Abstract
Epigean and hypogean populations of Asellus aquaticus (Linne) from Slovenia (A. a. aquaticus, A. a. carniolicus Sket, A. a. cavernicolus Racovitza) were compared morphologically with those from Romania (A. a. aquaticus, A. a. ssp. from Mangalia). The highly troglomorphic Slovenian race (A. a. cavernicolus) was the reference for assessing the degree of troglomorphism in the Romanian cave population. Of 61 measured characters, most proved discriminative and many were classified according to their presumed nature (reductive and progressive troglomorphisms, paedomorphoses, K-strategy traits).
In Slovenian hypogean population (A. a. cavernicolus), a combination of regressive and progressive troglomorphic traits is present: total depigmentation, eye and cuticular structural reduction, and body and appendage elongation. Some traits which might indicate paedomorphosis also occur.
The most significant shared characters of the assumed sister taxa A. a. cavernicolus (cave) and A. a. carniolicus (epigean) are isometric uropods and pereiopods, as well as the size of pleopod V and its large ‘area‘.
Although some progressive troglomorphisms (appendage elongation) are not present in the Romanian hypogean population (A. a. ssp.-Mangalia), a number of adaptive troglomorphic traits distinguish this population from the epigean one. It is totally depigmented, with reduced eyes and a smaller number of eggs. It also exhibits traits which might indicate paedomorphosis. Probable reasons for absence of the constructive troglomorphisms are discussed. The Romanian hypogean populations are not uniform. Specimens from Movile cave resemble some peltate asellids in head and pleotelson shape. In the peripheral range of this hypogean population, however, there are signs of an introgression with the epigean population. Details of the pleopods, as well as the biogeographical situation, support the conspecifity of A. a. ssp.-Mangalia with A. a. aquaticus.
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Turk, S., Sket, B. & Sarbu, Ş. Comparison between some epigean and hypogean populations of Asellus aquaticus (Crustacea: Isopoda: Asellidae). Hydrobiologia 337, 161–170 (1996). https://doi.org/10.1007/BF00028517
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DOI: https://doi.org/10.1007/BF00028517