Analysing stable feature selection through an augmented marine predator algorithm based on opposition-based learning

Retrieving the relevant information from the high-dimensional dataset enhances the classification accuracy of a predictive model. This research critique has devised an improved marine predator algorithm based on opposition learning for stable feature selection to overcome the problem of high-dimensionality. Marine predator algorithm is a population-based meta-heuristics optimization algorithm that works on the ‘survival-of-the-fittest’ theory. Classical marine predator algorithm explores the search space merely in one direction, affecting its converging capacity while being responsible for stagnation at local minima. The proposed opposition-based learning nuances enhance the exploration capacity of marine predator algorithm and productively converges the model to global optima. The proposed OBL-based marine predator algorithm selects stable, substantial elements from six different high-dimensional microarray datasets. The performance of the proposed method is investigated using five predominantly used classifiers. From the result, it is understood that the proposed approach outperforms other conventional feature selection techniques in terms of converging capability, classification accuracy, and stable feature selection.     

Intelligent computing for numerical treatment of nonlinear prey–predator models

In this study, a new computing paradigm is presented for evaluation of dynamics of nonlinear prey–predator mathematical model by exploiting the strengths of integrated intelligent mechanism through artificial neural networks, genetic algorithms and interior-point algorithm. In the scheme, artificial neural network based differential equation models of the system are constructed and optimization of the networks is performed with effective global search ability of genetic algorithm and its hybridization with interior-point algorithm for rapid local search. The proposed technique is applied to variants of nonlinear prey–predator models by taking different rating factors and comparison with Adams numerical solver certify the correctness for each scenario. The statistical studies have been conducted to authenticate the accuracy and convergence of the design methodology in terms of mean absolute error, root mean squared error and Nash-Sutcliffe efficiency performance indices.     

A Leslie–Gower-type predator–prey model with sigmoid functional response

In this work, a continuous-time predator–prey model of Leslie–Gower type considering a sigmoid functional response is analysed. Using the MatLab package some simulations of the dynamics are shown. Conditions for the existence of equilibrium points, their nature and the existence of at least one limit cycle in phase plane are established. The existence of a separatrix curve dividing the behaviour of trajectories is proved. Thus, two closed trajectories can have different ω-limits being highly sensitive to initial conditions. Moreover, for a subset of parameter values, it can be possible to prove that the point (0,0) can be globally asymptotically stable. So, both populations can go to extinction, but simulations show that this situation is very difficult. According to our knowledge no previous work exists analysing the model presented here. A comparison of the model here studied with the May–Holling–Tanner model shows a difference on the quantity of limit cycles.     

Predator-induced diel vertical migration inDaphnia: Enrichment and preliminary chemical characterization of a kairomone exuded by fish

Planktivorous fish release a cue of an unknown chemical nature into the water that induces diel vertical migration inDaphnia as predator avoidance response. We used a bioassay to obtain information about the chemical nature of the kairomone. We present a method to enrich the cue from holding water of fish by sorbent extraction. The kairomone exuded byLeucaspius delineatus can be characterized as a nonolefinic low-molecular-weight anion of intermediate lipophilicity. The presence of amino groups in the molecule can be excluded, whereas hydroxy groups are essential for activity. Separation by HPLC yielded only one active fraction. The kairomones released byCarassius carassius andRutilus rutilus showed the same chemical characteristics, suggesting that the kairomones from different species of fish, sensed byDaphia, are very similar, if not identical.     

污染斑块上具有扩散的Lotka-Volterra系统的持续生存与绝灭

建立了2个斑块上种群扩散的捕食—食饵系统,研究了当其中一个斑块受到输入量存在极限值的外来毒素污染时,由于扩散的存在,使另一斑块上的种群也受到毒素的影响,讨论此时2个斑块上3种群的持续生存与绝灭.结果表明,当扩散存在且扩散率满足一定条件时,食饵种群和捕食者种群在未来时刻将全部灭绝;而当扩散率满足另一条件时,它们将持续生存,进而会影响斑块上的生物多样性.     

Chemically mediated associative learning: An important function in the foraging behavior ofMicroplitis croceipes (Cresson)

When experienced by contact with feces from hosts feeding on cowpeas, laboratory-reared females ofMicroplitis croceipes, a larval parasitoid ofHeliothis spp., orient and fly to odors of the same feces, whereas naive laboratory-reared females do not. Flight-tunnel studies revealed that associative learning occurs during female encounters with hosts and host products. When females antennate host feces, they learn to recognize the volatile odors associated with the feces. Females even can be conditioned to respond to novel and otherwise unattractive odors such as vanilla extract by exposure to these volatile substances in association with a water extract of the feces. They apparently link the volatile odors with a nonvolatile hostspecific recognition chemical found in the feces. The antennating stimulant, 13-methylhentriacontane, was found to be a valuable ingredient, apparently as a facilitator of the initial antennation and subsequent linkage of the volatiles to the nonvolatile host recognition cue.     

Alarm response by a plethodontid salamander (Desmognathus ochrophaeus): Conspecific and heterospecific “Schreckstoff”

The detection of chemical alarm cues plays an important role for predator avoidance in many taxonomic groups, but little is known about the presence of such chemical cues in adult or caudate amphibians. We investigated the response (i.e., aversion or nonaversion) to chemical cues from damaged salamander skin and mealworms (Tenebrio molitor) in the plethodontid salamander,Desmognathus ochrophaeus. Avoidance responses were demonstrated to skin extracts of both conspecific and heterospecific salamanders. However, salamanders (D. ochrophaeus) did not avoid heated conspecific skin, fresh conspecific viscera, fresh mealworm, or freshPlethodon richmondi skin extracts. These results indicate that chemical alarm cues are: (1) present in the skin ofDesmognathus salamanders, (2) not present in mealworm or the viscera ofDesmognathus salamanders, and (3) denatured or deactivated by heating. These results also suggest that an avoidance response to chemical cues from damaged conspecifics has adaptive value in predator avoidance in terrestrial as well as aquatic vertebrates.     

Population and sex differences in antipredator responses of breeding fathead minnows (Pimephales promelas) to chemical stimuli from garter snakes (Thamnophis radix andT. sirtalis)

We conducted a predator bite survey on a population of fathead minnows (Pimephales promelas) considered to be under substantial predation pressure by western plains garter snakes (Thamnophis radix). Scarring, due to failed predation attempts by garter snakes and crayfish (Orconectes virilis), was observed significantly more often in breeding males than in breeding females and nonbreeding minnows. Likely, territorial nest defense under the edges of rocks along the water's edge, a habitat occupied by crayfish and frequented by snakes, caused the breeding males to be differentially vulnerable to predation. Under controlled laboratory conditions, breeding males from this population exhibited an antipredator response to chemical stimuli from live snakes (T. sirtalis andT. radix) significantly more often than breeding female minnows from the same population and breeding minnows of both sexes from a population that was presumed to be under lower predation pressure from snakes.     

Olfactory responses of yellowfin tuna (Thunnus albacares) to prey odors: Chemical search image

Yellowfin tuna can detect and distinguish between odors of intact prey organisms, responding to odor quality of various prey rinses with different amino acid profiles. Chemical fractions of natural prey odors and synthetic mixtures of amino acids are less effective than whole natural rinses. Assuming uniform dilution, tuna can detect amino constituents of prey odors at about 10^–11 M. Intensity of the behavioral response is modified by hunger. Feeding experience with new prey causes a gradual shift to maximum responses to its odor. We propose that one of the functions of the tuna's olfactory system is to form chemical search images which focus food search behavior for specific prey. The search image is thought to be modifiable and to be induced by prevailing prey abundance, so as to optimize the predator's feeding efficiency.     

Ovipositional behavior of lesser peachtree borer in presence of host-plant volatiles

Reactions of lesser peachtree borer [Synanthedon pictipes (G&R)] to volatiles of peach wood, either natural or chemically fractionated, were observed. Mated females were stimulated by and responsive to such materials and deposited significantly more eggs on substrates, including unnatural hosts, that had been treated with aqueous mixtures of bark-canker materials. Stimulation to oviposit occurred even when the female was blinded, indicating the presence of chemical cues. Natural canker-bark extracts immediately stimulated ovipostion and for a few hours significantly increased the number of eggs laid. However, average fecundity was not increased. Antennectomy did not significantly decrease response to volatiles by gravid females, and alternate sites of such chemoreception were not located. Complex mixtures derived by solvent extraction, steam distillation, and volatiles trapping from bark, canker, and gum all had activity. Observations of insect behavior in outdoor cages and also in the laboratory indicated that visual, chemosensory, and mechanosensory receptors are involved in host finding and oviposition.Mention of firm or product names does not imply recommendation or endorsement by USDA over others not mentioned.