Contents lists available at ScienceDirect Micron journal homepage: www.elsevier.com/locate/micron Short communication Sperm morphology of Elasmus polistis Burks, 1971 (Hymenoptera: Chalcidoidea: Eulophidae) Pedro Nere a , Glenda Dias a , Helen P. Santos b , André De Souza c , José Lino-Neto a, ⁎ a Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil b Instituto Federal de Minas Gerais, 36415-000, Congonhas, Minas Gerais, Brazil c Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto da Universidade de São Paulo, 14040-901, Ribeirão Preto, São Paulo, Brazil ARTICLE INFO Keywords: Insects Elasmidae Ultrastructure Electron microscopy Systematics ABSTRACT The sperm morphology of the parasitoid Elasmus polistis (Eulophidae) has been investigated with light and transmission electron microscopy. The sperm were filiform and spiraled, with 165.6 ( ± 4.6) μm in length, and showed a distinctive head, formed by a one-layered small acrosome and a nucleus, and a flagellar region. An extracellular sheath from which many long filaments radiated out covered the acrosome and part of the nucleus. The spiral nucleus, with 24.1 ( ± 1.3) μm in length, was filled with homogeneously compact chromatin. In the nucleus-flagellum transition, the centriole adjunct extended posteriorly from the nuclear base in a spiral around the basal body, which has two central microtubules, and axoneme for approximately 1.1 μm. The two mi- tochondrial derivatives began roughly at the same level and at the base of the centriole adjunct. In cross-section, they were symmetrical, with a slightly oval shape and a smaller diameter in comparison to the axoneme. The latter, also spiraled, consisted of 9 + 9 + 2 microtubules that was formed from the basal body situated just below and aligned with the nucleus. The E. polistis sperm showed the same basic structures and morphological characteristics as observed in other Chalcidoidea. However, it was possible to distinguish the sperm of this species from those of other Eulophidae by (i) the long length of the centriole adjunct on the flagellum, and (ii) the presence of two central microtubules within the basal body. The sperm characteristics suggest that Eulophidae is closely related to Trichogrammatidae and both families are more similar to Eurytomidae, Pteromalidae, and Torymidae than Agaonidae. 1. Introduction Chalcidoidea is the second most specious superfamily among the Hymenoptera including about 22,500 described species (Heraty et al., 2011, 2013; Heraty, 2017; Huber, 2017; Noyes, 2018). They are small parasitoid wasps; generally between 1.0 and 2.0 mm, have a global broad distribution and are known as parasites of Coleoptera, Diptera, Heteroptera, Homoptera, Hymenoptera, Lepidoptera, Neuroptera, Odonata, Orthoptera, Psocoptera, Siphonaptera, Strepsiptera, Thysa- noptera, among others. For this reason, these wasps have been widely used in biological control programs meant for controlling pest insects (Quicke, 1997; Heraty, 2017). Within Chalcidoidea, Eulophidae is one of the most specious fa- milies comprising 4472 described species, distributed in 297 genera. The genus Elasmus, currently the only member of the tribe Elasmini (Eulophidae: Eulophinae), has 258 described species, distributed in 36 countries (Noyes, 2018). Although some species of Elasmus are secondary parasitoids (hyperparasitoids) of Braconidae and Ichneu- monidae (Coote, 1997), the majority is a primary parasitoid of Lepi- doptera, Coleoptera and, a few, of Vespidae (Hymenoptera), as Elasmus polistis that parasites wasp pupae of the genus Polistes (Dorfey and Kohler, 2011). Although there are some studies using molecular and traditional morphological data, there still remain many doubts regarding the sys- tematic of Chalcidoidea. Some of many difficulties faced by taxonomists are due to (a) the morphological homoplasy abundance present in the group (Heraty et al., 2013) and (b) insufficient resolution upon ap- plying a limited number of molecular markers (Munro et al., 2011). Throughout the evolutionary process, the morphological variations that spermatozoa accumulated provide a surprising richness in the number of components (see Gottardo et al., 2016), in addition to shapes and interactions between them. For this reason, the morphological di- versity of the male germ cells has provided data sets that have been used to help in the understanding of the phylogenetic and taxonomic https://doi.org/10.1016/j.micron.2019.102757 Received 2 May 2019; Received in revised form 8 August 2019; Accepted 20 September 2019 ⁎ Corresponding author. E-mail address: linoneto@ufv.br (J. Lino-Neto). Micron 127 (2019) 102757 Available online 22 September 2019 0968-4328/ © 2019 Elsevier Ltd. All rights reserved. T