A new Bennettitalean trunk with unilacunar five-trace nodal structure from the Upper Cretaceous of Hokkaido, Japan.

A new species of Bucklandia is described based on a permineralized fossil trunk that was obtained from sediments of Upper Cretaceous age from Hokkaido, Japan. The quality of preservation is exquisite, and anatomical and morphological features are preserved at the cellular level. The specimen is clearly bennettitalean because of the cycadeoidean-type arrangement of vascular bundles in the petiole.

Molecular phylogeny and evolution of the deep-sea fish genus Sternoptyx.

A portion of mitochondrially encoded 12S and 16S ribosomal RNA genes were sequenced from all four valid species of the midwater deep-sea fish genus Sternoptyx (Teleostei: Sternoptychidae) and four sternoptychid outgroup taxa. Secondary structure-based alignment resulted in a character matrix consisting of 865 bp of unambiguously aligned, combined sequences of the two genes, which were subjected to phylogenetic analyses using the maximum parsimony and maximum likelihood methods. The resultant tree topologies from the two methods were congruent and supported by various tree statistics.

POPULATION STRUCTURE, LOCAL MATE COMPETITION, AND SEX-ALLOCATION PATTERN IN THE ANT MESSOR ACICULATUS.

Population-genetic structure and sex-allocation ratios were investigated for the ant Messor aciculatus, a species that conducts mass nuptial flights. An electrophoretic survey on two polymorphic loci revealed excessive homozygosities in two populations. Because inbreeding inside nests does not occur, the heterozygote deficiency may result from population subdivision rather than assortative inbreeding during nuptial flights.

Influence of food density on respiration rate of two crustacean plankters, Daphnia galeata and Bosmina longirostris.

The influence of food density on respiration rate was measured for two cladoceran plankton species, Daphnia galeata and Bosmina longirostris, over the range 0 to 2.5 mg C 1, using the modified Winkler technique in order to examine how this affects the respiration rate and whether the functional response is the same in the two species. The respiration rate for animals of equivalent body size did not differ significantly between the two species in the absence of food, but was significantly lower in Bosmina longirostris than Daphnia galeata at high food density.