Research Article |
Corresponding author: Agnieszka Nowińska ( agnieszka.nowinska@us.edu.pl ) Academic editor: Roger Blackman
© 2017 Agnieszka Nowińska, Ewa Mróz, Łukasz Depa.
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:
Nowińska A, Mróz E, Depa Ł (2017) Sexual morphs of Pterocomma tremulae Börner, 1940 (Aphididae, Aphidinae) with description of male reproductive system. ZooKeys 686: 125-136. https://doi.org/10.3897/zookeys.686.14493
|
Paper presents the first description of the so far unknown sexual generation of Pterocomma tremulae (Aphididae, Aphidinae): oviparous female and alate male. It also provides detailed description of the male reproductive system. Discussion focuses on comparative analysis of male reproductive system with other aphid groups and possible importance of its structure in resolving phylogenetic interrelationships within the genus Pterocomma. A key is provided to the known males of European Pterocomma species.
Aphid, phylogeny, Populus , reproduction, taxonomy
Pterocommatinae have long been a somewhat problematic group within Aphididae, having been placed in most systems in close relationship with Aphidinae. The detailed history of classification has been presented in revision of Palaearctic species of Pterocommatinae made by
However, within the genus Pterocomma itself, there are also some problems concerning the very variable morphology of a few species, making it difficult to distinguish closely related species e. g. Pterocomma pilosum Buckton, 1879; P. konoi Takahashi, 1939; P. dubium Börner, 1950; P. ringdahli Wahlgren, 1940; or various subspecies, of uncertain taxonomical status e.g. P. pilosum sarmaticum Szelegiewicz, 1967 (
Pterocomma tremulae, Börner 1940 is relatively well defined in terms of its morphological characteristics. There are some accounts of its intraspecific variation, but the species as whole may be well recognized as the only Populus-feeding species bearing few to many secondary rhinaria on antennal segment III, a trait occurring also only in Pterocomma kozhuchovae, most probably an eastern Palearctic vicariant species. Here we present the first description of the sexual morphs and also provide the first description of the male reproductive system of this species.
Collection data of specimens applied for taxonomical description:
17.10.2014, Katowice; Populus tremula; leg. A. Nowińska, det. Ł. Depa, 2 oviparous females.
17.10.2014, Katowice; Populus tremula; leg. A. Nowińska, det. Ł. Depa, 2 alate males.
Also 29 specimens of alate males were collected from the same collection site to anatomical studies. The provisional key to males of European representatives of the genus Pterocomma was prepared on the basis of morphological descriptions and measurements given by
Histological preparations
In order to analyse the anatomical structure of the male reproductive system of P. tremulae, the paraffin method was applied. The material was collected into Eppendorf microtubes containing 70% ethanol for keeping and preserving collected specimens. Next, insects were dehydrated in increasing concentration of ethanol (90%, 96%, 100%). In order to ensure transparency, specimens were kept in methyl benzoate for one night. Then, material was consecutively transferred to benzene, benzene with paraffin (in proportions 2:3 and 1:2), paraffin I (melting point: 56°C) and finally to paraffin II (melting point: 60°C), where it was kept for the night. After this process, material was immersed in paraffin II. The bars obtained were sectioned into 5 µm strips, which were stuck on slides in a 0.5% gelatine solution at temperature 50–52°C. Then, the slides were dried in 37°C.
Slides were next deparaffined in xylene and treated with a series of ethanol solutions (100–60%). They were rinsed in distilled water, stained with Ehrlich’s acid hematoxylin for about 20 minutes, rinsed again and differentiated with xylidine ponceau. After this process, preparations were treated with series of ethanol solutions (60–100%), rinsed twice in xylene and embedded in Canadian balm or DPX.
This process was applied to 17 individuals of P. tremulae. The following histological preparations were prepared: cross-sections from 9 individuals and longitudinal sections from 8 individuals. In total 171 microscopic slides were made, including 84 preparation of cross-section and 87 of longitudinal section.
Mounting of the whole tract
The specimens of P. tremulae were put into a droplet of 30% ethanol, on the microscopic glass, and with the mounting needles the whole reproductive system was extracted from the body. The extracted organs were preserved in glycerol and mounted, to make all the anatomical structures visible with the stereomicroscope. A total number of 12 preparations were made using this technique.
The documentation was prepared using Nikon Eclipse E6000, with measurements made by Lucia net program. The pictures of translucent specimens were taken with a stereomicroscope equipped with monochromatic camera Axio Cam programmed with Axio Vision.
Body oval, 3.66–4.03 mm long (Fig.
Abdomen membranous, covered with dense pubescence. Length of hairs on abdominal tergite V 0.17–0.19 mm. Spinal sclerites only on VI and VII segment: on VI weakly developed, broken into minute scleroites. Intersegmental sclerotic insertions dark. Marginal slerites present on abdominal tergites I and V, sometimes also on VI but broken into smaller scleroites. Marginal tubercles present always on abdominal tergites I-IV, sometimes also on V-VII, their diameter at most as the diameter of spiracles, always dark pigmented. Number of hairs on abdominal tergite VIII ca. 50, their length 0.16–0.17 mm. Cauda rounded, dark pigmented, covered with many hairs (Fig.
Body dark, brownish, 2.87–3.03 mm long (Fig.
Abdomen membranous, covered with hairs 0.010–0.015 mm long, with spino-pleural sclerites on abdominal segments I-VII often divided in the middle, and on segment V broken into smaller slceroits. Marginal sclerites present on all abdominal segments, with spiracles in the anterior margins of the sclerites and with conspicuous marginal tubercles (Fig.
The male reproductive system of Pterocomma tremulae extends parallel to the longitudinal axis of the body. It consists of two testes, located in the area of abdominal segments II and III, and a pair of accessory glands (Figs
Accessory glands, of ectodermal origin, are 0.6–1.06 mm long. In examined species they are club-shaped or elongated. At the widest point their diameter is 0.05–0.12 mm, while at the narrowest point the diameter is 0.04–0.07 mm. Glandular wall is built of cuboidal epithelium (Fig.
Depending on the age of the individual, testes and glands change their size. In younger individuals we observed testes several times larger than glands(Fig.
1 | Male apterous | P. jacksoni |
– | Male alate | 2 |
2 | Siphunculi strongly swollen medially | P. salicis |
– | Siphunculi cylindrical, at most slightly swollen distally | 3 |
3 | Antenna 0.6 of body length or longer | 4 |
– | Antenna less than 0.6 of body length | 6 |
4 | Less than 50 secondary rhinaria on antennal segment III, on Salix spp. | P. konoi |
– | More than 70 secondary rhinaria on antennal segment III, on Populus spp. | 5 |
5 | Less than 20 secondary rhinaria on antennal segment V | P. dubium |
– | 20 or more secondary rhinaria on antennal segment V | P. tremulae |
6 | Up to 15 secondary rhinaria on antennal segment IV | P. rufipes |
– | 18 or more secondary rhinaria on antennal segment IV | 7 |
7 | 80 or less secondary rhinaria on antennal segment III | P. pilosum |
– | 80 or more secondary rhinaria on abdominal segment III | P. populeum |
The male reproductive system of around 80 aphid species has been studied so far (
In Aphidoidea, the number of testicular follicles varies between 2 and 7 (
There are four testicular follicles in each testicle in Pterocomma tremulae (Figs