Correlating gene expression with larval competence and the effect of age and parentage on metamorphosis in the tropical abalone Haliotis asinina

The non-geniculate crustose coralline alga (CCA) Mastophora pacifica can induce the metamorphosis of competent Haliotis asinina (Vetigastropoda) larvae. The ability to respond to this natural cue varies considerably with larval age, with a higher proportion of older larvae (e.g. 90 h) able to metamorphose in response to M. pacifica than younger larvae (e.g. 66 h). Here we document the variation in time to acquisition of competence within a larval age class. For example, after 18 h of exposure to M. pacifica, approximately 15 and 36% of 84 and 90-h-old H. asinina larvae had initiated metamorphosis, respectively. This age-dependent response to M. pacifica is also observed when different aged larvae are exposed to CCA for varying periods. A higher proportion of older larvae require shorter periods of exposure to CCA than younger larvae in order to initiate metamorphosis. In this experiment, as in the previous, a small proportion of young larvae were able to respond to brief periods of CCA exposure, suggesting that they had developed the same state of competency as the majority of their older counterparts. Comparisons of the proportions of larvae undergoing metamorphosis between families reveals that parentage also has a significant (P < 0.05) affect on whether an individual will initiate metamorphosis at a given age. These familial differences are more pronounced when younger, largely pre-competent larvae (i.e. 66 h old) are exposed to M. pacifica, with proportions of larvae undergoing metamorphosis differing by as much as 10 fold between families. As these data suggest that variation in the rate of development of the competent state has a genetic basis, and as a first step towards identifying the molecular basis to this variation, we have identified numerous genes that are differentially expressed later in larval development using a differential display approach. Spatial expression analysis of these genes suggests that they may be directly involved in the acquisition of competence, or may play a functional role in the postlarva following metamorphosis.

Kierkegaard as a paradoxical therapist

The essential problem that Soren Kierkegaard is concerned with in his authorship is that of becoming a Christian. It is argued that Kierkegaard's authorial strategy reflects the principles of paradoxical psychotherapy. These principles indicate that both the psychological problem and its solution involve an ironic process. In the Kierkegaardian frame of reference, the situation of the immature self is paradoxical, and so is the pathway to full selfhood. The philistine and the aesthete attempt to secure autonomy and personal freedom through an external orientation. But the way to the self is inwards. Consequently, these personalities get caught in an ironic process. The further they push outwards, the further they move away from the locus of genuine selfhood and freedom. This immature form of life can only lead to a loss of self and the associated experience of despair. Paradoxically, Kierkegaard advocates the choice of despair as the way to find oneself in God.