Acquisition of species-specific perfume blends: influence of habitat-dependent compound availability on odour choices of male orchid bees (Euglossa spp.).

Male orchid bees (Euglossini, Apidae, Hymenoptera) expose species-specific blends of volatile chemicals (perfume bouquets) during their courtship display. The perfumes are acquired by collecting fragrant substances from environmental sources, which are then accumulated in specialised hind leg pouches. To balance the perfume composition, the males need to find and collect the required substances in specific relative amounts while facing seasonal, local or habitat-dependent differences in compound availability. Experience-dependent choice of odours, i.e. 'learned avoidance' of recently collected components, has been proposed as the mechanism that mediates the accumulation of the stereotypical compound ratios. In the present study, we used the presence of certain compounds in male hind leg pouches as proxy for the respective local compound availability, and investigated whether differences in content are correlated with differences in chemical choice assays. Our results suggest that volatile availability differs between localities (n = 16) as well as habitats (n = 2; coastal vs. inland) across the Yucatán peninsula, Mexico, for both studied species. Male Euglossa dilemma showed a pronounced preference for benzyl benzoate and eugenol at locations where those compounds were rare in hind leg extracts, as predicted by the learned avoidance model. No equivalent correlations were found for Euglossa viridissima. This is the first study to combine chemical analyses of perfumes with bioassays of odour choice. It strengthens the view that negative feedback from collected odours modifies future chemical choice and helps males to acquire specific perfume blends.

Genetic analysis of the antigens defined at the third international BoLA workshop.

A comparison of lymphocyte antigens showed that 32 of the 33 BoLA antigens defined at the third international BoLA workshop (Bull et al., 1989) corresponded to previously defined local antigens (Stear et al., 1988). The third workshop antigen w18 had no locally defined equivalent. All 32 antigens were shown in family studies to be expressed by autosomal co-dominant genes, and all 32 workshop antigens were shown to be products of the BoLA system. After excluding the supertypic antigens, nearly all animals tested possessed only one or two antigens and there were no observed recombinants in family studies. These results do not exclude the possibility that the 32 workshop antigens are the products of one locus (BoLA-A).

The relationships of birth weight, preweaning gain and postweaning gain with the bovine major histocompatibility system.

A total of 739 cattle from nine breeds maintained at the Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska were tested for 42 class I antigens of the bovine major histocompatibility system (BoLA). Each antigen appears to be the product of a distinct co-dominant allele of the BoLA-A locus. The number of antigens present in each breed ranged from a minimum of 10 in Hereford to a maximum of 21 in Charolais cattle. There were large differences among breeds in the frequencies of antigens. The effect of each antigen on birth weight, preweaning weight gain and postweaning weight gain was estimated in a gene substitution model. Each breed was analyzed separately. There were significant effects of some BoLA antigens on birth weight, preweaning weight gain and postweaning weight gain, which is consistent with previous reports showing associations between the major histocompatibility system and growth parameters in mice, rats and pigs. However, further research is necessary to confirm these findings and to determine the biological mechanisms underlying these associations.

The influence of the BoLA-A locus on reproductive traits in cattle.

Associations between the major histocompatibility complex (MHC) and reproductive performance have been reported in humans, mice, rats, pigs and chickens. Only the A locus of the bovine major histocompatibility complex (BoLA-A) has been well characterized, and 42 alleles of this locus have been identified in American cattle. Four studies were conducted to examine the association between alleles of the BoLA-A locus and reproductive performance. Testis size, which is an indicator of early puberty and increased fertility in young bulls, was examined in 440 yearling bulls from nine breeds with a gene substitution model that included the effects of breed, sire, age of dam and age or weight of the bull. Estimated breeding value for twinning was examined with a gene substitution model with 204 cattle from a herd with a high frequency of twinning. Fertility of potential partners having BoLA-A locus alleles in common was examined in a prospective study involving 101 pure-bred Hereford cows mated by artificial insemination to four pure-bred Hereford bulls. The effect of homozygosity on birth weight, preweaning weight gain and post-weaning weight gain was estimated in a sample of 683 calves from nine breeds; 22% of the calves were apparently homozygous and 78% were heterozygous at the BoLA-A locus. There were significant and large effects of some BoLA-A locus alleles on paired testicular volume, but the analyses on the other traits did not show significant associations. Substitution of the W6.1 allele for the W9A allele reduced paired testicular volume by 150 +/- 44 cm3. The W6.1 allele has now been shown to influence a reproductive trait, a production trait and susceptibility to an economically important disease. Selection for these traits may influence the frequency of the large number of alleles at the BoLA-A locus.

Breed differences in the distribution of BoLA-A locus antigens in American cattle.

A total of 627 cattle representing seven breeds from south central Nebraska, USA were tested for 37 BoLA antigens which behave as products of 37 distinct alleles of the class I BoLA-A locus. Four antigens were absent from all breeds tested. The other antigens showed marked and statistically significant differences in breed distribution. There was no evidence for blank (null) alleles. The number of alleles in each breed ranged from 10 to 20. The Hereford and Simmental populations tested were less polymorphic than the Angus, Brown Swiss, Charolais, Gelbvieh and Limousin populations.

Isolation of Streptococcus suis from swine in Nebraska.

Streptococcus suis was isolated from swine with localized and diffuse infections. The isolates (n = 121) were unable to grow in broth containing 6.5% NaCl. Their abilities to hydrolyze esculin were variable, as were their fermentative reactions in lactose, trehalose, raffinose, and inulin. Sorbitol was not attacked by any strain. Serologic reactions were obtained between the isolates and coagglutination reagents prepared from commercially available antisera to streptococcal groups D, R, or S.