Alternative life cycles controlled by temperature and photoperiod in the oligophagous bug, Dybowskyia reticulata

Abstract. Effects of temperature and photoperiod on the induction and re-induction of adult diapause were examined in Dybowskyia reticulata (Dallas) (Heteroptera: Pentatomidae). Adults collected from the field after overwintering in early summer continued oviposition under long-day conditions of LD 16:8 h at 20 or 25°C, while they re-entered diapause under short-day conditions of LD 12:12 h at 25, 27.5 or 30°C. By contrast, adults reared in the laboratory from eggs at 20 or 25°C entered diapause under both long-day and short-day conditions, whereas those reared at 27.5 and 30°C entered diapause only under short-day conditions. Under quasi-natural conditions in 1993, when summer temperature was low, most adults of the first generation entered diapause in late July. However, in the warmer summer of 1996, oviposition was recorded in many females that ecdysed into adults from July to early August. Even though the seeds of the host plants occur in a restricted period from early summer to early autumn, in warmer years D. reticulata may produce a second generation. The response to temperature with a threshold between 25 and 27.5°C in D. reticulata brings about a switch between the univoltine and bivoltine life cycles.     

The evolution of social behaviour in sentinel crabs (Macrophthalmus): implications from molecular phylogeny

Crabs of the genus Macrophthalmus are known to exhibit highly developed and diverse social behaviour, such as allocleaning, fighting and waving display behaviour, the first being observed widely throughout the genus. Fighting behaviour between males has been classified previously into grasping fighting and claw‐extending fighting, and male waving display into four patterns, the vertical non‐forward‐pointing type, vertical forward‐pointing type, lateral non‐forward‐pointing type and lateral forward‐pointing type, on the basis of interspecific behaviour comparisons. To understand the evolutionary pathways of these social behavioural activities, 978‐bp nucleotide sequences from mitochondrial 16S rRNA genes of 21 species, including two outgroup taxa, were analysed and a molecular phylogeny was reconstructed. The resultant tree demonstrated striking inconsistencies with the relationships inferred from morphological features. Species with similar habitat conditions showed similar morphological features, although they were not phylogenetically close relatives. Phylogenetic analysis of allocleaning behaviour suggested that it evolved once in the early history of the lineage. The analysis of fighting behaviour demonstrated that species with claw‐extending fighting, being a more complex behaviour than grasping fighting, are found in the most ancestral part of the phylogeny. The analysis also revealed that claw‐extending fighting has evolved secondarily on two occasions, suggesting that fighting behaviour is not characterized by sufficient phylogenetic components. The superimposition of a waving pattern on to the phylogeny indicated that the lateral non‐forward‐pointing type has evolved from the vertical non‐forward‐pointing type, the lateral forward‐pointing type having evolved from the vertical forward‐pointing type. This scenario also appeared reasonable with respect to the behavioural trends of cheliped movements in waving. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88 , 45–59.     

AUTOXIDATION OF OXYMYOGLOBIN: A MEETING POINT OF THE STABILIZATION AND THE ACTIVATION OF MOLECULAR OXYGEN

1. The primary events of haemoprotein reactions with molecular oxygen have been re-examined by placing special emphasis upon the reduction properties of dioxygen. 2. In the stepwise reduction of O2 to water via hydrogen peroxide, the addition of the first electron is an unfavourable, uphill process with the midpoint potential of -0.33 V, all the subsequent steps being downhill. This thermodynamic barrier to the first step is, therefore, a most crucial ridge located between the stabilization and the activation of dioxygen performed by haemoproteins. 3. If the proteins have a redox potential much higher than -0.33 V, molecular oxygen must bind to the proteins stably and reversibly. In Mb or Hb, however, the FeO2 centre is always subject to a nucleophilic attack of the water molecule or hydroxyl ion, which can enter the haem pocket from the surrounding solvent. These can cause irreversible oxidation of the FeO2 bonding to the ferric met-form with generation of the superoxide anion. 4. In cases of the oxygen activation, if haemoproteins have a redox potential lower than or close to -0.33 V, the first reduction of O2 to O2- would be a spontaneous process. Cytochrome P-450 provides such an example and can facilitate the subsequent addition of electrons that leads to the breaking of the O-O bond to yield the hydroxylating species. 5. As to the proteins whose redox potential is not facilitative and appreciably higher than -0.33 V, a bimetallic, concerted, two-equivalent reduction of the bound dioxygen to the peroxide level would be much more favoured without the intermediate formation of O2-. This is probably the case of cytochrome c oxidase for the reduction of O2 to water. 6. The redox potential diagrams thus visualize various aspects of the ways haemoproteins overcome their thermodynamic constraints and carry out their specific functions in the stabilization and the activation of molecular oxygen.     

Effects of temperature,photoperiod and soil humidity on induction of pseudopupal diapause in the bean blister beetle Epicauta gorhami

Larvae of the bean blister beetle Epicauta gorhami Marseul (Coleoptera: Meloidae) feed on grasshopper eggs in soil and undergo hypermetamorphosis. This beetle undergoes larval diapause in the fifth instar as a pseudopupa, a form characteristic of hypermetamorphosis in meloid beetles. The effects of temperature, photoperiod and soil humidity on larval development of E. gorhami are examined in a population in Miyazaki, Japan, using egg pods of Locusta migratoria L. as food. At lower temperatures (20 and 22.5 °C), all larvae become pseudopupae, regardless of the photoperiod. By contrast, at higher temperatures (27.5 and 30 °C), almost all larvae pupate at the end of the fourth instar, again regardless of the photoperiod. A long‐day photoperiodic response occurs only at an intermediate temperature (25 °C): under an LD 12 : 12 h photocycle, all larvae enter diapause, although the diapause incidence tends to decrease as the day length becomes longer. Pseudopupae are immobile and remain in diapause for ≥120 days when they are kept under the same conditions, except that diapause terminates within a relatively short time at 30 °C. Although lower soil humidity retards post‐feeding development, soil humidity has no effect on the diapause incidence. On the basis of the short developmental period and diapause avoidance under summer conditions, it is suggested that this beetle partially produces two generations a year in southwestern Japan.     

How can river-estuarine planktonic copepods survive river floods?

Distribution of brackish-water zooplankton was surveyed in the Chikugo River estuary, Japan, at 3-h intervals for 24h, including several hours when the river was heavily flooded because of rainfall and discharge from an upstream dam. The populations of the dominant copepods Pseudodiaptomus inopinus and Sinocalanus sinensis were concentrated in the mixing zone of the salt wedge before river flooding. During the period of flooding, they were almost completely swept out from the river, but examination of water trapped by a sediment grab sampler revealed that adults of Pseudodiaptomus inopinus were aggregated immediately above the bottom of the submerged channel outside the river mouth. After the flood, aggregations of both species appeared again in the river together with the salt wedge, and the proportion of adults in the aggregations became significantly higher than before. These results suggest that immature copepods suffer population losses through river flooding, but that the copepods can survive such flooding by means of both behavioral and reproductive mechanisms; that is, adult copepods maintain their position on the bottom of submerged channels outside the river mouth during a river flood and replace the population loss through reproduction after the flood. Channels outside river mouths are thus regarded as important topographic refuges for river-estuarine zooplankton to survive a flood.     

Characteristics of Sleep and Wakefulness inWild-Derived Inbred Mice

Genetic variations in the wild-derived inbred mouse strains are more diverse than that of classical laboratory inbred mouse strains, including C57BL/6J (B6). The sleep/wake and monoamine properties of six wild-derived inbred mouse strains (PGN2, NJL, BLG2, KJR, MSM, HMI) were characterized and compared with those of B6 mice. All examined mice were nocturnal and had a polyphasic sleep pattern with a “main sleep period” identified during the light period. However, there were three sleep/wake phenotypic differences between the wild-derived mouse strains and B6 strain. First, the amount of sleep during the dark phase was comparable with that of B6 mice. However, the amount of sleep during the light phase was more varied among strains, in particular, NJL and HMI had significantly less sleep compared with that of B6 mice. Second, PGN2, NJL, BLG2, and KJR mice showed a “highly awake period” (in which the hourly total sleep time was <10%) immediately after the onset of the dark period, which was not seen in B6 mice. Third, relative to that of B6 mice, PGN2 and KJR mice showed longer duration of wakefulness episodes during the 12-h dark phase. Differences in whole brain noradrenaline, dopamine, and 5-hydroxy-tryptamine contents between the wild-derived mouse strains and B6 strain were also found. These identified phenotypes might be potentially under strong genetic control. Hence, wild-derived inbred mice could be useful for identifying the genetic factors underlying the regulation of sleep and wakefulness.     

Hysteresis of Contraction-Extension Cycle of Glycerinated Vorticella

SYNOPSIS. The helical coiling state of a glycerinated stalk in the family Vorticellidae had been regarded, without any evidence, as a reversible and completely equilibrated mechano-chemical system regulated by the external free Ca²⁺ concentration. Our present detailed observations of many individual stalks of glycerinated Vorticella convallaria revealed that the contraction-extension cycle of the helical stalks caused by increasing and decreasing free Ca²⁺ concentrations in the medium represents a kind of hysteresis. This phenomenon was observed in extensively glycerinated Vorticella in a medium of very low or physiological ionic strength, as well as in briefly glycerinated ciliates. With regard to the configurational change in various parts of a glycerinated stalk during the contraction-extension cycle, it was found that the initial bending of the stalk caused by increasing free Ca²⁺ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca²⁺ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca²⁺ concentration takes place simultaneously throughout the entire stalk. The Ca²⁺ threshold for complete reextension of the part of the stalk near the rootlet was found to be much higher than that near the zooid.     

FORAGING AND SPAWNING RHYTHMS OF THE PULMONATE LIMPET SIPHONARIA SIRIUS (PILSBRY): SWITCHING OF ACTIVITY PERIOD BY A DIURNAL FORAGER

Foraging and spawning rhythms of the intertidal pulmonate limpetSiphonaria sirius were studied at Shirahama, Wakayama Prefecture,Japan. Continuous 24 h observations were made five times, andtwo series of daytimeobservations were conducted for over 10days almost successively. This species inhabited the lower intertidalzones and had a diurnal habit in spring to autumn. At springtide most marked individuals showed foraging activity when awashand submerged both in ebb and flood tides before and after thetime of lowest water. When the tide progressed towards neaps,the activity peaks became ca. 30 min later per day and smaller.A new activity peak appeared early in the morning at neap tidein waxinghalf moon, and in summer, many adult limpets copulatedduring the morning activity. Simultaneous spawning by such limpetsoccurred one or two days after the peak of copulation. S. siriusswitched the activity period from late evening back to earlymorning at neap tide. The adaptive significances of such activitypatterns are discussed focusing on the responses against daytimedesiccation and nocturnal aquatic predators. (Received 5 September 1994; accepted 30 October 1994)     

Spiral Motion of Paramecium caudatum in a Small Capillary Glass Tube

SYNOPSIS. The behavior of Paramecium caudatum in small capillary glass tubes was investigated under various ionic conditions and at the various tube diameters. Along the inner walls of the tubes ciliates undergo regular spiral motion, which is completely different from natural spirallings or random walk-like movements observed usually in large vessels. The curvature calculated from the tracks of spiral motions was independent of the inner diameters of capillary tubes, but depend specifically on ionic conditions.
A plausible law governing such regular spiral motions of Paramecium caudatum is proposed. A definite part of the anterior end of a ciliate seems to contact the curved surface of the inner wall of a capillary tube during the motion so that the organism receives a constant tactile stimulus, and the direction of motive force keeps a certain angle against the surface.     

Ancient genome‐wide admixture extends beyond the current hybrid zone between Macaca fascicularis and M. mulatta

Macaca fascicularis and Macaca mulatta are two of the most commonly used laboratory macaques, yet their genetic differences at a genome‐wide level remain unclear. We analysed the multilocus DNA sequence data of 54 autosomal loci obtained from M. fascicularis samples from three different geographic origins and M. mulatta samples of Burmese origin. M. fascicularis shows high nucleotide diversity, four to five times higher than humans, and a strong geographic population structure between Indonesian‐Malaysian and Philippine macaques. The pattern of divergence and polymorphism between M. fascicularis and M. mulatta shows a footprint of genetic exchange not only within their current hybrid zone but also across a wider range for more than 1 million years. However, genetic admixture may not be a random event in the genome. Whereas randomly selected genic and intergenic regions have the same evolutionary dynamics between the species, some cytochrome oxidase P450 (CYP) genes (major chemical metabolizing genes and potential target genes for local adaptation) have a significantly larger species divergence than other genes. By surveying CYP3A5 gene sequences of more than a hundred macaques, we identified three nonsynonymous single nucleotide polymorphisms that were highly differentiated between the macaques. The mosaic pattern of species divergence in the genomes may be a consequence of genetic differentiation under ecological adaptation and may be a salient feature in the genomes of nascent species under parapatry.