A rhizocephalan parasite of the hermit crab Pagurus minutus Hess, 1865 (Decapoda, Paguridae) is described from Russian waters using morphological and molecular methods. Partial sequences of the mitochondrial cytochrome c oxidase subunit I gene (COI) were used as a genetic marker. We refer this species to Peltogaster reticulata Shiino, 1943 (Rhizocephala, Peltogastridae) based on its morphological description, since genetic data for the species from its type locality are lacking. The species can be distinguished from its known congeners by the reticular pattern of the external cuticle. Peltogaster reticulata is the sister taxon to P. postica Yoshida & Osawa, 2011 (in Yoshida et al. 2011), inhabiting the same host in southwestern Japan. The complete larval development of Peltogaster reticulata, including five naupliar and one cypris stage, is described and illustrated using SEM.

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Mitochondrial DNA (mtDNA) at Co-1 gene region was sequenced for 7 scorpion fish species (in total, 16 sequences of at least 552 bp) from the Far East of Russia and compared with 15 other sequences of Scorpaeniformes comprising altogether 29 scorpion-like fish sequences and two outgroup sequences (Cypriniformes). The analysis of the protein-coding Co-1 gene revealed statistically substantiated bias in the (T + C) : (A + G) content, proving basic findings. The average scores of p-distances for different scales of the evolutionary history at Co-1 gene revealed a clear pattern of increased nucleotide diversity at four different levels: (1) intraspecies, (2) intragenus, (3) intrafamily, and (4) intraorder. The scores of average p-distances for the compared fish groups were: (1) 1.00 ± 0.20%, (2) 3.80 ± 0.20%, (3) 12.40 ± 1.20%, and (4) 18.00 ± 0.38%, respectively (mean ± SE). These data support the concept that speciation in the order Scorpaeniformes, in most cases, follows a geographic mode through accumulation of numerous small genetic changes over a long period of time. However, intraspecies diversity was surprisingly high among scorpionfish. Phylogenetic trees for 29 sequences of scorpionfish and 2 other fishes belonging to ray-finned fishes (Actinopterigii) were developed using Co-1 gene and four different analytical approaches: Bayesian (BA), maximum likelihood (ML), neighbour-joining (NJ), and maximum parsimony (MP). The analysis revealed a monophyletic origin for the representatives of Cottidae, which is the principal scorpionfish family investigated (100, 96, 98% support level in our BA, MP, and NJ analyses). Similarly, the monophyletic origin of up to the three compared scorpion-like fish genera was supported by molecular phylogenetic data. Species identification on individual basis (barcoding tagging) was high. A few taxonomic complications arose during the analysis and they are discussed here in.

The systematics and phylogeny of flatfish is investigated on the complete sequence of nucleotides at subunit 1 cytochrome c oxidase (Co-1) and cytochrome b (Cyt-b) genes. In total 17 species from our collection and some species from GenBank were analyzed. Four types of trees were built: Bayesian (BA), maximum likelihood (ML), maximum parsimony (MP), and neighbor joining (NJ). These trees showed similar topology. Two separate clusters on the trees support subfamily Hippoglossoidinae and Hippoglossinae subdivision and monophyletic status of these taxa. The subfamily Pleuronectinae also can be considered monophyletic, if the tribe Microstomini is excluded from it and genus Lepidopsetta is moved into the tribe Pleuronectini. Mitogenomes represented by 25 complete sequences from NCBI GenBank were analyzed. After alignment two sets of nucleotide sequences were formed and investigated independently. One set included 13 structural genes (14,886 bp), the second set comprised by the mtDNA without ND6 gene (10,457 bp). Both data sets give congruent phylogenetic signal that agreed with conventional views on the taxonomy of the order Pleuronectiformes; however, the first set gives better topology. In BA gene tree there are two well supported nodes which include the representatives of suborders Pleuronectoidei and Psettoidei. Within Pleuronectoidei two superfamilies, Pleuronectoidea and Soleidea are highly supported in BA but in all four kinds of gene trees (BA, ML, MP and NJ) the only superfamily Pleuronectoidea is well supported. At the top of hierarchy, all flatfishes belonging to the order Pleuronectiformes forming also a monophyletic clade in our data, with support level of 100% but in BA tree only. The monophyly of the family Pleuronectidae is well supported both by single gene data and by complete mtDNA sequences.

Mitochondrial DNA of the Co-1 gene region was sequenced for 8 fish species (in total 17 sequences of at least 532 bp) from the far east of Russia and compared to 3 other perciform sequences, altogether comprising 20 perch-like fish sequences and 2 outgroup sequences (Cypriniformes). The analysis of the protein-coding Co-1 gene revealed a statistically substantiated bias in the (T+C):(A+G) content, confirming the basic findings on the pyrimidines-prunes ratio. The average scores of p-distances for different scales of the evolutionary history of the Co-1 gene revealed a pattern of increased nucleotide diversity at 4 different levels: (1) intraspecies, (2) intragenus, (3) intrafamily and (4) intraorder. The scores of the average p-distances of the 4 categories of comparison were: (1) 0.11 ± 0.04%, (2) 1.87 ± 0.68%, (3) 12.67 ± 0.28%, and (4) 16.52 ± 0.10%, respectively (mean ± SE). These data support the concept that speciation in the order Perciformes in most cases follows a geographic mode through accumulation of numerous small genetic changes over a long time. The phylogenetic trees for 18 and 21 sequences of perch-like fishes together with 2 other fishes belonging to the ray-finned fishes (Actinopterygii) were developed using the Co-1 gene and 4 different analytical approaches: neighbour-joining (NJ), maximum likelihood (ML), Bayesian (BA) and maximum parsimony (MP). The analysis revealed a monophyletic origin for the representatives of the Stichaeidae, which was the principal percoid family investigated (86, 96 and 100% support in our NJ, ML and BA analyses, respectively). Species identification on a per individual basis or Co-1-based DNA barcoding was high.

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Abstract. This study deals with the biodiversity and distribution of cavernicolous Amphipoda in caves of the Arabika massif (Western Caucasus). The Sarma, Trojka and Orlinoe Gnezdo caves were explored during speleological expeditions over the years 2011-12. Two new species of Amphipoda were found: a sub-surface dweller Zenkevitchia sandroruffoi sp. nov. is reported from the Sarma, Trojka and Orlinoe Gnezdo caves at depths from -30 m to -350 m; the second one, a deep dweller Adaugammarus pilosus gen. et sp. nov. is reported from the Sarma Cave at depths of -1270 to -1700 m. Adaugammarus gen. nov. shares similarities with Typhlogammarus Schäferna, 1907 and Zenkevitchia Birstein, 1940. The species Anopogammarus birsteini Derzhavin, 1945 is also re-described herein based on new samples that suggest close affinity of this species with the family Gammaridae. The original taxonomic combination is resurrected for Zenkevitchia revazi Birstein & Ljovuschkin, 1970, comb. resurr. (from Anopogammarus Derzhavin, 1945. To accommodate morphologically different species in the genus Zenkevitchia, two new groups are proposed. These are the admirabilis-group (Z. admirabilis Birstein, 1940 and Z. yakovi Sidorov, 2015) and the sandroruffoi-group (Z. sandroruffoi sp. nov. and Z. revazi). An updated molecular (mt-cox1) phylogeny, an identification key to the genera and a distribution map for the typhlogammarid amphipod species of Transcaucasia are provided.