Workers of the Stingless Bee Melipona Scutellaris Are More Similar to Males Than to Queens in Their Cuticular Compounds Warwick Kerr, Harald Jungnickel, E

Workers of the stingless bee Melipona scutellaris are more similar to males than to queens in their cuticular compounds Warwick Kerr, Harald Jungnickel, E. David Morgan To cite this version: Warwick Kerr, Harald Jungnickel, E. David Morgan. Workers of the stingless bee Melipona scutellaris are more similar to males than to queens in their cuticular compounds. Apidologie, Springer Verlag, 2004, 35 (6), pp.611-618. 10.1051/apido:2004052. hal-00891852 HAL Id: hal-00891852 https://hal.archives-ouvertes.fr/hal-00891852 Submitted on 1 Jan 2004 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Apidologie 35 (2004) 611–618 © INRA/DIB-AGIB/ EDP Sciences, 2004 611 DOI: 10.1051/apido:2004052 Original article Workers of the stingless bee Melipona scutellaris are more similar to males than to queens in their cuticular compounds Warwick E. KERRa, Harald JUNGNICKELb,c, E. David MORGANb* a Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, 38400-902-Uberlândia MG, Brazil b Chemical Ecology Group, Lennard-Jones Laboratory, Keele University, Staffordshire ST5 5BG, UK c Present address: Department of Chemistry, UMIST, Sackville Street, Manchester M60 1QD, UK (Received 16 December 2003; revised 11 March 2004; accepted 17 March 2004) Abstract – The cuticular compounds from the wings of workers, males and queens of the stingless bee Melipona scutellaris Latreille 1811 were analysed by combined gas chromatography-mass spectrometry. This has shown that males, queens and workers have different patterns, but that the pattern of workers is much closer to that of males than it is to queens, supporting other evidence from morphology and behavior that Meliponinae workers are more similar to males than to queens. Meliponinae / cuticular signature / polyphenism / hydrocarbons / caste 1. INTRODUCTION species. Fertile female queens very likely separated much less from the common ancestor, Workers and queens of Apis mellifera L. are unlike what occurred with males and workers, so similar that beginner beekeepers have diffi- and this may explain the situation that fertile culty in distinguishing one from the other, but females very likely leave the nest only once to males are very different from both of them. On be inseminated, and then spend all their lives the contrary, males and workers of meliponine in the dark, where colours have few meaning bees are very similar, and difficult to differen- for them”. tiate. This was noted for the first time by the German emigré Fritz Müller in a letter of 12 Meliponine workers resemble males more September 1875, to Charles Darwin (quoted by than queens in their external morphology (Salt, Zillig, 1997). There Müller says: “In each spe- 1929; Kerr, 1974, 1987; Kerr and Cunha, 1990). cies (of stingless bees) males and workers Melipona queens are brown and dull in nearly extraordinarily resemble each other, mean- all species. However males and workers are while both differ very much from the fertile handsomely coloured, and some species have females (virgin queens). It is a curious fact to yellow bands on their abdomens (Kerr, 1974, me that both types of females (fertile and unfer- 1987). These similarities and differences between tile) are so different, and that the infertile are castes in stingless bees have been studied analogous to the males, and the fertile females through comparisons of morphology and behav- are more similar to fertile females of other spe- iour (Darchen, 1969; Winston and Michener, cies rather than to workers and males of its own 1977). * Corresponding author: [email protected] 612 W.E. Kerr et al. Table I. Generalized Mahalanobis distances (D) obtained from morphological data between queens, workers and males, standardized to units of 100 for comparison, among six species of Apidae. Generalized Distance (D) References Queen to male Queen to worker Male to worker Ratio Species (A) (B) (C) B/C Bombus atratus 100 83.56 31.34 2.7 Kerr, 1987 Melipona compressipes 100 76.58 41.99 1.8 Kerr et al., 1975 Melipona scutellaris 100 134.10 86.10 1.6 Almeida, 1985 Melipona marginata 100 56.27 41.07 1.4 Kerr et al., 1975 Melipona quadrifasciata 100 55.26 52.02 1.1 Campos, 1979 Above this line, workers are closer to males Below this line, workers are closer to queens Apis mellifera 100 59.93 109.06 0.6 Campos, 1979 Kerr (1975) proposed the hypothesis that lect wax, put it in wax deposits and are even similarity between workers and males in capable of using it for the construction of wax meliponines is under genetic control, which pillars (Kerr, 1997). means that in both castes, genes responsible for In contrast to males and workers, the evolu- similar morphology and behaviour are regu- tion of meliponine queens has been in the direc- lated and expressed in similar ways. Juvenile tion of more efficient reproductive aspects. In hormone was found to have an important role the majority of meliponine species studied so in caste phenotype expression in the larval far, the queens are singly mated with one male, stages of meliponine bees (Campos, 1975; Kerr only five species are known where the queen is et al., 1975; Bonetti and Kerr, 1985; Bonetti multiply mated with two to six males (Toth et al., 1994). et al., 2002). Physogastric queens of Melipona Using a program of numerical taxonomy compressipes fasciculata Smith have an aver- with 45 morphological characters of the castes age life expectancy of five years (unpublished of Melipona quadrifasciata Lepeletier, the observation of WEK), whereas most melipo- phenogram obtained showed that workers are nine males and workers live for only for a few more similar to males than to queens (Kerr weeks. et al., 1978). Estimation of the generalized It is becoming increasingly clear that cutic- Mahalanobis distances between queens, males ular hydrocarbons are important recognition and workers of six species, showed that in all substances in social insects as indicated by the investigated meliponines, workers are more results of many experiments (Singer, 1998; closely related to males than to queens (Tab. I). Breed, 1998). These cuticular hydrocarbons Campos (1979) generalized these findings to are characteristic of a group (species or colony) all meliponines. For Apis mellifera the study but may also vary within that specific group revealed the opposite, with workers being more with stage of development, caste, sex or pat- similar to queens than to males (Campos, riline (Blomquist et al., 1998; Monnin and 1979). Peeters, 1999; Sledge et al., 2001; Boomsma There are also behavioural similarities between et al., 2003). The cuticular substances pro- males and workers in stingless bees. Within the duced are a reflection of the enzymes and their nest, males secrete wax, like their worker coun- activity, and these reflect the genes activated to terparts (Drory, 1874, 1877, 1883). Cruz- produce them. We have examined the cuticular Landim (1963) performed histological studies compounds of adult queens, males and workers on the male wax glands and found a striking of a meliponine bee, Melipona scutellaris resemblance between male and worker wax Latreille to see if the similarities among work- gland morphology. Males are also able to work ers and males, besides morphological and with the produced wax inside the hive, they col- behavioural, can also be demonstrated in the Cuticular compounds of meliponine bees 613 chemical composition of the cuticle. We have 30 s later. The identification of compounds was con- indeed found such a similarity between worker firmed by comparison of their mass spectra and and male cuticular substances. retention times with those of standards and using MS-databases. The statistical analysis was performed using 2. MATERIALS AND METHODS SPSS (11.0.0). For the statistical analysis the peaks of each chromatogram were taken as 100% and the percentage of each peak calculated to standardize the Melipona scutellaris bees came from the data set. A normal Principal Component Analysis meliponary (apiary for Melipona colonies) of the and a Discriminant Analysis were used to show that Federal University of Uberlandia. This meliponary all queen samples can be separated from all worker has 70 hives that came from Diamantina forest samples. The low Wilks’ Lambda value of 0.044 (Bahia State, 13° S, 40° W). In order to avoid prob- indicates a good separation of the two groups by lems of immature individuals, care was taken to describing 95.66% of the variance. The leave-one- select mature, foraging workers, and males and out method was used to prove the separation. A sec- queens had been present in the nest for some days ond Discriminant Analysis was done with all male before collection. The wings of bees contain the samples as ungrouped cases. The statistical analysis same pattern of cuticular substances as is found on should show whether the ungrouped cases (= male the rest of the body, and the wings are less subject samples) were distributed either to the queen or to contamination from surfaces with which the bees worker samples, or to both of them, and therefore come into contact (Oldham et al., 1994). They can should show their relatedness towards the two be removed with the minimum of handling and by groups. our method of analysis (Morgan, 1990), the wings of a single individual give a sufficiently strong chromatogram and mass spectra for all the major substances to be identified.

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