Research Article |
Corresponding author: Geovanni M Rodríguez-Mirón ( geo20araa@yahoo.com.mx ) Academic editor: Michael Schmitt
© 2017 Geovanni M Rodríguez-Mirón, Santiago Zaragoza-Caballero, Sara López-Pérez.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Rodríguez-Mirón GM, Zaragoza-Caballero S, López-Pérez S (2017) Comparative morphology of the spermatheca in Megalopodidae (Coleoptera, Chrysomeloidea). In: Chaboo CS, Schmitt M (Eds) Research on Chrysomelidae 7. ZooKeys 720: 47-64. https://doi.org/10.3897/zookeys.720.14088
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The spermatheca is an organ that stores and maintains viability of sperm until fertilization. It has an important role in copulation and oviposition, and it is highly informative in species delimitation. Here, we present a comparative study of the spermathecal morphology in the coleopteran family Megalopodidae. The spermathecae of 34 species, representing 13 genera and all three subfamilies, were studied. Illustrations are newly provided for all species, except in 14 cases in which illustrations were reproduced from previously published literature. Our results show that each subfamily of Megalopodidae can be effectively differentiated based on the particular spermathecal anatomy. In addition, the spermathecal anatomy presents a range of variation within each subfamily, useful for diagnosing species and, in some cases, identifying groups of genera. For instance, the “American group” is thus recognized in this study.
Female genitalia, Zeugophorinae , Megalopodinae , Palophaginae , flagellum, taxonomic significance
The female internal reproductive organs in insects consist of several organs: a pair of ovaries with their respective oviducts, a median ectodermal tube, a vagina, a bursa copulatrix and the spermatheca (
The order Coleoptera exhibits five patterns of spermathecal morphology (
Classification systems have mainly utilized characters of the external morphology, such as wing venation; however, most of these classifications change constantly because of symplesiomorphy and homoplasy within these character sets. Therefore, taxonomists have studied internal morphology and genital features, which, in combination with the features mentioned above, will contribute to a more stable classification (
The female internal reproductive organs have been used less frequently; however, they have also been found useful in diagnosing certain groups (
The spermatheca in Chrysomeloidea has been useful to define subfamilies, genera, species, and groups of species (
Other megalopodid taxa that have had their spermathecae described and illustrated are: Mastostethus Lacordaire, 1845, Agathomerus Lacordaire, 1845, and Megalopus Fabricius, 1801 (
Megalopodidae currently consists of 552 described species, which are classified into three subfamilies (Megalopodinae, Zeugophorinae, and Palophaginae) (
The spermathecae of 34 species of Megalopodidae were examined. These species represent three subfamilies, 13 genera and two subgenera for one genus. Approximately 100 specimens were examined, distributed between the 34 species studied (Table
Species | Geographic information in label | No. specimens |
---|---|---|
Megalopodinae | ||
Agathomerus (Agathomeroides) flavomaculatus (Klug, 1824) | Brazil | 4 |
Agathomerus (Eugathomerus) sellatus (Germar, 1823) | Brazil | 6 |
Agathomerus rufus (Klug, 1834) | Mexico | 30 |
Agathomerus signatus (Klug, 1824) | Brazil | 3 |
Agathomerus sp. *1 | Panama | – |
Homalopterus tristis Perty, 1832 | Brazil | 2 |
Mastostethus hieroglyphicus (Klug, 1834) | Mexico | 9 |
Mastostethus nigrocinctus (Chevrolat, 1834) | Honduras, Costa Rica,Mexico | 25 |
Mastostethus novemaculatus (Klug, 1834) | Mexico, Costa rica | 6 |
Mastostethus variegatus (Klug, 1824) | Brazil | 1 |
Megalopus inscriptus Klug, 1824 | Peru | 3 |
Megalopus sp. 1 | Costa Rica | 2 |
Megalopus sp. 2 *1 | Panama | – |
Poecilomorpha atripes Lacordaire, 1845 | South Africa | 1 |
Poecilomorpha cyanipennis (Kraatz, 1879) | South Korea, Russia | 4 |
Psudohomalopterus carinatus Pic, 1920 | Brazil | 7 |
Sphondylia sp. | Africa | 1 |
Temnaspis septemmaculata (Hope, 1831) | Laos | 1 |
Temnaspis japónica Baly, 1873 *2 | Japan | – |
Temnaspis sp. *1 | – | – |
Temnaspis speciosus Baly, 1859 | Bhutan, Nepal | 4 |
Zeugophorinae | ||
Zeugophora annulata (Baly, 1873) *2 | – | – |
Zeugophora califórnica Crotch, 1874 | USA | 6 |
Zeugophora indica Jacoby, 1903 | Kashmir, India | 3 |
Zeugophora javana Reid, 1992 *3 | Indonesia: West Java | – |
Zeugophora toroja Reid, 1998 *4 | Indonesia: West Java | – |
Zeugophora varians Crotch, 1873 | Canada, USA | 4 |
Zeugophora vitinea (Oke, 1932) *5 | Australia | – |
Zeugophora williamsi Reid, 1989 *5 | Australia | – |
Zeugophorella riedeli (Medvedev, 1996) *6 | New Guinea | – |
Palophaginae | ||
Cucujopsis setifer Crowson, 1946 *7 | Australia | – |
Palophagoides vargasorum Kuschel, 1996 *8 | Chile | – |
Palophagus australiensis Kuschel, 1990 *7 | Australia | – |
Palophagus bunyae Kuschel, 1990 *7 | Australia | – |
For microscopic examination, the dried specimens were placed in hot water for 10 minutes to soften the tissues. Each abdomen was dissected along the abdominal pleura and boiled in a 10% KOH solution for five minutes. The spermatheca was dissected from the KOH preparation, washed with water, and mounted with glycerin in a glass slide for observation. Dissection and analysis were done using a Zeiss V–8 stereoscopic microscope. Photographs were made using a Zeiss Axio Zoom V–16 stereoscopic microscope equipped with an Axiocam MRC5 camera. After examination the spermatheca of each specimen was transferred to a microtube with glycerin, which was pinned underneath the specimen. The abdomen was attached to a white card using a drop of glue, also pinned underneath the specimen.
Specimens were borrowed from the following national and international museums and Institutions: BMNH–The Natural History Museum, London, U.K. (M. Geiser);
Spermathecal terminology follows
Our results showed that the three subfamilies of Megalopodidae can be effectively differentiated by their particular spermathecal anatomy (Table
SptC morphology | SptCp | SptGl | SptD | Hold the SptM | |
---|---|---|---|---|---|
Megalopodidae | complex | boomerang-shaped | not branched and longer | very long | apex and the stem |
Zeugophorinae | complex | crane’s neck-shaped | branched and longer | very long | apex and the terminal portion |
Palophaginae | simple | C-shaped | not branched and short | short | – |
Structure of the spermatheca in Megalopodinae: Agathomerus, Pseudohomalopterus, Homalopterus, and Mastostethus. a Agathomerus rufus b P. carinatus cA. (Eugathomerus) sellatusdA. (Agathomeroides) flavomaculatuse A. signatus f H. tristis g M. nigrocinctus h M. hieroglyphicus i M. variegatus.
Structure of the spermatheca in Megalopodinae: Megalopus, Temnaspis, Poecilomorpha, Sphondylia. a Megalopus inscriptus b Megalopus sp. c T. septemmaculata d T. speciosa e P. cyanipennis f apex of the spermatheca in P. cyanipennis g P. atripes, h apex of the spermatheca in P. atripes, i Sphondylia sp.
In this study the SptC was divided in two portions, the proximal part of spermathecal capsule (SptCp) and the distal spermathecal part (SptCd) (Fig.
In Megalopodinae, the differences among genera are especially evident in the shapes of the SptCp and SptCd. The genera Agathomerus, Homalopterus Perty, 1832, Mastostethus, and Megalopus (Figs
The apex of the SptCp in Temnaspis Lacordaire, 1845 (Figs
The genus Poecilomorpha Hope, 1840 has coarse walls in the SptCp, the apex is emarginate and without a velum (Fig.
The structure of the spermatheca in Zeugophorinae is notably different from Megalopodinae. The ventral wall of SptCp is narrow in Zeugophora californica Crothc (Fig.
The subfamily Palophaginae (Figs
The structure of the spermatheca in Megalopodidae (Palophaginae + Zeugophorinae + Megalopodinae) is complex, and it is associated with a high diversity in forms. This variability affords characters with great taxonomic and phylogenetic value at various taxonomic levels. The structure of the spermatheca has been used to delimited species, that is the case of the genus Mastostethus (
The spermatheca in Megalopodidae consists of a SptC, SptD, and SptGl, which is the arrangement that is the commonest in Coleoptera, including Chrysomeloidea, except in Vesperus luridus (Rossi, 1794) (Vesperidae), which does not have an SptD or an SptGl (
The SptC has a particular structure in the three subfamilies of Megalopodidae. The morphology of the SptCp and SptCd in Zeugophorinae and Megalopodinae is complex (
The C–shaped SptC is present in Palophaginae (Fig.
The shape and length of the SptGl and SptD are not taxonomically or phylogenetically diagnostic among families. These structures should be considered as homoplastic, in view of the heterogeneity in Cerambycidae and Chrysomelidae (see
The SptD in Megalopodidae is characterized by being longer than the SptC (Figs
The correlation of the lengths of the reproductive organs in Megalopodinae is characteristic of the genus Megalopus. However, in the genera Homalopterus, Temnaspis, and Agathomerus, this correlation is obscured because the SptD is very long and coiled (Figs
The SptM has an important function in reproduction. The SptC in Coleoptera is adapted in many ways to give two places of insertion of the muscle fibers, which form the SptM (
Some characters in the spermathecae possibly diagnose genera or groups of genera. For example, the arrangement of the SptC is similar within the American group (Agathomerus, Homalopterus, Megalopus, and Mastostethus), but is different from that found in Poecilomorpha, Temnaspis, and Sphondylia, because of the presence of a velum in the American group. Sphondylia differs from the rest of the genera of Megalopodinae, due to the tetrahedral arrangement of the SptCp (Fig.
The walls thickness of SptCp have differences among Megalopodinae. The apical portion in Poecilomorpha and Temnaspis is acuminate (Fig.
Within the subfamily Zeugophorinae, there are differences in the SptC. The genus Zeugophorella Sekerka, 2013 (Fig.
The present study compares the spermathecae of Megalopodidae, and it considers species from all three subfamilies (Megalopodinae, Zeugophorinae and Palophaginae). It describes for the first time this structure for 20 taxa.
We conclude that the SptCp variations are informative and useful in diagnosing these three subfamilies. In addition, the variations observed in the distal portion of the SPtCd are diagnostic of several genera, and, in some cases, groups of genera, such as the American group.
Finally, we believe that the spermatheca has a high taxonomic value for diagnosing taxa at various ranks within Megalopodidae. However, further testing of this hypothesis, to be provided by phylogenetic analyses, will establish the phylogenetic signal and corroborate the homology hypothesis of this character complex.
We thank to Michael Schmitt and Caroline Chaboo for the invitation to the volume 7 of Research on Chrysomelidae. We also thank to all the curators and collections that provided specimens. We also extend thanks to Fernando Alvarez Padilla and Shawn Clark for his valuable comments and improvements to the English, as well as to Juan J. Morrone, Yoko Matsumura, and anonymous reviewer for his valuable comments. The first author thanks the Posgrado en Ciencias Biológicas, UNAM. He also thanks the Consejo Nacional de Ciencia y Tecnología (CONACyT) for fellowship support, and to the Institute of Biology (UNAM) for the infrastructure provided.
Contribution to the 9th International Symposium on the Chrysomelidae, Orlando, FL, USA, September 28, 2016