Dwarf gynes in Nannotrigona testaceicornis (Apidae, Meliponinae, Trigonini). Behaviour, exocrine gland morphology and reproductive status Vl Imperatriz-Fonseca, C Cruz-Landim, Rlm Silva de Moraes To cite this version: Vl Imperatriz-Fonseca, C Cruz-Landim, Rlm Silva de Moraes. Dwarf gynes in Nannotrigona testa- ceicornis (Apidae, Meliponinae, Trigonini). Behaviour, exocrine gland morphology and reproductive status. Apidologie, Springer Verlag, 1997, 28 (3-4), pp.113-122. hal-00891410 HAL Id: hal-00891410 https://hal.archives-ouvertes.fr/hal-00891410 Submitted on 1 Jan 1997 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. Original article Dwarf gynes in Nannotrigona testaceicornis (Apidae, Meliponinae, Trigonini). Behaviour, exocrine gland morphology and reproductive status VL Imperatriz-Fonseca C Cruz-Landim RLM Silva de Moraes 1 Instituto de Biociências, Universidade de São Paulo, CP 11461, CEP 05508-900, São Paulo; 2 Instituto de Biociências, Universidade Estadual Paulista, CP 199, CEP 13506-900, Rio Claro, São Paulo, Brazil (Received 21 January 1997; accepted 14 April 1997) Summary—The behaviour and morphology of dwarf gynes produced in worker-sized cells of nor- mal colonies in Nannotrigona testaceicornis (Meliponinae, Trigonini) were studied. The behaviour of these dwarf virgin queens was the same as observed for normal Trigonine gynes. The glandular equipment is also the same: Dufour glands, fat bodies and spermathecae are present. Despite these similarities, their ovaries are different. The functional significance of dwarf gynes is unknown, but may be a basis for an alternative reproductive strategy. dwarf gynes / larval food / reproductive strategies / stingless bees / Trigonini / Nannotrigona tes- taceicornis INTRODUCTION quantities may have an additional influence in caste determination. In Trigonini, a Currently two main systems of raising trophic system occurs and it was assumed queens are known in stingless bees. In that caste is exclusively determined by the Meliponini, queens, males and workers orig- amount of food offered. Larvae producing inate from cells which are of the same size. queens are superfed, although the strategies This implies that larvae of both castes ingest to reach superfeeding may vary (Terada, almost similar amounts of food. Kerr (1950) 1974). Most of the bees belonging to the and Kerr et al ( 1966) suggested that in Trigonini construct large royal cells, which Meliponini caste is genetically determined, contain much more food than cells for although environmental factors and food workers and males. * Correspondence and reprints Tel: (55) 11 818 7515; fax: (55) 11 813 4151; e-mail: [email protected] In Schwarziana quadripunctata, a regu- dish, without any attendant workers. Among the lar production of gynes (in a range of sizes) emerged bees, workers and males, eight dwarf and a normal were found. One of the is normally observed throughout the year. gynes gyne dwarf gynes died inside the cell; it was weighed As many as 35 gynes can be simultaneously upon removal from the cell. The other gynes and found in the nest and (Imperatriz-Fonseca 17 workers were weighed as soon as they from cells of a sim- Zucchi, 1995), emerging emerged; gynes were also weighed on follow- ilar size as cells for workers and males. ing days. The behaviour of some of these gynes Camargo (1974) verified that combs with was observed in the Petri dish. After these obser- pupae giving rise to queens of various sizes, vations, four dwarf gynes were separated in boxes water and some presented larger cells in an irregular spatial containing cerumen, sugar pollen, where each dwarf gyne was attended by arrangement. Cells with slightly larger pupae, 20 workers that emerged from the same comb which medium-sized and a produce queens, the same day as the gynes. Each gyne was ran- few large royal cells which produce large domly observed during 5 days. or males, are their queens giant recognized by Three of the gynes used for behavioural obser- lower but differences them bottom, among vation were subsequently collected for morpho- are not apparent when cells are constructed. logical studies, as well as the normal gyne that Some of the gynes have the same size as the hatched later at the edge of the same comb, ten workers, others can be smaller and, there- workers 5-days-old and a physogastric queen from another To some of their fore, are called dwarf or miniature gynes. colony. study glands (mandibular, tergal and Dufour) and These gynes have less ovarioles (Camargo, ovaries, they were fixed in 4% paraformalde- than the ones. In 1974) larger Schwarziana, hyde and embedded in JB4 historesin. Sections the ovariole number in varied from six gynes were stained with hematoxylin and eosin. All of to nine per ovary, although most of them pre- the analyzed gynes remained unmated. Workers sent eight ovarioles per ovary. were studied for comparison with gynes. Other Trigonini besides Schwarziana The other dwarf gynes were deposited in the JMF bee collection de also produce dwarf gynes; these are reported Camargo (Universidade in Cephalotrigona femorata (Nogueira- São Paulo, Ribeirão Preto, Brazil). Neto, 1951), Plebeiajuliani (Juliani, 1962), P remota et al, 1975) (Imperatriz-Fonseca RESULTS and P emerina (Kleinert, personal commu- nication). However, these dwarf gynes are In the studied comb, the size of workers dif- rarely found, suggesting a different repro- fers from cell to cell. One for ductive strategy compared to Schwarziana. possibility detecting such variability is to consider their the process of cell construc- Recently, weight. Variation in gynes weight is tion and oviposition in Nannotrigona tes- expected, as it occurs among workers. Fig- taceicornis was studied by Sakagami et al ure 1 shows the weight of workers and dwarf (1993), but they do not report on virgin gynes, just after emergence. queens, differently sized cells, nor on dif- Dwarf at varied ferently sized workers. The occurrence of gynes’ weight emergence 6.5 to 9.3 = x = dwarf gynes is an unpredictable event. This from mg (n 8, 7.67 mg, SD = whereas workers’ var- paper compares dwarf gynes in Nannotrig- 0.87) weight x = 7.13 ona (Nannotrigona) testaceicornis with ied from 6.4 mg to 8.5 mg (n = 17, SD = all of them from the same workers and normal gynes. mg, 0.72), piece of comb. Development time of males, dwarf and workers was MATERIALS AND METHODS gynes apparently similar, although gynes raised in royal cells A mature comb was taken from a swarming hatch later, and often can be found in iso- colony of N testaceicornis, and kept in a Petri lated cells from a comb from which all bees already emerged, and where the cells have hatching, and 6.6 mg the next day). The been taken down by the workers. nature of the frequent trophallaxis that occurred among workers and gynes deserves Similar to the normal N testaceicornis special attention: workers often offered food workers and gynes at emergence, the dwarf to the gynes; nevertheless sometimes gynes were not and did not attract gynes pigmented also offered a to the work- workers. When observed in the yellowish liquid together ers. Petri dish, differences in attractiveness A of the exocrine appeared and the behaviour of a more attrac- comparative survey and fertil- tive dwarf virgin queen suggested aggres- glands of gynes (normal dwarf), ized and workers of N testaceicornis sion because she often tried riding over her queen is in table I. The mandibular and sister queens. The behavioural repertoire of presented the of the third were attaining attractiveness by these dwarf gynes epithelial glands tergite involved the inflation of the abdomen, rapid more developed in the dwarf gynes than in the workers. All had Dufour movements through the box, soliciting gynes glands, trophallaxis with workers and frequent exhi- which were absent in workers. Hypopha- bition of the abdominal tip to the surround- ryngeal glands were present in all queens ing workers. Aggression involved strong (poorly developed) and in workers (well Tarsal in the were abdominal movements by which the nearby developed). glands legs absent in mated but in the workers were pushed away, and the attack of queen, present and workers. the other dwarf gynes. During some peri- gynes ods dwarf gynes also rested, as do gynes Figure 2a shows the head glands of a that have a normal size. Although attractive dwarf gyne (salivary glands, mandibular dwarf gynes generally presented a distended glands with their reservoirs, intramandibu- abdomen, suggesting an increase in size, lar unicellular glands). Figure 2b shows the they lost weight as they got older (for tergal glands of third, fourth and fifth ter- instance, one of the marked gynes weighed gites, as well as fat bodies. Besides mor- 9.3 mg after hatching, and 8.5 mg 3 days phological differences in the glands and later; another had a weight of 7.5 mg after ovaries, the gynes had more fat body and urate cells than the workers. The amount of tiation. Hartfelder (1986) analyzed the larval fat body in dwarf queens was slightly lower food composition in N testaceicornis and than in the large one. other species, but did not find any special The number of ovarioles varied, ranging feature in it. Velthuis and Sommeijer ( 1991 ) discussed data from mixed colonies from four to 12 per ovary. The ovarioles were [con- of a of one long in gynes and short in workers.