Life Cycle of Aylax Hypecoi (Insecta: Hymenoptera: Cynipidae), a Gall Inducer on Hypecoum Ssp
Total Page：16
File Type：pdf, Size：1020Kb
Cent. Eur. J. Biol. • 3(2) • 2008 • 199–204 DOI: 10.2478/s11535-008-0009-6 Central European Journal of Biology Life cycle of Aylax hypecoi (Insecta: Hymenoptera: Cynipidae), a gall inducer on Hypecoum ssp. (Papaveraceae) Research Article Anelia M. Stojanova1*, Marian M. Draganov² 1 Department of Zoology, Faculty of Biology, University of Plovdiv, 4000, Plovdiv, Bulgaria ² Department of Developmental Biology, Faculty of Biology, University of Plovdiv, 4000, Plovdiv, Bulgaria Received 16 November 2007; Accepted 11 January 2008 Abstract: The life cycle and developmental stages of Aylax hypecoi (Trotter, 1913, Hymenoptera: Cynipidae: Aylacini) were studied in detail. Aylax hypecoi is known to induce galls in fruits of two Hypecoum species – H. imberbe and H. geslini (Papaveraceae) and the larva develops in host plant fruits. The morphology and development of egg, larva and pupa were investigated, which has previously not been done. The shape and size of terminal-instar larvae and associated galls are sex-specific. Overwintering stage, adult emergence and flying periods, and egg productivity were studied also. Keywords: Aylax hypecoi • Cynipidae • Gall inducer• Hypecoum imberbe • Egg • Larva • Pupa • Adult • Bulgaria © Versita Warsaw and Springer-Verlag Berlin Heidelberg. 1. Introduction subject to years of investigation [2,4,6], our knowledge of preimaginal stage morphology is fragmentary and, thus, Galls are often defined as an abnormal growth in plant far from complete. Recently, phylogenetic interpretations tissue caused by a foreign organism. Cynipid galls are were made from detailed examinations of the immature found on all plant organs (i.e., flowers, leaves, buds, stages of cynipids [2,5,7]. stems, twigs, roots) and may contain from one to more The genus Aylax Hartig, 1840 (Cynipidae, Aylacini) than 100 larval chambers [1]. Usually the gall has species- is currently represented by four species, three of which specific shape and forms around the developing larva are from the Western-Palaearctic region. The taxonomic after adult female deposits the egg on the target plant position of the fourth species, A. quinquecostatus organ [2]. The gall-induction mechanisms are not known (Provancher, 1883) located in Canada, requires further in details, but it is commonly assumed that the young investigation [6,8]. All species are monovoltine, and cynipid larvae manipulate the host plant development only the sexual generation induces galls on their target to its own benefit 3[ -5]. For successful ovipositioning, species, Papaver and Hypecoum. Aylax hypecoi is found gall inducers require specific meristematic plant host in Algeria, Greece, Bulgaria, Armenia and Turkmenistan tissue that is suitable for the development of nutritive on two host Hypecoum species – H. imberbe Sibthorp and protective gall layers. et Smith (also with synonym grandiflorum) and H. geslini Cynipid gall wasps are the second most species-rich Coss. et Kral. The taxonomic status, redescription and group of gall inducers after the gall midges (Diptera: biological notes of this species are recorded in Nieves- Cecidomyiidae) [6], with ca. 1400 described species, Aldrey & Melika [9]. Although they are distributed worldwide, and have been * E-mail: [email protected] 199 Life cycle of Aylax hypecoi (Insecta: Hymenoptera: Cynipidae), a gall inducer on Hypecoum ssp. (Papaveraceae) Hypecoum imberbe is typical Mediterranean plant 2.3. Adult life longevity and egg load distributed in Greece, Albania, Italy, Spain, France, After emergence from galls, 5 adult female wasps were Portugal (Flora Europaea Database, http://rbg-web2. kept isolated from each other in 10 ml glass vials, fed rbge.org.uk/FE.fe.html), and Turkey [10]. The plant with honey and water, and maintained under standard grows, blooms and produces fruits until the early (20oС, L16: D8 photoperiod regime) conditions until summer [11,12]. It springs up in autumn and overwinters termination of experiments. as a small rosette. To understand ovipositing preference, mated females Previously observed tight correlation and were exposed to host plants with available buds, flowers synchronization between the plant phenology and and fruits. To examine Aylax hypecoi eggs, virgin the gall inducer’s life cycle, provoked us to start detail (just emerged) and mated females were dissected. investigations along this line. In this paper, we clearly Dissections started in November, when already formed describe the life cycle and developmental stages of adult females were found in galls, and continued till Aylax hypecoi. the end of March next year. The mature eggs stored in egg reservoirs were counted. For the examination and measuring of eggs, microscope slides were prepared. 2. Experimental Procedures The length of the egg body was measured from the posterior tip to the transition between the egg body 2.1. Sampling and the peduncle. The width was measured at the The experimental sampling was carried out in Plovdiv maximum width of the egg body and at the swelling of City, on three rock hills – Dzhendem tepe, Sahat tepe the peduncle. and Bunardzhik during 2003-2007. Plovdiv is situated in central southern Bulgaria (42о 9’ N and 24о 45’ E) in 2.4. Measurements and statistical analysis the Upper Thracian Lowland at 160 m above sea level, All the laboratory measurements of the eggs, galls along the banks of the Maritsa river. and larvae were derived from examination with a Galls with larvae, pupae and imago of Aylax hypecoi Stereomicroscope MBS-2 and microscope Laboval-2 were collected from March to February next year. Fruits (Karl Zaiss, Germany). The data was tested statistically and galls were stored dried or in 70% ethanol. Most for homogeneity by analysis of variance (ANOVA) using of the collected galls overwintered outside, as would SPSS for Windows (Release 7.5.1, Standard Version; occur in natural settings, as only a part of them were Chicago, Ill: SPSS Inc.). The mean values were transferred to a laboratory for further analysis. compared for significant differences by Student-Fisher Species identification of Aylax hypecoi adults was t- criterion (n<30; P<0.05). confirmed by Dr. G. Melika (Systematic Parasitoid Pictures were taken by Canon A 550 and Olympus Laboratory, Tanakajd, Hungary) and Dr. J. L. Nieves- SP-500 UZ cameras. Aldrey (Museo Nacional de Ciencias Naturales, Madrid, Spain). Insect material was then deposited in the entomological collection at University of Plovdiv, 3. Results Bulgaria. 3.1. Egg 2.2. Larval morphology and growth Mature eggs are banana-shaped, with smooth surface A detailed study of the larval growth was conducted in and a long peduncle at the anterior end (Figure 1A). The 2007. To determine the larval stage development and egg body is about 3.0 times as long as broad (length = growth, host plants were transferred to the laboratory 196.9 ± 8.4 µm; width = 64.6 ± 8.9 µm (n = 50)). The from native location. Flowers and fruits were then peduncle is about 1.6 times as long as the egg body removed and buds of different ages were marked. As (length = 322.66 ± 24.5 µm; width = 10.2 ± 1.3 µm), maturation of these buds occurred over a short time, ending in an elongate swelling (width = 40.4 ± 5.2 µm). we assumed the oviposition of all females into the marked buds happened simultaneously. After these buds matured into fruits, they were dissected and 3.2. Larva Larvae have a well-developed head and 12-segmented Aylax hypecoi were measured immediately. Mandibles smooth, ventrally curved body. A newly-hatched larva is were excised and mounted on microscope slides for nearly transparent; posterior segments are smaller in observation of their shapes. diameter than segments of the thoracic region, giving larvae an elongate shape that appears to sharpen 200 A.M. Stojanova, M.M. Draganov Figure 2. Growth of Aylax hypecoi larvae in 2007 year. The lengths are presented in mean values (± SD). Empty bars – fe- Life cycle stages of Aylax hypecoi: A) egg; B) newly Figure 1. male larvae, hatched bars – male larvae. hatched larva; C) last-instar larvae, upper – female larva, lower – male larva; D) mandible of the larva; E) ovaries female larvae are clearly longer than males (3108.7 with growing eggs; F) pupa; G) female in a moment of ± µ ± µ oviposition. 98.7 m compared to 2538.4 55.7 m). During this growth period, female and male larvae increase posteriorly (Figure 1B). Newly hatched larvae were their length more than 9 and 7 times respectively. isolated from just overblown flowers, with ovary about The larval development is finishing in about 20 days. 7-8 mm long. In the growing period, larvae are milky Aylax hypecoi larva has asymmetrical mandibles white. Last-instar larvae differ in appearance from (Figure 1D). The right mandible has three teeth, where previous instars. Furthermore, shapes of last-instar the second tooth is blunt and broader that the other two. larvae are different between females and males. The In the left mandible the second and the third teeth are female larva has an elongated fusiform shape, and divided each into two unequal-sized lobes. The benefit body segments 1-3 are enlarged while the rest of the of this design is currently unknown. segments (excepting the last two) are almost equal in length and diameter, with distinct visible protuberances between segments 4 to 9 (Figure 1C, upper). The male 3.3. Galls larva has segments of even diameter along the whole Hypecoum imberbe has linear fruits, 3-5 cm long, 2-4 mm body (except for the last two) and a rectangular shape broad, which break into multiple one-seeded portions. (Figure 1C, lower). During the summer, when the larva Aylax hypecoi induces galls in the fruits of host without stopped feeding, colouration is yellow to amber yellow obstructing their development. Mature galls are single and the whole body appears less swollen in both sexes. chambered, elongated, from ovate to globose, with Growth rates of female and male larvae are presented 2.0-6.0 mm width (Figure 3); they are typically fragile in in Figure 2.