Temperature Effect on the Photo-Accumulation and Phobic Response of Volvox aureus*

SYNOPSIS. The effect of temperature on photoaccumulation and photophobic response of Volvox aureus were studied. The algae exhibited positive photoaccumulation at room temperature and negative at low temperature. When stimulated with light of intermediate intensiy (～ 5 × 10³ lux), the phobic response of the algae consisted of a decrease in the frequency or the cessation of flagellar movement in the anterior cells. At room temperature, an increase in light intensity elicited the phobic response, whereas at low temperature a decrease in light intensity was the effective stimulus. The phobic response lasted only a few seconds. The positive and negative photoaccumulations of the algae could be explained by the brief cessation of flagellar movement in the anterior cells, elicited by an increase of stimulus light at room temperature or a decrease of stimulus at low temperature.     

Taxonomic identity of a galling adelgid (Hemiptera: Adelgidae) from three spruce species in Central Japan

Gall‐forming insects are commonly highly host‐specific, and galling species once thought to be oligo‐ or polyphagous are often found to represent a complex of host‐specific races or cryptic species. A recent DNA barcoding study documented that an unidentified species of the genus Adelges is a gall‐former associated with four spruce species (Picea bicolor, P. koyamai, P. maximowiczii, P. polita) as the primary hosts, with little genetic differentiation among insects on different host species. In this study, we investigated the morphology of this galling adelgid to determine its taxonomic identity. Morphological inspection of insects collected from three of the spruce species confirmed that this adelgid is a single galling species, and is identified as Adelges (Sacchiphantes) kitamiensis, which was previously known only from the secondary host. We described the gallicola adults of this species, as well as the first‐instar exules which are the offspring of gallicolae. Finally, we verified the taxonomic identity of this species and discuss its life cycle and host distribution.     

Rumen microbes and fermentation of wild sika deer on the Shiretoko peninsula of Hokkaido Island,Japan

A total of 32 wild Hokkaido sika deer (Cervus nippon yesoensis) were shot (13 in summer, nine in autumn and 10 in winter) in the Syari district, Shiretoko Peninsula of Hokkaido Island, Japan. The ingested foods, rumen fermentation parameters and microbes were determined to evaluate digestive strategy and food availability in each season. Ingested foods and ruminal characteristics greatly varied by season. Rumen digesta mainly comprised of graminoids in summer, graminoids and agricultural products in autumn, and bark and twigs in winter. Rumen pH showed seasonal differences (P<0.05) and was lowest in summer, highest in winter, and intermediate in autumn, reflecting the seasonal differences in ruminal concentration of total volatile fatty acids which were significantly lower (P<0.05) in winter than in summer and autumn. Acetate proportions were significantly higher in winter than in other seasons (P<0.05), while the opposite trend was seen in proportions of propionate and butyrate. Rumen ammonia levels showed significant seasonal differences (P<0.05), decreasing from summer to autumn to winter. Rumen protozoa levels in autumn and winter decreased to 28 and 10% of the levels observed in summer, respectively (P<0.05 for both). The rumen bacteria level in winter was lower (P<0.05) than that in autumn, but no difference was seen for the other seasonal comparisons. Gram negative cocci were present in significantly higher proportions in winter than in other seasons (P<0.05), while Gram negative curved rods were less frequently observed in winter (P<0.05). Based on these results, wild sika deer in this area are shown to survive with rumen microbial populations altered with the dietary conditions that vary greatly by season.     

MOLECULAR PROPERTIES AND DIFFERENTIATION OF ACETYLCHOLINESTERASE IN SEA URCHIN EMBRYOS*

The two molecular forms of acethylcholinesterase (EC 3.1.1.7) in sea urchin embryos were characterized by several physical methods. The sedimentation coefficients determined by sucrose gradient centrifugation are 7.6S and 10.6S. The Stokes radii determined by gel filtration are 65 Å and 91 Å. From these parameters, molecular weights were estimated as 190,000 and 380,000; the one is twice as large as the other. Both forms have similar electric property and buoyant density in a CsCl gradient. When the enzyme solution was concentrated, the 10.6S form became predominant. These results suggest that the two forms are monomer and dimer. The sea urchin enzymes resemble globular forms of acetylcholinesterase of the electric organ of fishes. The activity of the enzyme abruptly increases in post-gastrulation embryos. Inhibition of concomitant protein synthesis by a specific inhibitor, emetine, does not affect the increase in enzyme activity. The result suggests that post-translational processes may be involved in the differentiation of this enzyme in sea urchin development. The following sea urchins were used in the study: Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, and Dendraster excentricus.     

DOES COLCHICINE AFFECT AGGREGATION OF NORMAL AND TRANSFORMED BHK CELLS DIFFERENTLY?

The effect of colchicine and vinblastine on cell aggregation was studied, using BHK cells and their transformed derivatives (pyBHK cells). When cells were dissociated with EDTA and the assay was made in a Ca²⁺-containing medium, the aggregation of transformed cells was prevented by colchicine and vinblastine, whereas the aggregation of normal cells was unaffected. When a Ca²⁺-free medium was used for aggregation, neither type of cell was influenced by these drugs. BHK and pyBHK cells, dissociated by trypsin in the presence of Ca²⁺, can aggregate only in the Ca²⁺-containing medium and the aggregation of both cell types was equally prevented by colchicine and vinblastine. Based on these results, it was concluded that colchicine and vinblastine inhibited the Ca²⁺-dependent mechanism of cell adhesion, but not the Ca²⁺-independent one which occurs in the Ca²⁺-free aggregation medium.     

Isolation and characterization of new microsatellite markers from the Japanese flounder (Paralichthys olivaceus)

The isolation and characterization of eight polymorphic microsatellite loci from a Japanese flounder partial genomic library are reported. The eight markers isolated in this study were highly polymorphic and their positions on the linkage genome map of the Japanese flounder were determined. Therefore, they are useful for ecological studies of wild populations. These markers are more effective than other markers with no information of chromosomal locations.     

Variation and evolution of the complex life cycle in Adelgidae (Hemiptera)

The family Adelgidae is a small group of insects within Aphidoidea (Hemiptera). Adelgids are typically holocyclic with host‐alternation between the primary and secondary hosts, but some anholocyclic species persist either on the primary or secondary host. Like Aphididae, complexities and variation of adelgid life cycles are good models for understanding the evolution of complex life cycles. In this review, we outline the complex life cycles of adelgids, and current status and recent advances in adelgid life cycle studies. We also discuss the evolution of adelgid life cycles by comparing them to closely related aphid life cycles. A switch from holocycly to anholocycly on the primary host needs evolutionary innovations in gallicola behavior and reproduction. This radical evolution can be explained by mutations in a regulatory system that controls the sequence of gene sets producing phenotypes of one morph. In contrast, anholocycly on the secondary host consists of a series of exulis generations already existing in the holocycle. Thus, it may evolve by loss of primary‐host generations through extinction of the primary host, expansion beyond the geographical range of the primary host, or loss of male‐producing sexuparae that return to the primary host. Although the holocycle and its anholocyclic derivatives have been regarded as different species, morphological, ecological and genetic differences are too subtle to separate them into different species. The holocycle and its anholocyclic derivatives should not be split into different species without clearly identifiable morphological differences.