The molecular mechanisms and factors affecting the feeding habits of silkworm (Lepidoptera: Bombyxidae)

Food is critical to the survival and development of insects. Bombyx mori (Lepidoptera: Bombycidae), a Lepidoptera model insect with economic significance, is a well-known oligophagous insect that mainly feeds on mulberry leaves. The feeding characteristics of this particular species provide an excellent model for studying the food selection of insect host plants. In recent years, there has been an increasing number of studies on the factors affecting the feeding of silkworms, especially with the development of molecular technology. Many mysteries have been gradually solved. This paper summarizes and discusses the factors that affect the feeding of silkworms, with a focus on the molecular mechanisms of silkworm feeding. It is hoped that this work will be helpful for further research on artificial diets for silkworms and disease control in lepidopteran insects.     

Daily movements and home range in mithrax spinosissimus (Majidae,Decapoda)†

Individuals of the spider crab Mithrax spinosissimus living in a canal in the Florida Keys were marked and their movements followed over a four‐month period. Individual home range size, extent of daily movement, and extent of day‐night movement were calculated. Although males and females moved similar distances when they did move from one crevice to another, males re‐located more frequently. There was no correlation between animal size and any measure of movement. Extent of daily movement was inversely correlated with spider crab density, especially for female crabs.     

The effects of hydrocarbon pollution from a two‐stroke outboard engine on the feeding behaviour of Lythrypnus dalli (Perciformes: Gobidae)

Feeding behaviour (time of attack on flake fish food) in Lythrypnus dalli was measured under pollution concentrations of 2.1 and 4.01mgl^?1 total extractable material produced by a two‐stroke outboard engine. The variance of the times increased in pollution versus control treatments for both concentrations. No significant difference was found between the mean times of the control and 2.1 mgl^?1 pollution treatments. A significant difference was found between the mean times of the control and pollution treatments for two different tests at 4.01 mgl^?1. The combination of the increase in mean time of food attack and the increase of variance indicates that pollution concentrations lower than LD50 levels change feeding behaviour, and thus may indirectly effect the survival of the organism.     

Relationships between unitary motor and sensory activity in the walking legs of cancer pagurus (Decapoda,Brachyura)†

Muscular tension and sensory activity in the flexor apodeme sensory nerve were recorded during stimulation of single motor afferents innervating the M‐C flexor. Muscular tension and unitary sensory activity both varied, depending upon the motor fiber stimulated. Differences in the abililty of individual motor fibers to elicit sensory activity were only partially accounted for by differences in tension development. Some tension afferent units were more readily excited by a muscular contraction elicited by one motor axon than they were by another, even when the tension elicited by the more effective motor fiber was less than that evoked by the less effective efferent.     

Surface EMG-force modelling for the biceps brachii and its experimental evaluation during isometric isotonic contractions

The aim of this study was to evaluate a surface electromyography (sEMG) signal and force model for the biceps brachii muscle during isotonic isometric contractions for an experimental set-up as well as for a simulation. The proposed model includes a new rate coding scheme and a new analytical formulation of the muscle force generation. The proposed rate coding scheme supposes varying minimum and peak firing frequencies according to motor unit (MU) type (I or II). Practically, the proposed analytical mechanogram allows us to tune the force contribution of each active MU according to its type and instantaneous firing rate. A subsequent sensitivity analysis using a Monte Carlo simulation allows deducing optimised input parameter ranges that guarantee a realistic behaviour of the proposed model according to two existing criteria and an additional one. In fact, this proposed new criterion evaluates the force generation efficiency according to neural intent. Experiments and simulations, at varying force levels and using the optimised parameter ranges, were performed to evaluate the proposed model. As a result, our study showed that the proposed sEMG–force modelling can emulate the biceps brachii behaviour during isotonic isometric contractions.     

Relations between apical structure and growth patterns in Pinus halepensis Mill,seedlings

Abstract

The process of primary growth in 2-year-old seedlings of 11 populations of Pinus halepensis Mill. is described. At the end of the first growing season one type of apical structure was observed: type-1, a tuft of primary needles placed close together, surrounding and protecting a meristematic apex.

At the end of the 2nd growing season, three types of apical structure were observed: type-1; type-2, a terminal winter bud; and type-3; a «bud» with characteristics of both type-1 and type-2.

Morphological observation along with an anatomical examination of the winter bud led to the conclusion that the definitive growth pattern in juvenile P. halepensis is monocyclic with a variable number of summer shoots. This growth pattern is reached by some P. halepensis populations in 3–4 years, by contrast, in other pine species two years are usually needed.

The populations studied differed both in growth potential (differences in number of cycles, ratio of first cycle to total growth, growth rates) and in the developmental stages of the apical meristem.

Four groups could be identified: (i) Morocco and Spain, (a limited growth, few cycles, a high ratio of 1st cycle to total growth, and growth in 2nd season almost entirely due to free growth); (ii) Algeria and Greece, (moderate to low growth, a large number of cycles, a low ratio of 1st cycle to total growth, and very early formation of apical structure with preformed primordia); (iii) Israel and Central Italy (a high growth, a large number of cycles, a medium ratio of 1st cycle to total growth, and early formation of apical structure with preformed primordia); (iiii) Greece, France and Italy, which was intermediate between group (i) and the other 2 groups.     

Methodology to Capture Children's Non-Dietary Ingestion Exposure Activities During Meal Events

During meal events, a child's food can be contaminated through contacts with objects and surfaces, and/or unwashed hands that have chemical residues, increasing ingestion exposure of contaminants for the child. This is not surprising, given that very young children eat more with the hands than adults, are active, and play with toys and objects while eating. In addition, children's unwashed hands and toys are commonly inserted into their mouths during meal events, increasing exposure. By observing children during their meal events, information can be gathered on the frequency and duration of contacts between objects, foods, and hands, and the sequence of events before the hands, foods, or objects are inserted into the mouth. This article describes the process of refining a videotaping and video-translation methodology to capture micro-level activity time series (MLATS), in order to better quantify total exposure for young children as a result of their behavior during meal events and cross-contamination of foods and hands. These MLATS can be seen as detailed activity patterns that provide useful data, along with transfer coefficients and environmental concentration to estimate exposures.