Polydomy and the organization of foraging in a colony of the Malaysian giant ant Camponotus gigas (Hym. / Form.)

In Kinabalu National Park, Borneo we observed four colonies of the Malaysian giant ant Camponotus gigas in a primary forest. These predominantly nocturnal ants have underground nests, but forage in huge three-dimensional territories in the rain forest canopies. The colony on which our study was mainly focused had 17 nests with about 7000 foragers and occupied a territory of 0.8 ha. To improve observation and manipulation possibilities, these nests were linked at ground level by 430 m of artificial bamboo trail. A group of specialist transport worker ants carried food from `source' nests at the periphery to the central `sink' nest of the queen. Transport of food between nests started immediately after the evening exodus of the foragers. Transporter ants formed a physical subcaste among the minors and behaved according to predictions of the central-place foraging theory. Their load size was about five times that of the average forager and grew proportionally with head width. Longer distances were run by ants with greater head width and larger gross weight. Transporter ants that ran more often took heavier loads. Experiments with extra-large baits revealed that C. gigas used long-range recruitment to bring foragers from different nests to “bonanzas” at far distant places. The foraging strategy of C. gigas is based on a polydomous colony structure in combination with efficient communication, ergonomic optimization, polyethism and an effective recruitment system. Received: 16 March 1998 / Accepted: 24 August 1998     

Molecular and chromosomal organization of two repetitive DNA sequences with intercalary locations in sugar beet and other Beta species

 In a search for repetitive DNA sequences in the sugar beet genome, two sequences with repeat unit lengths of 143 and 434 bp were isolated and characterized. The pSV family showed an unusual conservation of restriction sites reflecting homogenization of the analyzed repeats. Members of the family are organized as tandem repeats as revealed by PCR and sequencing of dimeric units. The pSV satellite occurs in large intercalary arrays which are present on all chromosome arms of sugar beet. The pSV sequence family is present in different abundance in the sections Beta, Corollinae and Nanae but is not detectable by Southern hybridization in the section Procumbentes. The pDRV family is characterized by an interspersed genomic organization. The sequence is detectable in all sections of the genus and is amplified in species of the section Beta but was also detected, although at lower abundance, in the remaining three sections. Fluorescent in situ hybridization has shown that the pDRV sequence family is dispersed over all chromosomes of the sugar beet complement with some regions of clustering and centromeric depletion. Received: 18 March 1998 / Accepted: 31 March 1998     

Conversion of a RAPD-generated PCR product,containing a novel dispersed repetitive element,into a fast and robust assay for the presence of rye chromatin in wheat

Bulk segregant analysis was used to obtain a random amplified polymorphic DNA (RAPD) marker specific for the rye chromosome arm of the 1BL.1RS translocation, which is common in many high-yielding bread wheat varieties. The RAPD-generated band was cloned and end-sequenced to allow the construction of a pair of oligonucleotide primers that PCR-amplify a DNA sequence only in the presence of rye chromatin. The amplified sequence shares a low level of homology to wheat and barley, as judged by the low strength of hybridization of the sequence to restriction digests of genomic DNA. Genetic analysis showed that the amplified sequence was present on every rye chromosome and not restricted to either the proximal or distal part of the 1RS arm. In situ hybridization studies using the amplified product as probe also showed that the sequence was dispersed throughout the rye genome, but that the copy number was greatly reduced, or the sequence was absent at both the centromere and the major sites of heterochromatin (telomere and nucleolar organizing region). The probe, using both Southern blot and in situ hybridization analyses, hybridized at a low level to wheat chromosomes, and no hybridizing restriction fragments could be located to individual wheat chromosomes from the restriction fragment length polymorphism (RFLP) profiles of wheat aneuploids. The disomic addition lines of rye chromosomes to wheat shared a similar RFLP profile to one another. The amplified sequence does not contain the RIS 1 sequence and therefore represents an as yet undescribed dispersed repetitive sequence. The specificity of the amplification primers is such that they will provide a useful tool for the rapid detection of rye chromatin in a wheat background. Additionally, the relatively low level of cross-hybridization to wheat chromatin should allow the sequence to be used to analyse the organization of rye euchromatin in interphase nuclei of wheat lines carrying chromosomes, chromosome segments or whole genomes derived from rye.     

Cloning and characterization of thewhite andtopaz eye color genes from the sheep blowflylucilia cuprina

Summary Clones carrying thewhite andtopaz eye color genes have been isolated from genomic DNA libraries of the blowflyLucilia cuprina using cloned DNA from the homologouswhite andscarlet genes. respectively, ofDrosophila melanogaster as probes. On the basis of hybridization studies using adjacent restriction fragments, homologous fragments were found to be colinear between the genes from the two species. The nucleotide sequence of a short region of thewhite gene ofL. cuprina has been determined, and the homology to the corresponding region ofD. melanogaster is 72%; at the derived amino acid level the homology is greater (84%) due to a marked difference in codon usage between the species. A major difference in genome organization between the two species is that whereas the DNA encompassing theD. melanogaster genes is free of repeated sequences. that encompassing theirL. cuprina counterparts contains substantial amounts of repeated sequences. This suggests that the genome ofL. cuprina is organized on the short period interspersion pattern. Repeated sequence DNA elements, which appear generally to be short (less than 1 kb) and which vary in repetitive frequency in the genome from greater than 10⁴ copies to less than 10² copies, are found in at least two different locations in the clones carrying these genes. One type of repeat structure, found by sequencing, consists of tandemly repeating short sequences. Restriction site and restriction fragment length polymorphisms involving both thewhite andtopaz gene regions are found within and between populations ofL. cuprina.     

华北晚古生代煤中一种科达叶的角质层研究

江苏徐州煤田太原组２０号煤层中一种分散角质层,根据其表皮构造特征及其它证据,认为是科达叶的角质层。利用光学显微镜和扫描电镜对这种角质层进行了详细研究,并与国内外研究较详细的几种科达叶的表皮构造进行了比较,表明当前标本是一种新和产达叶表皮构造类型。     

Dispersed information diffusion with level and schema-based coordination in mobile peer to peer networks

Several open ended issues for high resource availability in mobile peer to peer networks have been examined in the recent past. Different approaches were conducted for supporting information distribution and availability, through guided or unguided packet diffusion. The majority of the recently proposed approaches try to benefit from the spatial characteristics of the dynamically varying topologies. In this work a directed information diffusion scheme is examined using a level and schema-based coordination, applied in mobile peer to peer networks. The prioritization degree of any requested advert is modeled and enables directed prioritized diffusions to end mobile users that are traversing a certain geographic region (location based advertisements). The proposed method is robust in disseminating redundant messages to users while maintaining connectivity through Gradual Energy Tree-based (GET) configuration. Simulation is performed for the examination and performance evaluation of the proposed scheme, taking into account the modeled prioritization as well as the diffusion accuracy by using the Hierarchical and Non-hierarchical GET configuration.