Showing papers by "Fuminori Ito published in 1998"

Widespread occurrence of the micro-organism Wolbachia in ants

Abstract: For more than 20 years, sex allocation in hymenopteran societies has been a major topic in insect sociobiology. A recurring idea was that relatedness asymmetrics arising from their haplodiploid sex determination system would lead to various parent-offspring conflicts over optimal reproduction. A possible weakness of existing theory is that only interests of nuclear genes are properly accounted for. Yet, a diversity of maternally transmitted elements manipulate the reproduction of their host in many solitary arthropod groups. The bacterium Wolbachia is a striking example of such a selfish cytoplasmic element, with effects ranging from reproductive incompatibility between host strains, induction of parthenogenesis and feminization of males. This paper reports on a first PCR-based Wolbachia screening in ants. Out of 50 Indo-Australian species, 50% screened positive for an A-group strain. One of these species also harboured a B-group strain in a double infection. Various factors that might explain the unusually high incidence of Wolbachia in ants are discussed. In general, Wolbachia may represent a widespread and previously unrecognized party active in the conflicts of interest within social insect colonies.

Colony composition and specialized predation on millipedes in the enigmatic ponerine ant genus Probolomyrmex (Hymenoptera, Formicidae)

Abstract: Colonies of Probolomyrmex dammermani Wheeler were collected in West Java, Indonesia. The nests contained a few millipedes of the family Polyxenidae, all of which were completely divested of their covering setae. Laboratory experiments showed that the ants fed only on polyxenids. The following bionomic characteristics were also noted: colony size was small (14 workers on average; range 8-21) with one dealate queen who was mated and laid eggs; pupae were necked; and both workers and queens had only one ovariole per ovary, which is the lowest ovariole number for ant queens.

Larval hemolymph feeding and oophagy : behavior of queen and workers in the primitive ponerine ant prionopelta kraepelini (hymenoptera, formicidae)

Abstract: The behavior of the queen and workers in the amblyoponine ant Prionopelta kraepelini was observed and compared with th at of the queen and workers of P. amabilis. The queen fed mainly on larval hemolymph by pinching the lat·val body. Workers often laid trophic eggs, most of which were given to larvae. The fo raging and recruitment behavior of workers were sim ilar to P. amabilis.

The Mandibular Gland, Probably the Source of the Alarm Substance in Leptanilla sp. (Hymenoptera, Formicidae)

Abstract: Although ants represent one of the most dominant terrestrial animals [1], some of them are extremely rare, either because of a limited geographical distribution or because of a cryptic life style. The Leptanillinae, a small subfamily of the Old World tropics and subtropics, comprises seven mostly monospecific genera of which four are known from males only [2]. The main genus Leptanilla has ap-prox. 20 species, but these are equally very rare and extremely small ants with small colonies [3]. Due to the practical limitations in having live Leptanilla available for study, the information available on the biology of these ants is restricted to a behaviou-ral study on the peculiar larval hemo-lymph feeding by the queen of L. ja-ponica, whereas the workers are specialized centipede predators [3], and to a morphological study describing the exocrine system of Leptanilla with main emphasis on the abdominal glands [4]. The collection of a colony fragment with approximately 300 live workers and brood of Leptanilla sp. in the Bo-gor Botanical Gardens in West Java, Indonesia, by one of us (F.I.) allowed us to study the internal morphology and chemistry of the head in combination with behavioural observations. This multidisciplinary approach resulted in this first study of the mandi-bular glands in leptanilline ants. The species studied is new to science, and will be described elsewhere. Voucher specimens are deposited in the Bogor Zoological Museum. The colony fragment could be kept in the laboratory in good condition for 2 months, although the workers refused the centipedes that were collected at the same locality. To study the internal morphology, heads were fixed in 2% cold glutaral-dehyde and further processed along the standard techniques [6] for making semi-thin sections for light mi-croscopy. Chemical analysis of single heads was carried out using the solid sampling technique [7] on a polydi-methylsiloxane phase in a 12-m fused silica column in a Hewlett-Packard 5890 gas chromatograph coupled to a 5970B MSD (quadrupole mass spectrometer). Identification of compounds was confirmed by comparison of their mass spectra and retention times with those of standards and using MS databases. Semi-thin sections through the head revealed that well-developed mandi-bular glands occur, each gland containing approx. 10 large, rounded se-cretory cells (diameter approx. 20 mm), that are situated at the ectal side of the reservoir, into which they open through individual duct cells (Fig. 1). Although this arrangement is Fig. 1. Semi-thin cross section through the anterior part …

Worker reproduction in the ponerine ant odontomachus

Abstract: The occurrence of worker reproduction in queenright and orphaned conditions was studied in the monogynous south-east Asian ponerine ant Odontomachus simillimus. Age (physiological factor), body size and number of ovarioles (morphological factors) and antagonistic interactions among workers and egg cannibalism (social factors) were measured as possible correlates of reproductive activity. In presence of the queen, the majority of the dissected workers had weakly or undeveloped ovaries. Worker egg laying was only rarely observed and these eggs were offered to and eaten by the queen. After a two week orphanage period though, half of the workers had acquired moderately developed ovaries. Three weeks later, there was a drop in ovarian development of the majority of workers, but a small portion of the workers (± 20%) acquired strongly developed ovaries. Observations have shown that these were also the main egg layers, so male production in the absence of the queen was performed by only a limited portion of the workers. Ovarian development of workers was not correlated with body size or number of ovarioles, but there was a clear relationship with age, the young workers being the reproductive individuals. Vigorous antennations among the egg layers and attempts to steal each other’s eggs were observed and their significance as social factors regulating reproduction is discussed. Egg cannibalism occurred mostly during the first two weeks after orphanage, but its role concerning the regulation of worker reproduction is not clear.