Sexual Isolation Between Drosophila Melanogaster, D. Simulans and D. Mauritiana: Sex and Species Specific Discrimination

The sexual isolation among the related species Drosophila melanogaster, D. simulans and D. mauritiana is asymmetrical. While D. mauritiana males mate well with both D. melanogaster and D. simulans females, females of D. mauritiana discriminate strongly against males of these two species. Similarly, D. simulans males mate with D. melanogaster females but the reciprocal cross is difficult. Interspecific crosses between several populations of the three species were performed to determine if (i) males and females of the same species share a common sexual isolation genetic system, and (ii) males (or females) use the same genetic system to discriminate against females (or males) of the other two species. Results indicate that although differences in male and female isolation depend on the populations tested, the isolation behaviour between a pair of species is highly correlated despite the variations. However, the rank order of the isolation level along the populations was not correlated in both sexes, which suggests that different genes act in male and female sexual isolation. Neither for males nor for females, the isolation behaviour of one species was paralleled in the other two species, which indicates that the genetic systems involved in this trait are species-pair specific. The implications of these results are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Comparative Analysis of Mating Recognition Signals in Graylings: Hipparchia statilinus vs. H. semele (Lepidoptera: Nymphalidae, Satyrinae)

Courtship is an important character linked to fitness and can evolve in response to female mate choice, to ensure sex identity and quality of a potential mate. It can also be a major pre-mating isolating mechanism in butterflies and many other species. In this paper, aspects of the reproductive behaviour of Hipparchia statilinus are described. First, the ethogram and the sequential structure of courtship leading to copulation and female refusal behaviour are showed; second, the results are compared with the behaviour of the sympatric and syntopic species, H. semele. Sequential analysis of H. statilinus courtship showed that, once a male has started the sequence, the following steps most likely follow up to the end. Courtship seems to reflect female behaviour: the male can repeat the whole sequence or part of it more than once, waiting for female signals. The general pattern of sexual behaviour in H. semele and in H. statilinus is mainly identical: perching strategy, flight pursuit, courtship. In both species, courtship consists of a highly stereotypic sequence, and differences between sequences are primarily related to presence/absence, order and performance of steps. This study is the first step of an experimental design addressed to a better understanding of mating recognition signals in Hipparchia and provides more details to define the relative roles of phylogeny and environment in shaping boundaries among species.     

Effects of large Saduria entomon (Isopoda) on spatial distribution of their small S. entomon and Monoporeia affinis (Amphipoda) prey

We performed laboratory experiments to investigate the effects of predator avoidance and numerical effects of predation on spatial distribution of small Saduria entomon (Isopoda) and Monoporeia affinis (Amphipoda), with large S. entomon as predators. The horizontal distribution and mortality of the prey species, separately and together, were studied in aquaria with a spatial horizontal refuge. We also estimated effects of refuge on mortality of small S. entomon and M. affinis by experiments without the refuge net. In addition, we investigated whether predation risk from large S. entomon influenced the swimming activity of M. affinis, to clarify the mechanisms behind the spatial distribution. Both small S. entomon and M. affinis avoided large S. entomon. The avoidance behaviour of M. fffinis contributed about 10 times more to the high proportion in the refuge than numerical effects of predation. Due to the low mortality of small S. entomon the avoidance behaviour of this species was even more important for the spatial distribution. The combined effect of avoidance behaviour and predation in both species was aggregation, producting a positive correlation between the species in density. M. affinis showed two types of avoidance behaviour. In the activity experiments they reduced activity by 36% and buried themselves in the sediment. In the refuge experiments we also observed avoidance behaviour with the emigration rate from the predator compartment being twice the immigration rate. The refuge did not lower predation mortality in M. affinis, probably due to the small scale of the experimental units in relation to the mobility of the species. Predation mortality in small S. entomon was higher in absence of a refuge and especially high in absence of M. affinis.     

Variation in expression of trimorphic incompatibility in Pontederia cordata L. (Pontederiaceae)

Summary Pontederia cordata L. (Pontederiaceae), a perennial diploid, possesses the rare genetic polymorphism tristyly. A controlled pollination programme was conducted over a three year period, under glasshouse conditions, on 36 clones of P. cordata var. cordata to examine the nature of the self-incompatibility system. The three major findings of the pollination study were: (1) the three floral morphs display different levels of self-incompatibility, (2) pollen from the two anther levels within a flower exhibits different compatibility behaviour in self-pollinations, (3) considerable individual genetic variation in the expression of self-incompatibility is evident among clones within floral morphs. Similar results were also obtained from a smaller study on 15 clones of P. cordata var. lancifolia conducted over a 6 month period. In common with other Pontederia species the mid-styled morph (M) of P. cordata produces large amounts of seed when self-pollinated with pollen from long-level anthers. A developmental model is proposed to explain the high level of self-compatibility of the M morph in Pontederia species. Self-pollination of segregating progenies from M and S morphs of known incompatibility status demonstrated that the expression of incompatibility is closely associated with style length. It is suggested that overall differences in incompatibility behaviour among the floral morphs may be due to the pleiotropic effects of major genes controlling sub-characters of the tristylous syndrome, rather than linked modifier genes. However, the variable expression of trimorphic incompatibility within floral morphs suggests that this variation may be polygenic in origin.     

Ranunculus cacuminis andR. crenatus,representatives of theR. alpestris-group (Ranunculaceae) on the Balkan Peninsula

Morphological and karyological investigations as well as crossing experiments were carried out withR. cacuminis, R. crenatus, andR. alpestris. A key is presented including all 6 taxa of theR. alpestris-group. Ecological and geographical data for the Balkan Peninsula are also presented.R. cacuminis is diploid with 2n = 16 chromosomes as all taxa of the group, its karyotype exhibits no statistically significant differences to those from the 5 other taxa. In crossing experiments betweenR. cacuminis andR. alpestris, no hybrids could be obtained, whereas those betweenR. cacuminis andR. crenatus were slightly successful. According to its morphology, geographical distribution, and crossing behaviour,R. cacuminis is closely related toR. crenatus, and probably has originated fromR. crenatus by quantum speciation.     

THE HORMONAL INTEGRATION OF SEXUAL REPRODUCTION IN OEDOGONIUM

Rawitscher -Kunkel , Erika , and L. Machlis . (U. California, Berkeley.) The hormonal integration of sexual reproduction in Oedogonium. Amer. Jour. Bot. 49 (2) : 177–183. Illus. 1962.—Sexual reproduction in a heterothallic, nannandrous species of Oedogonium was investigated cytologically and physiologically. Several new observations are reported. Oogonial mother cells release a substance which attracts androspores to them. The androspores, when attached to the oogonial mother cells, grow in well-defined directions apparently in response to a hormone originating in the oogonial mother cells. An oogonial mother cell divides into an oogonium and a suffultory cell only after the attached androspores complete their development into dwarf males, each bearing an antheridium. Presumably the developing dwarf males provide a chemical stimulus for the division of the oogonial mother cell. During development, the oogonia become enveloped in a massive gel which also encases the antheridia cut off at the apical ends of the dwarf male plants. The gel appears to function as a sperm trap, preventing the dissemination of the sperm into the surrounding liquid. The sperm are attracted to the protoplasmic papilla which briefly protrudes through the oogonial pore indicating the operation of a second chemotactic agent.     

Meiotic pairing of the amphiploid Hordeum chilense X Triticum turgidum conv. durum studied by means of Giemsa C-banding technique

Summary The meiotic behaviour of the amphiploid Hordeum chilense X Triticum turgidum conv. durum using a C-banding staining method is studied. Nine pairs of chromosomes at metaphase-1 (4A, 7A and the seven of the B genome) were identified and the remaining wheat chromosomes (1A, 2A, 3A, 5A and 6A) and seven of the chilense (1 to 7 H ^ch chromosomes) were assigned to its particular genome. A similar mean number of univalents from parental genomes (wheat and wild barley) were found. No meiotic pairing between chilense and turgidum chromosomes was detected. Differences in the meiotic behaviour per chromosome and amongst genomes are explained on the basis of cytomorphological and heterochromatin characteristics.     

Superoxide dismutase in strains of the genus Flavobacterium: isolation and characterization

Two electrophoretically different forms of superoxide dismutase, one of them containing manganese-protein and the other iron-protein, were detected in eleven different strains of the genus Flavobacterium. The activities of the different strains were similar to those described for other bacteria. The two molecular forms of the enzyme differed clearly with regard to activity, electrophoretic behaviour, sensitivity to cyanide and peroxide, and NaCl requirement. Both molecular forms were isolated from Flavobacterium halmephilum. Molecular mass absorption spectra, metal content, optimum pH, heat-sensitivity and stability were described.     

Rheological properties of polysaccharides produced by a Zoogloea sp.

A newly isolated marine bacterium, identified as Zoogloea sp., produced two different polysaccharides: one was water-soluble and the other was cell-bound. Both had non-Newtonian, pseudoplastic fluid behaviour and the solutions had low activation energies. The solutions of these polysaccharides showed rheological behaviour over a wide range of pH (2–12) and temperature (20–80 °C), and compatibility with NaCl.     

Preferential feeding behaviour of Daphnia magna

Preferential feeding behaviour by Daphnia magna was shown when Daphnia were fed on a mixture of ¹⁴C-labelled algae (Chlorella vulgaris or Scenedesmus quadricauda) and ³H-labelled bacteria (Escherichia coli). Daphnia consumption of bacteria was equal or higher in the presence of algae. On the other hand, in the presence of bacteria, algal consumption decreased by 40–70% compared to algal consumption in the absence of bacteria. ¹⁴C radioactive uptake was in good agreement with the chlorophyll content and demonstrates the preferential feeding behaviour of Daphnia.     

Foraging behaviour of honey bees (Apis mellifera L.) on transgenic oilseed rape (Brassica napus L.var. oleifera)

The impact of genetically modified oilseed rape (Brassica napus L.) on the foraging behaviour of honey bees (Apis mellifera L.) was evaluated on two different lines transformed to express constitutively heterologous chitinase in somatic tissue for enhanced disease resistance. Experiments were conducted in confinement in an indoor flight room with controlled conditions and in an outdoor flight cage with conditions more representative of the open environment. Foraging behaviour was analysed by observations of general bee behaviour (total number of visits) and of individual bee behaviour (using a video camera coupled with a special software program to process the data). The plants were analysed in terms of nectar quantity and quality (nectar volume and sugar content). The results showed no effects on bee foraging behaviour due to the modification of the genome of these plants by the introduction of a chitinase gene even though some differences between lines were found in the nectar. The methods applied in this original approach for the evaluation of the impact of genetically modified oilseed rape were shown to be sufficiently sensitive to detect changes in bee behaviour resulting from differences between plants.     

Host plant selection by Helicoverpa spp. in chickpea-companion cropping systems

The potential of companion crops to serve as diversionary hosts for ovipositing Helicoverpa spp. moths in chickpea cropping systems was evaluated in a field experiment. Patterns of egg distribution by Helicoverpa spp. within paired combinations of chickpea and each of six companion crop species were documented in a split-plot design sampled four times during the 1999 winter growing season. Chickpea was attractive to ovipositing Helicoverpa moths from as early as 14 days after planting and throughout the experimental period. The companion crop species varied in relative attractiveness to ovipositing moths but none was able to effectively divert Helicoverpa egg pressure away from chickpea for the duration of the experiment. Of all Helicoverpa spp. larvae recorded from all samples and crop combinations, 98.3% were found on chickpea. A marked aggregative oviposition behaviour of Helicoverpa spp. on tall weeds growing through the chickpea canopy was recorded. The relevance of observed patterns of host selection and inferred moth behaviour to management of Helicoverpa populations on chickpea are discussed.     

On the feeding habits ofRhynchopsilopa [Dip.: Ephydridae]

Further evidence for the myrmecophagous habits of adultRhynchopsilopa flies is supplied. The genus probably evolved in association with ants of the genusCrematogaster. The feeding behaviour ofR. nitidissima Hendel on workers ofCrematogaster is described. Choice experiments show an absolute preference forCrematogaster over 3 other and genera. The mouth parts ofR. nitidissima are briefly described.

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Résumé Un témoignage supplémentaire des habitudes myrmécophages des adultes de DiptèresRhynchopsilopa est fourni. Le genre a probablement évolué en association avec les fourmis du genreCrematogaster. Le comportement alimentaire deR. nitidissima sur les ouvrières deCrematogaster est décrit. Les choix expérimentaux montrent la préférence absolue pour le genreCrematogaster à l'exclusion des 3 autres genres de fourmis. Les pièces buccales deR. nitidissima sont brièvement décrites.

     

Host-seeking behaviour of tracheal mites (Acari: Tarsonemidae) on honey bees (Hymenoptera: Apidae)

The behaviour of the endoparasitic tracheal mite, Acarapis woodi (Rennie) on honey bees (Apis mellifera L.) is a challenge to observe because of its small size. Through a microscope, we videotaped this mite's movement on young bees, dead bees and bees exposed to vegetable oil. Previous studies have shown that solid vegetable oil decreases mite infestations in a bee colony. We hypothesized that the oil alters mite behaviour to the detriment of the parasite, thus helping to safeguard the host. Habitat-seeking behaviour, identified as necessary for mites to locate a new host environment, was disrupted on both dead and oil-treated bees. Questing behaviour, which is associated with transfer between hosts, increased significantly on the dead and oily bees. The behaviours of mites were significantly different between all three treatments (x ²=494.96, p<0.001 on dead bees and x ²=851.11, p<0.001 on oily bees). Both questing and seeking behaviours were significantly different on each of the thoracic treatments (F _2,66=7.88, p<0.001 and F _2,66=21.28, p<0.001) and mite questing behaviour was not altered between males and females on live or oily bees (F _1,22=0.25, p<0.62), but habitat seeking was (F _1,22=7.42, p<0.012). The male questing and habitat-seeking behaviours were observed. We conclude that oil-treated bees gained protection from habitat-seeking mites because the normal behaviour of the mites seeking an oviposition site is interrupted.     

The influence of marking upon bee behaviour in circle tube experiments with a methodological comparison among studies

Summary. Circle tubes were used to investigate the influence of marking upon the behavioural profiles of two halictid species; one, Penapis toroi Rozen, putatively solitary, the other, Corynura chloris (Spinola) thought to be semisocial. Previous studies have shown that solitary bees tend to exhibit avoidance behaviour and those with a reproductive division of labour tend to behave aggressively within circle tube arenas. Marked pairs of C. chloris were significantly more cooperative than unmarked pairs and marked P. toroi showed significantly increased aggression and decreased cooperation. These findings suggest that marking bees may reduce behavioural differences among taxa with different types of social organization. Recommendations are made on how to use the circle tube apparatus to detect bee populations that might be worth more detailed studies of social organization and also for standardization in the way results of these studies are presented. Further experiments are suggested to clarify the effects of certain variables upon bee behaviour using this apparatus. The data presented here are the first for any member of the subfamily Rophitinae and the first for any bee thought to be primarily semisocial. A narrower range of behaviours were observed in the Rophitine, Penapis toroi Rozen, in comparison to species from other subfamilies of Halictidae and Corynura chloris Spinola had a behavioural profile similar to that of eusocial species.Received 15 December 2003; revised 12 September 2004; accepted 15 October 2004.     

Host specificity testing and suitability of the parasitoidMicroctonus hyperodae (Hym.: Braconidae,Euphorinae) as a biological control agent ofListronotus bonariensis (Col.: Curculionidae) in New Zealand

The behaviour of the parasitoidMicroctonus hyperodae Loan was studied under quarantine conditions to determine its likely host range in New Zealand. The species was imported from South America as a potential biological control agent of Argentine stem weevil,Listronotus bonariensis (Kuschel). The study involved systematic evaluation of the parasitoid's behaviour when exposed to 24 non-host weevil species; all but three of these were native to New Zealand. Of those tested, four were found to sustain someM. hyperodae development. However, further examination showed that in all but one species,Irenimus aequalis (Broun), parasitoid development was impeded, with up to 50% of the larvae becoming encapsulated. Overall, those weevil species that were attacked produced only 19% of the parasitoids derived fromL. bonariensis controls. As an adjunct to this quarantine study, a review of the habitats of the native weevil and target pest populations indicated that refugia would probably exist for native alpine species. I. aequalis was not considered to be threatened byM. hyperodae as this weevil has benefited from the advent of European agricultural systems to the extent that it is now recognised as a minor pest. In view of its relatively oligophagous behaviour, the parasitoid was recommended as suitable for release.      

Swimming Behaviour of <Emphasis Type="Italic">Chironomus acerbiphilus</Emphasis> Larvae in Lake Katanuma

We conducted a seasonal survey of the swimming behaviour of Chironomus acerbiphilus larvae in volcanic Lake Katanuma from April 1998 to December 2001. Swimming C. acerbiphilus density was much higher than other chironomid species in lakes. All C. acerbiphilus larvae (1st through 4th instars) swam, but the earlier instars (especially the 1st) had the greatest densities and fluctuations. First instars were never found in the benthic population. This result indicates that the 1st-instar larvae are planktonic. Low water temperature (below about 10 °C) resulted in the seasonal disappearance of swimming chironomid larvae. Chemical factors – oxygen depletion or presence of hydrogen sulfide – also restricted the distribution of swimming and benthic larvae. Larvae were distributed only in the oxygen-rich part of the lake bottom and swam only in the oxygen-rich layer of the water column. The density of older swimming C. acerbiphilus (3rd and 4th instars) tended to increase with increasing benthic larval densities. The chemical stress of oxygen depletion or presence of hydrogen sulfide during holomixis within and after the stratification period leads to conspicuous swimming behaviour of benthic C. acerbiphilus larvae. Almost all C. acerbiphilus larvae died on this occasion.     

Biosynthesis of active spinach-chloroplast thioredoxin f in transformed E. coli

The recently cloned gene for spinach chloroplast thioredoxin f was subcloned in a modified pKK233-2 expression vector and used for transformation of Escherichia coli cells containing the I^q plasmid. After induction with IPTG (isopropyl--D-thiogalactoside) the transformed cells produce the chloroplast protein in large amounts as insoluble deposit within the cell. The protein has been solubilized, purified and analysed for activity. It shows no difference in catalytic activity from native spinach chloroplast thioredoxin f. Its electrophoretic behaviour suggests that the native thioredoxin f may have a different N-terminus than was assumed on the basis of the protein sequencing results.     

nrDNA internal transcribed spacer data reveal that Rhodoplagiochila R.M. Schust. (Marchantiophyta: Jungermanniales) is a member of Plagiochila sect. Arrectae Carl

The monospecific genus Rhodoplagiochila, previously known only from the type collected in the Venezuelan Andes, has been collected at a second site close to the type locality. Up to now, generic status of Rhodoplagiochila has been accepted by most authors, but the taxon had been alternately assigned to Plagiochilaceae or Lophoziaceae. Phylogenetic analyses of nrITS sequences from Rhodoplagiochila and other representatives of the Plagiochilaceae clearly reveal the former to be in a clade with members of the Neotropical–Atlantic European Plagiochila sect. Arrectae. Within the Arrectae, Rhodoplagiochila is positioned in a robust clade made up of several accessions of Plagiochila bifaria. Morphologically, Rhodoplagiochila differs from other phenotypes of P. bifaria by the papillose leaf surface and a leaf margin which is ciliately toothed all-around. As an outcome of the molecular and morphological investigations, Rhodoplagiochila rosea is treated as a variety of P. bifaria, and the new combination P. bifaria var. rosea comb. et stat. nov. is proposed. In tropical America the family Plagiochilaceae seems to be represented only by Plagiochila.