Impact of Tail Loss on the Behaviour and Locomotor Performance of Two Sympatric Lampropholis Skink Species

Caudal autotomy is an anti-predator behaviour that is used by many lizard species. Although there is an immediate survival benefit, the subsequent absence of the tail may inhibit locomotor performance, alter activity and habitat use, and increase the individuals' susceptibility to future predation attempts. We used laboratory experiments to examine the impact of tail autotomy on locomotor performance, activity and basking site selection in two lizard species, the delicate skink (Lampropholis delicata) and garden skink (L. guichenoti), that occur sympatrically throughout southeastern Australia and are exposed to an identical suite of potential predators. Post-autotomy tail movement did not differ between the two Lampropholis species, although a positive relationship between the shed tail length and distance moved, but not the duration of movement, was observed. Tail autotomy resulted in a substantial decrease in sprint speed in both species (28–39%), although this impact was limited to the optimal performance temperature (30°C). Although L. delicata was more active than L. guichenoti, tail autotomy resulted in decreased activity in both species. Sheltered basking sites were preferred over open sites by both Lampropholis species, although this preference was stronger in L. delicata. Caudal autotomy did not alter the basking site preferences of either species. Thus, both Lampropholis species had similar behavioural responses to autotomy. Our study also indicates that the impact of tail loss on locomotor performance may be temperature-dependent and highlights that future studies should be conducted over a broad thermal range

The caudal regeneration blastema is an accumulation of rapidly proliferating stem cells in the flatworm Macrostomum lignano

Background: Macrostomum lignano is a small free-living flatworm capable of regenerating all body parts posterior of the pharynx and anterior to the brain. We quantified the cellular composition of the caudal-most body region, the tail plate, and investigated regeneration of the tail plate in vivo and in semithin sections labeled with bromodeoxyuridine, a marker for stem cells (neoblasts) in S-phase. Results: The tail plate accomodates the male genital apparatus and consists of about 3,100 cells, about half of which are epidermal cells. A distinct regeneration blastema, characterized by a local accumulation of rapidly proliferating neoblasts and consisting of about 420 cells (excluding epidermal cells), was formed 24 hours after amputation. Differentiated cells in the blastema were observed two days after amputation (with about 920 blastema cells), while the male genital apparatus required four to five days for full differentiation. At all time points, mitoses were found within the blastema. At the place of organ differentiation, neoblasts did not replicate or divide. After three days, the blastema was made of about 1420 cells and gradually transformed into organ primordia, while the proliferation rate decreased. The cell number of the tail plate, including about 960 epidermal cells, was restored to 75% at this time point. Conclusion: Regeneration after artificial amputation of the tail plate of adult specimens of Macrostomum lignano involves wound healing and the formation of a regeneration blastema. Neoblasts undergo extensive proliferation within the blastema. Proliferation patterns of S-phase neoblasts indicate that neoblasts are either determined to follow a specific cell fate not before, but after going through S-phase, or that they can be redetermined after S-phase. In pulse-chase experiments, dispersed distribution of label suggests that S-phase labeled progenitor cells of the male genital apparatus undergo further proliferation before differentiation, in contrast to progenitor cells of epidermal cells. Mitotic activity and proliferation within the blastema is a feature of M. lignano shared with many other regenerating animals

Retest effects in operational selection settings: Development and test of a framework

This study proposes a framework for examining the effects of retaking tests in operational selection settings. A central feature of this frame-work is the distinction between within-person and between-person retest effects. This framework is used to develop hypotheses about retest ef-fects for exemplars of 3 types of tests (knowledge tests, cognitive ability tests, and situational judgment tests) and to test these hypotheses in a high stakes selection setting (admission to medical studies in Belgium). Analyses of within-person retest effects showed that mean scores of re-peat test takers were one-third of a standard deviation higher for the knowledge test and situational judgment test and one-half of a standard deviation higher for the cognitive ability test. The validity coefficients for the knowledge test differed significantly depending on whether ex-aminees ’ test scores on the first versus second administration were used, with the latter being more valid. Analyses of between-person retest ef-fects on the prediction of academic performance showed that the same test score led to higher levels of performance for those passing on the first attempt than for those passing on the second attempt. The implications of these results are discussed in light of extant retesting practice. In employment settings, the Uniform Guidelines on Employee Selec-tion Procedures (1978) state that organizations should provide a reasonable opportunity to test takers for retesting. Hence, most organizations in the private and public sector have installed retesting policies in promotion and hiring situations (e.g., Campbell, 2004; McElreath, Bayless, Reilly, & Hayes, 2004). In the educational domain, the Standards for Educational and Psychological Testing (APA/AERA/NCME, 1999) state that retest op-portunities should be provided for tests used for promotion or graduation decisions. The opportunity for retesting is also mandated for tests used in making admission, licensing, or certification decisions. A previous version of this manuscript was presented at the Annual Convention of th