Anisops sardeus

N. Soós, A. Petri, Zs. Nagy-László & Z. Csabai, 2010, Anisops sardeus Herrich-Schaeffer, 1849: first records from Hungary (Heteroptera: Notonectidae), Folia Entomologica Hungarica 71, pp. 15-18 : 16-17

Anisops sardeus HERRICH- SCHAEFFER, 1849

( Figs 1–2)

Material examined – Csongrád county: Atkai-Holt-Tisza (Algyõ) [oxbow lake of River Tisza near village Algyõ ], N 46°22’58”, E 20°11’53”, 10× 10 km UTM grid-code: DS 33, 04. VIII. 2010. leg. ATTILA PETRI & ZSOLT NAGY- LÁSZLÓ (1 male) ; Pusztaszeri-Büdösszék (Pusztaszer) [a sodic pond near village Pusztaszer ], N 46°32’58”; E 20°01’41” , 10× 10 km UTM grid-code: DS 25, 04. VIII. 2010. leg. ATTILA PETRI & ZSOLT NAGY- LÁSZLÓ (2 males, 5 females, 24 larvae of three different larval instars) .

Voucher specimens are deposited in the collection of Hungarian Natural History Museum (Budapest), reference collection of the Measurement Center of Lower-Tisza Regional Environment, Nature Conservation and Water Management Inspectorate (Szeged) and Department of Ecology and Hydrobiology, University of Pécs (Pécs).

Morphology – As the genus Anisops is not included in the keys used frequently for identification of aquatic Heteroptera in Hungary and Central Europe, we give a short morphological description of the genus and the species.

Prima facie, Anisops adult looks like a Notonecta larva, but Anisops specimens are much more slender in every developmental stage than those of Notonecta . Body length of European Anisops species is 4.8–8.4 mm, body width is 1.3–2.0 mm, body shape is elongated, laterally slightly flattened. The most conspicuous descriptive marks, which separate Anisops species from all genera in the family Notonectidae are (1) the hemielytral pit which can be seen behind the posterior edge of the scutellum, in the suture of the hemielytra; (2) extension of the ventral abdominal keel onto the last abdominal segment; and (3) one-segmented front tarsi of the males. Genital capsulae of Anisops species are asymmetrical, but symmetrical in the case of Notonecta .

The species of the genus could be identified by the following features: (1) length and width of the body, (2) distances between the eyes measured at anterior and posterior edges of the eyes, and proportion of these distances, (3) shape of the 3rd and 4th rostral segments of the males, and (4) characteristics of the stridulatory combs on the femur of the front legs of the males. Genital parts do not play crucial role in the identification procedure on the species level ( BROOKS 1951).

Anisops sardeus is the largest among the European species (body length of males 7.5–8.4 mm, females 7.2–7.5 mm, maximum width of males 1.8–1.9 mm, females 1.9–2.0 mm). Head is yellow coloured with brown eyes. Hemielytra are transparent, but their colour are defined by the colour of the underlying body parts, so it appears to be yellow, just like the whole dorsal side of the body. Ventral surface is brown or black. Legs are yellow.

In males of A. sardeus , the front edge of the head is conically protruded; it is clearly visible in dorsal or lateral view. The initial form of this protrusion can be seen also in the older larval stages. The head of the females is rounded ( BROOKS 1951).

Habitat – Hungarian specimens of A. sardeus were captured in two totally different water bodies: (1) many specimens (adults and larvae) were captured in a sodic pond of an alkaline wetland dominated by Bolboschoenus maritimus stands. Normally the water of the pond is strongly salty, the conductivity of the water is around 4000 μS/cm, the pH is around 9–10, and the transparency is only 2–3 cm (a “white water sodic pond”). Due to the extremely rainy weather of the spring and summer of 2010, the alkaline character of the th water was not expressed markedly, at the time of the samplings (4 August 2010) the conductivity was 1050 μS/cm and the pH was 8.4 only. Moreover besides Bolboschoenus maritimus , densely grown mixed stands of Lemna minor and Ceratophyllum demersum appeared in 2010. These plant species were not typical for this wetland in the previous years. Based on BROOKS (1951) the species can tolerate mixed, brackish and even marine water, so occurrences in alkaline inland waters are not surprising. (2) Only one male specimen was captured on the same day from an oxbow lake of River Tisza, approximately 20 km SE from the other locality. Chemical characteristics of the water are absolutely different; actually this is not an alkaline water body. Vegetation is composed of Nuphar lutea , Nymphea alba , Phragmites australis and smaller amount of Ceratophyllum demersum . The shoreline is emarginated by reed stands or agricultural fields and at some places trees and shrubs of Robinia pseudoacacia . Branches of the trees reached the water surface and submerged into the water; the captured specimen was collected among these branches.