Showing papers in "Naturwissenschaften in 1997"

Survival of Protein in an Organic-Rich Sediment: Possible Protection by Encapsulation in Organic Matter

Abstract: Nitrogen is a major nutrient elementinfluencing the cycling of organicmatter in the biosphere. Both its or-ganic and inorganic forms are closelyrelated to biological productivity andtake part in a series of interconnectedreactions which form the nitrogen cy-cle [1–3]. Part of the nitrogen is in-corporated into organic material andis moved from the active pool and nolonger available for biological produc-tivity. Little is known of the chemicalcomposition of this refractory N orthe processes responsible for its recal-citrance. Traditionally, this refractorynitrogen has been viewed as consist-ing of heterocyclic nitrogen com-pounds [4, 5]. However, we reporthere solid-state

New criteria for the identification of animal fats preserved in archaeological pottery

Abstract: R.P. Evershed, H.R. Mottram, S.N. Dudd, S. Charters, A.W. Stott,G.J. LawrenceOrganic Geochemistry Unit, School of Chemistry, Cantock’s Close,University of Bristol, Bristol, BS8 1TS, UKA.M. GibsonClwyd-Powys Archaeological Trust, 7a Church Street, Welshpool Powys,SY21 7DL, UKA. ConnerCambridgeshire County Council Archaeology Unit, Fulbourne CommunityCentre, Haggis Gap, Fulbourne, Cambridge, CB1 5HD, UKP.W. BlinkhornOxford Archaeological Unit, Janus House, Osney Mead, Oxford, OX2 0ES, UKV. ReevesCentral Archaeological Services, English Heritage, Fort Cumberland,Fort Cumberland Road, Eastney, Portsmouth, PO4 9LD, UK

The study of bird migration by radar. part 1 : the technical basis

Abstract: Since the 1960s radar has been an established research tool in bird migration studies. Radar informs us about the actual course of migration under various environmental conditions: it covers wide distances, is independent of light and reasonably independent of weather, provides data on migratory intensity, flight paths and with special equipment the wing-beat pattern of birds. It thus fills an important gap left by other methods such as visual and auditory observations, laboratory research, trapping, and ringing studies. For an appropriate use of the sophisticated tool, however, it is important to know its capabilities and limitations.

A Magnetic Polarity Compass for Direction Finding in a Subterranean Mammal

Abstract: Correspondence to: S. Marhold While magnetic compass orientation in diverse representatives of birds, reptiles, amphibians, fishes, and insects has been intensively studied over the past three decades, in mammals it is poorly understood (e.g., compared to birds) and most of the evidence is still controversial [1]. The research in nonmammalian classes has focused mainly upon determining the global position and orientation by magnetic cues [2, 3] and examining the biophysical and neuronal features and constraints of magnetic compass orientation, with the ultimate goal of revealing the sensory and neuronal basis of the magnetic perception. On the other hand, studies in mammals are still at the stage of determining whether mammals have a magnetic compass [1]. Most of the earlier evidence was negative or, if positive, not conclusive. The problem in all of these studies was both methodological and the lack of a spontaneous directional behavior in a suitable animal. Experiments were designed to test the ability of mammals either to find a homeward direction when displaced [4] or tested in a circular arena [5] or to be trained to move in a certain direction, for example, to find food [6]. The results of those experiments were problematical because of the difficulty of removing other sensory cues or the lack of motivation, or because the magnetic compass orientation was tested out of its natural context. In addition, the experiments were performed indirectly, i.e., the magnetic field was artificially changed before (e.g., while transported to the release site or the test arena) rather than during the test. A few years ago we found a suitable way in which to investigate a possible magnetic compass in Zambian Gray’s common mole-rats,Cryptomys spp. These animals are small rodents of the family Bathyergidae with a body mass of about 100 g, which, as their more popular relatives, the naked mole-rats, live socially in large family groups (up to about 25 animals) underground. In our earlier study [7] we demonstrated that these subterranean mole-rats housed in a circular arena prefer to build their nests in its southeastern sector, and that they change their directional preference if the magnetic field is shifted by means of Helmholtz coils. Two sibling species of Cryptomysfrom Zambia were involved in our recent experiments: mole-rats originating from the Lusaka area with a karyotype 2n=68 [8] and mole-rats from Itezhi-Tezhi (Kafue National Park) with a karyotype 2n=58. (We have referred to the 2n=68 species as to C. hottentotusin our earlier papers, but later it emerged that both groups are new and as far unnamed species [9].) The experimental design was described in detail previously [7]. In brief, the animals (all members of one family group) were released in groups in a circular arena (diameter 82 cm) with a scattered nest material (slips of tissue papers, etc.). The animals gathered the material and within one to few hours built a nest, the position of which was recorded. The magnetic field conditions were manipulated by Helmholtz coils. The various experimental trials and control trials alternated in an irregular fashion. The northern direction and inclination were measured by means of a special inclination compass. Total intensities of the various magnetic field conditions were controlled by a calibrated gauss meter (Bell, Orlando, mod. 640 and MAG 01, Bartington). Light intensity inside the arena was determined by a calibrated luxmeter (United Detector, Santa Monica CA, model UDT-111A) in four compass directions and perpendicular from bottom to top. The following experiments were carried out in a wooden cottage far enough from other buildings (e.g., the animal house) with respect to the natural magnetic field conditions. The exact results and statistics are provided in Figs. 1–3.

The study of bird migration by radar . part 2 : major achievements

Abstract: This is a brief review of the main insights into bird migration provided by radar. Radar is the main tool to study the flight behavior of migratory birds under the influence of environmental factors, i.e., the ecology of migratory flights, ranging from the large-scale pattern of migration in relation to the distribution of land masses, geomorphology, and weather systems down to the variation of flight behavior of single birds in response to leading lines, obstacles, particular atmospheric conditions, and flight phases. Radar has revolutionized research on bird migration. It provides data on the patterns of migration in various geographical areas and is the main tool for studying the reactions of migrants to topographical features and weather, and the variation of flight behavior in time and space under the influence of environmental conditions. It will continue to play an important role, particularly for the analysis of flight and orientation strategies. This review briefly summarizes the major contributions of radar ornithology to our knowledge of bird migration. To limit the reference list I refer to review papers whenever possible. The most comprehensive synopses are [1] for migration as a whole (with an update on migratory strategies in [2]), [3] for radar ornithology, and [4, 5] for weather-dependence of migration. A methodological update is provided in [6].

Evidence for a Magnetite-Based Navigational “Map” in Birds

Abstract: * Present address: University of Technology, Sydney, Department of Environmental Biology and Horticulture, P.O. Box 123, Broadway, NSW 2007, Australia Birds may use the magnetic field in two ways: as a compass for locating directions and as a component of the navigational “map” for determining position. Due to the different types of magnetic information involved, two different systems of magnetoreception have been proposed, and it has been speculated that one of these receptors is based on biogenic magnetite. Treatments with a brief, high-intensity magnetic pulse designed to alter the magnetization of magnetite particles found in the birds’ heads indeed affected orientation behavior. This supports the hypothesis that a magnetitebased receptor provides orientational information. However, since all birds tested previously had homing and/or migratory experience, it could not be decided whether the pulse has affected their “map” or their compass. Here we present data obtained on inexperienced juvenile birds which strongly suggest that the “map” rather than the compass is based on magnetite. Ever since magnetite crystals of biogenic origin have been found in organisms [1, 2], it has been speculated that these particles are involved in magnetoreception [3]. Many birds show accumulations of magnetite in the ethmoid region [4, 5], which is consistent with the possibility of a magnetite-based sensor. Behavioral studies support this hypothesis. Subjecting birds to a brief high-intensity Naturwissenschaften 84, 26–28 (1997) © Springer-Verlag 1997

The contents of maternal testosterone in house sparrow passer domesticus eggs vary with breeding conditions

Abstract: 1. Smith, B.D.: The Emergence of Agriculture. New York: Scientific American Library 1995 2. Gibson, A., Woods, A.: Prehistoric Pottery for the Archaeologist. Leicester: Leicester University Press, 1990 3. Rice, P.: Pottery Analysis: A Sourcebook. Chicago: University of Chicago Press 1987 4. Evershed, R.P.: World Archaeol. 25, 74–93 (1993) 5. Heron, C., Evershed, R.P.: Archaeological Method and Theory, Vol. 5. Tucson: Arizona Press 1993 6. Passi, S., Rothschild-Boros, M.C., Fasella, P., Nazarro-Porro, M., Whitehouse, D.: J. Lipid Res.22, 778–784 (1981) 7. Evershed, R.P., Heron, C., Goad, L.J.: Antiquity 65, 540–544 (1991) 8. Mills, J.S., White, R.: Archaeometry 31, 37–44 (1989) 9. McGovern, P.E., Glusker, D.L., Exner, L.J., Voigt, M.M.: Nature381, 480–481 (1996) 10. Rottlander, R.C.A.: Archaeo-Physika 12, 1–354 (1990) 11. Evershed, R.P., Heron, C., Goad, L.J.: Analyst115, 1339–1342 (1990) 12. Evershed, R.P., Stott, A.W., Raven, A., Dudd, S.N., Charters, S., Leyden, A.: Tet. Letts.36, 8875 (1995) 13. Evershed, R.P., Heron, C., Charters, S., Goad, L.J.: Proc. Brit. Acad. 77, 187– 219 (1992) 14. Evershed, R.P., Charters, S., Quye, A.: Mat. Res. Soc. Symp. Proc. 352, 85–95 (1995) 15. Enser, M., in: Analysis of Oilseeds, Fats and Fatty Foods, pp. 329–394. (J.B. Rossel, J.L.R. Pritchard, eds.). London: Elsevier 1991 16. Rottlander, R.C.A., Schlichtherle, H.: Naturwissen.70, 33 (1983) 17. McCarthy, M.R., Brooks, C.M.: Medieval Pottery in Britain AD 900–1600 (1988) 18. Santrock, J., Studley, S.A., Hayes, J.M.: Anal. Chem.57, 1444 (1985) 19. Woodbury, S.E., Evershed, R.P., Rossell, J.B., Griffiths, R.E., Farnell, P.: Anal. Chem.67, 2685–2690 (1995) 20. Friedli, H., Lotscher, H., Oeschger, H., Siegenthaler, U., Stauffer, B.: Nature 324, 237–238 (1986) 21. DeNiro, M.J., Epstein, S.: Geochim. Cosmochim. Acta42, 495–506 (1978) 22. Koch, P.L., Fogel, M.L., Tuross, N., in: Stable Isotopes in Ecology and Environmental Science, pp. 63–92. (K. Lajtha, R.H. Michener, eds.). London: Blackwell 1994 23. Francis, G.W.: Chem. Phys. Lipids 29, 369 (1981) 24. Hastorf, C.A., DeNiro, M.J.: Nature 315, 489–491 (1985)

Cooperative Care of Young in Mammals

Abstract: The provision of care to non-offspring in animal societies has attracted substantial scientific attention because of its apparent contradiction to the concept of individual selection. In mammals such cooperative care of alien young has been described for both non-breeding and breeding females. I first review the types of non-offspring care that are known from mammals and then discuss the actual and potential fitness benefits and costs for the donors and recipients of this cooperative behaviour. For many species, however, quantitative analysis is still missing. Non-offspring care provided by non-breeding individuals may best be explained by indirect fitness benefits due to improved reproduction of a related breeder under environmental conditions in which successful direct reproduction is not possible. Cooperative care of young among breeding females is also directed preferentially to non-descendant kin and may have evolved due to mutualistic benefits. Our current knowledge of mammalian cooperative care of the young raises questions that must be answered in order to fully understand the evolution of social behaviour.

Spontaneous Daily Torpor in Malagasy Mouse Lemurs

Abstract: 5. Beason R,C., Brennan W.J.; J. Exp.Biol. 125, 49 (1986)6. Wiltschko, W., Beason, R.C.: Verh.Dtsch. Zool. Ges. 83, 435 (1991)7. Beason, R.C., Harper, J., McNulty, S.,Dussourd, N., Freas, J.: J. Ornithol. 135,Suppl., 88 (1994)8. Wiltschko, W., Munro, U., Beason,R.C., Ford, H., Wiltschko, R.: Experien-tia 50, 697 (1994)9. Beason, R.C., Dussourd, N., Deutsch-lander, M.E., J. Exp. Biol. 198, 141(1995)10. Wiltschko, W., Wiltschko, R.: J. Comp.Physiol. 177A, 363 (1995)11. Walcott, C.: I.E.E.E. Trans. Mag. 16,1008 (1980)12. Wiltschko, R., Wiltschko, W.: MagneticOrientation in Animals. Berlin: Springer199513. Perdeck, A.C.; Ardea 46, 1 (1958)14. Lane, S.G., Battam, H.: Aust. Bird Ban-der 9, 80 (1971)15. Emlen, S.T., Emlen, J.T.: Auk 83, 361(1966)16. Wiltschko, W., Munro, U., Ford, H.,Wiltschko, R.: Nature 364, 525 (1993)17. Batschelet, E.: Circular Statistics inBiology. London: Academic Press 198118. Berthold, P.: in: Acta XIX Congr. Int.Ornithol., p. 215 (H. Ouellet, ed.). Otta-wa: University of Ottawa Press 198819. Kramer, G.: Ibis 99, 196 (1957)20. Phillips, J.B., Borland, S.C.: Nature359, 142 (1992)21. Phillips, J.B., Borland, S.C.: J. Exp.Biol. 188, 275 (1994)28 Naturwissenschaften 84 (1997) © Springer-Verlag 1997

Directional Swimming of Fish Larvae Determines Connectivity of Fish Populations on the Great Barrier Reef

Abstract: Evidence of contamination in PCR laboratory disposables. Naturwissenschaften 82, 423–431 (1995) 18. Taberlet P, Griffin S, Goossens B, Questiau S, Manceau V, Escaravage N, Waits LP, Bouvet J: Reliable genotyping of samples with very low DNA quatities using PCR. Nucl Acids Res24, 3189– 3194 (1996) 19. Zierdt H, Hummel S, Herrmann B: Amplification of human short tandem repeats from medieval teeth and bone samples. Hum Biol 68: 185–199 (1996)

Near East Desertification: Evidence from the Dead Sea

Abstract: Christoph Heim, Norbert R. Nowaczyk, Jo¨rg F.W. NegendankGeoForschungsZentrum, Bereich 3.3 Sedimente und Beckenbildung,Telegrafenberg A26, D-14473 Potsdam, GermanySuzanne A.G. LeroyCentre for Palaeoecology, School of Geosciences,Queen’s University of Belfast, Northern Ireland, UKZvi Ben-AvrahamDead Sea Research Center, Tel Aviv University, Ramat Aviv, 69978, Israel

Even N-Alkane Predominances on the Amazon Shelf and A Northeast Pacific Hydrothermal System

Abstract: Correspondence to: B.R. T. Simoneit An odd-over-even predominance in the n -alkanes >C23H48 has often been used as a marker for a direct input of terrestrial plant wax into geological and environmental samples [1, 2]. On the other hand, an even-over-odd predominance, although much less common, has been reported more frequently in recent years and seems to be generally associated in recent sediment samples with the occurrence of specific inputs from organisms already containing this predominance, such as bacteria and diatoms [3–5]. Several reports show that bacterially produced n -alkanes ranging from C14H30 to C31H64 with strong maxima at one or two carbon numbers are relatively common [6–11]. Many sources have been attributed to the even n -alkanes predominance found in the geosphere and most of those point to a microbial origin. Actually the origin of this unusual carbon number preference has been interpreted as (a) microbial alteration of algal detritus, (b) reductive processes acting on alkanoic acids or other lipid compounds, and (c) direct microbial input (e.g. [3, 12–19]). This paper reports the predominance of n -alkanes with even carbon numbers in samples of dissolved and particulate matter from the Amazon continental shelf (Fig. 1), where the even n -alkanes are of a microbial origin and from alteration of algal detritus. This is contrasted with examples of sediment samples from a hydrothermal system in Middle Valley, Northeast Pacific Ocean, which contain even n -alkanes as a result of reductive processes occurring during the hydrothermal alteration of immature organic matter [19]. Briefly, the Amazon continental shelf (Fig. 1) is characterized by the interaction of an estuarine like, fresh water-seawater frontal system seaward of the river mouth, with strong rotary tidal currents (north-northwest, southsouthwest) and wind-driven surface currents (northwest, southwest) [20]. Bulk sediment C/N ratios are low (2.5–10) [21], indicating a dominance of soil humus from terrestrial sources with a relatively small component of woody (structured) plant material [22]. The analysis of the dC of bulk organic matter revealed a trend for isotopically heavier values seaward [23]. The details of the extraction, fractionation, and lipid analyses are given elsewhere [24]. Middle Valley, NE Pacific, is a faultbounded, “failed” spreading center with large-scale hydrothermal activity and mineral deposits. Abundant turbidite and hemipelagic sedimentation has filled the graben to depths of up to 1.5 km in the center, with as little as 100 m of deposition at the eastern edge. Hydrothermal mounds rise as topographic features above the valley floor [25, 26]. Efficient fluid circulation results in hydrothermal alteration of the sedimentary organic matter from immature precursors to mature petroleum [19]. Sediments from Middle Valley were sampled on Ocean Drilling Project Leg 139 from Sites 857 and 858 [19]. The detailed experimental procedure is given elsewhere [19].

Monitoring the routing of dietary and biosynthesised lipids through compound--specific stable isotope (delta 13C) measurements at natural abundance.

Abstract: mother’s cousins’ grand-offspring of the workers [13, 14]. This hardly suggests that the wasps will be unwilling to rear brood of different levels of relatedness. The most likely explanation for our results is therefore that cofoundresses forced to nest alone are incapable of rearing as much brood as queens forced to nest alone or a solitary foundress, and hence we suggestion that wasps may choose their nesting strategies based on their broodrearing abilities.

DNA typing in forensic medicine and in criminal investigations: a current survey.

Abstract: Since 1985 DNA typing of biological material has become one of the most powerful tools for personal identification in forensic medicine and in criminal investigations [1-6]. Classical DNA "fingerprinting" is increasingly being replaced by polymerase chain reaction (PCR) based technology which detects very short polymorphic stretches of DNA [7-15]. DNA loci which forensic scientists study do not code for proteins, and they are spread over the whole genome [16, 17]. These loci are neutral, and few provide any information about individuals except for their identity. Minute amounts of biological material are sufficient for DNA typing. Many European countries are beginning to establish databases to store DNA profiles of crime scenes and known offenders. A brief overview is given of past and present DNA typing and the establishment of forensic DNA databases in Europe.

Octadecanoid-Mediated Signal Transduction in Higher Plants

Abstract: The observation that methyljasmonate is a strong promoter of senescence marked the discovery of lipid-derived signaling molecules of higher plants. This group of compounds, now collectively termed octadecanoids, is derived from the fatty acida-linolenic acid and involved in physiological processes such diverse as the triggering of defense reactions against herbivores and pathogens, mechanotransduction, plant volatile emission, potato tuberization, and many others. Recent research has yielded clues to a deeper understanding of octadecanoid biology. Control over this central signaling system may open new avenues in biological pest control through plant defense regulators. I n recent years many novel and highly potent lipoid signaling molecules have been recognized. These comprise lipophilic compounds not derived from lipids, such as the triterpenoid brassinosteroids, others that are partly of lipid origin such as the lipo-oligosaccharides, nodulation factors of Rhizobiumspecies that may have relatives endogenous to plants, and a third group, the octadecanoids, whose structures are derived from plant fatty acids. Lipid-mediated signaling is an important aspect of plant life and a rapidly growing area of research. Due to space constraints only the octadecanoids are discussed here. However, the interested reader is referred to recent reviews on brassinosteroid biology [1] and lipo-oligosaccharide biology [2] which introduce topics that cannot be addressed here. Also, the topic of lipidic second messengers is beyond the scope of this review.

Evolution of the freshwater eels.

Abstract: The freshwater anguillid eels have an unusual life history and world-wide distribution. Questions about the phylogenetic relationships of this group and how their long spawning migrations and larval phase may contribute to their global distribution have not been addressed. This paper is first presentation of molecular phylogeny of Anguilla species, and based on this phylogenetic tree we suggest new aspect of the evolution of this group. Namely, ancestral eels originated during the Eocene or earlier, in the western Pacific Ocean near present-day Indonesia. A group derived from this ancestor dispersed westward, probably by larval transport in the global circum-equatorial current through the northern edge of the Tethys Sea. This group split into the ancestor of the European and American eels, which entered into the Atlantic Ocean, and a second group, which dispersed southward and split into the east African species and Australian species. Thus the world-wide distribution of the eel family can be understood from knowledge of continental drift, ocean currents, a specialized larva and evolutionary forces favoring dispersal and speciation of segregated gene pool.

New findings concerning vertebrate porin

Abstract: Eukaryotic porin can be considered to be a good candidate for forming the channel component of the protein complex which, depending on the approach used, may realize its expression either as the outwardly-rectifying depolarization-induced chloride channel or as the volume-sensitive organic osmolyte-anion channel. As a basis for this proposition, we point to a series of correspondences in properties between mammalian porin and the ORDIC channel complex. Specifically, mammalian porin is expressed in the plasmalemma of different cells and chloride channels can be blocked by anti-human porin antibodies in astrocytes and endothelial cells. There is an indication of colocalisation of human porin and the cystic fibrosis (CF) gene product, CFTR, in the apical region of epithelial cells. The primary structure of porin from a CF patient was found to be normal. Cytosol and amniotic fluid fractions influence the channel characteristics of mammalian porin. Channel-active mammalian porin binds ATP and the stilbene disulphonate grouping of the chloride channel inhibitor DIDS. Human porin in black membranes is a pathway for taurine, and biogenic polyamines reduce the voltage dependence of human porin. Assuming the relationship between human porin and the ORDIC channel/VSOAC complex, studies on plasmalemma-integrated human porin have a relevance for CF research. In addition, we refer to a case study on a child with encephalomyopathy in which porin could not be detected using monoclonal anti-human porin antibodies. Our studies were based on purified and sequenced human porin from different cells and from different cell compartments. In addition, we raised antibodies against mature human porin or synthetic parts of the molecule. This provided a firm foundation for our topochemical work with which we were able to establish the multi-topological expression of eukaryotic porin channels. The data are summarized and discussed.

High Humidity in the Honey Bee (Apis mellifera L.) Brood Nest Limits Reproduction of the Parasitic Mite Varroa jacobsoni Oud.

Abstract: Factors influencing reproduction of the parasitic mite Varroa jacobsoni have become a central theme of honey bee pathology. In large parts of the world the mite has made it impossible for colonies of the honey bee Apis mellifera to survive if no measures of treatment are applied [1]. Originally a parasite of the Eastern honey bee A. cerana, the mite was detected in colonies of A. mellifera only less than 4 decades ago [2]. A. cerana colonies are not damaged by V. jacobsoni because several factors prevent the build-up of a large mite population [3]. The most important factor is that in colonies of A. cerana the parasite, which can reproduce only in capped brood cells, reproduces exclusively in drone brood cells while in colonies of A. mellifera it reproduces in worker brood cells as well [4]. In cold, temperate, and Mediterranean climates the mite population grows exponentially until the colony collapses, due mainly to a high percentage of bees damaged by V. jacobsoni during their pupal development [5].

Lake Formation and Catastrophic Dam Burst during the Late Pleistocene Laacher See Eruption (Germany)

Abstract: and rising more than 15m above the pre-eruptive land surface. Collapse of the unstable dam prior to the final phase of the eruption resulted in sudden drainage of the lake. Deposits laid down by the catastrophic floodwaves occur at least as far north as Bonn, more than 50km downstream from Andernach.

Molecular phylogenetic information on the identity of the closest living relative(s) of land vertebrates.

Abstract: The phylogenetic position of tetrapods relative to the other two living sarcopterygian lineages (lungfishes and the coelacanth) has been subject to debate for many decades, yet remains unresolved. There are three possible alternatives for the phylogenetic relationships among these three living lineages of sarcopterygians, i.e., lungfish as living sister group of tetrapods, the coelacanth as closest living relative of tetrapods, and lungfish and coelacanth equally closely related to tetrapods. To resolve this important evolutionary question several molecular data sets have been collected in recent years, the largest being the almost complete 28S rRNA gene sequences (about 3500 bp) and the complete mitochondrial genomes of the coelacanth and a lungfish (about 16,500 bp each). Phylogenetic analyses of several molecular data sets had not provided unequivocal support for any of the three hypotheses. However, a lungfish + tetrapod or a lungfish + coelacanth clade were predominantly favored over a coelacanth + tetrapod grouping when the entire mitochondrial genomes alone or in combination with the nuclear 28S rRNA gene data were analyzed with maximum parsimony, neighbor-joining, and maximum likelihood phylogenetic methods. Also, current paleontological and morphological data seem to concur with these molecular results. Therefore the currently available molecular data seems to rule out a coelacanth + tetrapod relationship, the traditional textbook hypothesis. These tentative molecular phylogenetic results point to the inherent difficulty in resolving relationships among lineages which apparently originated in rapid succession during the Devonian.

Molecular Evidence for a Jurassic Origin of Ants

Abstract: The ants, a group of ecologically important insects [1], are commonly found in Oligocene and Miocene ambers, whereas fossils of apparent antwasp intermediates are well known from the mid-Cretaceous [2]. Based on this record, it has become commonly accepted that the ants arose no earlier than the late Cretaceous and that the adaptive radiation of extant ant genera took place no later than the start of the Tertiary [2]. The recent discovery of Cariridris bipetiolata, a Brazilian fossil from the Aptian of the early Cretaceous which has been placed in the ant subfamily Myrmeciinae [3] (represented today by the Myrmecia bulldog ants of Australia and nearby islands, has shown, however, that the ants diversified much earlier than previously thought, with Cariridris, an undoubted ant, roughly contemporaneous with the previously known ant-wasp intermediates. In this review, we estimate the time of origin of the ant family using the divergences between mitochondrial DNA sequences from ants of six subfamilies and a vespid wasp. We used mitochondrial cytochrome b sequences from Myrmecia gulosa and the karyotypically diverse [4] M. pilosula group [5] to calibrate the evolutionary rate of this sequence in ants. The evolutionary rate was calibrated using codon positions 1 and 2 only (base composition differences at position 3 indicate a lack of stationarity [6]) under the assumption that nucleotide substitutions follow Kimura’s two-parameter model [7]. A conservative estimate of 124.5 Ma for the age of Cariridris was used, this being the lower boundary of the Aptian, i.e., 112–124.5 Ma ago [8]. To check the suitability of the data for estimating divergence times, we applied the relative rate test of Wu and Li [9] (as implemented by Muse and Weir [10]), obtaining the results in Table 1, finding that the data do not violate the assumptions of a molecular clock. Using (1) this age, (2) the evolutionary distances between Myrmecia species, and (3) the hierarchical phylogenetic approach, i.e., a method for increasing the precision in estimating the distance between a group of taxa (the M. pilosula group) and their outgroup (M. gulosa ) by taking into account both phylogenetic structure and variation in component distances [11], yields an estimate of the evolutionary rate for ants of 0.165±0.023% (95% confidence intervals) substitutions per million years. To estimate the date of origin of the ants, we obtained mitochondrial DNA sequences homologous to those mentioned above (positions 11427–12134 in the honeybee mitochondrial genome [12]) from five further ant subfamilies believed to represent the most divergent lineages, and took the largest divergence value as giving the best estimated of the age of the group. This approach yields an age of 185 ±36 Ma ago (95% confidence limits derived from the SE of the divergence estimate; Fig. 1). Similar results follow from an analysis using nonsynonymous substitutions [13]. The larger distances to the wasp, with a relatively narrow spread compared to those between ants, indicate that saturation has not been a serious problem in this calculation. Our finding thus places the origin of the ants in the early Jurassic, at least 70 Ma earlier than recorded by fossils [3], and placing the group within the

Behavioral Plasticity in Division of Labor in the Lower Termite Reticulitermes fukienensis

Abstract: A major principle in the study of the social organization of insect colonies is that members of the worker caste partition tasks required for colony growth and survival. Division of labor according to worker size and age has resulted in systems of division of labor commonly described, respectively, as physical polymorphism and age polyethism [1]. However, in addition to these biological markers of task performance, workers may show considerable behavioral flexibility and adjust their labor to the current demands of a colony [2]. This flexibility in task performance involves processes such as behavioral acceleration and behavioral reversion as well as other more immediate shifts in the temporal patterns of attending to colony needs [2]. Through these methods of compensatory task switching workers begin to carry out age-correlated tasks ahead of their typical temporal schedule [3]. Several studies have demonstrated that task flexibility can accompany alterations in colony demography and colony needs in the social Hymenoptera. However, in the Isoptera division of labor is poorly understood, and there are no published data demonstrating whether behavioral flexibility in task performance can occur. Division of labor in termites appears to be highly variable, and termites may or may not divide labor according to morph and age, depending upon the species [4–6], but will individuals of one caste compensate behaviorally when a caste that typically performs certain tasks is absent? In this paper we describe behavioral flexibility among workers of different instars of the subterranean termite Reticulitermes fukienensis. Colonies of R. fukienensiswere acquired in Tai Po Kau Nature Reserve, Hong Kong. Head widths of 501 larvae and workers from a single mature colony were measured using a dissecting microscope with an ocular micrometer. Size variation among workers and larvae, measured as headwidth, was found to be comprised of five peaks (Fig. 1), which we [7, 8] refer to as: small larva (SL; head widths 0.36–0.44 mm), large larva (LL; 0.48–0.58 mm), small worker (SW; 0.66–0.72 mm), medium worker (MW; 0.88–0.94 mm), and large worker (LW; 1.00–1.08 mm). Measurements and following successive molts indicate SL, LL, SW, and MW correspond to instars 1, 2, 3, and 4, respectively, and that LW corresponds to the 5th and later instars [7, 8]. After the 5th instar headwidth shows little increase in Reticulitermes [9]. Details of these size categories are described elsewhere [7, 8]. Termites used in experiments had been established in laboratory stock colonies for no more than 3 months from the time of field collection. Worker subgroups were maintained in 9-cm-diameter petri dishes, each containing a pine block (3.0́ 2.0́ 0.5 cm) and moistened filter paper to provide food and water. To maintain a high humidity level, dishes were stacked in transparent plastic boxes lined with moist towel. Throughout all experiments termites were kept at 22°±2°C under 24 h fluorescent light (65 W). Each stock colony was used to establish one to six pairs of subcolonies of different caste proportions. Ten individuals each of SL, LL, SW, MW, and LM comprised the first set of subcolonies (“control”). The second set of subcolonies (“experimen-

Pollen Eating, Storing, and Spitting by Ants

Abstract: A number of insects feed on pollen, but there are only a few, mainly episodic, records of pollen-eating ants. Worker ants do not fly and can reach only a limited number of flowers. We report here on a group of neotropical ants relying largely on pollen for their food. These ants walk short distances only and compensate for their incapacity to visit many flowers by licking wind-transported pollen from leafs. Pollen is regularly stored in the foregut as reserve and regurgitated to nestmates as food, and indigestible pollen membranes are disposed of outside the nest. We explain in this way the enigmatic production of “infrabuccal pellets” repeatedly described in the literature and thought until now to be a water retention mechanism. We show that storing of pollen in the crop is enabled by a sophisticated filtering mechanism of the alimentary canal. There are only three published, explicit mentions of pollen-eating ants. All of them refer to two species of Zacryptocerus: Z. texanus [1, 2], confined to Texas and Nuevo León in Mexico and Z. rohweri [3], recorded from Arizona and from Sonora in Mexico. Together these two species are the two northernmost representatives of a tribe of neotropical ants (Cephalotini) currently containing 137 species in three genera. We observed several Cephalotini in the field and kept laboratory colonies of the following seven Brazilian species: Cephalotes atratus (Linnaeus), Zacryptocerus clypeatus (Fabricius), Z. pusillus (Klug), Z. angustus (Mayr), Z. borgmeieri (Kempf), Z. targionii (Emery), and Z. pallens (Smith). All showed a marked preference for (some species of) pollen among a variety of diets offered. Under natural conditions most Cephalotini nest in dead parts of trees and walk slowly and over short distances only, rendering improbable an efficient exploitation even of the pollen produced by the tree that they inhabit. Foragers patrol and lick pollen from leaves [2, 3]. Our laboratory colonies systematically refused pollen kneaded by honeybees and pollen from ornamental flowers, which may suggest a preference for wind-dispersed pollen.