Egg size and form as taxonomic criteria in Diphyllobothrium (Cestoda, Pseudophyllidea)

The size and form (length, width, and length: width ratio) of eggs of Diphyllobothrium dendriticum, D. ditremum and D. latum vary considerably among individual worms within each species. The size of eggs varies with host species and a decrease in egg size with increasing intensity of infestation is indicated. The egg size of D. latum increases during the first 10-12 days of egg production. For single worm infections in golden hamsters the mean egg length and width of D. ditremum are significantly smaller than the corresponding means of D. dendriticum and D. latum, while D. latum has significantly wider eggs than D. dendriticum. As taxonomic characteristics, egg size and form may contribute to species delimitation at the population level. For identification at the individual level the best possible accuracy is about 80%. This accuracy is considerably reduced when variation in host species and intensities of infestations are introduced. Scanning electron microscope studies did not reveal any differences among eggs of the three species.     

Water and ion fluxes of abscisic acid-treated root systems of pear, Pyrus communis

Water and ion fluxes of intact root systems of Pyrus communis L. cv. Old Home × Farmingdale 97 immersed in a nutrient solution were determined at various pressures and temperatures. Water flux (J_v was normalized on the basis of initial flow rates of a root system after 30 min at 0.50 MPa and 25°C, expressed as the ratio Q_v. Q_v responded linearly to pressures between 0.20 and 0.62 MPa, implying a constant root hydraulic conductivity (L_p) within this range. Similarly Q_v was linearly related to temperatures between 7 and 35°C; however, large, rapid temperature changes resulted in a break of the Arrhenius plot of Q_v versus the reciprocal of temperature, Abscisic acid (ABA) from 2 × 10⁻⁶ to 10⁻⁴ M , applied to intact root systems, increased Q_v within 10–20 min, with the effect leveling off after 1.5 h. At a pressure of 0.50 MPa, ABA at 10_-4 M enhanced Q_v by 28%. The stimulation of Q_v was not due to the ethanol solvent since 0.13 or 1.33% ethanol decreased Q_v-, The osmotic potential of the xylem fluid was determined and was used to calculate total normalized solute flux. The results suggest that ABA-induced or ethano1-induced changes in Q_v were mainly due to changes in L_p and not to changes in ion transport to the xylem.     

The stabilization of locust cuticle

Cuticle from the metathoracic femur of adult locusts (Locusta migratoria) is characterized with respect to changes in water content and in protein extractability during maturation. The swelling behaviour and extractability of fully-sclerotized cuticle are compared to those of chemically-modified, unsclerotized cuticle.It is concluded that although dehydration may contribute to the stabilization of cuticle, it cannot account for the observed differences. The properties of mature cuticle can best be explained by the assumption that covalent cross-links are present between protein molecules.     

Space use and temporal partitioning of sympatric Tasmanian devils and spotted‐tailed quolls

Sympatric species can minimise interspecific competition by spatial avoidance or by altering their temporal activity to reduce encounter rates. The Tasmanian devil (Sarcophilus harrisii), the largest carnivorous marsupial, coexists with the smaller spotted‐tailed quoll (Dasyurus maculatus) in Tasmania, Australia. Quolls may be susceptible to interspecific competition from devils, because they utilise similar habitats, consume similar prey species and are displaced by devils at food sources. Such competition might cause quolls to spatially or temporally avoid devils. To investigate whether spatial or temporal avoidance occurred, we deployed GPS collars on sympatric devils and quolls and conducted a camera survey at a site in northwest Tasmania where the devil population was not affected by devil facial tumour disease. GPS tracking coincided with the lactation period when devils and quolls had young in dens and continued until weaning occurred. We found little spatial segregation of home range and core area placement between devils and quolls and among devils. Quolls showed more spatial segregation within the sexes than between them. Devils had larger home ranges than quolls. Male devils had larger home ranges than females, but there was no difference in home range size between the sexes of quolls. Females of both species travelled significantly further per night than did males. There was moderate temporal partitioning between the two species: devil activity peaked after dusk and devils remained active until the early morning, while quoll activity showed distinct peaks around dusk and dawn. In conclusion, quolls did not spatially avoid devils but moderate temporal partitioning occurred. It is plausible that quolls are active at different times of the diel cycle to reduce encountering devils, but further studies are needed to resolve the cause of this temporal partitioning.