Territory strategy of the migratory Brown Shrike Lanius cristatus

Brown Shrikes Lanius cristatus are both transients and winter residents in Taiwan. Large numbers of birds crowd into the available habitat during the transient period, and the cost of maintaining territories changes greatly, depending on the number of shrikes present. This study examined how wintering Brown Shrikes adapt to the changing level of competition in territory establishment. About 24% of autumn transients arrived before any wintering birds, while 73% of wintering birds arrived during autumn transient time. The frequency of aggression recorded was significantly related to the number of birds seen along the transect line that day. Among ringed birds that returned during transient time, 80% returned directly to their previous territories, but some waited for the departure of transient birds before establishing territories. Territory compression occurred at high population densities. Departure from and arrival at the study area were frequent during the winter, but no birds moved territories within the study area. On average, 25% of ringed wintering shrikes returned to the study site in the subsequent years, while no transients returned. This low site tenacity may be. in part, a result of a high persecution rate along the migration route.     

External factors determining seasonal breeding in a subtropical population of the shore crab Pachygrapsus transversus (Gibbes, 1850) (Brachyura,Grapsidae)

Summary

Monthly samples of the shore crab Pachygrapsus transversus from two distinct annual periods showed that ovigerous females are present throughout the year in the population. However, the relative ovigerous abundance of specimens among sexually mature changes from less than 10% during the winter months to almost 80% in summer. Linear correlations for each year revealed that both temperature and photoperiod were positively associated with relative abundance of ovigerous females. Multiple regression analyses suggested that photoperiod was the main factor affecting breeding in this species. Timing of observed reproductive pattern may enhance larval survival because of particular oceanographic conditions in the study region and favor early juvenile development due to certain species-specific growth features.     

Effect of thermal acclimation on preferred temperatures in two mygalomorph spiders inhabiting contrasting habitats

Variations in the preferred temperatures during the rest periods of Grammostola rosea Walckenaer and Paraphysa parvula Pocock, two mygalomorph spiders occupying different habitats in central Chile, are analyzed. The former inhabits arid and semi‐arid lowland near plant communities, composed of shrubs (evergreens with small leathery leaves) and small trees; the latter is found in the central mountains of the Chilean Andes, above 2000 m.a.s.l. The preferred temperatures of these spiders at different times of day and exposure to cold (15 °C) and warm (25 °C) acclimation temperatures are compared. Body mass does not affect the preferred temperature of the larger spider G. rosea, although P. parvula, a spider with half of the body mass of G. rosea, shows a decrease in preferred temperature with body mass. This can be explained by a higher plasticity and thermal sensitivity of the smaller species as result of increased surface : volume ratio. The preferred temperature increases with the hour of the day under both acclimation conditions in P. parvula and in cold‐acclimated G. rosea, which is likely associated with crepuscular and nocturnal behaviour in both species. Grammostola rosea shows temperature preferences lower than those of P. parvula under both acclimation conditions. The increase of the acclimation temperature from 15 to 25 °C results in an increment of 2–3 °C in the preferred temperature of P. parvula but only 0.2 °C in that of G. rosea. Two contrasting lifestyle strategies are found: a small mygalomorph spider with phenotypic plasticity and adaptation to the fluctuating environment of high altitude, and a large mygalomorph spider with higher thermal inertia adapted to the more stable environment of lowlands.     

Antigenic Differences Among Epimastigotes,Amastigotes and Trypomastigotes of Trypanosoma cruzi*

Antigenic differences were demonstrated among trypomastigotes, amastigotes, and epimastigotes of Trypanosoma cruzi by the indirect fluorescent antibody method. Tests using cross-absorbed sera were included in the study.