A NEW LOCATION OF TADPOLE SHRIMP (TRIOPS CANCRIFORMIS L.) IN LITHUANIA

Abstract

Tadpole shrimps (Triops cancriformis L.) were registered on 10 August 2007 and during the repeated observation on 8 September 2007 (Fig. 1). Only two habitats of this species of triops are known to exist in Lithuania (Raðomavieius 2007). To date no records of T. cancriformis have been reported from the northern part of Lithuania (Raðomavieius 2007). The habitat of these rare crustaceans (Red Data Book of Lithuania category 2 (V), MoE 2007) has formed in quite an unexpected place – at the sodden edge of a rape field situated at a distance of 5.5 m from the carriageway side (Fig. 2). From the viewpoint of administrative division, the habitat of Triops cancriformis L. is in Pasvalys region, on the left side of the No. 150 motorway (Ðiauliai–Pakruojis–Pasvalys), 59.7 km from Ðiauliai. The nearest settlement Meðkalaukis lies 3.70 km south-west of the location. Coordinates of the location are 24°16'11.2'' east longitude and 56°01'53.0'' north latitude (error – 6 m). In the north of the habitat there is a 150 m wide tract of a rape field with a mediumaged mixed forest behind it. Approximately 50 m east of the habitat, there is a mature deciduous forest and a wheat field (Triticum sp. L.) to the south of it (on the other side of the above mentioned motorway). Suitable conditions for the development of T. cancriformis in the rape field formed for several reasons, water accumulation being of the primary importance. The location is situated in the lowland of central Lithuania, in a moderate descent of the flat landscape relief, just 41 m above sea level. However, the presumption that the habitat is supplied with groundwater has to be ruled out, for 45 m north-east of the site there is a ~10 m wide and ~5 m deep drain ditch which drains underground water. The only source of moisture for this temporary water body is precipitation. Thus, the second prerequisite for the formation of the T. cancriformis habitat comes out. It is specificity of soil. According to Miliauskas and Nedzinskas (2000), soils in these areas are periodically dry. Hence, soil moisture regime is mainly preconditioned by the amount of precipitation. Surface layers of carbonate-rich morenic clay loam and clay have formed a natural hydrological barrier (Galvydyte 2000). In 2007 the amount of precipitation was sufficient for the formation of a perennial puddle and develoment of T. cancriformis eggs. The fact that a number of water plants, plants of damp sites and algae managed to root and even to flourish there – some of them reaching generative and senile stages, proves that the terrain has been sodden for a long period of time (Vilkonis 2001). Among such plants the following should be mentioned: great reedmace (Typha latifolia L.), common reed-grass (Phragmites australis (Cav.) Trin. Ex Steud.), marsh woundwort (Stachys palustris L.), murr marigold (Bidens tripartita L.), marsh cranesbill (Geranium palustre L.), common water-plantain (Alisma plantagoaquatica L.), common mudwort (Limosella aquatica L.), muskgrasses (Chara sp.) (Gudþinskas 1999; Vilkonis 2001). The following water animals managed to inhabit the temporary water reservoir: pond scatter (Gerris sp.), great diving beetle (Dytiscus marginalis L.), and a lot of fire-bellied toads (Bombina bombina L.).