Ceraphron krogmanni (Hymenoptera: Ceraphronidae), a new species from Lower Saxony with unusual male genitalia

Abstract Background Male genitalia phenotypes of Ceraphron (Jurine, 1807) are informative for species delimitation, but due to their minute size, these characters have not been used extensively. Recent developments in visualisation techniques, e.g. confocal laser scanning microscopy and high resolution bright field imaging, allow for more thorough examination of these minute anatomical structures and the development of a robust, male genitalia-based taxonomic system. We also establish a character set, a template, that will facilitate future revisions of these wasps. New information Ceraphron krogmanni sp. nov. is described with outsized male genitalia and multiple diagnostic traits that are unique amongst Ceraphron species.


Introduction
The family Ceraphronidae holds 302 species, classified in 14 genera. More than 90% of the species belong in two genera, Ceraphron (n=185) and Aphanogmus (n=94) (Johnson andMusetti 2004, Various Contributors 2017). Genus-level identifications of female ceraphronids are sometimes complicated because the only diagnostic feature, the width/ height ratio of the mesosoma (higher than long in Aphanogmus and wider than high in Ceraphron) is dubious (e.g. females of Aphanogmus fumipennis Thomson 1858 species group are often as wide as high, Mikó, pers. obs.). On the other hand, male Ceraphron specimens are easy to distinguish from Aphanogmus by the morphology of the antenna; the flagellomeres in Ceraphron are cylindrical and covered with sensillum trichodeum curvatum (sickle-shaped sensilla), while, in Aphanogmus, they are trapezoidal in lateral view and equipped with erect and elongate setae Mikó and Deans (2009).
The external morphology of Ceraphronoidea is monotonous relative to other microhymenoptera (e.g. other taxa in Proctotrupomorpha; Klopfstein et al. 2013) and the few characters that do appear suitable for species delineation (e.g. anatomical line ratios or microsculpture) are often affected by allometry Deans 2012, Mikó et al. 2016). On the other hand, male genitalia characters have revealed themselves to be consistently informative systematically (Dessart 1972, Dessart 2001, Mikó and Deans 2012. Studying ceraphronid male genitalia is difficult with the traditional taxonomist tool set, due to the structures' extremely small size (100 -200µm) and a functional, male genitalia-based taxonomic system remaining elusive. These limitations have restrained further exploration of ceraphronid fauna and only species with very peculiar external traits have been described (Dessart 1984, Dessart 1975, Dessart 1981. The male genitalia have been documented for only 13 species of Ceraphron (Dessart 1963, Dessart 1964, Dessart 1965, Dessart 1975,Dessart 1981, Dessart 1989. After decades of dysfunction in Ceraphron taxonomy (the last species, C. bestiola, was described 22 years ago, based on a single female specimen from Switzerland by Cancemi and Dessart 1995), we describe a new species with distinct male genitalia. We also establish a character set, a template, that will facilitate future revision of these wasps.

Materials and methods
Specimens were examined and dissected under an Olympus SZX16 stereomicroscope, with an Olympus SDF PL APO 1× PF objective (115×) and an SDF PL APO 2× PFC Objective (230×). Dissections were performed using #2 insect pins and Rubis 5A-SA forceps. Genitalia were removed and placed on to a separate concave slide in glycerol.
Diagnostic measurements were performed on the specimens and genitalia using a KR 851 stage micrometer attached to the examination stereomicroscope.
Bright field images were taken with an Olympus ZX41 compound microscope and attached Olympus DP71 digital camera. Genitalia were imaged in glycerol and specimens, including dissected segments, were imaged on Bostik Blu-Tack Reusable Adhesive (Ellsworth Adhesives, Germantown, WI, USA) to stabilise and position for imaging. Images were aligned using Zerene Stacker Version 1.04 Build T201404082055. Annotation and colour correction was performed in Adobe Photoshop CS4.
Genitalia were imaged using an Olympus FV10i Confocal Laser Scanning Microscope (CLSM) following the protocol from Mikó et al. (2014) using 60× objective.
Specimen data, including figures and character states were imported to MX (http:// mx.phenomix.org). The diagnostic characters, description and materials examined were autogenerated by the same content management system. Morphological terms used in the description and diagnosis are derived from phenotype class based ontologies.
All phenotypic descriptions were expressed as semantic statements using Protégé Version 5.0.0 (Build beta 17) using the method provided by Balhoff et al. (2013) and Mikó et al. (2014).
The holotype is deposited at the State Museum of Natural History (SMNS) in Stuttgart, Germany and the paratype will be retained at the Pennsylvania State University Frost Entomological Museum (PSUC).

Diagnosis
Based on the presence of sickle-shaped sensilla on the male flagellomeres and the dorsoventrally compressed mesosoma (wider in dorsal view and high in lateral view), the new species belongs to the genus Ceraphron. Ceraphron krogmanni differs from all other Ceraphron species by the presence of a proximomedial harpal brush (mhb: Fig.  4c, d), the presence of ventromedial and dorsomedial ridges of the basal ring (vmr, dmr: Fig. 4a, b) and the unusually large male genitalia Fig. 2b (more than half the length of the syntergum in C. krogmanni whereas less than 1/3 of the syntergum in other Ceraphron species).

Etymology
The species epithet is a patronym, honouring Lars Krogmann, Staatliches Museum für Naturkunde Stuttgart, who collected the specimens observed in this study.