Reproductive and subsocial behaviour in the ovoviviparous leaf beetle Gonioctena sibirica (Coleoptera: Chrysomelidae)

Abstract.

• 1 In the spring, females of the leaf beetle Gonioctena sibirica deposited larvae on the ventral surface of growing young leaves situated on the apical position of shoots of the willow Salix bakko.
• 2 The parent females remained with the larvae usually on the underside of the basal part of leaves, facing toward the base of shoots. When other arthropods approached, the females temporarily moved towards these intruders, showing aggressive behaviour such as swinging the body or stamping the legs. Many females remained with their larvae until the larvae grew into the final (fourth) instar. No female produced an additional brood in the field.
• 3 Broods from which parent females were experimentally removed suffered higher mortality than those in which females were left intact. Arthropods such as spiders and ants were observed preying on the larvae. In contrast, the survivorship of broods from which females were removed and intruders were excluded with a sticky substance applied to the base of twigs was not different from that of control broods. These results demonstrate that the main mortality factor of offspring is pedestrian arthropod predators and females physically repel the predators.
• 4 Potentially alternative reproductive strategies, such as producing a large number of offspring by iteroparity and/or larger brood(s) with less or no care, seem to be inhibited in G.sibirica by larval dependence on growing young leaves which are temporally limited and by ovoviviparity which may have limited brood size.

     

CYTOPLASMIC DYNEIN OF THE SEA URCHIN EGG I. PARTIAL PURIFICATION AND CHARACTERIZATION*

Cytoplasmic ATPase of sea urchin eggs was partially purified by ammonium sulfate fractionation, DEAE-cellulose chromatography, gel-filtration chromatography and sucrose density gradient centrifugation. The specific activity increased to 0.7 μmole/min/mg protein indicating 100 fold purification. The ATPase had a sedimentation constant of 12S and was highly specific for ATP. The enzyme fraction contained neither (Na, K)-ATPase, Ca-ATPase, oligomycin-sensitive ATPase, phosphatases, nor myosin. This cytoplasmic ATPase was inhibited by a low concentration of vanadate (V). Half-maximal inhibition was observed at a vanadate concentration of 1 μM at low ionic strength. The inhibition was almost totally reversed by addition of norepinephrine. The vanadate-sensitivity of cytoplasmic ATPase decreased with increasing KCl concentration. The activation by Mg²⁺ or Ca²⁺, and dependence of the activity on KCl concentration characteristic of dyneins from sea urchin sperm flagella and the embryonic cilia were observed with cytoplasmic ATPase. These results allowed the cytoplasmic ATPase to be classified as a dynein. In addition, this designation was reinforced by the fact that an oligomeric 23S form of cytoplasmic dynein was identified in the cytoplasm as well as in the isolated mitotic apparatus.     

Nature of the 1-Methyladenine-Requiring Phase in Maturation of Starfish Oocytes

Reinitiation of meiosis in starfish oocytes requires the continuous presence of 1-methyladenine (1-MeAde) in the surrounding medium for a definite period. The length of the 'hormone-dependent phase' (HDP) in Asterina pectinifera , which was defined as the time necessary for induction of 50% germinal vesicle breakdown (GVBD), was found to be about 11 min at 17°C, and 8 min at 20°C. Repeated treatments for shorter periods with 1-MeAde revealed that the action of this agent was cumulative, and that stable intermediate states between the unstimulated and fully stimulated levels existed during the HDP. Measurement of the stiffness of oocytes also demonstrated this stable intermediate state. Thus, there may be a factor(s) in the cytoplasm that accumulates continuously during the HDP and triggers GVBD when it reaches a critical level(s). When dithiothreitol (DTT) was used as an artificial maturation-inducing agent, the intermediate state was far less stable, suggesting a difference in the modes of action of 1-MeAde and DTT. Isotonic CaCl₂, the Ca²⁺ ionophore (A 23187) and methylxanthines, which are known to cause increase in intracellular Ca²⁺, had additive effects with 1-MeAde. These results suggest that part of the action of 1-MeAde is to release Ca²⁺ in the oocyte cytoplasm.     

PERIODIC CHANGES IN THE CONTENT OF PROTEIN-BOUND SULFHYDRYL GROUPS AND TENSION AT THE SURFACE OF STARFISH OOCYTES IN CORRELATION WITH THE MEIOTIC DIVISION CYCLE*

The sulfhydryl content of protein and the tension at the surface were measured for starfish oocytes from the first meiotic division to the cleavage stage. A cyclic change in both the protein-SH and the tension at the surface was found to accompany the division cycle, including the first and second meiotic divisions. It is concluded that the unequal meiotic divisions share the same character with the equal divisions of cleavage, with respect to changes both in the protein-SH and the tension at the surface.     

SPORULATION OF THE YEAST, HANSENULA SATURNUS: II. INFLUENCE OF CARBON-NITROGEN RATIO OF CULTURE MEDIUM

1. Several factors affecting sporulation of a wild yeast, Hansenulasaturnus, especially carbon sources and the carbon-nitrogenratio of sporulation medium were studied.
2. The sporulationis stimulated at a certain definite C/N ratioof glucose medium.
3. Several carbon sources such as ethanol, acetate, lactate,glycerol,succinate, glucose, gluconate and citrate are utilizedby theorganism both for growth and sporulation.
4. The numberof spores in an ascus depends on the C/N ratio ofthe medium.An increase in the ratio stimulates the yield of2-and 3-sporedasci, especially of the former. One-spored ascibecome abundantas this ratio decreases.
5. Lysine promotes sporulation in anacetate medium, and its presencein a large amount in glucosemedium also stimulates sporulation,while a small amount isinhibitory. When lysine was employedas the sole nitrogen source,most of the asci were 1-spored.
6. It is discussed that sporulationof yeast is induced by a balanceof metabolism, rather thanby one definite "sporulation substrate".

¹ Present address: Laboratory of Microbiology, Department ofAgriculture, T{circumflex}hoku University, Sendai. (Received May 23, 1961; )     

Competition between relatives and the evolution of dispersal in a parasitoid wasp

Evolutionary theory predicts that levels of dispersal vary in response to the extent of local competition for resources and the relatedness between potential competitors. Here, we test these predictions by making use of a female dispersal dimorphism in the parasitoid wasp Melittobia australica. We show that there are two distinct female morphs, which differ in morphology, pattern of egg production, and dispersal behaviour. As predicted by theory, we found that greater competition for resources resulted in increased production of dispersing females. In contrast, we did not find support for the prediction that high relatedness between competitors increases the production of dispersing females in Melittobia. Finally, we exploit the close links between the evolutionary processes leading to selection for dispersal and for biased sex ratios to examine whether the pattern of dispersal can help distinguish between competing hypotheses for the lack of sex ratio adjustment in Melittobia.     

Indirect effects of the algivorous fish Plecoglossus altivelis altivelis on the growth of two insectivorous benthic fish

1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fish Plecoglossus altivelis altivelis (known as the ayu) on two species of insectivorous benthic fish, Pseudogobio esocinus esocinus and the goby Gymnogobius petschiliensis .
2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue-green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased.
3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores.
4. In field experiments, the introduction of ayu into habitats with P. esocinus esocinus or G. petschiliensis reduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in the G. petschiliensis habitat, the population density of the goby decreased when ayu were stocked.
5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.