Nuclear 18S rRNA Gene Research Articles

Melitapanda, a new species of Melitidae (Crustacea, Amphipoda) from Japan.

A new intertidal species of the melitid amphipod, Melitapanda, from the Wakayama Prefecture, Japan, is identified and described. Melitapanda sp. nov. differs from the similar M.koreana and M.nagatai by its black-and-white body color, well-developed anterodistal projection of the male gnathopod 1 propodus, and telson armature. Molecular phylogenetic analyses based on the nuclear 28S rRNA and mitochondrial COI genes support that M.panda sp. nov. is closely related to M.koreana and M.nagatai.

Trematode metacercariae parasitic in the estuarine crustacean Cyathura muromiensis Nunomura, 1974 (Peracarida: Isopoda: Anthuroidea)

This is the first report of trematodes parasitic in the estuarine isopod crustacean Cyathura muromiensis, and the fourth report from anthuroid isopods worldwide. From 52 of 54 host individuals collected qualitatively on the tidal flat of the Muromi River estuary, Fukuoka, Japan, 389 cysts of metacercariae were extracted (sample prevalence = 96.3 %). Host individuals contained from one to 71 metacercarial cysts. The range in cyst diameter was 172.3–252.1 μm, and the distribution of cyst sizes contained only one component. Cysts occurred in pereonites 2–7 and the pleon of the host, but not in the head, pereonite 1, or telson. There was no correlation between the number of cysts and host sex or size. Sequences of the nuclear “ITS1 region,” from the 3´ region of 18S rRNA to the 5´ region of internal transcribed spacer I gene (ITS1), from five cysts ranging in size from nearly the lowest diameter to the greatest diameter in our sample showed p-distances of 0.0–0.2 %, suggesting that all cysts obtained were conspecific. A phylogenetic reconstruction based on nuclear 28S rRNA gene sequences showed that the trematode belongs in the genus Microphallus. The definitive host of our trematode species is likely a bird, since the definitive hosts of microphallids are chiefly birds, and birds are known to prey on Cyathura isopods.

From ctenophores to scyphozoans: parasitic spillover of a burrowing sea anemone

Most host-parasite associations are explained by phylogenetically conservative capabilities for host utilization, and therefore parasite switches between distantly related hosts are rare. Here we report the first evidence of a parasitic spillover of the burrowing sea anemone Edwardsiella carnea from the invasive ctenophore Mnemiopsis leidyi to two scyphozoan hosts: the native Mediterranean barrel jellyfish Rhizostoma pulmo and the invasive Indo-Pacific nomad jellyfish Rhopilema nomadica, collected from the Eastern Mediterranean Sea. Edwardsiella carnea planulae found in these jellyfish were identified using molecular analyses of the mitochondrial 16S and nuclear 18S rRNA genes. Overall, 93 planulae were found on tentacles, oral arms, and inside of the gastrovascular canals of the scyphomedusae, whereas no infection was observed in co-occurring ctenophores. DNA metabarcoding approach indicated seasonal presence of Edwardsiella sp. in the Eastern Mediterranean mesozooplankton, coinciding with jellyfish blooms in the region. Our findings suggest a non-specific parasitic relationship between Edwardsiella carnea and various gelatinous hosts based on shared functionality rather than evolutionary history, potentially driven by shifts in host availability due to jellyfish blooms. This spillover raises questions about the ecological impacts of parasitism on native and invasive scyphozoan hosts and the potential role of Edwardsiella in controlling their populations.

New species of Kontrimavichusia Makarikov & Binkienė, 2022 (Eucestoda: Hymenolepididae) from arvicoline rodents (Rodentia: Cricetidae) from the North Caucasus

Two previously unrecognized species attributable to the genus Kontrimavichusia Makarikov & Binkienė, 2022 in arvicoline rodents from the North Caucasus are described. Kontrimavichusia testiculata sp. nov. is described from Microtus majori (Thomas, 1906) from the northwestern Caucasus (Republic of Adygeya and Karachay-Cherkess Republic, Russia) and Kontrimavichusia hobergi sp. nov. is described from Microtus daghestanicus (Shidlovsky, 1919) from the central Caucasus (Republic of North Ossetia, Russia). Kontrimavichusia testiculata is readily distinguishable from K. asymmetrica (Janicki, 1904) and K. hobergi in having a larger number of testes (4–6 per proglottis), larger suckers and a longer cirrus and cirrus-sac. In addition, the new species differs from its congeners by the position of the cirrus-sac with regard to the poral osmoregulatory canals and position of distal end of the rostellar pouch relative to the posterior margins of the suckers. Kontrimavichusia hobergi can be readily distinguished from its congeners by the arrangement of the testes in a triangle and the position of the cirrus-sac with regard to the poral osmoregulatory canals. In addition, this previously unrecognized species differs from K. asymmetrica and K. testiculata by the smaller dimensions of the fully developed strobila and a narrower ovary. The cirrus-sac of K. hobergi is larger than that in K. asymmetrica but smaller than that in K. testiculata. We also used partial sequences of the nuclear ribosomal 28S rRNA gene and mitochondrial nad1 gen to justify the generic arrangement and independent status of these two new species which are characterized in the current manuscript.

The first report of digenean infecting short mackerel (Rastrelliger brachysoma) from Chon Buri Province, the Gulf of Thailand

Rastrelliger brachysoma (Bleeker, 1851), the short mackerel, is a dietary staple and of significant economic demand in Southeast Asia and Thailand. However, the demand for short mackerel has precipitated an overfishing crisis, leading to a depletion of fish stocks. Overfishing, coupled with parasitism, may result in a decline in the population of R. brachysoma. Digenetic trematode infection is prevalent in marine fish and has a considerable impact on the overall health of the fish. Here, to identify digenetic trematodes infecting R. brachysoma, we aim to determine the identity, prevalence, and intensity of digenean infections in R. brachysoma from the Gulf of Thailand. A total of 194 short mackerel were obtained from Chon Buri Province, where digeneans were isolated and identified. The molecular identity of the digeneans was confirmed using the nuclear 28S rRNA gene. Of the 194 short mackerel, 100% were found to be infected with digeneans, comprising of Lecithocladium, Prodistomum, Opechona, and Aphanurus. Lecithocladium was the most prevalent (98%) and had the highest intensity of infection (37 mean intensity), followed by Prodistomum (75% prevalence and 17 mean intensity). Our study thus presents the first evidence of digeneans infecting the economically important short mackerel from the Gulf of Thailand. The high infection rate of digenetic trematodes may have implications on the health of R. brachysoma, further driving their population decline. These data underscore the importance of safeguarding fisheries resources in the Gulf of Thailand, and downstream conservation efforts are crucial for evidence-based management decisions to safeguard the long-term sustainability of fish resources.

A contribution to the taxonomy and phylogeny of the genus Chaetonotus (Gastrotricha, Paucitubulatina, Chaetonotidae), with the description of a new species from Italian inland waters

Gastrotrichs of the genus Chaetonotus Ehrenberg, 1830 (Chaetonotida, Chaetonotidae) are known to be a speciose and pervasive group in both the marine and freshwater ecosystems, and recent investigations indicate that there is a significant amount of species diversity yet to be discovered. In the present study, a new species of this genus is described from two quarry lakes in northern Italy and characterized using an integrative morphological and molecular approach. Chaetonotus polites n. sp. is recognized by a rather stocky body, a five-lobed head, and the cuticular covering resolved in 13 alternating columns of partially imbricated scales, trilobed on the head and pentagonal on the trunk; each scale bears a peculiar simple, very thick, curved spine with a truncated apex. The new species is also distinguished by four putative molecular apomorphies at the 18S rRNA gene and two at the 28S rRNA gene. The location and type of these unique traits in the predicted secondary structure of the ribosomal genes is provided. The phylogenetic analysis based on concatenated sequences of three genes (the nuclear 18S and 28S rRNA genes and the mitochondrial COI gene) derived from 123 selected chaetonotidans, including the novel species, confirms that the genus Chaetonotus is a polyphyletic group, with several of its members resolved together with species of other genera. The new species forms a cluster with species of the subgenus Hystricochaetonotus Schwank 1990, suggestive of its potential stem lineage. LSIDurn:lsid:zoobank.org:pub:9A5DCE75-2EF2-41B0-863E-BB9237476F7F LSIDurn:lsid:zoobank.org:act:6C35E40A-6ED4-40C8-8A0D-DBBF33D01A07

Isospora and Lankesterella Parasites (Eimeriidae, Apicomplexa) of Passeriform Birds in Europe: Infection Rates, Phylogeny, and Pathogenicity.

Wild birds are common hosts to numerous intracellular parasites such as single-celled eukaryotes of the family Eimeriidae (order Eucoccidiorida, phylum Apicomplexa). We investigated the infection rates, phylogeny, and pathogenicity of Isospora and Lankesterella parasites in wild and captive passerine birds. Blood and tissue samples of 815 wild and 15 deceased captive birds from Europe were tested using polymerase chain reaction and partial sequencing of the mitochondrial cytochrome b and cytochrome c oxidase I and the nuclear 18S rRNA gene. The infection rate for Lankesterella in wild birds was 10.7% compared to 5.8% for Isospora. Chromogenic in situ hybridization with probes targeting the parasites' 18S rRNA was employed to identify the parasites' presence in multiple organs, and hematoxylin-eosin staining was performed to visualize the parasite stages and assess associated lesions. Isospora parasites were mainly identified in the intestine, spleen, and liver. Extraintestinal tissue stages of Isospora were accompanied by predominantly lymphohistiocytic inflammation of varying severity. Lankesterella was most frequently detected in the spleen, lung, and brain; however, infected birds presented only a low parasite burden without associated pathological changes. These findings contribute to our understanding of Isospora and Lankesterella parasites in wild birds.

Paratrypaea Komai & Tachikawa, 2008 (Decapoda: Axiidea: Callianassidae): more than two or three species

Abstract Paratrypaea Komai & Tachikawa, 2008 has for more than a decade been thought to contain only two species, both widespread throughout the Indo-West Pacific, or briefly three species. Molecular studies using mitochondrial 16S rRNA and 12S rRNA plus nuclear H3 and 18S rRNA genes, repeated here with samples from more individuals, have shown well separated clades within the genus. Morphological examination has found differences, especially in the form of the adult male cheliped, between the clades leading to the conclusion that Paratrypaea comprises at least eight species of which four are new and described herein. Not all closely related clades could be morphologically distinguished. Some species are narrowly and others widely distributed. The species are: P. baliensissp. nov. from Indonesia; P. bouvieri (Nobili, 1904) from the Red Sea and Indian Ocean; P. chichijimaensis (Sakai, 2015) comb. nov. from Japan; P. dworschakisp. nov. from the Hawaiian Islands; P. maldivensis (Borradaile, 1904) from the eastern Indian Ocean, Papua New Guinea, and possibly western Pacific; P. niuginiensissp. nov. from Papua New Guinea; P. rectangularis (Ngoc-Ho, 1991) from French Polynesia to the Red Sea; and P. rempiensissp. nov. from Papua New Guinea. A published partial 16S sequence from Japan has provided evidence of one more species than those proposed here. Paratrypaea cristata (Borradaile, 1910) comb. nov. remains a species inquirenda.

A new parasitic barnacle (Crustacea, Cirripedia, Rhizocephala, Mycetomorpha) from the abyssal zone in the northwestern Pacific

I describe the parasitic barnacle Mycetomorpha abyssalissp. nov. from the crangonid shrimp Sclerocrangon zenkevitchi collected from 3893–3890 m depth off the eastern coast of Iwate, Japan, northwestern Pacific. This is the first Mycetomorpha rhizocephalan from the abyssal zone and the third species in Mycetomorpha. Mycetomorpha abyssalissp. nov. differs from its congeners M. vancouverensis and M. albatrossi in (1) triangular shield lacking, (2) stalk one-quarter of length from posterior end of externa, (3) mantle opening clearly anterior to stalk, (4) different host genus, and (5) depth range much deeper. I determined partial sequences for the mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA genes and nuclear 18S rRNA and 28S rRNA genes from M. abyssalissp. nov. for future DNA barcoding and phylogeny. Kimura 2-parameter distances between M. abyssalissp. nov. and M. vancouverensis were 21.2% (16S), 0.6% (18S), and 1.5% (28S).

A cyst-forming coccidian with large geographical range infecting forest and commensal rodents: Sarcocystis muricoelognathis sp. nov.

BackgroundThe geographic distribution and host-parasite interaction networks of Sarcocystis spp. in small mammals in eastern Asia remain incompletely known.MethodsExperimental infections, morphological and molecular characterizations were used for discrimination of a new Sarcocystis species isolated from colubrid snakes and small mammals collected in Thailand, Borneo and China.ResultsWe identified a new species, Sarcocystis muricoelognathis sp. nov., that features a relatively wide geographic distribution and infects both commensal and forest-inhabiting intermediate hosts. Sarcocystis sporocysts collected from rat snakes (Coelognathus radiatus, C. flavolineatus) in Thailand induced development of sarcocysts in experimental SD rats showing a type 10a cyst wall ultrastructure that was identical with those found in Rattus norvegicus from China and the forest rat Maxomys whiteheadi in Borneo. Its cystozoites had equal sizes in all intermediate hosts and locations, while sporocysts and cystozoites were distinct from other Sarcocystis species. Partial 28S rRNA sequences of S. muricoelognathis from M. whiteheadi were largely identical to those from R. norvegicus in China but distinct from newly sequenced Sarcocystiszuoi. The phylogeny of the nuclear 18S rRNA gene placed S. muricoelognathis within the so-called S. zuoi complex, including Sarcocystisattenuati, S. kani, S. scandentiborneensis and S. zuoi, while the latter clustered with the new species. However, the phylogeny of the ITS1-region confirmed the distinction between S. muricoelognathis and S. zuoi. Moreover, all three gene trees suggested that an isolate previously addressed as S. zuoi from Thailand (KU341120) is conspecific with S. muricoelognathis. Partial mitochondrial cox1 sequences of S. muricoelognathis were almost identical with those from other members of the group suggesting a shared, recent ancestry. Additionally, we isolated two partial 28S rRNA Sarcocystis sequences from Low’s squirrel Sundasciurus lowii that clustered with those of S. scandentiborneensis from treeshews.ConclusionsOur results provide strong evidence of broad geographic distributions of rodent-associated Sarcocystis and host shifts between commensal and forest small mammal species, even if the known host associations remain likely only snapshots of the true associations.Graphical

Taxonomic study of the polyphyletic Dudresnaya (Dumontiaceae, Florideophyceae) with descriptions of Dudresnaya ryukyuensis sp. nov. and two new genera, Himehibirhodia and Nudresdaya

SUMMARYThe red algal genus Dudresnaya (Dumontiaceae, Gigartinales) has traditionally been a morphologically well‐defined taxon, but its molecular phylogeny has rarely been studied. To examine the phylogenetic relationships among Dudresnaya species, we generated new partial sequences of mitochondrial cox1, chloroplast rbcL and nuclear 28S rRNA genes from an undescribed Dudresnaya species from Okinawa Island, Japan, alongside five additional described species. Our phylogenetic analyses show that Dudresnaya is genetically diverse and polyphyletic. Based on molecular phylogeny and morphological data, we describe the Okinawan Dudresnaya as a new species, Dudresnaya ryukyuensis, and transferred Dudresnaya minima and Dudresnaya littleri, which were phylogenetically and morphologically distinct from the genuine Dudresnaya, to the new genera Himehibirhodia and Nudresdaya, respectively. Our phylogenetic analyses also showed that the Dumontiaceae is not a monophyletic group including the Gainiaceae and Rhizophyllidaceae (DGR complex). Considering that the DGR complex exhibits female reproductive structures and their post‐fertilization development that are similar to each other, the DGR complex appears to be recognized as the Dumontiaceae sensu lato.

Microeukaryotes have unexpected importance in cold seep food webs through predation and parasitism

Cold seeps are inhabited by a high abundance of chemosynthetic prokaryotes and invertebrates. However, a complete food web between invertebrates and prokaryotes cannot be established without the important link of microeukaryotes. Yet, question such as which microeukaryotes are at work in cold seeps is still mostly open. We, therefore, compared the biological communities in cold seeps and adjacent areas of the South China Sea by the metabarcoding and quantitative PCR (qPCR) of nuclear 18S and 16S rRNA genes, and estimated the potentially ecological roles of microeukaryotes by cross-domain microbial network analysis. The anaerobic methane oxidizing archaea (ANME), sulfate-reducing bacteria (SRB) and Radiolaria accounted for most variations between microbial communities from the cold seeps and adjacent areas. A significant correlation was detected between the copy numbers of 18S rRNA gene and communities of the ANME and SRB in cold seeps, indicating close links between microeukaryotes and chemosynthetic prokaryotes. After adding microeukaryotic nodes microbial network became more complex, and the negative correlation proportion and average path length increased, suggesting increased predation and parasitism. The ANME and SRB groups were mainly negatively correlated with and potentially preyed by Acantharea and Cercozoa, which were then negatively correlated with annelids and mollusks. Parasitic microeukaryotes of Syndiniales widely existed in cold seeps and had close relationships with Polycystinea. Parasitism might cause the death of Polycystinea and the release of Syndiniales spores, which may be an important carbon source for the cold seep biota. Using Mantel analyses, we also demonstrated that trophic relationships are closer in cold seeps than in the adjacently deep-sea sediments, and that microeukaryote-metazoans linkages in cold seeps are closer than those between prokaryotes and metazoans. Overall, our study outlines the main components of food webs in cold seeps and highlights that microeukaryotes have an unexpected importance in the carbon cycle.

The Extraordinary Diversity of Merodon avidus Complex (Diptera: Syrphidae)-Adding New Areas, New Species and a New Molecular Marker.

In this paper, the Merodon avidus (Diptera, Syrphidae) species complex was revised, whereupon we discovered and described four new species for science: Merodon atroavidus Vujić, Radenković et Likov sp. nov., M. magnus Vujić, Kočiš Tubić et Ačanski sp. nov., M. nigroscutum Vujić, Radenković et Likov sp. nov. and M. pseudomoenium Vujić, Kočiš Tubić et Ačanski sp. nov. An integrative taxonomy approach was used to delimit species boundaries. Two molecular markers (the mitochondrial COI gene and nuclear 28S rRNA gene-newly analysed marker for the complex) and geometric morphometry of the wing shape, together with morphological data and distribution, successfully separated all species from the complex. The morphological variability of the analysed species is described and discussed and an illustrated diagnostic key for typical morpho-forms of species from the M. avidus complex is presented. A distribution map of all investigated species from the complex is provided. The level of endemicity of the M. avidus complex was discussed.

Resettlement of Eurytemora velox (Crustacea: Copepoda) in Europe, the Urals and Western Siberia

The recent distribution of the Ponto-Caspian calanoid copepod, Eurytemora velox, in Western and Eastern Europe has been well-documented; however, there are no studies on the genetic diversity of the recently discovered Western Siberian species population. To contribute towards filling this gap, genetic diversity and distribution were investigated for E. velox collected in the Urals and Western Siberia of the Russian Federation to compare with the European populations. In this study, 44 specimens were dissected for the morphological studies, and 22 specimens of E. velox from different geographical points were analyzed for mitochondrial cytochrome oxidase I (CO1), nuclear ITS1-ITS2 (nITS) and nuclear ribosomal RNA (18SrRNA) gene fragments. Analysis of the CO1 gene region showed that the studied populations from the Urals and Western Siberia differ significantly from European ones and represent a separate genetic line. However, the nuclear nITS and 18SrRNA genes, as well as the results of morphological analysis, did not show such isolation of the Trans-Ural populations from those in Europe. As in many studies on E. velox, we found atypical structural features of the fifth prosomal leg among females in the Ob Bay. Their share was 36% of the number of studied individuals. The CO1 shows that the divergence of genetic lines occurred approximately in the Middle Pleistocene, and the species itself is Paleogene–Neogene by origin. Based on these data, a different scenario of E. velox distribution or possible refuge survival is discussed.

Assessing the applicability of nuclear 18S and ITS2-28S rRNA genes for diagnostics of Bactrocera dorsalis (Diptera: Tephritidae) in the Philippines

Fruit flies belonging to the Bactrocera dorsalis species complex pose a significant threat to mangoes and other crops in the Philippines and worldwide. Identifying cryptic species within this complex is challenging, particularly when relying solely on morphological analysis. In this study, we sequenced two fragments of the nuclear 18S and ITS2-28S rRNA genes from specimens of Bactrocera dorsalis Hendel collected in the Philippines to assess their applicability for species diagnostics. Subsequent sequencing and analysis revealed that the 18S and 28S rRNA gene fragments matched B. dorsalis sequences in NCBI but also displayed high similarity with other Bactrocera and insect species. On the other hand, sequences of the ITS2 segment showed hits specific to B. dorsalis. Further analysis of the 18S rRNA gene in fruit flies collected from various sources and host plants in the country suggests conserved sequences among Bactrocera samples, irrespective of collection site and host plant species. In conclusion, our findings suggest that, among the tested nuclear DNA fragments, only the ITS2 demonstrates sufficient species-level nucleotide variation for effective use as a molecular diagnostic marker for B. dorsalis identification.

Filter no more: A modified plankton sampler for rapid in‐water eDNA capture

Abstract The combination of an efficient sampling method and high‐throughput analysis of environmental DNA (eDNA) can be a powerful approach for characterising biodiversity across aquatic ecosystems. Plankton net tows are one of the oldest, simplest, and least expensive methods for seston and eDNA collection, but require laborious filtration steps which often lead to clogging and/or the introduction of contaminants. In this study, we used a cruising speed net (CSN) device enabling the collection of seston‐derived eDNA at 5 knots speed combined with a novel modified cod‐end with 20 μm nylon mesh inserts enabling eDNA capture while towing. We compared the performance of the CSN sampling protocol with the original conventional filtration of water sample versus the modified cod‐end. Samples were collected in parallel horizontal tows along New Zealand's North‐Eastern coastline. Concentrated water was filtered on conventional 5 μm cellulose acetate membranes, while the 20 μm nylon mesh inserts were immediately isolated post‐towing. Metabarcoding of bacterial 16S rRNA, eukaryotic nuclear 18S rRNA and mitochondrial COI genes, revealed no significant difference in alpha diversity between filtration techniques. In terms of community composition, a clear and significant shift could be observed between sampling sites and environments. Significant differences could be detected between filtration methods for 16S and COI markers, likely driven by fine‐scale differences at more turbid sheltered sites. Nonetheless, each technique could detect shifts in communities between sites and environments with similar sensitivity. Our results demonstrate the promising potential of the modified cod‐end to enable practical and cost‐effective isolation of eDNA‐derived biodiversity data from any vessel types (at ≤5 knots) across a large range of aquatic ecosystems and biogeographic scales.

First record of Ixodes (Scaphixodes) caledonicus in the Carpathian Basin and first time molecular-phylogenetic analysis of this tick species with updated host records and geographical range

Four Ixodes species represent the subgenus Scaphixodes Schulze, 1941 in Europe, but none of them were reported to be compared in a molecular-phylogenetic context. This study compensates for this lack of data. A tick larva, morphologically identified as Ixodes (Scaphixodes) caledonicus Nuttall, 1910, was collected from an Alpine swift (Tachymarptis melba) during its nesting period in Transylvania, Romania. Following DNA extraction, PCR analyses and sequencing in part with newly designed primers, three genetic markers of this specimen were amplified and compared to GenBank data, and two were analyzed phylogenetically. Based on sequence comparisons of its mitochondrial cytochrome c oxidase subunit I (cox1) and nuclear 28S rRNA genes I. caledonicus appeared to be closely related to members of the subgenus Pholeoixodes. However, the topology of the concatenated cox1 and 16S rRNA gene phylogenetic tree clearly showed its clustering with Ixodes (Scaphixodes) philipi. In conclusion, I. caledonicus is part of the tick fauna of Romania and is expected to occur also in other countries of the Carpathian Basin where rocky cliffs are available for nesting of swifts and other birds. This is the first species of the subgenus Scaphixodes in Europe, for which the traditional (morphology-based) taxonomic assignment is confirmed by molecular-phylogenetic analyses.

Molecular phylogeny of the land snail family Euconulidae in Thailand and its position in the superfamily Trochomorphoidea (Stylommatophora: Limacoidei), with description of a new genus

The Euconulidae is a globally distributed land snail family but there is no record of this family from Thailand. In this study, we describe a new genus, Siamoconus gen. nov., based on comparative studies of the shell characteristics, external morphology of animals, radula, genital and spermatophore structures, and molecular phylogeny. We performed phylogenetic analyses of two mitochondrial gene fragment (cytochrome c oxidase I, COI; and 16S rRNA) and one nuclear (28S rRNA) gene fragment to clarify the relationships with other euconulid genera and its position in the superfamily Trochomorphoidea. We also analysed shell morphometrics, male genitalia and mantle pigmentation of Siamoconus gen. nov., confirming the status of three new species with keeled shells (S. boreas sp. nov., S. coleus sp. nov. and S. geotrochoides sp. nov.) and one new species with a rounded shell (S. destitutus sp. nov.). These new species are restricted to limestone areas in northern and north-eastern Thailand. We also re-examined the status of other genera in the superfamily Trochomorphoidea based on shell features, body pigmentation, radula, genital anatomy, spermatophore morphology, and a phylogenetic analysis of all available trochomorphoidean DNA sequences. Our analysis suggests that the family Geotrochidae, previously synonymised with the Trochomorphidae, should be resurrected to represent the genus Geotrochus from Borneo, and this family is retrieved as the sister clade of the Dyakiidae. ZooBank: urn:lsid:zoobank.org:pub:C5205F4E-5DDE-42E6-A532-761CAFE099C3

Pathogenesis of black shell disease and its effects on survival and growth in the noble scallop Chlamys nobilis

The parasitic disease of mollusks has severely affected the aquaculture industries around the world, and the infestation of polydorids in commercially important mollusks is a serious problem in aquaculture. The black shell disease of noble scallop Chlamys nobilis often occurs, however, pathogeneses and effects on this scallop are unknown. In this study, two species, Polydora haswelli and Polydora lingshuiensis, were identified based on both morphological characteristics and nuclear 18S rRNA gene sequences. Slice observation showed that the tissues of black shell diseased scallops are abnormal compared to the healthy scallops, indicating that infestation of Polydora affects scallop tissues' structure. Metabolomic analysis of polydorids showed harmful metabolites (such as Microcystin LW, Cyclolinopeptides, and Neurosporaxanthin) were significantly higher than these beneficial metabolites (such as Lablabsaponin I, Notoginsenoside E, Taxoprexin, and Candicidin), suggesting these metabolites may cause detrimental effects on hosts. Pathway enrichment analysis of DEGs indicated metabolic pathways (such as amino acid and fatty acid metabolic pathways) and immune-related pathways (such as vibrio, pathogenic, and virus infection pathways) were significantly enriched, which may influence the nutritional quality and immunocompetence. More importantly, the black shell disease can cause high mortality and slow growth in the scallop. This study is the first investigation on the pathogenesis of black shell disease and its effects on survival and growth in the scallop, which is useful for controlling the Polydora infestation in scallop aquaculture.

Updated phylogeny of Vestimentifera (Siboglinidae, Polychaeta, Annelida) based on mitochondrial genomes, with a new species

Siboglinid tubeworms are found at chemosynthetic environments worldwide and the Vestimentifera clade is particularly well known for their reliance on chemoautotrophic bacterial symbionts for nutrition. The mitochondrial genomes have been published for nine vestimentiferan species to date. This study provides new complete mitochondrial genomes for ten further Vestimentifera, including the first mitochondrial genomes sequenced for Alaysia spiralis, Arcovestia ivanovi, Lamellibrachia barhami, Lamellibrachia columna, Lamellibrachia donwalshi, and unnamed species of Alaysia and Oasisia. Phylogenetic analyses combining fifteen mitochondrial genes and the nuclear 18S rRNA gene recovered Lamellibrachia as sister to the remaining Vestimentifera and Riftia pachyptila as separate from the other vent-endemic taxa. Implications and auxiliary analyses regarding differing phylogenetic tree topologies, substitution saturation, ancestral state reconstruction, and divergence estimates are also discussed. Additionally, a new species of Alaysia is described from the Manus Basin.