The first cases of gynandromorphism in oil-collecting bees (Hymenoptera, Apidae: Centridini, Tapinotaspidini)

Abstract

Here we provide descriptions of gynandromorphs of two species oil-collecting bees: Lophopedia nigrispinis and Epicharis iheringii, both with partial bilateral phenotypic asymmetry. The bees have a female phenotype predominantly on mesosoma and metasoma. The specimen of L. nigrispinis has distinct characteristics on legs, suggesting a mosaic pattern of gynandromorphism. The pollen and oil loads on legs suggest that the bee was foraging normally. The gynander specimen of E. iheringii has mostly a female phenotype, except for head, with right half female type and left half male type. The specimen of L. nigrispinis was collected foraging on flowers of Bidens sp. at Parque Nacional Iguazú, Argentina with loads of pollen on legs suggesting it was reproductive and was provisioning a nest. The specimen of Epicharis iheriingi has no evidence of any oil or pollen collection, despite its mostly female phenotype.

Key-Words
Gynander; Epicharis; Lophopedia; Intersex; Pollinators; Mosaic gynandromorphy

INTRODUCTION

Gynandromorphs are sexually abnormal individuals that display secondary sex characters of both sexes simultaneously (Lucia & González, 2013). The occurrence of gynandromorphy is widespread in arthropods, with numerous records reported in Hymenoptera, especially in bees (Engel, 2007; Hinojosa-Díaz et al., 2012). Gynandromorphs are characterized in three main types according to Michez et al. (2009): mosaic, transverse and bilateral. Despite its common occurrence in insects, very little is known on about potential behavioural changes, with scarce data on lycaenid butterflies (Dantchenko et al., 1995), driprionid sawflies (Mertins & Coppel, 1971), drosophilids (Nissani, 1977), locusts (Maeno & Tanaka, 2007), bumblebees (Ugajin et al., 2016; Matsuo et al., 2018) and mason bees (Sampson et al., 2010). Most of these reports about the behaviour of gynandromorphy suggest a predominance of female characteristics, with the persistence of the reproductive capacity in some gynandromorphs (Wcislo et al., 2004).

The oil-collecting bees occur in at least six lineages distributed in Neotropical and Palearctic regions. In Neotropical region there are three of the main tribes of oil-collecting bees, with more than two hundred species. Among them, Centridini and Tapinotaspidini are the most diverse groups in terms of abundance and richness (Roig-Alsina, 1997; Michener, 2007). These bees have specialized structures to collect oils, mainly combs or pads of setae, typically in forelegs and middle legs (Neff & Simpson, 1981; Cocucci et al., 2000). This oil is used presumably to provision larval cells or cell lining (Michener, 2007).

Herein, we document for the first time two specimens of oil-collecting bees with mixed gynandromorphy: Lophopedia nigrispinis (Vachal, 1909) (Tapinotaspidini) and Epicharis (Epicharitides) iheringiiFriese, 1899 (Centridini).

MATERIAL AND METHODS

External morphological features were studied using a Nikon SMZ 745T and Leica M125 stereomicroscope. Photographs were taken with a Canon T3i and AmScope MU 500 digital cameras attached to a steromicroscope, and images were assembled using CombineZM open software. Morphological terminology follows Michener (2007). The abbreviations T and S for metasomal terga and sterna, respectively. Measurements were taken with an ocular micrometer and mean values and ranges are given in millimeters. Total body length was measured from the head to the apex of metasoma in lateral view; mesosoma width was measured between the outer borders of the tegulae; metasoma width was measured across the second tergum. Series of other specimens of the same species were studied to compare the morphological variation between the gynandromorphs and the male and female normal phenotypes.

The specimen of L. nigrispinis was collected at Parque Nacional Iguazú (Argentina) and is deposited in the entomological collection of the Museo de La Plata, Argentina (MLP). The specimen of E. iheringii was collected on a cerrado habitat, at Parque Nacional de Brasília (Brazil, DF, Brasília) and is deposited on entomological collection of the Universidade de Brasilia (collection voucher UNB008980). The first species occurs only in forested areas in Southern America (Brazil, Paraguay, Argentina) (Aguiar, 2009; Torretta & Roig-Alsina, 2017) and the second is mainly related to cerrado areas in Brazil (Moure et al., 2007).

RESULTS

Lophopedia nigrispinis - gynandromorphy

Description: Body length 7.5, head length 1.9, head width 2.5, mesosoma width 2.8, metasoma width 2.6. Head: mixed. Partial bilateral gynandromoph, right side mostly male and left side female; integument mostly black except mandible pale yellow with apex and posterior basal angle black; right side of labrum pale yellow like male and left side black as female; clypeus with lower margin yellow on right side and black on left side; left half of supraclypeal area without lower margin surpassing the upper margin of clypeus as female; paraocular area with a narrow yellow stripe occupying less than the lower part. Both antennae have 11 flagellomeres as is typical for male. Pubescence on mandibles, labrum, clypeus, frons, paraocular area and gena, mostly white and not distinct between sides, vertex with sparse erect simple setae light brown; left half of labrum with long light brown setae as female, distinct longer than male right side (Fig. 1B). Mesosoma: general appearance male-like, except for the legs with a mix of male and female features. Integument black and pubescence brown to black; mesoscutum and scutellum with sparse punctures and lamella of pronotal collar with lateral portions high, characteristic of males. Legs with mixed secondary sex characteristics, with integumental color black and most distitarsi yellow as in normal male. Forelegs male-like modified to collect oil, however basitarsi narrower than female basitarsi (Fig. 1C, D). Middle legs female-like with ventral surface of tibiae with spatulate setae, except for left distitarsi yellow as male and the right mixed with yellow and brown coloration (Fig. 1E, H). Hind right leg male-like; the left hind scopa blackish composed of dense plumose pubescence with integument mostly black except the distal part of tibia, basitarsus and mediotarsus light brown, distitarsus yellow; tibial spurs light brown; pubescence mostly black except by pale yellow on tibial postero distal margin and basitarsus (Fig. 1G). Right hind leg female-like, with plumose pubescence not so dense as left scopa, with numerous simple setae; mediotarsus and distitarsus brown; tibial spurs dark brown (Fig. 1H). Wing membrane dark brown infumated. Metasoma: symmetric female-like, with six exposed terga and sterna. Genital structure developed as a normal sting (Fig. 1A).

Figure 1
Gynandromorph of Lophopedia nigrispinis (Vachal): (A) Habitus in lateral view. (B) Head in frontal view. (C) Foreleg right basitarsus in inner view. (D) Foreleg left basitarsus in inner view. (E) Left middle leg in inner view. (F) Right hind leg in external view. (G) Left hind leg in external view. (H) Right middle leg in inner view. Scale bars: (A) 2 mm. (B) 1 mm. (C) 0.25 mm. (D-H) 0.5 mm.

Material Examined: One gynandromorph, Argentina, Misiones, Parque Nacional Iguazú, 28-IX-2016, Coll. L. Alvarez-M. Lucia-P. Ramello.

Epicharis (Epicharitides) iheringii - gynandromorphy

Description: Body length 16.2, head length 4.0, head width 4.3, mesosoma width 4.9, metasoma width 6.7. Head: Bilateral gynandromoph, left side male-like and right side female; integument mostly black; labrum and clypeus yellow on left side as male, and black on right side as female; right paraocular area with a yellow stripe occupying half area like female. Both antennae have 10 flagellomeres as is typical for females. Pubescence on mandibles, frons, paraocular area, gena and clypeus not distinct between sides; right half of labrum with light brown setae as female, distinct longer than on male left side; left side of vertex with yellowish setae as male and right side with blackish setae as female (Fig. 2B). Mesosoma: general appearance female-like. Integument black and pubescence brown to black; mesoscutum and scutellum with sparse punctures. Legs female-like (Fig. 2A), with integument color black as in normal female. Fore and mid legs female-like, modified to collect oil on ventral surface. Hind legs female-like; the scopa yellowish composed of dense plumose pubescence with integument yellowish except the distitarsus and mediotarsus light brown; tibial spurs light brown; pubescence mostly yellowish. Metasoma: symmetric female-like, with six exposed terga and sterna, and symmetric yellow marks on terga as female (Fig. 2C).

Figure 2
Gynandromorph of Epicharis (Epicharitides) iheringii Friese: (A) Habitus in lateral view. (B) Head in frontal view. (C) Metasoma in dorsal view.

Material Examined: One gynandromorph, Brazil, Brasília, Parque Nacional de Brasília, 23-XI-2012, Coll. J.C.S. Oliveira.

DISCUSSION

Gynandromorphism in bees are known from more than 140 species and 36 genera belonging to all families, though most of these records belong to the long-tongued bee families (Almeida et al., 2018; Prashantha et al., 2018). Within the family Megachilidae, the records of gynandromorphs are in three tribes (Anthidini, Megachilini and Osmiini), but mainly are present in the genus Megachile Latreille (Hinojosa-Díaz et al., 2012; Coelho et al., 2016). In the family Apidae, the records of gynandromorphs were recorded from numerous genera and tribes as Anthophorini, Apini, Bombini, Epeolini, Eucerini, Euglossini, Melictini, Meliponini, Nomadini and, Xylocopini (Urban, 1999; Wcislo et al., 2004; Michez et al., 2009; Hinojosa-Díaz et al., 2012; Lucia & González, 2013; Alvarez et al., 2014; Le Féon et al., 2016; Onuferko, 2018). Despite the great diversity and abundance in the Neotropical region, this is the first reported case of gynandromorphism in oil-collecting bees. The gynandromorphs described here have a mix of male and female features in head and mesosoma, and the metasoma is female like in both species, and thus it can be assigned to the mosaic category (see Michez et al., 2009). The morphological differences of the legs on L. nigrispinis of the two sexes are not very clear because the males can also collect oil on flowers, however the males have a scopa on the hind leg not developed as females.

The specimen of L. nigrispinis was captured, along with numerous normal females and males, foraging on flowers of Bidens sp. at Parque Nacional Iguazú, Argentina in October 2016. Their foraging behaviour was normal and indistinguishable from the other females. The gynander carries pollen mixed with oil in all middle and hind legs. The gynander of E. iheringii has mostly a female phenotype, except the head, with structures for collecting and transport floral oils and pollen on legs. Despite the male phenotypes, it is suggested that both specimens are reproductively functional, due their well developed metasoma and oil and pollen collecting apparatus.

The causes of gynandromorphism in bees are unknown, but some hypotheses suggest that they may be result of problems in fertilization or related to genetic factors (Michez et al., 2009; Narita et al., 2010). Polyspermy in an egg is suggested as one of the causes of gynandromorphism, when a secondary spermatozoa do not degenerated and persist as a male tissue in an original female embryo (Aamidor et al., 2018). However, it was reported also two spermatozoa fusing to form a diploid female ginandromorphy (Woyke, 1986). Studies with the objective of understanding the causes of gynandromorphism in bees are necessary for the greater understanding of this anomaly.

ACKNOWLEDGEMENTS

We would like to thank to Administración de Parques Nacionales (APN) for awarded permit (NEA344 project) and two anonymous reviewers for their helpful comments on the manuscript. Financial support to L.J.A. and M.L. was provided by the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina (CONICET), and to A.J.C.A. provided by FAPDF, and W.P. Silva by CAPES.

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• Edited by: Kelli dos Santos Ramos
• Published with the financial support of the Committee of "Programa de Apoio às Publicações Científicas Periódicas da USP" (SIBi-USP)

Publication Dates

• Publication in this collection
  03 Oct 2019
• Date of issue
  2019

History

• Received
  12 Apr 2019
• Accepted
  01 July 2019