Petri dish was counted every 3 days until only one remained (or until death of the solitary spiderling). Our results show that the rate of cannibalism was lower with increasing spiderling density and when fresh flies were replenished more frequently, whereas the number of flies that were provided did not affect cannibalism. In S. grossa, juvenile cannibalism occurs primarily under conditions of extreme food limitation, although in synanthropic habitats where the spider is abundant, it may be an adaptive strategy owing to the potential scarcity of prey. Under certain conditions, cannibalism in spiderlings is adaptive by eliminating competitors and providing nutrient‐rich food.

Suboptimal macronutrient ratios promote cannibalism in a generalist herbivore (Trichoplusia ni)

Abstract Discretional cannibalism is a widespread phenomenon among lepidopteran herbivores. Herbivores encounter variation in dietary nutrient quality when foraging, which alters feeding behaviour, as well as population‐ and trophic‐level dynamics. For example, plant resistance traits directly influence feeding patterns in insect herbivores through reduced consumption of plant tissue and increased rates of cannibalism. However, the effects of dietary composition, in particular unbalanced macronutrient ratios, on driving cannibalism remain unknown. We examined the effects of unbalanced macronutrient ratios on cannibalism in the generalist caterpillar Trichoplusia ni using an artificial diet experiment with varied ratios of two important macronutrients: protein and carbohydrates. We quantified cannibalistic behaviour from the second instar to pupation and measured survival among cannibals and non‐cannibals to understand the long‐term and short‐term costs and benefits of cannibalism. Caterpillars in high carbohydrate, low protein treatments cannibalised 20% more than the optimum control diet treatment, whereas herbivores in high protein, low carbohydrate treatments cannibalised 33% more than herbivores reared on the optimum macronutrient diet treatment. Survival of cannibals in macronutrient‐deficient diet treatments was 10.4%, compared with 76.9% for cannibals in the optimal macronutrient diet treatment. While previous work demonstrates the importance of induced chemical defence in promoting shifts to cannibalism, our results indicate that unbalanced macronutrient ratios can also promote cannibalism in insect herbivores. We propose that understanding how unbalanced macronutrient ratios drive cannibalism yields insight into how dietary quality, including both plant resistance traits and plant nutrients, influences behavioural plasticity and mediates plant–herbivore interactions.