Concanavalin A-Induced Morphological Changes and Its Binding Sites in Starfish Follicle Cells as Revealed by Electron Microscopy

Concanavalin A (Con A) stimulates the production in starfish follicle cells of 1-methyladenine, a hormone which induces oocyte maturation. We have therefore investigated Con A-induced morphological changes and Con A-binding sites in the follicle cell using native Con A and horseradish peroxidase- or ferritin-labeled Con A (HRP-Con A, Fer-Con A). After isolated follicle cells were incubated with Con A (1 mg/ml), vacuoles, the Golgi complex and multivesicular body-like organelles (MVBs) became prominent in most of the cells. After follicle cells were prefixed and then incubated with Fer-Con A for 60 min, tagged ferritin was diffusely and randomly distributed as single or small clustered particles on the cell surface. The incubation of isolated follicle cells with Fer-Con A for 10 min before fixation resulted in numerous ferritin particles localized along the internalized membrane, and also in vacuoles, MVBs and small lysosome-like structures. After 60 min incubation with Fer-Con A, ferritin was further located in large lysosome-like structures and in vesicles near and in the Golgi area as well as in the organelles described above. HRP-Con A binding sites were also observed in vacuoles and MVBs of the intact cells.
These results suggest that Con A binds at first to the cell surface and causes rapid internalization and that membrane-bound Con A is easily endocytosed into vacuoles, MVBs and lysosome-like structures, and is later incorporated in some vesicles in the Golgi area.     

Tea leaf peroxidase--Isolation and partial purification

Tea leaf peroxidase occurred as the insoluble form in a homogenate.A large part of the peroxidase from tea leaves was solubilizedin a homogenate by adding Tween-80. After fractionation by 0.3saturation with (NH₄)₂SO₄ and filtration of the homogenate througha Sephadex G-25 column, specific activity of the peroxidasein the effluent increased about 25 times. Crude peroxidase wasfractionated into six components; A-l, A-2, B-l, B-2, B-3 andC, by DEAE- and CM-cellulose column chromatography. The fractionsshowed different mobilities on disc gel electrophoregram atpH 4.2. An isoelectric focusing experiment indicated that pivalues of the A-l and A-2 components are 5.4 and 5.0, repsectively. ¹ Present address: National Institute of Agricultural Science,Ministry of Agriculture and Forestry, Nishigahara, Kita-ku,Tokyo, Japan. (Received October 19, 1970; )     

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.     

Effect of island geological age on the arthropod species richness of Azorean pastures

Species richness of six pasture arthropod assemblages (total arthropod species, total herbivore species, sucking and chewing herbivores, total predatory species and spiders) were regressed against several geographical variables (area, distance from the nearest mainland, maximum elevation and geological age of the islands) of three Azorean islands (S. Maria, Terceira and Pico). The species were sampled by the fixed-quadrat size sampling method and the results obtained are consistent with the geological age hypothesis, i.e. the species richness of the six indigenous arthropod assemblages increases with the geological age of the islands, both at local and regional scales. Higher values of indigenous and endemic species richness were consistendy found on the older island (S. Maria), and the lowest values on the most recent island (Pico). Moreover, when considering the age of Faial (an older island probably once connected with Pico) as a estimate of the age of Pico, correlations between species richness and island age were improved, thereby strengthening the relationship. The older island (S. Maria) has more specialized herbivores and a greater proportion of herbivores in relation to predatory arthropods. Ecological and biogeographical studies in the Azores should take into account the effects of the time each island has been available for colonization and evolution.