Contribution to the knowledge of the caddisfly fauna of Montenegro – New data and records from the karstic springs of Lake Skadar basin

Caddisfly larvae were collected in 11 karstic springs located in Lake Skadar drainage basin in the Mediterranean part of Montenegro on May and June 2018. Three species are new records for the caddisfly fauna of Montenegro: Brachycentrus subnubilus , Lepidostoma hirtum , Triaenodes ochreellus lefkas . One is a confirmed record of a previously thought absent species Thremma anomalum. Future caddisfly surveys in the region will contribute significantly to the partially known Trichoptera fauna of Montenegro.


Introduction
The Balkan Peninsula is an important biodiversity hot-spot of the West Palaearctic, characterized by a rich and diverse freshwater fauna. Despite its high fauna diversity, data and information on the Balkan Trichoptera, especially from Montenegro is still limited. The first caddisfly study was carried out by Radovanovic (1935Radovanovic ( , 1953 in northwestern Montenegro at Durmitor Mt. who recorded 19 species. The next study followed much later by Marinkovič-Gospodnetič;(1981) who recorded 48 caddisfly species from the Morača and the Plavnica River drainages. Krusnik (1987) recorded 95 species again from Durmitor Mt., 67 being new for the fauna of Montenegro. Few other studies were published during the last years with the discovery of new species, such as Agapetus kampos Oláh, 2013and Drusus gombos Oláh, 2013(Oláh, 2010Oláh & Kovács, 2013). Recently Ibrahimi et al. (2019) recorded six species new for the fauna of Montenegro. Despite the recent surveys, there are still poorly investigated areas in Montenegro, mostly from springs and streams. Compared with the northern part of Montenegro, the Trichoptera fauna of the Lake Skadar drainage basin has only been partially studied (Pešić et al. 2018). In the present study, 11 karstic springs located in Lake Skadar basin in the Mediterranean part of Montenegro were investigated for its caddisfly fauna. The aim of this work is to contribute to the inventory of the caddisfly fauna of Montenegro and to expand the knowledge about the composition of the caddisfly fauna of the springs of Skadar Lake river basin.

Study area
Caddisfly larvae were collected from 11 springs situated in the drainage basin of Lake Skadar in Montenegro (Fig. 1, Table 1). In each spring two samples were taken: (1) in the spring source (eucrenal, "A"), and (2) at some distance (2-19 m) from the source (springbrook -hypocrenal, "B") (see Pešić et al. 2019 for additional information).
Besides usage of the springs as drinking water supplies for humans and livestock, no other types of anthropogenic impact were observed. The basin consists mainly of carbonate rocks and limestones. The climate in the main part of Lake Skadar basin is Mediterranean-Adriatic, typically with hot and dry summers and an average air temperature of the warmest month > 20 °C, whereas in the winter the average air temperature varies from 6 to 9 °C (Kostianoy et al. 2018). The average yearly precipitation in the entire basin ranges from 1800 to 2200 l m−2 with the maximum in November (Kostianoy et al. 2018).  Table 1. Larvae of B. subnubilus usually occur in large rivers and streams in lower river sections and can even be found in brackish water (Waringer & Graf, 2011;Wallace et al. 2003).

Family Limnephilidae
Halesus digitatus (Schrank, 1781) Based on currents records, Sericostoma personatum Kirby & Spence, 1826 has not been recorded from most of the Balkans; thus it is probable that the species present in the drainage basin of Lake Skadar is Sericostoma scheideri Schneider, 1845. However, it must be noted that molecular analysis carried out by Leese (2004) revealed that the division of the Central European Sericostoma "species" into S. personatum and S. schneideri seems to be questionable. Considering the current state of knowledge, the species status of Sericostoma species may change in the future.

Family Uenoidae
Thremma  (Ţivić et al. 2013). Macrozoobenthos research within Serbian watercourses between 1989 and 2010 suggested a shift of the western boundary of its distribution. In Bosnia and Herzegovina, the species was found in only one of ten former localities, implying that the species might entirely vanish from zoographic region 5 in the near future (Ţivić et al. 2013). The finding of T. anomalum in this study confirms its presence in Montenegro; however more research is needed in the region to confirm the findings of Ţivić et al. (2013).
Faunistic surveys and records based on larvae are not frequently used or recommended, due to inability and uncertainty of identification to the species level in some cases (Waringer & Graf, 2011). However, we considered the current data as an important contribution to the knowledge of caddisfly fauna of Montenegro and it was proven that in some cases faunistic data based on larvae can be useful (e.g. Previšić et al. 2013). Nevertheless, future caddisfly surveys in the region, preferably based on adult material, will contribute significantly to the Trichoptera fauna of Montenegro. In addition, molecular analysis (DNA barcoding) will increase the knowledge of the species present in the area, where the caddisfly fauna is partially known. During this investigation, fourteen Trichoptera species were found; three being new records for Montenegro (Brachycentrus subnubilus, Lepidostoma hirtum, Triaenodes ochreellus lefkas) and one being a confirmed record of a previously thought lost species (Thremma anomalum). This investigation with several first records is a result of a few days collecting effort in Montenegro and shows that the country is still underinvestigated.