Molecular phylogeny of Heritiera Ait on (Sterculiaceae), a tree mangrove: variations in RAPD markers and nuclear DNA content

Random amplified polymorphic DNA (RAPD) markers are used to estimate interspecific variation among mangrove and non-mangrove Heritiera fomes, H. littoralis and H. macrophylla. All the species have 2n = 38 chromosomes, with minute structural changes distinguishing the karyotype of each species. Significant variation of 4C DNA content occurs at the interspecific level. Interspecific polymorphism ranged from 14.09% between H. fomes and H. littoralis to 52.73% between H. fomes and H. macrophylla. H. macrophylla showed wide polymorphism in the RAPD marker with H. littoralis (51.23%) and H. fomes (52.73%). Two distinct RAPD products obtained from OPA-10 (1000 bp) and OPD-15 (900 bp) found characteristic molecular markers in H. macrophylla , a species from a non-mangrove habitat. H. macrophylla was more distantly related to H. fomes [genetic distance (1-F) = 0.305] than to H. littoralis [genetic distance (1-F) = 0.273]. H. littoralis was of a closer affinity to H. fomes [genetic distance (1-F) = 0.218] than to H. macrophylla.     

The American Avocet (Recurvirostra americana) as a paradigm for adult automimicry

Summary The body of theory concerning life-history strategies predicts that the duration of high-mortality stages should be minimized by natural selection. This is especially applicable to the avian pre-flight stage, during which growth rates typically are rapid. Using the American Avocet (Recurvirostra americana) as a paradigm, I propose a developmental strategy by which young animals can lower their mortality rates by an accelerated (and deceptive) acquisition of adult or adult-like characters. The benefit accrues when predators misidentify the vulnerable young as adults and fail to attack them because adults are much less vulnerable. This strategy, termed adult automimicry, is most likely to occur in precocial species living in open habitats.American Avocets are large, precocial, open-country shorebirds that first fly when about 4–5 weeks old. They develop a juvenal, plumage in their third week that resembles adult breeding plumage in pattern and color, even though plumage details are different. At this time chicks begin using adult foraging techniques and tend to move away rather than hide from potential predators. A few weeks later they acquire a first winter plumage that resembles adult winter plumage. Thus, avocet chicks appear unusually adult-like after their second week. This should make it difficult for distant predators to distinguish flightless chicks from volant adults.     

Predation pressure on an imperfect Batesian micicry complex in the presence of alternative prey

Summary Differential predation pressure and the probability of predation on a Batesian mimicry complex and on alternative prey were estimatedin a field experiment. The mimicry complex was composed of a noxious model (Eleodes obscura (Say)) and a palatable mimic (Stenomorpha marginata (LeConte)). House crickets (Acheta domesticus) (Linn.) were used as alternative prey. The experiment was conducted for 23 nights in August and September to approximate the peak seasonal activity time period during which both models and mimics normally are exposed to predation while foraging and depositing eggs. Each night thirty prey in ratios of 16 models: 7 mimics: 7 crickets were exposed for 2.5 h to a suite of predators consisting of pallid bats (Antrozous pallidus), striped skunks (Mephitis mephitis) and ringtails (Bassariscus astutus) that had free access to the prey. The model-mimic ratio was similar to that found in nature. Predators obtained prey on 11 of the 23 nights and preferred the alternative prey (crickets) in proportions higher than was expected from a predation rate that was equal on all species of prey. Mimics were taken by predators at a rate proportional to their abundance, while models were taken at a rate considerably lower than their relative abundance. This suggests that at least some of the predators could distinguish between models and mimics and were willing to eat the mimics at higher frequencies than they were willing to eat the models. However, although the mimicry is not perfect with respect to the entire predator suite, the mimics still gain an advantage by resembling the models, compared to the predation levels on the alternate prey.     

Molecular mimicry and the autoimmune response to the peripheral nerve myelin PO glycoprotein

In the Lewis rat immunisation with the myelin PO glycoprotein can induce an inflammatory demyelinating disease of the peripheral nervous system, experimental allergic neuritis (EAN), which has many clinical and histopathological parallels with the human disease the Guillain-Barre syndrome. In view of the reported association of GBS with a number of infectious agents we have investigated whether molecular mimicry may occur between microbial antigens and the PO protein that could possibly trigger a similar pathogenic autoimmune response in man. A computer search of the available protein sequence data bases identified several absolute sequence homologies between PO and viral proteins that involve five or more consecutive amino acid residues. Four of these sequence homologies involved viral pathogens previously associated with the Guillain-Barre syndrome, namely Epstein-Barr virus (EBV), cytomegalovirus (CMV), Varicella zoster virus (VZV) and human immunodeficiency virus I (HIV I). Although, sequence homologies were also found between viral peptides and the neuritogenic determinants of PO, residues 56–71 and 180–199, these homologies proved incapable of eliciting EAN in the Lewis rat. These observations are discussed with reference to the role that molecular mimicry between T cell epitopes on pathogen derived antigens and the PO protein may play in the pathogenesis of the Guillain-Barre syndrome.Abbreviations EAN Experimental allergic neuritis - EAE experimental allergic encephalomyelitis - PNS peripheral nervous system - CNS central nervous system - MBP myelin basic protein - GBS Guillain Barre syndrome - CFA complete Freund's Adjuvant - LPC lysophosphatidyl choline - VZV Varicella zoster virus - CMV cytomegalovirus - EBV Epstein Barr virus - HIV I human immunodeficiency virus I Special issue dedicated to Dr. Alan N. Davison     

中国人ε珠蛋白基因5′侧序列中多态性Hinc Ⅱ位点的进一步研究

本文进一步研究了我国不同民族的正常个体以及β地中海贫血患者θ珠蛋白基因5′侧序列中的多态性HincⅡ位点及其遗传性质。在广西壮族正常个体和β地中海贫血纯合子中,该多态性位点的发生频率均为75％,与正常汉族人测得值相近。家系分析资料表明,该多态性位点完全按照孟德尔规律进行遗传。     

Pyrazines as warning odour components in the Monarch butterfly, Danaus plexippus, and in moths of the genera Zygaena and Amata (Lepidoptera)

2-Methoxy-3-alkylpyrazines have been identified as odour components in Danaus plexippus, Zygaena lonicerae and an Australian Amata species, by means of coupled gas chromatography/mass spectrometry, with selected ion monitoring. Wide variability in pyrazine content was observed with D. plexippus and this was correlated with similar variability in the larval food-plants, Asclepias spp., which are presumed to be the odour sources for this butterfly. The importance of pyrazines in the biology of aposematic insects and their role as ingredients of a generalized warning system are discussed.