Ophioglossaceae: a hypothetical archetype for the angiosperm carpel

KATO, M., 1990.Ophioglossaceae: a hypothetical archetype for the angiosperm carpel. In the light of a recently proposed phylogenetic position of Ophioglossaceae as living progymnosperms, a new archetype model for the angiosperm carpel is proposed. The three-dimensional construction of ophioglossoid fertile leaves with epiphyllous sporophores may be comparable to angiosperm carpels with adaxial ovules. The orientation of erect sporangia on young sporophores dorsiventrally facing the trophophores resembles that of anatropous ovuleS. Glossopterid fructifications may be interpreted as having the same construction as ophioglossoid leaveS. In the present hypothesis, the adaxial position of the ovules arose prior to the evolutionary process leading from gymnospermy to angiospermy. Previous hypotheses involving origins from Caytonia and Glossopteris are criticized.     

Differential responses to predator cues between two mosquito species breeding in different habitats

1. Natural selection favours females who can correctly assess the predation risk and hence avoid high‐risk oviposition sites and reduce the mortality rate of their offspring. In spite of the potential significance of such behaviour, relatively few studies have assessed the relationship between oviposition behaviour and predation risk. 2. The present study aimed to determine the sublethal effects of predators on oviposition site selection by gravid females, the foraging activity of larvae, and the life history traits of two mosquito species that breed in different habitats, Aedes albopictus Skuse (container breeder) and Culex tritaeniorhynchus Giles (wetland breeder). 3. Female C. tritaeniorhynchus avoided laying eggs at oviposition sites in the presence of a predator cue. In contrast, female A. albopictus laid eggs in both the absence and presence of the predator cue. 4. To examine the effects of predator cues on larval behaviour, experiments were conducted in the absence and presence of a predator cue. Although larval activity was lower in the presence of the predator cue than that in its absence in both species, C. tritaeniorhynchus responded to the predator cue more strongly than A. albopictus. Female A. albopictus that had been reared with caged predators exhibited an extended larval development period, whereas the adult C. tritaeniorhynchus reared in the presence of predators were smaller than those reared in their absence. 5. This finding might explain why C. tritaeniorhynchus avoid laying eggs in predator‐conditioned water, for example to increase the fitness of their offspring, but A. albopictus either cannot detect predator cues or are not sensitive to them.     

Meiosis-Reinitiation-Inducing Factor of Tetrahymena Functions Upstream of M-Phase-Promoting Factor

Reinitiation of meiosis (maturation) of amphibian Bufo and Xenopus oocytes can be induced if Tetrahymena extract is injected into them. The activity differed from M-phase-promoting factor, because action of the former factor on the induction of maturation was inhibited by treatment of the oocytes with cycloheximide. Activity of M-phase-promoting factor was not detected in Tetrahymena extract regardless of the presence of cdc2 homologues in the extract. However, cycloheximide-resistant-maturation-inducing activity appeared in the recipients, when the maturation was induced by injection of Tetrahymena extract. Immunoblots using antibodies against cdc2 showed that injection of Tetrahymena extract induced fast mobility of the recipient cdc2 in the presence of the recipient protein synthesis. The same mobility shift of the cdc2 was also induced when M-phase-promoting factor containing Xenopus oocyte extract was injected into immature oocytes or when the immature oocyte extract was treated with alkaline phosphatase. These results indicate that meiosis-reinitiation-inducing factor of Tetrahymena functions upstream of M-phase-promoting factor to induce dephosphorylation of the recipient cdc2. Tetrahymena cdc2 homologues also showed fast mobility when the Tetrahymena extract was treated with alkaline phosphatase. Preliminary experiments showed that the meiosis-reinitiation-inducing factor of Tetrahymena was a soluble protein.     

Spatial variability and major controlling factors of CO2 sink strength in Asian terrestrial ecosystems: evidence from eddy covariance data

Asian terrestrial ecosystems cover an extensive area characterized by a large variety in climates and ecosystem properties. The observations of ecosystem CO₂ flux in this area are increasing both in duration and spatial density, but no synthesis has yet been conducted. We surveyed CO₂ flux observation data obtained by eddy covariance methods at 49 sites in terrestrial Asia. The measurements at most sites (44 of 49) began after 2000. The net ecosystem uptake of CO₂ (NEE) varied greatly among sites and years and averaged −132.6±73.7, −250.1±206.1, and −180.1±361.7 g C m⁻² yr⁻¹, in boreal, temperate, and tropical Asia, respectively, and the coefficient of variation among sites increased from boreal to tropical Asia. The site-averaged annual NEE was correlated linearly with the mean annual temperature (T_air) and also correlated logarithmically with the precipitation. Multiple regression analysis and stepwise analysis indicated that photosynthetic active radiation (PAR) and T_air were the most significant predictors of the annual NEE. The study results suggest that Asian terrestrial ecosystems are currently significant net CO₂ sinks and that the sink strength is largely controlled by temperature, moisture, and light conditions.     

MAINTENANCE OF PHENOTYPIC PROPERTIES BY CHONDROCYTES CULTURED IN SUSPENSION*

Sternal chondrocytes obtained from 13-day-old chick embryos could be cultured in suspension without any mechanical agitation for 8 weeks. The cells in suspension retained all characteristics of chondrocytes when examined from morphological, histochemical and biochemical points of view. The floating cells were round in shape, rich in Golgi apparatus-associated vesicles. Each cell was covered with a thin coat of matrix showing metachromasia when stained with toluidine blue. Autoradiographic studies suggested an active synthesis of proteochondroitin sulfates by the individual floating cells. The biochemical analyses revealed that the floating cells continued to synthesize type H proteochondroitin sulfate and type II collagen, both of which are known to be characteristic products of differentiated chondrocytes.     

Role of photoperiod and temperature in seasonal morph determination of the butterfly Eurema hecabe

ABSTRACT. Environmental cues affecting seasonal morph determination of the pierid butterfly Eurema hecabe L. were examined in laboratory experiments and in the field. A sexual difference exists in the photoperiodic response for seasonal morph determination: in short days at 25C the proportion of the autumn morph is higher in females than in males, and as the rearing temperature is decreased the proportion of autumn morphs increases in both sexes. A 5C drop in temperature during the final larval stadium induces 100% autumn morph production in short-day animals. This increase in autumn morph production induced by temperature decrease explains the seasonal morph change of this butterfly occurring in early autumn in the field. The role of this sex-linked photoperiodic response is discussed as a seasonal strategy of reproduction.     

Three Groups of Teratocarcinoma Antigens Co-Expressed in the Visceral Endoderm are Located in Mutually Exclusive Sites in the Adult Kidney

Monoclonal rat antibodies were prepared against glycoproteins isolated from murine teratocarcinoma OTT6050 by affinity chromatography on Ricinus communis agglutinin (RCA). These antibodies defined three distinct groups of antigens (OR antigens) commonly expressed in teratocarcinoma cells and in restricted sites of the kidney. OR 17 antigen was a new glycoprotein antigen and the biochemical properties were different from any membrane glycoprotiens or matrix glycoproteins so far described in teratocarcinoma cells. In the kidney, the antigen was found in the glomerular basement membrane, and to lesser extent in the endothelium of the glomerulus and blood vessels. On the other hand, OR 8 antigen corresponded to "brushin" defined by conventional antibodies, while OR 4 and 19 antigens were carbohydrate antigens resembling "TC antigen". OR 8 antigen was detected in the tubular brush border and the epithelium of Bowman's capsule. OR 4 antigen was present in the collecting tubules and the thin loop of Henle. Although OR 19 antigen showed distribution similar to OR 4 antigen, there were genetic differences in the expression of the former antigen. All of the antigens were present in early postimplantation embryos of the mouse, notably in the visceral endoderm. These antigens are interesting subjects to study the mechanism of differentiation-dependent control of gene expression, since antigenic distribution is specialized as the result of differentiation.     

Wolbachia‐induced feminisation newly found in Eurema hecabe,a sibling species of Eurema mandarina (Lepidoptera: Pieridae)

1. Complete feminisation of genetic males into functional females, a unique case among insects, is known in Eurema mandarina (former Eurema hecabe Y type) that are infected with two strains of Wolbachia, wCI^Em and wFem^Em. 2. Here, we newly found that a proportion of wild‐caught E. hecabe (former E. hecabe B type) produced only female offspring. Cytogenetic observations indicated that individuals of E. hecabe displaying the all‐female trait were genetically male (i.e. feminisation). 3. Multilocus sequence typing analyses demonstrated that the feminised individuals of E. hecabe were infected with two Wolbachia strains, wCI^Eh and wFem^Eh, that were indistinguishable from wCI^Em and wFem^Em, respectively. 4. Even identical strains of Wolbachia can be regulated differently depending on the host genetic background. Therefore, we compared the infection densities and vertical transmission efficiencies of Wolbachia between feminised E. mandarina and E. hecabe, but detected no significant differences in these traits. 5. The possible routes by which the two Wolbachia strains have transferred between E. mandarina and E. hecabe are discussed.