Interaction of intrinsic and extrinsic chemical cues in the behaviour of Bursaphelenchus xylophilus (Aphelenchida: Aphelenchoididae) in relation to its beetle vectors

Bursaphelenchus xylophilus, its host trees and beetle vectors represent an unusual ecological system. The fourth stage, dispersal juvenile (JIV) of B. xylophilus is a specialised life stage that must alter its response to a variety of chemical cues over time to properly enter and exit its beetle vector. Neutral storage (NS) lipid content is proposed as a modifier of nematode response to beetleand tree-produced volatiles. The chemotactic response of JIV to a variety of chemicals was tested and the lipid contents of JIV attracted to particular chemicals were quantified. Nematodes with the lowest NS lipid content were attracted to β-myrcene, a pine volatile, while nematodes with the highest NS lipid content were attracted to toluene, a beetle cuticular hydrocarbon. A rolling fulcrum model of the integration of intrinsic (NS lipid) and extrinsic (volatiles) cues is proposed to explain the behavioural ontogeny of JIV in relation to the beetle vector.

Associations between Behavioural Ontogeny and Habitat change in Clupeoid Larvae

The ontogeny of evasive behaviours was examined in Atlantic menhaden (Brevoortia tyrannus, Clupeidae) and bay anchovy (Anchoa mitchilli, Engraulidae), with supplemental data for scaled sardine (Harengula jaguana, Clupeidae). Predicted relationships between ecology and behavioural ontogeny were tested using the different patterns of inshore vs offshore habitat utilization displayed by these species. In two of the species, menhaden and anchovy, the roles of vision, mechanoreception, and audition in evasive behaviours were examined ontogenetically and compared to the morphological development of these sensory systems. Anchovy early larvae were more responsive to a predatory stimulus than were menhaden; sardine early larvae were intermediate in responsiveness. By the end of the larval period most individuals tested in all three species responded. These results matched the pattern predicted by larval habitat. Ontogenetic trends in reactive distance did not match predictions based on habitat for these species but instead appeared to be more dependent upon changes in sensory morphology. In menhaden, ontogenetic changes in responsiveness were more dependent upon neuromast proliferation and cephalic lateral-line canal formation, while in anchovy these behavioural changes were more dependent upon ontogeny of the retina. Auditory stimuli were not implicated for either menhaden or anchovy in responding to the stimulus used.

Relation Between Behaviour and Physiological Maturation in a Ponerine Ant

In the ponerine ant, Ectatomma tuberculatum, workers pass through successive functional stages over the course of their adult life. This behavioural ontogeny from brood care to foraging activity appears to be closely related to glandular changes. Intranidal workers have growing or mature ovaries, while extranidal workers have degenerated ovaries but a well-developed reservoir of the poison gland. Our study, which was based on individual marking and multidimensional analyses, evidenced that the behavioural differences recorded among workers of a same age class are related to at least one physiological parameter. It means that variations in the course of the functional stages as compared to a basic age polyethism, may be partly explained by physiological maturation. We suggested then to substitute the term of 'age polyethism' by a more appropriate one, such as 'maturation polyethism'.

A Note on the Scope of Developmental Behaviour Genetics

The behaviour genetic decomposition of individual differences has been presented as being irrelevant to the study of human behavioural ontogeny. This introduces two problems. First, the analysis of systematic differences constitutes the basis for most statistical models used in the social sciences. If, generally speaking, this type of analysis is uninformative regarding development, how then can one empirically investigate human development? Second, behaviour genetic analyses are the only way to arrive at meaningful statements regarding the contributions of heredity and environment to human development. If results thus obtained are irrelevant, it is impossible to say anything on the subject of heredity, environment, and human ontogeny that is both meaningful and informative. It is argued that developmental behaviour genetics should not be viewed as a theory of development, but rather as a method of testing certain well-defined hypotheses regarding the contributions of genetic and environmental influences to human development. Individual differences assessed at any point in time reflect developmental processes prior to that time-gene-environment models are in a very basic sense inherently developmental... (Loehlin, 1975, p.41). Obviously the finding of innate differences in behaviour does not illuminate the development of that behaviour in any way (Johnston, 1988, p. 623).

Behaviour and use of space by juvenile Columbian ground squirrels (Spermophilus columbianus)

The behavioural ontogeny of the Columbia ground squirrel (Spermophilus columbianus) was examined using livetrapped and marked individuals in a population in southwestern Alberta, Canada. Observations using scan and all-occurrence sampling recorded the activities and locations of individuals. Differences between sexes in the movement of juvenile squirrels were apparent after the first 10 days from emergence from the natal burrow. Males travelled further from the natal burrow, had larger home ranges, and shifted their activity centres more than did females. Females remained nearest their sisters and rates of play between sisters were the highest of all interacting pairs. Although there was no difference in the mean distance from the mother for males and females, females greeted their mothers three times more frequently than did brothers. The consequences of such different social and spatial experiences are discussed in light of female site fidelity and male dispersal.