Costs and benefits of colony aggregation in the social wasp, Polistes annularis

Females of the social wasp, Polistes annularis, nest in largeaggregations onriverside cliffs in central Texas. Aggregationsoccur where there is an overhang under which wasps build theirnests. Colony aggregations appear to occur partly because individualfemales do notdisperse far from the natal site where most coloniesare successful. In most taxa greater reproductive success nearthe natal nest site is related to unique physical features orto advantages ofbeing in a group. In P. annularis, the physicalfactors and not the social factors appear to be most important.Advantages to remaining near the natal nest site include protectionprovided by the cliff overhang from rain and afternoon sun.Central colonies are as likely to suffer predation as are peripheralcolonies, which indicates an absence of selfish herd advantagesto being in the center of the group. A cost of being in a denseaggregation is often increased reproductive competition, andthis is the case for P. annularis. Colonies in the center ofthe aggregation suffer high usurpation rates by unrelated femalesand in 1 of 3 years produced fewer reproductives than edge colonies.     

Fanconi anemia: evidence for linkage heterogeneity on chromosome 20q

Fanconi anemia is a rare autosomal recessive disorder in which affected individuals are predisposed to acute myelogenous leukemia and other malignancies. We report the results of a genetic linkage study involving 34 families enrolled in the International Fanconi Anemia Registry. A significant lod score was obtained between D20S20, an anonymous DNA segment from chromosome 20q, and Fanconi anemia (Zmax 3.04, theta max = 0.12). However, six other anonymous DNA segments from chromosome 20q, including D20S19, which is highly polymorphic and tightly linked to D20S20, showed no or only weak evidence for linkage to Fanconi anemia. An admixture test revealed significant evidence for linkage heterogeneity (chi 2 = 6.10, P = 0.01) at the D20S19 locus. Lod scores suggestive of linkage between Fanconi anemia and this locus were obtained with two of the largest kindreds studied (lods = 2.6 and 2.1, at theta = 0.001). Thus, our data support the provisional assignment of a Fanconi anemia gene to chromosome 20q.     

A simulation of evasive mimicry in the wild

The hypothesis of evasive mimicry proposes that: (a) the conspicuous coloration of some animals has evolved to warn predators that they are good at avoiding capture; and (b) this conspicuous coloration is mimicked by other, less evasive species which thus gain protection from predation. We have tested these ideas with wild birds as the predators and red and yellow pastry 'baits' as the prey. We used a specially constructed bird table to make one of the colours good at 'escaping': when a bird was about to eat a bait the observer pulled a cord which activated a mechanism that made the baits of one colour (but not the other) drop out of the bird's reach. We first measured the overall selection by the naive birds by presenting, for one day, a 'control' of equal numbers of non-evasive red and non-evasive yellow baits. The birds were then trained for 20 days on equal numbers of evasive yellow and non-evasive red baits, and were then again given a second control (in which the yellows were now non-evasive 'mimics'). The training was repeated for 18 days but with red as the evasive colour, and a third control was then presented (with reds now as the mimics). The proportions attacked daily in the two training sessions suggested that the birds were learning to ignore yellows in the first and reds in the second. In comparison with the first control, fewer yellows were eaten after they had been trained to ignore escaping yellows, and more were eaten after they had been trained on escaping reds. We conclude that the results are further evidence for the hypothesis of evasive mimicry.     

Basophils in skin reactions of mast cell-deficient mice infested with Dermacentor variabilis

Acquired resistance to ticks in guinea pigs has been found to be associated with basophil-rich skin reactions. Mice, which are generally believed to possess few, if any basophils, also acquire resistance following repeated tick infestations and this has been found to be associated with increased numbers of dermal mast cells. Mast cell-deficient W/Wv mice have, however, also been shown capable of acquiring resistance after two infestations with Dermacentor variabilis larvae. In the studies described here, we have examined, with the electron microscope, skin reactions in W/Wv and +/+ mice undergoing their third infestation with Dermacentor variabilis. Basophils, along with neutrophils and eosinophils, were identified using established criteria. The possibility that basophils contribute to various pathogenetic mechanisms in these and other strains of mice is discussed.     

Determination of 35S-aminoacyl-transfer ribonucleic acid specific radioactivity in small tissue samples

Rate determination of protein synthesis utilizing tracer amino acid incorporation requires accurate assessment of the specific radioactivity of the labeled precursor aminoacyl-tRNA pool. Previously published methods presumably useful for the measurement of any aminoacyl-tRNA were unsuccessful when applied to [³⁵S]methionine, due to the unique chemical properties of this amino acid. Herein we describe modifications of these methods necessary for the measurement of ³⁵S-aminoacyl-tRNA specific radioactivity from small tissue samples incubated in the presence of [³⁵S]methionine. The use of [³⁵S]methionine of high specific radioactivity enables analysis of the methionyl-tRNA from less than 100 mg of tissue. Conditions for optimal recovery of ³⁵S-labeled dansyl-amino acid derivatives are presented and possible applications of this method are discussed.     

Yeasts from Marine and Estuarine Waters with Different Levels of Pollution in the State of Rio de Janeiro, Brazil

Yeast counts were made at 24 marine and estuarine sites in the vicinity of Rio de Janeiro, Brazil. Mean salinities of estuarine sites ranged from 14.2 to 27.4‰, and mean temperatures ranged from 25 to 28°C. Total coliform counts varied from 80% above 100,000 colony-forming units (CFU)/100 ml at heavily polluted sites to 100% below 100 CFU/100 ml at unpolluted sites. Total yeast counts above 100 CFU/100 ml were typical of heavily and moderately polluted water but atypical of lightly polluted and unpolluted water. Mean total yeast counts were 2,880 CFU/100 ml for heavily polluted sites, 202 CFU/100 ml for moderately polluted sites, and 3 CFU/100 ml for lightly polluted and unpolluted sites. Total yeast counts had a positive response to increased pollution levels, and Candida krusei and phenotypically similar yeasts as a group were prevalent in polluted estuarine water but rare in unpolluted seawater. The 549 strains of yeasts and yeast-like organisms isolated were grouped into 67 species, of which the 21 most prevalent made up 86% of the total yeast population. The prevalent genera in the polluted estuary were Candida, Rhodotorula, Torulopsis, Hanseniaspora, Debaryomyces, and Trichosporon.     

Progestin binding in mammary tissue of prepartum,nonlactating and postpartum,lactating cows

Binding of [³H]R5020 (17,21-dimethyl-19-nor-4,9-pregnadiene-3, 20-dione) to bovine mammary cytosol indicated the presence of progestin binding sites of high-affinity and low-capacity in tissue from prepartum, nonlactating and from postpartum, lactating cows. To prevent binding of [³H]R5020 to glucocorticoid binding sites, a 200-fold molar excess of nonradioactive cortisol was included during all incubations, thus specific binding was limited to progestin binding sites. Nonradioactive R5020 and progesterone effectively inhibited [³H]R5020 binding to progestin binding sites, while estradiol-17β, dihydrotestosterone (17β-hydroxy-5α-androstan-3-one), dexamethasone (9-fluoro-11β, 17, 21-trihydroxy-16α-methyl-1,4-pregnadiene-3,20-dione) or additional cortisol were ineffective. Dissociation constants for specifically bound [³H]R5020 in cytosol from mammary tissue of nonlactating and lactating cows were nearly identical, averaging 1.9 ( ± 0.3) and 0.8( ± 0.2) × 10?⁹M, respectively. However, binding capacities (fmol/mg cytosolic protein) were greater in cytosol from prepartum, nonlactating (179 ± 53) than postpartum, lactating (41 ± 15) cows. Specific binding components in cytosol from lactating cows sedimented in the 6-7S region on linear sucrose density gradients. When subjected to isoelectric focusing, specific binders with isoelectric points (pI) of approximately 6.1, 7.9 and 8.3 were resolved. The decrease in number of binding sites during lactation was due to the virtual absence of the anionic binding species, suggesting that their presence is necessary for progesterone to inhibit milk secretion.     

Complete amino acid sequence of a variant surface glycoprotein (VSG 117) from Trypanosoma brucei

The amino acid sequence of a variant surface glycoprotein (VSG 117) of Trypanosoma brucei has been determined by manual sequencing of tryptic. staphylococcal protease and cyanogen bromide peptides and fragments derived from these peptides. Some overlaps needed for completion of the sequence were deduced from the nucleotide sequence of complementary DNA derived from messenger RNA coding for VSG 117. The glycoprotein consists of 470 amino acid residues with two carbohydrate chains attached at Asn420 and Asp470. No pronounced hydrophobic regions, which are characteristic of many membrane proteins, are present in the isolated glycoprotein, and the carboxy-terminal region, which is close to the membrane, is remarkably hydrophilic. These observations indicate that the molecule probably does not penetrate the lipid bilayer of the plasma membrane. The high proportion of charged residues in the carboxyterminal region is more consistent with electrostatic interaction with the polar head groups of the phospholipids.     

Reliability theory and foraging by ants

Reliability theory is used to explore the consequences of ant colony's foraging techniques for the evolution of individual competence. Five fundamental strategies are outlined according to Oster & Wilson (1978) and corresponding probabilities of food being returned to the nest are derived. The strategies differ in redundancy schemes and levels of worker reliability. Colony-level selection produces workers of imperfect competence. System reliability can be very high even when the workers are inept, if the foraging strategy is complex and redundant. Individual competence of foragers in a colony depends on diet breadth, caste polymorphism, and tempo. The implications of each variable for colony survival are discussed.