Cycloheximide Insensitive Amoebo-Flagellate Transformation in Starved Amoebae of Physarum polycephalum

The requirement of protein synthesis for amoebo-flagellate transformation of Physarum polycephalum was re-examined. When amoebae were grown on nutrient agar in association with live food bacteria and harvested in mid-exponential phase of growth, it took ca. 2 hours for half the cells to form flagella after suspension in phosphate buffer. The transformation was completely inhibited by 5 μg/ml cycloheximide. To the contrary, when the amoebae in mid-exponential phase were starved for 3 hr on non-nutrient agar and then suspended in phosphate buffer, the duration required for this process was shortened to ca. 8 min and it was not inhibited by up to 100 μg/ml cycloheximide. A similar result was obtained using bactobolin, another inhibitor of protein synthesis. When amoebae were starved on non-nutrient agar containing 5 μg/ml cycloheximide, however, the starvation effect described above was not observed. The results indicate that protein(s) necessary for the transformation might be synthesized during the starvation period, and that the amoebo-flagellate transformation may or may not require concomitant protein synthesis depending upon preculture conditions.     

LABORATORY OBSERVATIONS ON THE EARLY LIFE STAGES OF THE DIAMOND SQUID THYSANOTEUTHIS RHOMBUS

The early life stages of the diamond squid Thysanoteuthis rhombusfrom early embryogenesis to post-hatching (0–7 days old)were observed through laboratory incubation using egg massescollected in the southern Sea of Japan. The egg diameter andmantle length increased during embryonic development throughhatching. Mantle-length growth was linear over time, and thegrowth rate was significantly higher at 25°C than at 20°C.The inner yolk was located on the dorsal side of the mantlecavity and increased in volume through hatching. Immediatelyafter they hatched, the hatchlings remained on the bottom ofculture plates with their ventral sides facing up, but 2–3days after hatching they began to swim with their dorsal sidesfacing up. Feeding experiments were conducted, but none of thehatchlings fed. Statolith growth increments were shown to formdaily. Ontogenetic changes that occur from fertilization throughpost-hatching are discussed. (Received 8 June 2005; accepted 2 November 2005)     

Circadian rhythm of locomotor activity in the Japanese honeybee, Apis cerana japonica

Abstract.  To reveal circadian characteristics and entrainment mechanisms in the Japanese honeybee Apis cerana japonica , the locomotor-activity rhythm of foragers is investigated under programmed light and temperature conditions. After entrainment to an LD 12 : 12 h photoperiodic regime, free-running rhythms are released in constant dark (DD) or light (LL) conditions with different free-running periods. Under the LD 12 : 12 h regime, activity offset occurs approximately 0.4 h after lights-off transition, assigned to circadian time (Ct) 12.4 h. The phase of activity onset, peak and offset, and activity duration depends on the photoperiodic regimes. The circadian rhythm can be entrained to a 24-h period by exposure to submultiple cycles of LD 6 : 6 h, as if the locomotive rhythm is entrained to LD 18 : 6 h. Phase shifts of delay and advance are observed when perturbing single light pulses are presented during free-running under DD conditions. Temperature compensation of the free-running period is demonstrated under DD and LL conditions. Steady-state entrainment of the locomotor rhythm is achieved with square-wave temperature cycles of 10 °C amplitude, but a 5 °C amplitude fails to entrain.     

Acoustic emission monitoring of the effect of temperature on activity rhythms of the subterranean termite Reticulitermes speratus

Daily activity rhythms are widespread characteristics among many organisms and are usually related to one or more physical environmental variables, such as light and temperature. Even organisms that are not obviously exposed to wide fluctuations in environmental variables, such as troglodytic and endogeic species, exhibit some daily activity patterns. Termites inhabit underground areas or tree trunks where little or no fluctuation in light occurs. In the present study, the activity rhythms of field colonies of the subterranean termite Reticulitermes speratus Kolbe (Blattodea: Termitidae) are examined, during all four seasons, by monitoring their acoustic emissions using a newly‐modified method. Nest temperature affects termite activity significantly during all four seasons. By contrast, no significant effect of time is observed during the different seasons, with the exception of autumn. Activity and nest temperature are negatively correlated in summer and autumn, although thay are are positively correlated during winter and spring. The greatest activity occurs at 23–25 °C. The experimental observations suggest that the activity of R. speratus termite colonies is affected mainly by ambient temperature, in a manner that is based on optimum temperature.