Life history traits of the exotic freshwater snail Melanoides tuberculata Müller, 1774 (Gastropoda, Thiaridae), and its sensitivity to common stressors in freshwaters

Aim In the present study has analyzed several aspects of the life history traits of Melanoides tuberculata, an exotic species, under laboratory conditions, and its response to some stressors has also been applied. Methods Sensitivity to two toxic substances was tested. The mollusks were collected and cultured in the laboratory under controlled conditions of temperature of 25 ± 1 °C and ad libitum food regime. Growth rates and biomass were experimentally obtained and the individual growth curve obtained. Results The experiment lasted 287 days and the maximum shell lengths registered was 11.67 mm. The growth curve indicated a rate of 3.98 year-1 and a maximum theoretical length of 10.61 mm. The mean post-embrionary development time until first reproduction was 275 days and the size of the primipara was 10.13 mm. An accelerated growth of juveniles was observed with fast increase in the shell length until sexual maturity, but growth rate decreased afterwards as more energy was devoted to reproduction. Under the combination of 25 °C and fed on alternate days, M. tuberculata had a slow growth and a long-life expectancy under laboratory conditions. The tolerance of this mollusk to temperature as a stressor ranged between 16 °C and 37 °C, being the optimum temperature situated between 29 °C and 34 °C. The LC(I)50-24h for reference substances were: 0.70 g L-1 for KCl and 9.05 g L-1 for NaCl. Conclusion Based on these results, we can conclude that M. tuberculata is a species tolerant to temperature and salinity, what partially explains to accordance to its wide and rapid dispersion throughout tropical waters.

Objective Outcome Evaluation of the Project P.A.T.H.S. in Hong Kong: Findings Based on Individual Growth Curve Models

The Tier 1 Program of the Project P.A.T.H.S. (Positive Adolescent Training through Holistic Social Programmes) is a curricular-based program that attempts to promote positive youth development in Hong Kong. In the second year of the Full Implementation Phase, 20 experimental schools (n = 2,784 students) and 23 control schools (n = 3,401 students) participated in a randomized group trial. Analyses based on linear mixed models via SPSS showed that participants in the experimental schools displayed better positive youth development than did participants in the control schools based on different indicators derived from the Chinese Positive Youth Development Scale. Differences between experimental and control participants were also found when students who joined the Tier 1 Program and perceived the program to be beneficial were employed as participants of the experimental schools.

Childhood personality pathology: Dimensional stability and change

Studies on the developmental course of personality disorders have suggested that adult personality disorders enclose both features with a natural plasticity over time, as well as stable components represented by underlying trait dimensions. The current study broadens this dimensional stability perspective toward an earlier developmental stage, and describes with different indices of stability the longitudinal behavior of basic childhood maladaptive trait dimensions in a community sample of 477 Flemish children. The results underscore structural, rank-order, and within-person stability for the disagreeableness, emotional instability, introversion, and compulsivity dimensions and suggest a similar maturation principle as has been proposed for adults. Individual growth curve analyses indicate that children's maladaptive trait scores generally decrease as they grow older, with a smaller decline for high-scoring individuals. Childhood maladaptive traits and general psychopathology dimensions show similar longitudinal patterns in terms of shape and change over time, supporting a spectrum conceptualization of Axis I related pathology and personality disorder precursors at young age. The implications of these findings for a developmental perspective on dimensional conceptualizations of personality disorders are discussed.