The complete mitochondrial genome of a marine polychaete, Prionospio cf. japonica (Annelida: Spionidae)

Prionospio Malmgren 1867 is one of the abundant genera of the family Spionidae Grube, 1850. Despite its rich diversity, information on their complete mitochondrial genome has remained unknown. In this study, we determined the complete mitochondrial genome of a spionid polychaete, Prionospio cf. japonica Okuda 1935. The specimen was collected from the fine sand in the intertidal zone of South Korea. The mitogenome consists of 15,267 base pairs, harboring 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The maximum-likelihood phylogenetic tree based on the 11 PCGs showed that Prionospio cf. japonica grouped with other spionid polychaetes and formed a monophyletic group. Also, the mtDNA of P. cf. japonica was more closely related to that of non-polydorin spionid, Marenzelleria neglecta, than polydorin spionids. The molecular data will be valuable for studying evolutionary relationships among annelids.

A new species of the genus Cephalodella (Rotifera, Monogononta) from Korea, with reports of four additional cephalodellid species

A new monogonont rotifer, Cephalodella binoculatasp. nov., was described from a soil sample collected in Korea. The new species is morphologically similar to C. carina but is distinguished by having two frontal eyespots, a vitellarium with eight nuclei, and the shape of its fulcrum. We also described four other cephalodellid species collected in Korea; Cephalodella auriculata, C. catellina, C. gracilis, and C. tinca. Of these four species, C. gracilis and C. tinca were newly recorded in Korea. We provided the morphological characteristics of the five Cephalodella species along with photographs of trophi observed with a scanning electron microscope. Furthermore, we provided the mitochondrial cytochrome c oxidase subunit I gene sequences of the five species.

Changes in Fecal Pellet Microbiome of the Cold-Adapted Antarctic Copepod Tigriopus kingsejongensis at Different Temperatures and Developmental Stages

Tigriopus kingsejongensis, a copepod species reported from the King Sejong Station, Antarctica, serves as a valuable food resource in ecosystems. We cultured T. kingsejongensis at three different temperatures (2 °C, 8 °C, and 15 °C) in a laboratory to observe the changes in its fecal pellet microbiome depending on the cultivation temperatures and developmental stages. We observed that the fecal pellet microbiome of the copepod changed with temperature: a lower microbial diversity, higher abundance of the aquatic bacterium Vibrio, and lower abundance of the psychrophilic bacterium Colwellia were noted at higher temperatures. In addition, the fecal pellet microbiome of the copepod changed according to the developmental stage: a lower microbial diversity was noted in egg-attached copepods than in nauplii at 8 °C. We further analyzed three shotgun metagenomes from the fecal pellet samples of T. kingsejongensis at different temperatures and obtained 44 metagenome-assembled genomes (MAGs). We noted that MAGs of V. splendidus D contained glycosyl hydrolases (GHs) encoding chitinases and virulence factors at a higher relative abundance at 15 °C than at lower temperatures. These results indicate that increasing temperature affects the fecal pellet microbiome and the development of copepods. The findings are helpful to understand the changes in cold-adapted copepods and the effect of temperature on their growth.

A new species of Allobathynella (Crustacea, Bathynellacea, Parabathynellidae) from the hyporheic zone of the Hangang River, South Korea

Bathynellacea including the parabathynellid genus Allobathynella Morimoto & Miura, 1957 is commonly found across the subterranean environment. The genus Allobathynella is the most species-rich genus known in Korea, and it now contains 23 species and one subspecies from South Korea and Japan. In this paper, we described a new species of Allobathynella from Danyang, South Korea. Allobathynella danyangensissp. nov. can be distinguished from its congeners by the presence of five simple setae on the antennule, seven spines on the maxillule and 3-5-10-6 setal formula of the maxilla. We describe the new species with molecular diagnosis based on the mitochondrial c oxidase subunit 1, the mitochondrial 16S rDNA, and the nuclear 18S rDNA gene sequences and morphological study.

A new species of Gammarus (Crustacea, Amphipoda, Gammaridae) from South Korea

A new species of freshwater gammarid, Gammarussomaemulensis sp. nov., was collected from Somaemuldo Island, South Korea. This new species is morphologically characterised by the absence of calceoli in antenna 2, absence of anteroproximal setae on bases in pereopods 6 and 7, outer ramus in uropod 3 with plumose setae on both margins, and a small terminal article of the outer ramus, which is shorter than adjacent spines. A description of the new species and morphological differences from related species are provided in the text. The new species was also compared to related species using partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Genetic distances of COI sequences between the new species and related species, consisting of 21.5-26.3% difference, support Gammarussomaemulensis sp. nov. as a valid species. Additionally, a key to identifying Gammarus species in South Korea is provided.

Rhynchospioaciliata sp. nov., a new spionid species (Annelida, Spionidae) from the Korea Strait

A new spionid polychaete, Rhynchospioaciliata sp. nov., was discovered in the fine sandy sediments of an intertidal habitat from Korean waters. The new species is considered a simultaneous hermaphrodite, but no brooding embryos were found in any of the specimens collected in this study. This species is unique in the absence of ciliation in the anteriormost chaetigers. Rhynchospioaciliata sp. nov. is morphologically most similar to Rhynchospiofoliosa Imajima, 1991 from Japan in having an elevation on the prostomium, conspicuously large and foliaceous branchiae, and intersegmental lateral pouches. However, the new species differs from the latter by the following characteristics: (1) large and lanceolate notopodial postchaetal lamellae of chaetiger 1, (2) transverse ciliated bands and ciliation on the inner branchiae absent in anteriormost chaetigers, and (3) pygidium with one pair of ventral cirri and numerous elongated dorsolateral cirri. Detailed description and illustrations of the new species are provided with molecular information on mitochondrial cytochrome c oxidase subunit I (COI), 16S ribosomal DNA (rDNA), nuclear 18S rDNA, and 28S rDNA.

Two new species of feather mites (Acariformes, Astigmata) from the black-tailed godwit, Limosa limosa (Charadriiformes, Scolopacidae), in Korea

Two new species of feather mites are described from two individuals of the black-tailed godwit, Limosa limosa (Linnaeus, 1758), in Korea: Alloptes (Conuralloptes) neolimosaesp. nov. (Analgoidea, Alloptidae) and Phyllochaeta limosaesp. nov. (Pterolichoidea, Syringobiidae). Males of A. (C.) neolimosaesp. nov. are distinguished from A. (C.) limosae in having the hysteronotal shield with a straight anterior margin, setae h2 enlarged and slightly flattened in the basal half, and the terminal lamella monotonously transparent without sclerotized patches; females differ in having legs IV with ambulacral discs extending to or slightly beyond the level of setae f2. The discovery of P. limosaesp. nov. represents the first record of the feather mite genus Phyllochaeta on godwits of the genus Limosa Brisson, 1760 (Scolopacidae, Limosinae). Males of P. limosaesp. nov. are distinguished from P. secunda in having the terminal cleft semi-ovoid with a length-to-width ratio of 1.7, and the terminal membranes with 15 or 16 finger-shaped denticles; females differ in having the hysteronotal shield bearing faint longitudinal striations in the posterior third and lacking lacunae, and setae c1 situated posterior to the level of setae c2. Additionally, we obtained partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene from A. (C.) neolimosaesp. nov. and estimated genetic distances from 10 other Alloptes species based on comparisons of COI sequences.

New species of the genus Spio (Annelida, Spionidae) from the southern and western coasts of Korea

A new spionid polychaete, Spiopigmentatasp. nov., is described from the southern and western coasts of Korea. This new species differs from its congeners by the combination of the following morphological characteristics: the presence of orange-brown pigmentation on the anterior part of the prostomium, black pigmentation on the peristomium and along the body, U-shaped nuchal organs, a comparatively long extension of metameric dorsal ciliated organs, three pairs of white dots per chaetiger, two to three posterior abranchiate chaetigers, and the presence of tridentate neuropodial hooded hooks. The partial 16S ribosomal DNA (rDNA) and nuclear 18S rDNA sequences of the new species and Spio sp. 2 reported by Abe and Sato-Okoshi (2021) from Japan showed high similarity, indicating that these two specimens belong to the same species. A detailed description and illustrations of the new species, together with molecular information, are provided.

Feather mites (Acariformes, Astigmata) from marine birds of the Barton Peninsula (King George Island, Antarctica), with descriptions of two new species

We report on the first investigation of feather mites associated with birds living on the Barton Peninsula (King George Island, Antarctica). We found seven feather mite species of the superfamily Analgoidea from four host species. Two new species are described from two charadriiform hosts: Alloptes (Sternalloptes) antarcticussp. nov. (Alloptidae) from Stercorariusmaccormicki Saunders (Stercorariidae), and Ingrassiachionissp. nov. (Xolalgidae) from Chionisalbus (Gmelin) (Chionidae). Additionally, we provide partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI), which was utilized as a DNA barcode, for all seven feather mite species.

The complete mitochondrial genome of Boccardiella hamata (Annelida: Polychaeta: Spionida)

In this study, the complete mitogenome sequence of Korean Boccardiella hamata was determined. This is the first complete mitogenome in the order Spionida. The complete mitogenome of B. hamata is 17,561 bp in length with 12 protein-coding genes (atp8 gene absent), 23 transfer RNAs, 2 ribosomal RNAs, and 1 control region. Interestingly, the gene arrangement of the 12 PCGs of B. hamata is unique, which is very different from that of the other polychaetes currently known. The phylogenetic tree supported the traditional taxonomic position of Spionidae within subclass Sedentaria.

A new species of Hangangbathynella (Crustacea, Bathynellacea, Parabathynellidae) from South Korea

A new parabathynellid bathynellacean species, Hangangbathynella mihoensis sp. nov., was found in the groundwater of the Geumgang River in South Korea. This is the first report of Hangangbathynella from a tributary of the Geumgang River. All previously-reported species were found in the Hangang River and the origins of the two rivers are distinct from each other. The new species can be distinguished from its congeners by the two-segmented mandibular palp and the absence of epipods on thoracopod II. In this study, we provide a description of the new species and an identification table for the genus Hangangbathynella. In addition, we obtained partial sequences of the mitochondrial cytochrome c oxidase subunit I gene for DNA barcoding.

Antarctic population of Anteholosticha sigmoidea (Foissner, 1982) Berger, 2003 (Ciliophora: Urostylidae) with notes on its phylogenetic position

Anteholosticha sigmoidea (Foissner, 1982) Berger, 2003 was isolated from a wet soil sample collected on King George Island, Antarctica. Morphological observations and molecular phylogenetic analyses based on the gene sequences of small subunit ribosomal RNA (18S rRNA) were used to identify the species. Anteholosticha sigmoidea can be divided into two groups: group I (three populations described by Foissner 1982) and group II (described by Foissner 1984) based on the morphological differences. Group I differs from group II by the length of the midventral complex (65.1% vs. 52.5% of the cell length), the number of adoral membranelles (25-28 vs. 16-24), and the number of dorsal bristles in kinety 1 (16 bristles vs. nine bristles). Group I differs from the Antarctica population by the absence/presence of the collecting canals of the contractile vacuole and the number of macronuclear nodules (6-12 vs. 13-19). Group II differs from the Antarctica population by the number of macronuclear nodules (five to nine vs. 13-19); the arrangement of cortical granules (forming longitudinal rows vs. irregularly distributed); the length of the midventral complex (64.7% vs. 53.8% of cell length). In the phylogenetic analyses, A. sigmoidea was not nested with any species, and the gene tree indicated polyphyly of the genus Anteholosticha.

Three new species of subterranean amphipods (Pseudocrangonyctidae: Pseudocrangonyx) from limestone caves in South Korea

PseudocrangonyxAkatsuka & Komai, 1922 is the most diverse group of subterranean amphipods in the groundwater communities of Far East Asia. In Korea, the diversity of the group has been underestimated due to the records of morphological variants of Pseudocrangonyx asiaticusUéno, 1934. To estimate the species diversity, we analyzed the morphological characteristics and conducted molecular analyses of specimens collected from Korean caves that we treated as morphological variants of P. asiaticus. We described three new subterranean pseudocrangonyctid amphipod species, P. deureunensissp. nov., P. kwangcheonseonensissp. nov., and P. hwanseonensissp. nov., from the groundwater of limestone caves in South Korea. Additionally, we determined sequences of the nuclear large subunit ribosomal RNA and the mitochondrial cytochrome c oxidase subunit I gene of the new species for molecular analyses. Molecular phylogenetic analyses revealed that the three new species formed a monophylum together with P. joolaeiLee et al., 2020 and P. wonkimiLee, Tomikawa & Min, 2020, which are species that are endemic to Korean caves.

Anteholosticha foissneri n. sp., a marine hypotrich ciliate (Ciliophora: Spirotrichea) from Vietnam: Morphology, morphogenesis, and molecular phylogeny

In a study of marine ciliate diversity, we collected an Anteholosticha monilata-like population from Vietnam. To identify this population, we analyzed its morphology, some morphogenetic stages, and molecular phylogeny. Based on these data, we conclude that the Vietnamese population is new to science. Anteholosticha foissneri n. sp. resembles Anteholosticha monilata-like species considering (1) the number and arrangement of macronuclear nodules and micronuclei; (2) the presence of cortical granules; and (3) the saline habitat. However, the new species can be easily distinguished from these species by the arrangement, color, and shape of the cortical granules. The divisional morphogenesis commences with the de novo proliferation of basal bodies as a single longitudinal patch left of the posteriormost midventral cirral pair. This character state has not been reported before in Anteholosticha (based on check of the available data) and probably reflects a distinct clade within the nuclear small subunit ribosomal RNA gene tree.

A new cave amphipod, Pseudocrangonyx wonkimi sp. nov. (Crustacea, Amphipoda, Pseudocrangonyctidae), from the Korean Peninsula

A new species of pseudocrangonyctid amphipod, Pseudocrangonyx wonkimi sp. nov., was found in the groundwater of a cave in the southwestern Korean Peninsula. Pseudocrangonyx wonkimi sp. nov. is morphologically most closely related to P. joolaeiLee et al., 2020. However, P. wonkimi is clearly distinguished from P. joolaei by lacking sternal gills, fewer setae on maxilla 1 inner plate, fewer serrate robust setae on the carpus of the gnathopods, lacking bifid setae on the inner ramus of pleopod 3, and fewer articles of rami on pleopod 3. We also determined sequences of mitochondrial cytochrome c oxidase subunit I (COI) of P. wonkimi sp. nov. for molecular diagnosis. From the molecular analysis based on COI sequences, P. wonkimi showed the closest relationship with P. joolaei with 15.1% genetic distance.

Complete mitochondrial genome of Pseudocrangonyx joolaei (Crustacea: Amphipoda: Pseudocrangonyctidae)

The complete mitochondrial genome of a subterranean pseudocrangonyctid amphipod, Pseudocrangonyx joolaei, was determined in this paper. The complete mitogenome of P. joolaei was 14,814 bp in length with the typical 13 protein-coding genes, 22 transfer RNAs, two ribosomal RNAs, and a control region (CR). The gene order of P. joolaei was unique in that the CR was an inversion, and the gene order of Pseudocrangonyx was not concordant when compared to that of P. daejeonensis, a subterranean amphipod found in Korea. A maximum-likelihood tree, constructed based on 26 eumalacostracan mitogenomes, confirmed that P. joolaei supported monophyly in the family Pseudocrangonyctidae and is most closely related to the superfamily Crangonyctoidea.

The complete mitochondrial genome of Jesogammarus (Jesogammarus) hinumensis (Crustacea: Amphipoda: Anisogammaridae)

We determined the mitogenome sequence of Jesogammarus (Jesogammarus) hinumensis Morino, 1993, which is the first complete mitogenome sequence in the family Anisogammaridae Bousfield, 1977. The complete mitogenome of J. (J.) hinumensis was 15,186 bp in length with the typical 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and a control region (CR). The gene order of J. (J.) hinumensis was in accordance with the typical pan-crustacean ground pattern. A maximum-likelihood tree constructed using 25 eumalacostracan mitogenomes confirmed that J. (J.) hinumensis is most closely related to the family Micruropodidae, and supported the monophyly of the superfamily Gammaroidea.

A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from Simbok Cave, Korea

A new subterranean species of pseudocrangonyctid amphipod, Pseudocrangonyx joolaei, is described from the groundwater of a cave in South Korea. Pseudocrangonyx joolaei sp. nov. can be distinguished from its congeners by the number of sternal gills as well as a combination of the antennal sinus, the accessory flagellum of antenna 1, and the terminal article of uropod 3. Molecular phylogenetic analyses based on nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes revealed that P. joolaei sp. nov. formed a clade with P. akatsukai Tomikawa Nakano, 2018 that inhabits limestone caves in the western Honshu island, Japan.

The complete mitochondrial genome of the South American freshwater crayfish, Parastacus nicoleti (Crustacea, Decapoda, Parastacidae)

We determined the complete mitochondrial genome (mitogenome) sequence of a Chilean freshwater crayfish, Parastacus nicoleti (Philippi, 1882). This is the first complete mitogenome sequence of a non-Australian crayfish belonging to the family Parastacidae. The complete mitogenome of P. nicoleti is 20,894 bp in length and contains 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs) and a putative control region (CR). In the phylogenetic analysis, freshwater crayfishes were clearly divided into two monophyly groups, Northern and Southern Hemisphere groups. The P. nicoleti exhibited a sister-group relationship with all other Australian parastacid crayfishes.

The complete mitochondrial genome of Gruberia lanceolata (Gruber, 1884) Kahl, 1932 (Ciliophora: Heterotrichea)

The ciliate Gruberia lanceolata (Gruber, 1884) Kahl, 1932 belonging to the class Heterotrichea was sampled from the coastal waters of South Korea. The complete mitogenome in its linear form and large size (∼40 kb) was obtained. It consisted of 27 protein-coding genes (PCGs), two ribosomal subunit RNA (rRNA) genes, four transfer RNAs (tRNAs), and ten unclassified open reading frames (ORFs). Their telomeric structures were capped, with repeat regions at both ends. We analyzed its phylogenetic tree using the data of its respiratory chain complex I genes. It can be suggested that the complete mitochondrial genome of G. lanceolata can be recorded as a new class of the mitogenome.

The complete mitochondrial genome of the Antarctic marine triclad, Obrimoposthia Wandeli (Platyhelminthes, Tricladida, Maricola)

For the first time, we report the complete mitochondrial genome (mitogenome) sequence of the marine triclad species, Obrimoposthia wandeli. The complete mitogenome of O. wandeli was 15,185 bp in length, contains 12 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and 2 ribosomal RNAs (rRNAs). Compared to previously reported gene orders from the order Tricladida, O. wandeli had unique gene order. We constructed a phylogenetic tree based on the mitogenomes belonging to Rhabdocoela, Polycladida, and Tricladida and confirmed that O. wandeli is located in the basal position in the Tricladida.

A study on the non-monophyletic genera Australothrix and Holostichides based on multigene and morphological analyses with a reexamination of type materials (Protozoa: Ciliophora)

In a study of ciliate diversity, we collected two new species of the genera Australothrix and Holostichides. Based on nuclear ribosomal genes, our study shows that these two genera are genetically non-monophyletic. To clarify the issues of the non-monophyly, we reexamined type material of H. heterotypicus, H. terrae, and Birojimia soyaensis. Based on multigene and morphometric analyses, Australothrix and Holostichides are clearly non-monophyletic even in mitochondrial CO1 gene trees. The multigene analyses show a clade composed of A. lineae sp. nov., H. terrae, and B. soyaensis, suggesting that a cytopharynx with argyrophilic structures might be their synapomorphy. A list of species with this type of cytopharynx is provided for further studies to either accept or reject this hypothesis. Based on the reexamination, we discriminate the morphologically nearly identical (cryptic/sibling) species H. obliquocirratus sp. nov. from H. heterotypicus and they show significant genetic dissimilarities in the multigene trees. They showed only few morphological (non-quantitative) differences and thus distinguishing them morphologically needs careful investigation.

Can tidal events influence monitoring surveys using periphytic ciliates based on biological trait analysis in marine ecosystems?

To identify the influence of tidal events on community functioning of periphytic ciliates for monitoring program and community research using biological trait analysis, a 3-month baseline survey was conducted in Korean coastal waters using the polyurethane foam enveloped slide system (PFES) and conventional slide system (CS). Although the periphytic ciliate communities had similar biological trait categories, they represented considerable differences in community functioning and functional diversity measures within the PFES and CS systems. Multivariate analyses revealed different ways of the temporal shift in community functioning of the ciliates in both systems. The dispersion analysis demonstrated that the CS system was sensitive to the strong disturbance of tidal current and circulation compared to the PFES system. These findings suggest that the strong tidal event may significantly influence the output of analysis on community functioning of periphytic ciliates for bioassessment in marine ecosystems.

Morphology and Molecular Analyses of a New Marine Ciliate, Arcuseries minima sp. nov. (Ciliophora: Urostylidae)

A new marine urostylid ciliate, Arcuseries minima sp. nov., was discovered in South Korea. Morphological observations and molecular phylogenetic analyses based on small subunit ribosomal DNA (18S rDNA) sequences were used to describe the new species. Arcuseries minima is most similar to A. scutellum among all Arcuseries species, but differs in the following main characters: number of adoral membranelles (13–16 vs. 17 or 18), cortical granules (yellowish, clustered around cirri and dorsal bristles vs. colorless, irregularly scattered), number of macronuclear nodules (20–27 vs. 42–90), number of midventral cirri (5–10 vs. 12–14), and number f transverse cirri (5 or 6 vs. 8). The new species and A. scutellum differ from A. petzi and A. warreni in having smaller body size (≤80 μm vs. ≥80 μm) and fewer cirri: left marginal (≤ 17 vs. ≥ 18) and transverse (≤ 8 vs. ≥8) cirri. This relationship was supported by the phylogenetic tree, where these two groups were separated into two branches.

First records of Gnathia Leach, 1814 and Tachaea Schioedte & Meinert, 1879 from South Korea, with descriptions of two new species (Isopoda, Cymothoida, Cymothooidea)

Two new species of cymothoid isopods, Gnathiakoreana sp. n. and Tachaeakoreaensis sp. n., are described from South Korea. The genera Gnathia Leach, 1814 and Tachaea Schioedte & Meinert, 1879 are recorded for the first time in South Korea. Gnathiakoreana sp. n. is distinguished from its congeners by having the smooth dorsal surface of the pereon, the strongly ridged unornamented paraocular ornamentation, the strong bifid mediofrontal process, and the serrated superior frontolateral process. Tachaeakoreaensis sp. n. is distinguished from its congeners by having the expanded propodus with serrated inferior margins in pereopods 1-3, the propodus with serrated inferodistal margins in pereopods 4-7, one seta on the apical lobe of the maxilla, and ten robust setae on the posterior margin of the pleotelson.

Morphology and phylogeny of a new species, Uroleptus (Caudiholosticha) antarctica n. sp. (Ciliophora, Hypotricha) from Greenwich Island in Antarctica

This paper describes the morphological features based on standard methods and estimates their phylogenetic position using small subunit ribosomal RNA (SSU rRNA) sequences of a Uroleptus (Caudiholosticha) antarctica n. sp. population investigated from moss of the Greenwich Island, Antarctica. The morphology of Uroleptus (Caudiholosticha) antarctica n. sp. is characterized as follows: 213.0-238.0×67.5-74.5 μm size in vivo; contractile vacuole located slightly above left of mid-body; cortical granules lacking; three frontal and two frontoterminal cirri; five to six transverse cirri; one pretransverse cirri; one right and one left marginal rows; six to seven dorsal kineties; three caudal cirri.

New molecular sequences for two genera of marine planarians facilitate determination of their position in the phylogenetic tree, with new records for two species (Platyhelminthes, Tricladida, Maricola)

For the first time, molecular sequences of the 18S ribosomal DNA were generated for representatives of the genera Obrimoposthia Sluys & Ball, 1989 and Paucumara Sluys, 1989 of the suborder of the marine triclads, or Maricola, by analyzing the species Obrimoposthiawandeli (Hallez, 1906) and Paucumaratrigonocephala (Ijima & Kaburaki, 1916). On the basis of this molecular data the phylogenetic position of these two genera in the phylogenetic tree of the Maricola was determined and compared with their position in the phylogeny based on the analysis of anatomical features. New records for these two species are documented and their taxonomic status is determined on the basis of histological studies.

New molecular sequences for two genera of marine planarians facilitate determination of their position in the phylogenetic tree, with new records for two species (Platyhelminthes, Tricladida, Maricola)

For the first time, molecular sequences of the 18S ribosomal DNA were generated for representatives of the genera Obrimoposthia Sluys & Ball, 1989 and Paucumara Sluys, 1989 of the suborder of the marine triclads, or Maricola, by analyzing the species Obrimoposthiawandeli (Hallez, 1906) and Paucumaratrigonocephala (Ijima & Kaburaki, 1916). On the basis of this molecular data the phylogenetic position of these two genera in the phylogenetic tree of the Maricola was determined and compared with their position in the phylogeny based on the analysis of anatomical features. New records for these two species are documented and their taxonomic status is determined on the basis of histological studies.

The complete mitochondrial genome of Pseudocrangonyx daejeonensis (Crustacea: Amphipoda: Pseudocrangonyctidae)

The complete mitogenome sequence of a subterranean pseudocrangonyctid amphipod, Pseudocrangonyx daejeonensis, was determined. The complete mitogenome of P. daejeonensis was 15,069 bp in length with the typical 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region (CR). This is the first complete mitogenome sequence in the family Pseudocrangonyctidae. Interestingly, gene arrangements of most amphipod species were almost identical to the typical pan-crustacean ground pattern, whereas two PCGs, both of rRNAs and CR were translocated in P. daejeonensis. A maximum-likelihood tree, constructed based on 30 eumalacostracan mitogenomes, confirmed that P. daejeonensis is closely related to the crangonyctid Stygobromus indentatus and S. tenuis potomacus and supported the monophyly of the superfamily Crangonyctoidea.

The complete mitochondrial genome of Belzebub intermedius (Decapoda, Dendrobranchiata, Luciferidae)

We determined the mitochondrial genome (mitogenome) sequence of Belzebub intermedius (Hansen, 1919). To the best of our knowledge, this is the first complete mitogenome in the family Luciferidae. The complete mitogenome of B. intermedius is 16,001 bp in length, with 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs), and a control region (CR). The gene arrangement of B. intermedius is almost identical to that of the same sergestoid species, Acetes chinensis Hansen, 1919, except that there is no additional trnS1. A maximum-likelihood tree, constructed using 18 decapod mitogenomes, confirmed that B. intermedius occupied the most basal position within the suborder Dendrobranchiata.

Utility of mitochondrial CO1 sequences for species discrimination of Spirotrichea ciliates (Protozoa, Ciliophora)

Ciliates are a diverse species group of the Protozoa, and nuclear and mitochondrial genes have been utilized to discover new species and discriminate closely related species. The mitochondrial cytochrome c oxidase subunit 1 (CO1) gene has been used to discriminate metazoan species and has also been applied for some groups in the phylum Ciliophora. However, it is difficult to produce a universal primer as a standard barcode, because unlike metazoans, mitochondrial DNA sequences of ciliates are long and highly variable. Therefore, to design the new primer set, we sequenced the mitochondrial genomes of two pseudokeronopsids in the class Spirotrichea using next-generation sequencing technology (HiSeq™ 2000). Based on putative CO1 gene fragments of the pseudokeronopsids, we designed the new primer set and successfully sequenced the CO1 of 69 populations representing 47 species (five orders, 14 families, and 27 genera). We found that CO1 showed higher resolution for separating congeneric species than did nuclear SSU rRNA gene sequences, and we identified some putative cryptic species.

The first records of Stenobermuda Schultz, 1982 and Tenupedunculus Schultz, 1979 from Australia, with description of two new species from the Great Barrier Reef (Isopoda, Asellota, Stenetriidae)

The genera Tenupedunculus Schultz, 1982 and Stenobermuda Schultz, 1979 are recorded for the first time from beyond the Southern Ocean, at the Great Barrier Reef, Australia. Tenupedunculusserrulatussp. n. and Stenobermudawaroogasp. n. are described from Heron Island and Lizard Island respectively, both in the Great Barrier Reef. The genus Tenupedunculus is revised and a new diagnosis presented, with Tenupedunculusvirginale Schultz, 1982, T.pulchrum (Schultz, 1982), and T.serrulatussp. n. being retained within the genus, and the remaining species here regarded as Stenetriidaeincertae sedis (eight species).

A new species of the genus Pseudocrangonyx (Crustacea, Amphipoda, Pseudocrangonyctidae) from Korea

A new subterranean species of pseudocrangonyctid amphipod, Pseudocrangonyx daejeonensissp. n. is described from the interstitial waters in Daejeon, Korea. Pseudocrangonyx daejeonensissp. n. is distinguished from three morphologically similar congeners, P. coreanus Uéno, 1966, P. febras Sidorov, 2009, and P. gudariensis Tomikawa & Sato, 2016, by the characteristics of antenna 1, antenna 2, mandible, gnathopod 2, pleopods, uropods 1-2, and telson. Molecular phylogenetic analyses based on nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes revealed that P. daejeonensis is a sister species of the unnamed Pseudocrangonyx sp. 3 inhabiting central Japan.

The complete mitochondrial genomes of two talitrid amphipods, Platorchestia japonica and P. parapacifica (Crustacea, Amphipoda)

In this paper, we determined the complete mitochondrial genome (mitogenome) sequences of two talitrid amphipods, Platorchestia japonica and P. parapacifica. The complete mitogenomes of P. japonica and P. parapacifica were 14,780 and 14,787 bp in length, respectively, with the typical 13 protein coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs) and a control region (CR). In the gene order analysis, two PCGs (nad3 and nad6) were rearranged in comparison to the typical pan-crustacean ground pattern. A maximum-likelihood tree, constructed based on 31 eumalacostracan mitogenomes, confirmed that P. japonica and P. parapacifica (Talitridae) were closely related to Parhyale hawaiensis (Hyalidae), and supports the monophyly of the superfamily Talitroidea.

The complete mitochondrial genome of epitokous Nereis species (Phyllodocida, Nereididae) from Dok-do, Korea

The mitogenome sequence of the epitokous Nereis species (Phyllodocida, Nereididae) was determined first in the genus Nereis. The complete mitogenome is 15,667 bp in length, containing 13 protein-coding genes, two ribosomal RNAs, 22 transfer RNAs and a control region, and their gene order and structure is identical to those of other nereidid species. The mitogenome consists of 33.5% A, 20.0% C, 13.3% G, 33.1% T, showing a high content of A + T similar to the other phyllodocid polychaetes. These results will be useful for inferring the phylogenetic relationships among the members of Nereididae within the phyllodocids.

Complete mitochondrial genome of the feather mite Ardeacarus ardeae (Acari, Sarcoptiformes, Pterolichidae)

In this study, we determined the mitogenome sequence of Ardeacarus ardeae (Canestrini, 1878) in the family Pterolichidae (Acari, Sarcoptiformes), which is the first complete mitogenome sequence in feather mite. The mitogenome of A. ardeae is 14,069 bp in length and contains 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region (CR). The phylogenetic tree shows that A. ardeae belong to the supercohort Desmonomatides within the order Sarcoptiformes.

First Insights into the Subterranean Crustacean Bathynellacea Transcriptome: Transcriptionally Reduced Opsin Repertoire and Evidence of Conserved Homeostasis Regulatory Mechanisms

Bathynellacea (Crustacea, Syncarida, Parabathynellidae) are subterranean aquatic crustaceans that typically inhabit freshwater interstitial spaces (e.g., groundwater) and are occasionally found in caves and even hot springs. In this study, we sequenced the whole transcriptome of Allobathynella bangokensis using RNA-seq. De novo sequence assembly produced 74,866 contigs including 28,934 BLAST hits. Overall, the gene sequences were most similar to those of the waterflea Daphnia pulex. In the A. bangokensis transcriptome, no opsin or related sequences were identified, and no contig aligned to the crustacean visual opsins and non-visual opsins (i.e. arthropsins, peropsins, and melaopsins), suggesting potential regressive adaptation to the dark environment. However, A. bangokensis expressed conserved gene family sets, such as heat shock proteins and those related to key innate immunity pathways and antioxidant defense systems, at the transcriptional level, suggesting that this species has evolved adaptations involving molecular mechanisms of homeostasis. The transcriptomic information of A. bangokensis will be useful for investigating molecular adaptations and response mechanisms to subterranean environmental conditions.

The genome of the Antarctic-endemic copepod, Tigriopus kingsejongensis

Background

The Antarctic intertidal zone is continuously subjected to extremely fluctuating biotic and abiotic stressors. The West Antarctic Peninsula is the most rapidly warming region on Earth. Organisms living in Antarctic intertidal pools are therefore interesting for research into evolutionary adaptation to extreme environments and the effects of climate change.

Findings

We report the whole genome sequence of the Antarctic-endemic harpacticoid copepod Tigriopus kingsejongensi . The 37 Gb raw DNA sequence was generated using the Illumina Miseq platform. Libraries were prepared with 65-fold coverage and a total length of 295 Mb. The final assembly consists of 48 368 contigs with an N50 contig length of 17.5 kb, and 27 823 scaffolds with an N50 contig length of 159.2 kb. A total of 12 772 coding genes were inferred using the MAKER annotation pipeline. Comparative genome analysis revealed that T. kingsejongensis -specific genes are enriched in transport and metabolism processes. Furthermore, rapidly evolving genes related to energy metabolism showed positive selection signatures.

Conclusions

The T. kingsejongensis genome provides an interesting example of an evolutionary strategy for Antarctic cold adaptation, and offers new genetic insights into Antarctic intertidal biota.