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Folia faunistica Slovaca (2011) 16 (1): 1-3 |
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The first record of Porrhomma oblitum (Araneae, Linyphiidae) in Slovakia |
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Anna Šestáková |
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Department of Zoology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-1, 84215 Bratislava, Slovakia [asestakova@gmail.com] |
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Received: 1.12.2010; Accepted: 9.3.2011; Published: 22.3.2011 |
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Abstract |
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The occurrence of a mature female linyphiid Porrhomma oblitum from Slovakia is reported for the first time. I provide a brief illustrated description of this species with comments on its distribution. |
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Key words |
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Linyphiid spider, Porrhomma, new record, Palaearctic, Slovakia. |
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Introduction |
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The genus Porrhomma is thoroughly discussed because of its difficult species identification, especially the females. It is a very homogenous group of small spiders. The works by Thaler (1968) and Wiehle (1956) were focused not only on genitals, but also on leg spination, size of eyes, colouration, measurements of habitus, carapax, legs etc. Determination of the females is predominantly based on internal structures of vulva. They can be seen partly through integument, but for detailed examination further preparation and macerating with sodium (or potassium) hydroxide solution are needed. A single female of a linyphiid spider Porrhomma oblitum was recorded for the first time in Slovakia. It is not surprising because of the presence of the taxon in other European countries - especially in neighbouring countries Czech Republic, Austria and Poland. Other countries, where P. oblitum occurs, are Belgium, Switzerland, Germany, Denmark (Mainland), Finland, France, Great Britain, Ireland, Iceland, Italy, Lithuania, Netherlands, Norway (Mainland), Romania and European part of Russia (Helsdingen 2010). Concerning the presence of the genus Porrhomma in Slovakia Gajdoš at al. (1999) mentioned 13 species including P. lativelum Tretzel, 1956 which is synonymous with P. microps (Roewer, 1931) (Platnick 2010). |
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Material and methods |
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Material examined: SW Slovakia, Bratislava (7868 - grid reference number of the databank of Slovak Fauna, 48° 9’ 37.89” N, 17° 3’ 52.93” E). Study plot – sheet on the student’s bed: 1 ♀, 15 November 2009, leg. M. Kostrab, det. A. Šestáková. The specimen was collected using a vacuum cleaner (the specific method for sampling the dust mites) during the research of synanthropic mites at student campus in Bratislava (Kostrab 2010). To isolate the animals from the material from the dust bag Tullgrens apparatus was used. The specimen is preserved in 75% alcohol and was examined and drawn under a ZEISS Stemi 2000-C stereomicroscope. All measurements are given in millimeters. Prosoma length was measured medially, from the anterior margin to the rear margin. Total length is the sum of prosoma and opisthosoma length. The studied specimen was identified to the species level using the publications by Locket & Millidge (1953), Thaler (1968), Merrett (1994) and Russell-Smith (2009). The determination of the specimen was confirmed by V. Růžička. Systematics and nomenclature follow the World spider catalogue (Platnick 2010). |
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Results |
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Porrhomma oblitum (O.P.-Cambridge, 1871) Female 1.51 long; prosoma 0.76 long, 0.53 wide; opisthosoma 0.75 long, 0.48 wide. Carapax brown, opisthosoma pale brown without patterns, legs yellowish-brown (Fig. 1).
Whereas other authors (Russell-Smith 2009, Thaler 1968, etc.) described P. oblitum as a very dark spider, the main reason for confusion with bigger P. pygmaeum (Blackwall, 1834), the studied specimen has untypical colouration – pale brown. Several authors (Locket & Millidge 1953, Russell-Smith 2009 etc.) divided the species of the genus Porrhomma on the basis on leg spination into four or five groups. The first leg in P. oblitum lacks the femoral dorsal spines, while they are presented in P. pygmaeum. The group for which absence of the femoral spines is typical contains also P. montanum Jackson, 1913. All mentioned species can be distinguished from each other on the basis of small details of the vulva (Fig. 2). Finger-shaped spermathecae of these species direct inwards, but in different distance to median line. It is nearest to the median line in P. montanum, the farthest in P. pygmaeum. Spermathecal ducts are the shortest and direct upward in P. montanum. In P. pygmaeum they are the longest and direct obviously upward, but they are almost straight in P. oblitum.
Generally, P. oblitum is a Palaearctic spider preferring open or partly shaded habitats with wet, broad-leaved litter in floodplain forests. It occurs often under tree barks (Buchar & Růžička 2002, Harvey et al. 2002). Stańska (2007) mentioned the presence of the species in Poland occurring in the alder forest, wetlands but also in xerothermic grasslands. Unfortunately, the studied specimen comes from a rather unspecific habitat (the bed at the student campus), therefore no further conclusions on its ecology can be made. Adults occur from October to early June (Helsdingen 1997). |
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Acknowledgements |
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I would like to thank Dr. Vlastimil Růžička for his special help in confirming the specimen identification, the research of the home dust mites – especially to Matúš Kostrab for material and to Dr. Zuzana Krumpálová who read an earlier version of the manuscript. Last but not least I thank to Matúš Hyžný who reviewed the English of the manuscript. The study was supported by grant VEGA 1/0176/09. |
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References |
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Buchar J & Růžička V, 2002: Catalogue of spiders of the Czech Republic. Peres, Praha, 351 pp. Helsdingen P, 1997: The spider fauna of Scragh Bog in Co Westmeath, Ireland (Arachnida: Araneae). Zool. Verh. Leiden 323, 31.XII.1998: 407-415, Available online at <http://www.repository.naturalis.nl/document/148969>. Helsdingen P, 2010: Fauna Europaea: Araneae, Linyphiidae. Fauna Europaea version 2.2, Available online at <http://www.faunaeur.org>. Locket GH & Millidge AF, 1953: British spiders. Ray Society, London, 2: 1-449. Platnick NI, 2010: The world spider catalog version 11.0, Am. Mus. Nat. Hist., New York, Available online at <http://research.amnh.org/iz/spiders/catalog/INTRO1.html>. Russell-Smith A, 2009: Identification of Porrhomma species. Newsl. Br. Arachnol. Soc., 114: 18-23. |
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