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Amphipods from the genus Niphargus represent an important part of the Western Palearctic subterranean fauna. The genus is morphologically diverse, comprising several distinct ecomorphs bound to microhabitats in the subterranean environment. The most impressive among them are “lake giants,” a series of massive, large-bodied species. These range from morphologically distinct to morphologically cryptic taxa. We analysed the taxonomic structure of the Niphargus arbiter–Niphargus salonitanus species complex, belonging to “lake giants” from the Dinaric Karst (West Balkans), and assessed their phylogenetic, morphological and ecological diversity. Multilocus phylogeny suggested that the complex is monophyletic and nested within other cave lake ecomorphs. Unilocus and multilocus coalescence species delimitations indicated that the complex totals nine species. These species substantially overlap in morphology and cannot be unambiguously told apart without the use of molecular markers. An analysis of splitting events within a palaeogeological context, and modelling of environmental characteristics on the phylogeny unveiled a complex history of diversification. Part of this diversification might have been influenced by ecological divergence along the altitudinal gradient reaching from the Adriatic coast to inland Dinaric mountain chains and Poljes. Other splits coincide with the marine regression–transgression cycles during Pliocene. We describe Niphargus alpheus sp. n., Niphargus anchialinus sp. n., Niphargus antipodes sp. n., Niphargus arethusa sp. n., Niphargus doli sp. n., Niphargus fjakae sp. n. and Niphargus pincinovae sp. n., and by doing so hope to prompt their further research.

Niphargus is the largest genus of freshwater amphipods. Its systematics from the species to the family level has always been problematic. This study is the first comprehensive phylogenetic treatment of the chiefly subterranean group in 160 years of its taxonomic history. It includes 103 niphargid species plus outgroups, representing about one-third of all nominal species. The samples originated mainly from type localities or adjacent sites and covered most of the morphological variability of the genus. Character sampling included nuclear 28S and mitochondrial 12S rDNA sequences, and 122 morphological characters. Quantitative morphological traits were coded using two alternative methods. The first one searches for gaps in the variability range of each character, while the second one uses absolute differences between the standardized raw data as weights. Different data sets yielded alternative topologies. All data support the monophyly of Niphargidae, while Niphargopsis— another niphargid genus — was consistently nested within Niphargus, loosing justification for its separate status. We predict a similar fate for all or most of the remaining six small niphargid genera, which were not yet scrutinized phylogenetically. Different topologies agreed in species composition of five large, well-supported clades, although the hierarchic relationships between them remain unresolved. These clades reject all previously proposed taxonomic subdivisions of Niphargus, implying a high degree of morphological homoplasy that renders any morphology-based groups questionable. The clade members are distributed within well-established zoogeographical regions that do not exceed 1300 km across the longest diagonal. These results provide a framework for future studies on niphargid systematics, the evolution of endemism and cryptic diversity in subterranean environments, the mechanisms leading to exceptional morphological heterogeneity, historical biogeography, and applied ecological issues.

Phylogenetic relationships of all genera of the fish leech subfamily Pontobdellinae were investigated using mitochondrial (12S rDNA, COI, tRNA-Leu, ND1) and nuclear (28S rDNA) DNA sequences under maximum likelihood, Bayesian inference and parsimony. All methods resulted in trees that corroborated the monophyly of the family Piscicolidae, but recovered their subfamily Pontobdellinae as non-monophyletic. Based on the basal position of the giant Antarctic Megaliobdella szidati, it is hypothesized that the putative ancestor of fish leeches was a free-ranging, large bodied, muscular leech. The next branch contains parasites of cartilaginous fishes, Pontobdella muricata and Pontobdella macrothela. Two remaining genera of the subfamily (the Arctic Oxytonostoma and the Antarctic Moorebdellina) showed weak affinities to other piscicolid taxa. The obtained phylogenetic hypothesis suggests a possible transition from an ancestral free-ranging life style and temporary parasitism, to parasitism on cartilaginous fishes, followed by parasitism on bony fishes.

Utevsky, S. Y. & Trontelj, P. (2004). Phylogenetic relationships of fish leeches (Hirudinea, Piscicolidae) based on mitochondrial DNA sequences and morphological data. — Zoologica Scripta, 33, 375–385. Phylogenetic relationships of fish leeches (Piscicolidae) were deduced from combined mitochondrial DNA sequences of 12S rDNA and COI genes using Bayesian inference and Maximum Likelihood, as well as from a combined molecular-morphological data matrix using Maximum Parsimony. Monophyly of the family was confirmed. The traditional subdivision into three subfamilies, the Platybdellinae, Pontobdellinae, and Piscicolinae, received weak support, but was not challenged by alternative groupings. In contrast to prior classifications, a basal split emerged between the Pontobdellinae on the one hand, and the Platybdellinae and Piscicolinae on the other. The complex coelomic system of pontobdellines is viewed as plesiomorphic, and independent reductions of the coelom in other fish leech groups are hypothesized. According to the inferred phylogeny, seawater was the primary habitat of fish leeches. Eurasian freshwaters were colonized by a species-rich freshwater clade (genera Piscicola, Baicalobdella, Cystobranchus and Caspiobdella) and, probably independently, by the Asian genus Limnotrachelobdella.

Croatobranchus mestrovi is a troglobitic leech from deep shaft-like caves in the Velebit Mountain, Dinaric karst, Croatia, living in cold (4–6 °C) water. Its oral sucker extends to form four pairs of triangular tentacles, each with about five finger-like papillae, but widening into a marginally crenulated disc when attached to a substrate. Pairs of stiff, finger-like lateral projections, probably gills, occur along the body behind the clitellum. Somites are simple five-annulate. Despite the unique head morphology and the presence of lateral outgrowths, the anatomy and 18S rRNA gene sequence of this species indicate that it is a member of the Erpobdellidae, closely related to Dina.