Boletín de la RSEHN. Sección Biológica

En este artículo describimos una nueva especie de Arion de la Sierra de Espadán, en la provincia de Castellón (E España) y la comparamos con las especies más semejantes y de distribución más cercana: A. baeticus, A. gilvus y A. hispanicus. Finalmente incluimos una pequeña discusión sobre la asignación subgenérica en Arion y la ubicación taxonómica de A. luisae spec. nov.

In this paper we describe a new species of Arion from the Sierra de Espadán in Castellón province (E Spain), and we compare it with the most similar species of closer geographical distribution: A. baeticus, A. gilvus and A. hispanicus. Finally we comment about the subgeneric allocation in Arion and the position of A. luisae spec. nov. The Iberian peninsula is one of the areas of greater diversity of arionids. In fact, nowadays are known four species of the genus Geomalacus and around twenty of Arion which would add at least one more recently described: A. ponsi from Menorca. Also in twenty Arion cited by Castillejo (1997) there are eight of them of fairly recent description. Nevertheless Arion are little known and scarce in the province of Castellón (East of Spain) existing only a few quotations of A. gilvus, A. intermedius, and A. lusitanicus auct. non Mabille all them since the last twenty years. These three species are clearly distinct and distinguishable of our new species even by external characteristics. Only A. gilvus is of a similar size, but quite anatomical characters distinguish them. A. luisae spec. nov. in terms of size and overall external appearance resembles rather the complex A. subfuscus which would be composed of the following species in the Iberian peninsula: A. subfuscus s.s. in some Pyrenees localities; A. molinae, also of the Pyrenees and the catalan pre-Pyrenees; A. iratii and A. lizarrustii both from Navarre and A. gilvus, the Mediterranean taxon of the complex which is considered endemic from the northeast of the Iberian peninsula. Well already in its external appearance A. gilvus differs from A. luisae spec. nov.. because it is pretty dark reddish brown and has a thin orange fringe that separates the back of the sole. It also has characteristic orange yellow mucus. Genitalia presents some similarity but i) there are three portions in the oviduct of A. luisae spec. nov., and only a proximal narrowing in A. gilvus, ii) a thickening of the wall of the duct of the bursa copulatrix in A. luisae spec. nov., not in A. gilvus, iii) the papilla that accompanies the annular thickening at the entrance of the epiphallus into the atrium in A. luisae spec. nov., inexistent in A. gilvus, iv) finally, in A. gilvus the relationship vd/e is 0.71, so the epiphallus is rather longer than the vas deferens. In A. luisae spec. nov., it is also longer but the disproportion is lower (0.81 vd/e). As for the Arion of small size, belonging to subg. Kobeltia as A. intermedius and A. hortensis agg., all they have orange or yellow sole, and are quite smaller. A. intermedius has no ligula or thickened oviduct and the complex A. hortensis, of Northern distribution in the Iberian peninsula, have the oviduct thickened and divided into different functional parts, which resemble them to our new species, although the much greater size of A. luisae spec. nov. and its cream sole, not yellow or orange, separate them, in addition to other aspects of the genitalia. After that we have only as similar species not too remote geographically A. hispanicus and A. baeticus: a) A. luisae spec. nov. differs from A. hispanicus in the following characteristics: A. hispanicus is black with bluish nuances and bands are generally unobservable. A. luisae spec. nov. is grey-brown rather clear and has well-marked bands. The general topography of the genital is similar but with significant differences: i) dark pigmentation more intensive and extensive in A. hispanicus than in A. luisae spec. nov., ii) presence in A. hispanicus of a papilla at the entrance of the bursa copulatrix, non-existent in A. luisae spec. nov., which only has the duct with a thickened wall, iii) oviduct of A. luisae spec. nov. divided into three parts (subg. Kobeltia), character that is not in A. hispanicus, iv) distal genitalia much bigger and thicker in A. luisae spec. nov. b) Arion baeticus is another Arion of similar size to A. luisae spec. nov. and similar genital topography. Its external at the entrance of the bursa copulatrix duct in the atrium and the epiphallus is longer than the vas deferens. Both characters match A. luisae spec. nov. that nevertheless differs from A. baeticus in other features: i) black or very dark back, with strips hardly observable in A. baeticus; light grey-brown back with very visible bands in A. luisae spec. nov., ii) female part of genitalia dyed in dark in A. baeticus; only slightly pigmented genitalia in A. luisae spec. nov., iii) oviduct divided into three parts in A. luisae spec. nov., non-existent feature in A. baeticus. Finally, we express our doubts about the subgeneric division in Arion, but provisionally, and mainly by the oviduct divided into three portions, as in A. hortensis we place A. luisae spec. nov. into the subgenus Kobeltia.