Research Article |
Corresponding author: Kyle N. Burks ( kyleburks@gmail.com ) Academic editor: Michael S. Engel
© 2016 Kyle N. Burks, Istvan Miko, Andrew R. Deans.
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:
Burks KN, Mikó I, Deans AR (2016) Dendrocerus mexicali (Hymenoptera, Ceraphronoidea, Megaspilidae): Novel antennal morphology, first description of female, and expansion of known range into the U.S. ZooKeys 569: 53-69. https://doi.org/10.3897/zookeys.569.6629
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Dendrocerus mexicali has been described by Paul Dessart from a single male specimen collected in Mexico. Using 87 newly identified specimens we expand the known range to include the Southwestern United States and Florida, provide an expanded description of the species, and provide the first record of the female. We also use confocal laser scanning microscopy and in vitro hydrostatic pressure changes to investigate the functional morphology of apparently unique basally flexible antennal branches.
Dendrocerus , morphology, taxonomy, flabellate, ramose, antennae
Ceraphronoidea (Hymenoptera) is a widespread superfamily of parasitoid wasps comprised of two extant families: Ceraphronidae and Megaspilidae. Little is known about the biology of Ceraphronidae, but there are quite a few host records for Megaspilidae, especially for the genus Dendrocerus Ratzeburg, 1852 (
Host records suggest that Dendrocerus parasitizes a broad range of orders, including Hemiptera, Neuroptera, Coleoptera, Diptera, Hymenoptera, (
Dendrocerus mexicali was first described from a single male specimen collected on wild mustard in Mexicali, Mexico (
Dendrocerus mexicali, like other Dendrocerus species of the halidayi species group, have antennae with long flagellar projections (flagellomeres are “branched” or “ramose”). The antennae of the male D. mexicali is perhaps its most distinguishing feature (
All specimens are point-mounted and air-dried. Specimens are deposited in the
Dissections were performed in glycerol or on Blue-Tack (Bostik, Inc., Wauwatosa, WI, USA) using number 2 insect pins and an Olympus SZX16 stereomicroscope, with an Olympus SDF PLAPO 1XF objective (115×) and an Olympus SDF PLAPO 2XPFC objective (230× magnification).
CLSM was used to image the male antenna and genitalia. Dissected male D. mexicali antennae and genitalia were placed in a droplet of glycerol between two no. 1.5 coverslips with a small amount of Blue-Tack as a spacer (
Bright field images were taken using an Olympus ZX41 compound microscope with an attached Olympus DP71 digital camera. Images were stacked and aligned using Zerene Stacker Version 1.04 Build T201404082055.
Following the methods described by
Specimen data, specimen images, OTU concepts and phenotypes expressed in natural language were compiled in mx (http://purl.org/NET/mx-database) and the description and material examined sections of this article were automatically generated from this software. Morphological terminology in the description and diagnosis are linked to classes in phenotype-relevant ontologies (
Phenotype descriptions expressed as semantic statements (Suppl. material
CSB: cephalic size, HH: head height, EH: eye height, HL: head length, HW: head width, IOS: interorbital space, OOL: ocular ocellar length, LOL: lateral ocellar length, POL: posterior ocellar length, MscL: median mesoscutal line, AscW: anterior mesoscutal width, PscW: posterior mesoscutal width.
Male flagellomeres have projections with flexible, wrinkled regions at base (Figures
Confocal laser scanning microscopic images of male D. mexicali antenna. A Antenna with the most basal branch (branch of 1st flagellomere) missing. Bluish area at base of branches indicates a high concentration of resilin; orange and red indicate sclerotized regions; green indicates softer, non-sclerotized regions B Magnified view of branch articulation. Purple and pink areas indicate high concentrations of resilin in the cuticle; blue indicates areas of extremely high resilin concentration; red indicates strongly sclerotized regions.
Body length universal: 1.4–1.7 mm (n=10). Color hue pattern: antenna, legs, mouthparts ochre; rest of body dark brown. Color intensity pattern: flagellomeres and their branches darker than scape and pedicel. Scape and pedicel same as legs. Cephalic size (csb): Mean: 400–500μm. Head height (lateral view) vs. eye height (anterior view): HH:EHf=1.4–1.8 (n=5). Head height vs. head length: HH:HL=1.4–1.8 (n=5). Head width vs. interorbital space: HW/IOS=1.8–2.0 (n=5). Head width vs. head height: HW/HH=1.2–1.4 (n=5). Male OOL:LOL: OOL/LOL=0.75–1.0 (n=2). Male OOL:POL: OOL/POL=0.24–0.43 (n=2). Female OOL:LOL: OOL 0.625–0.75× as long as LOL (n=3). Anterior ocellar fovea shape: fovea not extended ventrally to the dorsal margin of antennal scrobe. Occipital carina sculpture: smooth. Submedial flange of occipital carina count: absent. Median flange of occipital carina count: absent. Preoccipital carina and occipital carina structure: the occipital carina extends ventrally to the oral foramen with the preoccipital carina present on the vertex, but not extendinig ventrally along the gena. Preoccipital carina count: present . Preoccipital carina shape: present medially, absent laterally to lateral ocelli. Preoccipital lunula count: present. Preoccipital furrow count: present. Preoccipital furrow anterior end: preoccipital furrow ends inside ocellar triangle. Dorsal margin of occipital carina vs. dorsal margin of lateral ocellus in lateral view: occipital carina is ventral to lateral ocellus in lateral view. Transversely reticulate region on frons count: absent. Rugose region on frons count: absent. Facial pit count: facial pit present. Intertorular carina count: present. Ventral margin of antennal rim vs. dorsal margin of clypeus: not adjacent. Median region of intertorular area shape: flat. Subtorular carina count: absent. Torulo-clypeal carina count: present. Supraclypeal depression count: present. Supraclypeal depression structure: present medially, inverted U-shaped. Antennal scrobe count: absent. Flagellomere shape (male): branched. Scape length relative to length of F1+F2 (male): longer or equal. 6th male flagellomere length vs. width, “sensillar” view : elongate, more than 2× as long as wide. Flagellomere branch count: 5 branches. Branch of male flagellomere 5 length compared to flagellomere 6: Longer than length of flagellomere 6. Branch of male flagellomere 5 length compared to flagellomere 5: Longer than length of flagellomere 5. Flagellomere 6 length compared to flagellomeres 7+8: Equal to the length of flagellomere 7+8. Sensillar patch of the male flagellomere pattern: F6—F9. Basal resilin-rich area of male antennal branches count: present. Female first flagellomere length vs. pedicel : F1 as long as pedicel (1.0–1.1) (n=3). Female ninth flagellomere length: F9 less than F7+F8. Mandibular tooth count: 2. Mandibular lancea count: present. Ventrolateral invagination of the pronotum count: present. Atrium of the anterior thoracic spiracle size: as wide as distal trachea. Notaulus posterior end location: adjacent to transscutal articulation. Epicnemial carina count: complete. Epicnemium posterior margin shape: anterior discrimenal pit absent; epicnemial carina straight. Speculum ventral limit: extending ventrally of pleural pit line. Sternaulus count: absent. Median mesoscutal line length vs. anterior mesoscutal width: MscL/AscW=0.6–0.9 (n=5). Anterior mesoscutal width vs. posterior mesoscutal width: AscW/PscW=0.9 (n=5). Median mesoscutal sulcus posterior end: adjacent to transscutal articulation. Axillular carina count: absent. Posteromedian process of the mesoscutellum count: present. Posteromedian process of the mesoscutellum shape: blunt. Scutoscutellar sulcus vs. transscutal articulation: adjacent. Mesometapleural sulcus count: present. Posterodorsal metapleural area shape: trapezoid. Metapleural carina count: present. Anteromedian projection of the metanoto-propodeo-metapecto-mesopectal complex count: absent. Lateral propodeal carinae shape: inverted “V” (left and right lateral propodeal carinae are adjacent medially at their intersection with antecostal sulcus of the first abdominal tergum). Lateral propodeal carina count: present. Transverse line of the metanotum-propodeum vs. antecostal sulcus of the first abdominal tergum: adjacent sublaterally. Distal margin of male abdominal sternum 9 shape: convex. Median conjunctiva of abdominal tergum 9 count: absent. Proximolateral corner of abdominal sternum 9 shape: blunt. Proximodorsal notch of cupula count: absent. Gonostyle/volsella complex proximodorsal margin shape: with deep concavity medially. Submedian conjunctiva on distoventral margin of gonostyle/volsella complex: length (range of fusion of parossiculus/parossiculus complex from gonostipes): more than 4/5. Apical parossiculal seta number: two. Dorsal apodeme of penisvalva count: absent. Distal projection of the penisvalva count: absent. Sensillar plate of the aedeagus shape: enlarged, about half as wide as the genitalia, and strongly sclerotized. Carina limiting posteriorly antecosta count: present. Distal projection of the parossiculus count: absent. Dorsomedian conjunctiva of the gonostyle-volsella complex count: absent. Cupula length vs. gonostyle-volsella complex length: cupula less than 1/2 the length of gonostyle-volsella complex in lateral view. Parossiculus count (parossiculus and gonostipes fusion): absent (fused with the gonostipes). Distoventral submedian corner of the cupula count: absent. Harpe length: harpe shorter than gonostipes in lateral view.
Mexico (Mexicali), California, Arizona, Texas, and Florida.
Other material (60 females, 27 males): USA:Arizona:Santa Cruz Co.: 1 male. PSUC_FEM 86285 (
After rehydration of the specimens, the rami of the flagellomeres were very flexible at their bases. After the antenna were placed in distilled water, the apical flagellomeres of both specimens curled very slightly. There was no change in the angle of the flagellomere projections or movement at their bases.
Branched antennae are common among various groups of insects. Many Diprionidae have pectinate and bipectinate antennae, though articulated branches have not been described (
This ramose flagellomere increases the surface area of the antenna, which could aid males in detecting female pheromones. Although nothing is known of D. mexicali mating behavior, male D. carpenteri have been shown to be attracted to sex pheromones released by the females (
Dessart postulated that the wrinkled regions at the bases of the male antennal branches were points of movement, which is extremely likely given the high resilin content of the cuticle that we found there (Figure
Conceived the project: IM, KNB. Character concept generation, semantic statement generation, specimen visualization and creation of plates: KNB, IM. Wrote the manuscript: KNB, IM, ARD. Commented on the final stage of the manuscript: IM, ARD.
We would like to thank Carolyn Trietsch for creating semantic statements to describe many phenotypes and character states applicable to Ceraphronoidea. We would like to thank Lubomír Masner from the Canadian National Collection for his mentorship and access to specimens. We would like to thank the Penn State Microscopy and Cytometry Facility - University Park, PA for access to the confocal laser microscopes. This material is based upon work supported by the U. S. National Science Foundation, under Grant Numbers DBI-0850223, DBI-1356381, and DEB-1353252. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Table 1S. Phenotype descriptions expressed as semantic statements
Data type: Excel file
Table 2S. Phenotype descriptions expressed as semantic statements
Data type: Excel file
Semantic statements for the taxonomic treatment of Dendrocerus mexicali
Data type: OWL file