Using mitochondrial DNA (mtDNA) variations, the phylogenetic position of Croatian populations of spined loaches within the European genus Cobitis was assessed. Spined loaches from the Matica, Neretva, Cetina, Zrmanja, Jadova, Sava, Drava and Kupa Rivers are included in two previously described groups: a) Cobitis sensu stricto group, and b) Adriatic group. The Danubian populations of C. elongatoides and its hybrids from the Kupa and Drava Rivers are related to the species included in the Cobitis s. str. group, whereas all other analysed populations clustered within the Adriatic group, which is divided into the “Bilineata”, “Elongata” and “Ohridana-zanandreai” clades. The Croatian spined loaches from the Adriatic watershed are included in the first two clades. Four mitochondrial lineages were revealed within the “Bilineata” clade: 1. ”C. bilineata” lineage containing loaches from the Zrmanja River and Italian and Spanish representatives of C. bilineata; 2. “Neretva-Cetina” lineage included loaches from the Cetina River (C. dalmatina) and the Neretva River (C. narentana); 3. “Jadova” lineage included specimens from the Jadova River; and 4. “Matica” lineage comprised spined loaches from the Matica River. Cobitis elongata from the Kupa and Drava Rivers belonged to the “Elongata” clade with two sublineages. Allozyme analyses of the C. taenia complex revealed the presence of both C. elongatoides and its all-female triploid hybrids in the Danube basin of Croatia.
Taxonomic analyses of four Sabanejewia balcanica populations from Croatia included morphological (morphometric, meristic, phenotypical) and mitochondrial DNA analyses. Comparative analyses of 24 morphometric characters revealed some differences between populations. The specimens from the Drava River are significantly larger than specimens from other populations, whereas the individuals from the Voćinska River represent the smallest European S. balcanica specimens. Due to similarities in morphometric ratios, in the Tree Diagram of Euclidean distances, the Drava and Petrinjčica Rivers populations formed a separate cluster, while the populations from the Rijeka and Voćinska Rivers formed a second cluster. These morphometrical differences are also corroborated by t-test results. Differences among fishes from different populations also exist in external morphology characters, such as spots on the caudal peduncle and the position of the suborbital spine. Mitochondrial DNA analyses enabled us to infer the phylogenetic placement of four Croatian populations within the genus Sabanejewia. All Croatian samples clustered within the two sublineages of the Danubian-Balkanian complex. Samples from the Voćinska River, as well as one sample from the Drava River were included in the “S. balcanica” (VI) sublineage. The remaining samples, including the two remaining haplotypes from the Drava River, were comprised within “S.montana-S.bulgarica-S.balcanica” (III) sublineage.
A new spined loach species Cobitis jadovaensis is described from the Jadova River in Croatia. This species differs from its congeners in the Croatian Adriatic basin with a unique set of characters: a very short dorsal fin base; short anal fin base; narrow head; a single lamina circularis; a single small prominent dark inclined spot on the upper part of the caudal base; all four Gambetta zones well developed and reaching beyond the dorsal base; zones Z1 and Z3 with many irregular spots; zone Z1 narrower than Z2; zone Z2 as wide as Z3; zone Z2 with spots larger than a pupil size fuses with Z3 on caudal peduncle; zone Z4 wider than Z2 and Z3, with 11 – 14 roundish to oval blotches.