Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 DOI: 10.13102/sociobiology.v63i4.1263Sociobiology 63(4): 1069-1072 (December, 2016) Rediscovery of the morphologically remarkable social parasite Pheidole acutidens (Santschi, 1922), with the first records for Brazil Pheidole Westwood, 1839 (Formicidae: Myrmicinae) is considered one of the largest ant genera, with more than 1,000 valid names (Bolton, 2016). The species are generally known for being prevalent in all environmental strata making it a group of primordial ecological importance, especially in tropical forests (Wilson, 2003). Amongst the reproductive strategies found in Pheidole, social parasitism is certainly the most remarkable. Social parasites are exquisitely adapted to exploit their hosts, totally depending on them for food and brood care, since they do not produce workers (Wilson, 1971; Hölldobler & Wilson, 1990; Buschinger, 2009). We currently recognize nine species of social parasites in Pheidole: P. acutidens (Santschi, 1922), P. argentina (Bruch, 1932), P. symbiotica (Kusnezov, 1951), P. elecebra (Wheeler, 1973), P. inquilina (Wheeler, 1965), P. lanuginosa Wilson (1984), P. neokholi Wilson (1984), P. parasitica Wilson (1984), and P. kosnezovi Wilson (2003). Like other social parasites P. acutidens presents a morphological syndrome that includes reduced size, Abstract Pheidole acutidens is a social parasite of the congeneric species P. nitidula. Since its description, the species was considered native to Argentina. In this paper we report the first records of P. acutidens for Brazil in the southern states of Santa Catarina and Rio Grande do Sul. These records extend the known distribution of the species at least 1,000 km to the north. We suggest that the scarce representation of this species in entomological collections is due to its peculiar reproductive strategy, which renders the species inconspicuous and limits its dispersion. Sociobiology An international journal on social insects A Casadei Ferreira, MFO Martins, RM Feitosa Article History Edited by Gilberto M. M. Santos, UEFS, Brazil Received 05 December 2016 Initial acceptance 12 December 2016 Final acceptance 13 December 2016 Publication date 13 January 2017 Keywords Geographical distribution, myrmicine, native ant, taxonomic problem. Corresponding author Alexandre Casadei Ferreira Laboratório de Sistemática e Biologia de Formigas, Departamento de Zoologia Universidade Federal do Paraná, Curitiba-PR, Brasil E-Mail: acf.casadei@gmail.com lengthening of antennal scapes, reduction of the mandibles, smooth and shining body surface, and broadening of the postpetiole (Wilson, 1971). Also, queens of this species have a rounded head, falcate toothless mandibles ending in an extremely acute angle, antennae with 9-11 articles, a single pair of wings without venation, and a globose gaster, (Santschi, 1922; Bruch, 1931; Wilson, 1984) (Fig. 1). Male morphology is even more bizarre. Presenting a rounded head, 12 segmented antennae, and physiogastry. Also, according to Wilson (2003) the male also has vestigial or absent falcate mandibles, and pupiform body. In addition, males of P. acutidens are brachypterous (Bruch, 1931; Wilson, 1984). The taxonomic history of Pheidole acutidens reflects its unique behavior and morphology. Santschi (1922) described the monotypic genus Bruchomyrma with Bruchomyrma acutidens as its type species based on a single dealate queen collected by Carlos Bruch (1869-1943) in 1916. He also characterized Bruchomyrma through an extensive diagnosis, and mentioned its morphological similarity to Anergatides Universidade Federal do Paraná, Curitiba-PR, Brazil SHORT NOTE A Ferreira, MFO Martins, RM Feitosa – Rediscovery of the social parasite Pheidole acutidens1070 kohli Wasmann, 1915, despite the “easily recognizable differential characters”. He also suggested that B. acutidens could be a social parasite of Pheidole, as reported for A. kohli. Wilson (1984) performed a comprehensive study on social parasites of Pheidole and combined several genera under this genus, including Anergatides and Bruchomyrma. The combination made by Wilson for P. acutidens was mostly based on evidence mentioned by Brown (1973), which assumed that the different parasitic species of Pheidole evolved independently, with the parasitic syndrome arising convergently. In this context, the nomenclatural act proposed by Wilson (1984) may also be justified considering “Emery’s rule” (Emery, 1909) which states that social parasites are closely related to their host species. Pheidole acutidens is currently known as a social parasite of P. nitidula. So far, the species distribution is restricted to Argentina, specifically to Las Flores (35°57’49.5”S 58°56’20.4’’W) (Buenos Aires) and Alta Gracia (31°39’25.6’’S 64°26’05.1’’W) (Córdoba) (Bruch, 1931; Wilson, 2003). A hundred years after its discovery (Bruch, 1931), we rediscovered the species and present the first records for Brazil. We examined two specimens, both queens. The first specimen is alate and was collected in Caxias do Sul (29°10’05’S 51°10’46’’W), state of Rio Grande do Sul, on 21 March, 1988. There is no mention about the sampling method. The specimen is deposited in the myrmecological collection of the Museu de Zoologia da Universidade de São Paulo (MZSP), São Paulo, Brazil. The second specimen is a dealate queen from a pitfall sample collected in the municipality of Otacílio Costa (27°29’03.9’’S 49°54’14.4’’W), state of Santa Catarina, between December 2011 and January 2012 (Bartz et al., 2014; Rosa et al., 2015). The specimen was deposited in the Coleção Entomológica Padre Jesus Santiago Moure (DZUP) of the Universidade Federal de Paraná, Curitiba, Brazil. The distribution map was generated by the program QGis v.2.16.3 using data from geographic coordinates in Google Earth Pro 7.1.1.1580. Images of specimens were acquired with stereomicroscope Leica M205C coupled to a camera Leica DFC295 at Laboratório de Sistemática, Evolução e Biologia de Hymenoptera of MZSP. The images of the layers were aligned and combined in program Zerene Stacker v. 1.04, and posteriorly treated in Adobe Photoshop CS6 for brightness and contrast corrections. These new records suggest the apparently restricted distribution of the species may be an artifact from lack of adequate sampling. Besides this collecting bias, the unique morphology and reproductive biology of P. acutidens may also explain the considerably low number of specimens in ant collections. Queens present an extremely enlarged mesosoma and have lost the hindwings, while males show extreme reduction in wing size and venation (brachyptery). Fig 1. Pheidole acutidens queens from Caxias do Sul (A, C) and Otácilio Costa (B, D). A, B: full-face view; C, D: body in lateral view. Scale bars: 0,5mm. Sociobiology 63(4): 1069-1072 (December, 2016) 1071 These unusual morphological features suggest limited flight capability and restricted dispersion rates in P. acutidens. As described by Bruch (1931), P. acutidens queens are only accepted and adopted by P. nitidula workers in queenless nests. This limitation probably also restricts their dispersion, due the difficulty of finding suitable nests without host queens. However, once established, queens of P. acutidens can produce approximately 300 eggs and complete their life cycle in about three months (Bruch, 1931). This mass production of individuals may be linked to the trial and error way of infestation, with a great number of founding queens searching for queenless colonies of P. nitidula. The intrinsic relationship between P. acutidens and P. nitidula can also be evidenced by the dependence of newly-hatched P. acutidens queens on P. nitidula workers to remove their cocoon and unfold their rudimentary wings after emergence. In addition, when invading a host colony, mated queens of P. acutidens rely entirely on the workers of P. nitidula to remove their wings and establish themselves in the new colony (Bruch, 1931). Considering the intrinsic association between both species, P. acutidens probably occurs in the same range as P. nitidula - recorded from Argentina to the states of Rio de Janeiro, southeastern Brazil (Wilson, 2003). In this scenario, the records presented here represent the first step towards a more complete mapping of P. acutidens distribution. Acknowledgements We would like to thank Dr. Carlos Roberto F. Brandão for permission to access the myrmecological collection of the MZSP and for providing the equipment for acquiring high- resolution images. Brendon Boudinot identified the specimen from Caxias do Sul. Dr. John Lattke and Thiago S. R. Silva made important suggestions in a previous version of this paper. ACF (140260/2016-1) and MFOM (130387/2015- 0) thanks the fellowships granted by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC) (Process 6.309/2011-6/FAPESC) and CNPq (Process 563251/2010-7) for the financial support. Fig 2. Distribution of Pheidole acutidens in Argentina and Brazil. A Ferreira, MFO Martins, RM Feitosa – Rediscovery of the social parasite Pheidole acutidens1072 References Bartz, M. C.; Brown, G. G.; Rosa, M. G.; Klauberg Filho, O.; James, S. W.; Decaëns, T. & Baretta, D. 2014. Earthworm richness in land-use systems in Santa Catarina, Brazil. Applied Soil Ecology. doi: 10.1016/j.apsoil.2014.03.003 Bolton, B. 2016. An online catalog of the ants of the world. Available from http://antcat.org. Acess October 2016. Brown, W. L. 1973. Hylean and Congo-West African rain forest ant faunas, In: B.J. Meggers, E.S. Ayensu, W.D. Duckworth (editors): Tropical Forest Ecosystems in Africa and South America: A comparative Review. Smithsonian Institution Press. Washington, D.C. p. 161-185. Bruch, C. 1931. 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