Characterization of restricted area searching behavior following consumption of prey and non-prey food in a cursorial spider, Hibana futilis

Cursorial spiders are important predators of crop pests in a variety of agricultural systems. Their survivorship, growth, and fecundity can be enhanced by the consumption of extra‐floral nectar. We recently showed that Hibana futilis (Banks) (Araneae: Anyphaenidae) engages in restricted area search following contact with nectar, is stimulated by nectar aroma, and can learn to recognize novel aroma cues. Studies have shown that H. futilis is also responsive to solvent extracts of the eggs and scales of the corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), one of its primary prey insects in cotton. The arrestment behavior of cursorial spiders following consumption of prey and non‐prey food has not been characterized. In the present study, the responses of spiders were measured following consumption of prey (H. zea eggs) or non‐prey (droplets of dilute honey) food items and compared with individuals tested without food items. The food items were presented to the spiders in test arenas constructed from the top of an inverted glass Petri dish cover. A combination of real time and recorded observations were made via a video camera attached to a computer. The behaviors and movement patterns of individual spiders were analyzed with behavioral tracking software. Significant differences in the behaviors and motion paths of spiders tested in the different treatments were observed. Hibana futilis displayed significantly more dispersal behavior on a blank test arena, than on test arenas supplied with honey droplets or moth eggs. Likewise, spiders tested on the blank arena crawled faster and their motion paths were significantly less tortuous than those of spiders tested in the arenas with honey or moth eggs. Following consumption of both the honey droplets and moth eggs, spiders showed elevated levels of restricted area search and lowered levels of dispersal behavior. The analysis showed that these spiders could crawl rapidly for extended distances. Behaviors such as restricted area search and learned recognition of food‐based stimuli would facilitate efficient location of the food resources needed to maintain their high activity levels.     

Thermal behaviour of crustaceans

Specific thermoreceptors or putative multimodal thermoreceptors are not known in Crustacea. However, behavioural studies on thermal avoidance and preference and on the effects of temperature on motor activity indicate that the thermosensitivity of crustaceans may be in the range 0.2-2 degrees C. Work on planktonic crustaceans suggests that they respond particularly to changes in temperature by klinokinesis and orthokinesis. The thermal behaviour of crustaceans is modified by thermal acclimation among other factors. The acclimation of the critical maximum temperature is an example of resistance acclimation, while the acclimation of preference behaviour may be classified as capacity acclimation of some other function. In crustaceans, the use of the concepts stenothermy and eurythermy at the species level is questionable, and it is not possible to divide crustacean species into thermal guilds as suggested for fishes. Thermal preference behaviour contributes to fitness in different ways in different species, often by maximising the aerobic metabolic scope for activity. In crustaceans the peripheral nervous system seems to have retained the capacity for thermosensitivity and thermal acclimation independently of the central nervous system control of behaviour.     

The location of parasites within their hosts: The influence of host feeding and diet on the dispersion of adults of Nippostrongylus brasiliensis in the intestine of the rat

This paper is the first in a series to experimentally examine factors which determine the location of parasites within their hosts. Nippostrongylus brasiliensis is typically found one third of the way along the small intestine of the rat between days 7 and 12 of a primary infection. When rats were fasted for 2 days, N. brasiliensis became evenly distributed along the intestine and many individuals, mostly females, entered the caecum. Upon being fed again, the parasites were at their ‘normal site’ within 24 h. Experimental diets of α-cellulose, or simple dietary compounds caused the same re-distribution as did normal food. By sectioning the rat intestine when it was full of food and relating the dispersion of worms to the presence of intestinal contents, it was confirmed that N. brasiliensis is found amongst the intestinal contents of its host. The notion of a ‘site’ is critically discussed and the merit of ‘habitat’ is argued because the ‘site’ of N. brasiliensis would appear to be less a ‘place’ but rather a combination of environmental factors.     

The location of parasites within their hosts: The influence of surgical manipulation of the intestine and mesenteric blood supply on the dispersion of Nippostrongylus brasiliensis in the rat

In the early stages of a primary infection with N. brasiliensis in rats, adults are characteristically located about one-third of the distance anad of the pyloric sphincter. As one of a series of experimental investigations of this phenomenon, surgical manipulation of the site has been attempted. The normal site has been surgically removed, it has been reversed while keeping the blood system intact and the mesenteric arterial and venous supply has been locally restricted. In no case did surgical intervention significantly lower the number of adult parasites. In all cases there was a shift from the normal dispersion to one more orad. It has been conclusively demonstrated that there is no specific structural or physiological factor in the normal site of N. brasiliensis, which is critical for its survival. All results indicate as proposed in an earlier paper, that N. brasiliensis is a lumenal dweller and is most frequently recovered from the intestinal contents.     

Warm Microgradients Elicit Adaptive Behavior in Isotropically Cooled, Inert Populations of Oxytricha bifaria (Ciliophora, Hypotrichida)

In order to investigate the physiological potentialities of behaviorally inert Oxytricha bifaria, cooled from 24 to 9° C according to an already standardized protocol, a warm microgradient was created in the experimental chamber and the behavior of ciliates was analyzed both at the level of the passing warm wave front (dynamic microgradient), and, afterwards, when the thermal gradient stabilized (static microgradient). We monitored the general behavior of the experimental populations by means of (i) their centroid, (ii) the ethograms of single oxytrichas, and (iii) calculating the numerical indices and rates of their creeping tracks. It was found that (a) the population moves towards the heating source, (b) the oxytrichas react immediately to the thermal stimulus, (c) creeping forwards (d) at very high velocity (e) along uninterrupted looping tracks (f) according to precise mechanisms of positive/negative orthokinesis, thus orientating towards the environmental optimum. Moreover, (g) the ciliates accumulate in the warmest area, correcting their creeping by means of many specific behavioral patterns (the Side Stepping Reaction) once the gradient is stabilized. At 9° C, despite their inertness, the ciliates are still able to behave adaptively reacting immediately and orientatedly, once a directional factor (the thermal gradient) arises in an isotropic environment.