REVISION OF THE GENUS SERBOIULUS STRASSER , 1962 ( DIPLOPODA , JULIDAE )

Serboiulus lucifugus Strasser, 1962 and S. deelemani Strasser, 1972 are upgraded to the species level from subspecific status under Serboiulus Strasser, 1962. The position of the genus Serboiulus in the tribe Typhloiulini Verhoeff, 1930 is discussed, and a key to serboiulid species is presented. UDC 595.61(497.11-11)(497.2-15)

The main reason for establishing this genus was the presence of a reduced flagellum (Strasser, 1962).The distribution of representatives of the genus Serboiulus is restricted to a few caves in Eastern Serbia and Western Bulgaria.Zoogeographically, these regions belong to the massif of the Stara Planina Mountain.
On the basis of abundant material from the typelocalities of both subspecies of Serboiulus lucifugus, viz., S. lucifugus lucifugus and S. lucifugus deelemani, we analyzed their taxonomic status, as well as relationships with S. spelaeophilus and the representatives of closelyrelated genera.
Remarks.Gulička (1967) established the new subgenus Balkaniulus on the basis of structure of the promerite, which in S. spelaeophilus has a wide apico-lateral lobe and an opisthomeral lamella.Shape of the mesomerite and that of the opisthomerite are somewhat peculiar and clearly separate this species from other Serboiulus representatives.However, it is known that shape of the promerite is highly variable within the Julidae (Mauriès et al. 1997) and that in different typhloiulines the opisthomeral lamella is well-developed, vestigial, or even reduced.We assume that all characters mentioned by Gulička(1967) in his erection of the new subgenus reflect only the species level, so we treat the subgenus Balkaniulus as a synonym with the genus Serboiulus.

DISCUSSION
In his excellent review of the Typhloiulini, Strasser (1962) pointed out the existence of some body structures (number of pleurotergites, body length, length of antennomeres or length/breadth ratios of antennomeres) in this tribe, that can be very useful for distinguishing some representatives of even closely-related taxa.In Table 1 we summarize some of the main characters of S. lucifugus lucifugus and S. lucifugus deelemani pointed out by Strasser(1962).It is evident that, as far as the genus Serboiulus is concerned, most of these characters are not valid for discrimination of the given subspecies.The only more or less useful features are the number of sensillae on antennomeres V and VI and the number of setae on pleurotergite VII (Table 1).Generally, males of S. lucifugus lucifugus have more than 16 setae on somite VII, while males of S. lucifugus deelemani have less than 16 setae on the same somite.On the other hand, lucifugus males have a smaller number of sensillae on antennomeres V and VI than deelemani ones.However, on the basis of the analyzed males we have to note that the number of setae on the above-mentioned structures is highly correlated with body size.Larger males have a high number of sensillae on both antennomeres, as well as numerous setae on somite VII.We suppose that in a larger sam-
PDF created with FinePrint pdfFactory Pro trial version www.pdffactory.comple these characters will be similar and cannot be used for valid discrimination.
We thoroughly analyzed structure of body parts which are more or less in direct correlation with sperm transfer and which in our opinion have great taxonomic and phylogenetical value.Legs of the first pair, as in numerous julids, are hook-shaped.In adult males from the Vetrena Dupka Cave, the tibiotarsal part is without setae (Fig. 1); all males from the Prekonoška Pećina Cave have two setae on the tibiotarsal part (Fig. 2).Moreover, in S. lucifugus lucifugus the border between basal podomerae is much more distinct than in S. lucifugus deelemani.The penis in both subspecies is quite similar.The basal part is expanded and rounded; the median part is almost parallel-sided; and the apical part is bi-lobed (Figs.3-4).
Great differences exist in shape and size of the gonopods.In both taxa promerites are without an external lobe.In S. lucifugus lucifugus, the promerite is elongated and quadrangular (Fig. 8), but in S. lucifugus deelemani it is clearly triangular, with a wider basal part and a considerably tapering top (Fig. 5).The mesomerite in lucifugus is of the same height as the promerite and apically has a clear row of teeth on the anterior side (Figs.7-8); in deelemani the mesomerite is considerably longer than the promerite, strongly curved cephally, and with only a few teeth on the anteroapical side (Fig. 5).Moreover, in the latter taxon the mesomerite possesses strongly developed lateral outgrowths (Fig. 6); such structures do not exist in the subspecies lucifugus.The opisthomerite is generally similar in both taxa, but in males from the Vetrena Dupka Cave the velum is well-developed, terminating subapically in the solenomerite; as a result, the free part of the solenomerite in these taxa is very short (Fig. 6).In lucifugus the velum is much shorter and the apical free part of the solenomerite is considerably longer (Fig. 7).We think it unnecessary to explain the importance of this character because the apical part of the solenomerite is directly involved in sperm transfer to female vulvae.
On the basis of both body and gonopod structure, we feel that important differences exist between the two subspecies and that both taxa deserve full specific rank as Serboiulus lucifugus and S. deelemani.Both species differ greatly from S. spelaeophilus in shape of both the promerite and the mesomerite, as well as in structure of the opisthomerite (see Key to the species of Serboiulus).
The genus Serboiulus possesses some apomorphies, such as: absence of eyes, hook-shaped legs of the first pair, absence of a flagellum, presence of only one lobe on the caudal side of the promerite, and development of the mesomerite as an independent branch.Generally, the trend in evolution of the gonopods in julids involves the appearance of a free mesomerite (Enghoff, 1987).This means that Serboiulus members are highly evolved taxa.It is interesting that a flagellum is also absent in representatives of the genus Trogloiulus Manfredi, 1931 from Northern Italy.It is probable that both taxa have evolved independently and represent two phyletic lineages within Typhloiulus sensu lato.One strongly plesiomorphic feature is retention of pigments in all Serboiulus species.Unusual dark pigmentations may be a result of their recent isolation in cave systems.
Zoogeographically, the genus Serboiulus belongs to the category of Balkan elements, and its evolution is probably correlated with geotectonic events in the Carpatho-Balkan Arc in the past.

Key to the species of Serboiulus
This key is based mainly on structure of the gonopods in adult males: