Nuclear 18S rRNA Gene Research Articles

Description and molecular phylogeny of a new species of Phoronis (Phoronida) from Japan, with a redescription of topotypes of P. ijimai Oka, 1897

We describe Phoronis emigi sp. n. as the eighth member of the genus based on specimens collected from a sandy bottom at 33.2 m depth in Tomioka Bay, Amakusa, Japan. The new species is morphologically similar to P. psammophila Cori, 1889, but can be distinguished from the latter by the number of longitudinal muscle bundles in the body wall (56–72 vs. 25–50 in P. psammophila) and the position of the nephridiopores (situated level with the anus vs. lower than the anus in P. psammophila). Using sequences of the nuclear 18S and 28S rRNA genes and the mitochondrial cytochrome c oxidase subunit I (COI) gene, we inferred the relationship of P. emigi to other phoronids by the maximum likelihood method and Bayesian analysis. The analyses showed that P. emigi is closely related to P. hippocrepia Wright, 1856 and P. psammophila Cori, 1889. We describe the morphology of the topotypes and additional material for P. ijimai Oka, 1897. Neither our morphological observations of P. ijimai, nor the phylogenetic analyses based on 18S and COI sequences, contradicts that P. vancouverensis Pixell, 1912 is conspecific with P. ijimai, a synonymy that has long been disputed.

Phylogeographical analysis ofLigia oceanica(Crustacea: Isopoda) reveals two deeply divergent mitochondrial lineages

Isopods of the species Ligia oceanica are typical inhabitants of the rocky intertidal of the northern European coastline. The aim of this study was to assess the genetic structure of this species using mitochondrial and nuclear sequence data. We analysed partial mitochondrial cytochrome c oxidase subunit I (CO1) and 16S rRNA gene sequence data of 161 specimens collected from ten sites ranging from Spain to Norway. For selected specimens, we also sequenced the hypervariable V7 expansion segment of the nuclear 18S rRNA gene as a supplementary marker. Furthermore, we studied the infection rate of all analysed specimens by the alphaproteobacterium Wolbachia. Our analyses revealed two deeply divergent mitochondrial lineages for Ligia oceanica that probably diverged in the late Pliocene to mid Pleistocene. One lineage comprised specimens from northern populations (‘lineage N’) and one primarily those from France and Spain (‘lineage S’). Distribution patterns of the haplotypes and the genetic distances between both lineages revealed two populations that diverged before the Last Glacial Maximum. Given that we found no homogenization of mitochondrial haplotypes, our present results also reject any influence of Wolbachia on the observed mtDNA variability. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 16–30.

Vicariant versus dispersal processes in the settlement ofPseudamnicola(Caenogastropoda, Hydrobiidae) in the Mediterranean Balearic Islands

The genus Pseudamnicola comprises a group of tiny springsnails inhabiting several continental and insular regions of the Mediterranean basin. Given the limited dispersal capabilities of these animals, it is difficult to explain the wide distribution range of the genus and, more specifically, its presence in isolated habitats, such as on islands. Thus, to investigate the process(es) that may explain these distribution patterns, we morphologically re-described and genetically analysed the six Pseudamnicola (Pseudamnicola) species occurring in the Iberian Peninsula and the nearby Balearic Islands. Genetic relationships were explored by sequencing two mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and one nuclear (28S rRNA) gene in 19 populations. Our morphological study confirmed the presence of previously described species, whereas our phylogenetic results revealed three lineages within the subgenus: one clade grouping the species from Minorca Island with an Iberian Peninsula species, a second clade grouping the three species from Majorca Island, and a third clade that consists of a single species, which occurs in both the Iberian Peninsula and Ibiza Island. Calculated speciation times show that the cladogenetic events involving the insular species seem to have occurred after the current conformation of the Balearic Islands (c. 20 Mya). Therefore, the speciation process may have been related to subsequent transmarine colonizations, probably during the Messinian Salinity Crisis, and the Pleistocene glaciations when landmass corridors connected the islands with the continent. © 2014 The Linnean Society of London

Burmoniscus kitadaitoensis Nunomura, 2009 (Crustacea, Isopoda, Oniscidea) from southern Japan, a junior synonym of B. meeusei (Holthuis, 1947)

Re-examination of the holotype of Burmoniscus kitadaitoensis Nunomura, 2009 from Kitadaitojima Island, southern Japan reveals that this species is a junior synonym of B. meeusei (Holthuis, 1947). Partial regions of mitochondrial COI, 12S and 16S rRNA genes, and nuclear 18S and 28S rRNA genes were detected for species identification in the future.

Two new species in the Echinoderes coulli group (Echinoderidae, Cyclorhagida, Kinorhyncha) from the Ryukyu Islands, Japan

Two new species belonging to the Echinoderes coulli group are described with their external morphologies and sequences of nuclear 18S rRNA and 28S rRNA genes, and mitochondrial COI gene. The first species, Echinoderes komatsui sp. n., is characterized by absence of acicular spines, and presence of lateroventral tubules on segments 5 and 8, laterodorsal tubules on segment 10, inverted triangle or wide oval shaped large sieve plates, lateral terminal accessory spines in female, and short tips of ventral pectinate fringe on segment 10. The second species, Echinoderes hwiizaa sp. n., is characterized by absence of acicular spines, and presence of lateroventral tubules on segments 5 and 7–9, midlateral tubules on segment 8, laterodorsal tubules on segment 10, large narrow oval shaped sieve plates on segment 9, and thick, short and blunt lateral terminal spines about 10–15% of trunk length. The diagnostic characters and key to species of E. coulli group are provided as well.

Pseudorientalia Radoman, 1973 (Caenogastropoda: Rissooidea) on Samos Island, Aegean Sea

1. Davis G. M., Wilke T., Spolsky C., Qiu C.-P., Qiu D.-C., Xia M.-Y., Zhang Y., Rosenberg G. 1998. Cytochrome oxidase I-based phylogenetic relationships among the Pomatiopsidae, Hydrobiidae, Rissoidae and Truncatelidae (Gastropoda: Caenogastropoda: Rissoacea). Malacologia 40: 251–266. Google Scholar

Systematics and biology of the aberrant intertidal parasitoid wasp Echthrodesis lamorali Masner (Hymenoptera : Platygastridae s.l.): a parasitoid of spider eggs

The platygastroid wasp Echthrodesis lamorali has been of considerable interest since its description in 1968, primarily because of its highly modified, densely pilose, wingless body, its distribution and unusual biology. The species is endemic to the Cape Peninsula, South Africa, where it is an endoparasitoid of eggs of the marine spiders Desis formidabilis (Desidae) and Amaurobioides africanus (Anyphaenidae) in the intertidal region. Although a highly aberrant monospecific genus, the phylogenetic relationships of Echthrodesis are confused, in part due to convergence in body form across numerous unrelated platygastroid genera. We used sequence data from the nuclear 28S rRNA and 18S rDNA genes, and the mitochondrial cytochrome oxidase 1 (CO1) gene, to determine the phylogenetic affinities of E. lamorali. We present a revised taxonomic description for the genus and species, as well as new morphological information on the structure of its mouthparts and ovipositor system. Phylogenetic analyses of molecular data place E. lamorali within one of two independent clades of platygastroid wasps that use spider eggs as hosts. Echthrodesis is sister to a group of three genera: Neobaeus (New Zealand; host unconfirmed); Mirobaeoides (Australia; spider eggs); and Embidobia (near cosmopolitan; embiid eggs). Details on the biology, behaviour and morphological adaptations of E. lamorali are provided.

Patterns of hind-wing degeneration in Japanese riffle beetles (Coleoptera: Elmidae)

We conducted a molecular phylogenetic analysis based on mitochondrial cytochrome oxidase subunit I and nuclear 28S rRNA gene sequences of species of Japanese elmids (23 species from 12 genera) and examined the hind-wings of 24 species in order to determine the incidence of hind-wing degeneration among species and the presence of dimorphic species with respect to hind- wing degeneration. Based on the molecular phylogenetic analysis, we determined that the previously separated winged and wingless species, Stenelmis vulgaris and S. miyamotoi, and Leptelmis gracilis and L. parallela, are two forms of the same species. Of the 24 species whose hind wings were studied, we found apterous (3 species of Zaitzeviaria), brachypterous (2 species of each of Optio- servus and Paramacronychus) and dimorphic species (2 species as above) in separate clades of the phylogeny. These were the smallest or medium-sized species. Dimorphic species occurred in mid- to downstream areas and used reeds and wood as substrates. The percentage of species with hind-wing degeneration (wingless or dimorphic) was high among the species (29%) studied com- pared to the perceived percentage for temperate beetles (< 10%). Thus, we found that the degeneration of hind wings has occurred repeatedly in these elmid species. However, we identified only ambiguous habitat and life history correlates of hind-wing degenera- tion, and the adaptive significance of hind-wing degeneration in these species of elmids remains unclear.

Five subspecies of the Dorogostaiskia parasitica complex (Dybowsky) (Crustacea: Amphipoda: Acanthogammaridae), epibionts of sponges in Lake Baikal

Based on morphological and molecular characters, the gammaroid amphipod Dorogostaiskia parasitica, living as an epibiont on sponges in Lake Baikal, Siberia, is here split into five parapatrically or allopatrically distributed subspecies: D. p. parasitica (Dybowsky, Horae Societatis Entomologicae Rossicae 10(Beiheft):1–218, 1874), D. p. kamaltynovi subsp. nov., D. p. hanajevi subsp. nov., D. p. ushkaniensis subsp. nov., and D. p. stenocephala subsp. nov. Diagnostic differences are described in the shape of dorsal keels, shape of head, length of antenna 1, number of segments of accessory flagellum, shape and armature of coxal plates, relative lengths of pereopod segments, and body coloration. Each subspecies is characterized by a distinct mitochondrial lineage, differing from others by 5–11% in the sequence of the COI gene, while they do not differ in nuclear 28S rRNA gene sequence. The question of taxonomic ranks for members of intralacustrine species complexes is considered and an argument is presented for a use of the subspecies rank for parapatrically distributed population segments that are distinguished by multiple independent geographically congruent character differences. This usage sorts out a pattern of systematic diversity lower than one based on documented reproductive isolation (e.g., sympatry) of full species but stronger than that based on single-gene genealogies alone.

Rare Failures of DNA Bar Codes to Separate Morphologically Distinct Species in a Biodiversity Survey of Iberian Leaf Beetles

During a survey of genetic and species diversity patterns of leaf beetle (Coleoptera: Chrysomelidae) assemblages across the Iberian Peninsula we found a broad congruence between morphologically delimited species and variation in the cytochrome oxidase (cox1) gene. However, one species pair each in the genera Longitarsus Berthold and Pachybrachis Chevrolat was inseparable using molecular methods, whereas diagnostic morphological characters (including male or female genitalia) unequivocally separated the named species. Parsimony haplotype networks and maximum likelihood trees built from cox1 showed high genetic structure within each species pair, but no correlation with the morphological types and neither with geographic distributions. This contrasted with all analysed congeneric species, which were recovered as monophyletic. A limited number of specimens were sequenced for the nuclear 18S rRNA gene, which showed no or very limited variation within the species pair and no separation of morphological types. These results suggest that processes of lineage sorting for either group are lagging behind the clear morphological and presumably reproductive separation. In the Iberian chrysomelids, incongruence between DNA-based and morphological delimitations is a rare exception, but the discovery of these species pairs may be useful as an evolutionary model for studying the process of speciation in this ecological and geographical setting. In addition, the study of biodiversity patterns based on DNA requires an evolutionary understanding of these incongruences and their potential causes.

Genetic Characterization of Clinical Acanthamoeba Isolates from Japan using Nuclear and Mitochondrial Small Subunit Ribosomal RNA

Because of an increased number of Acanthamoeba keratitis (AK) along with associated disease burdens, medical professionals have become more aware of this pathogen in recent years. In this study, by analyzing both the nuclear 18S small subunit ribosomal RNA (18S rRNA) and mitochondrial 16S rRNA gene loci, 27 clinical Acanthamoeba strains that caused AK in Japan were classified into 3 genotypes, T3 (3 strains), T4 (23 strains), and T5 (one strain). Most haplotypes were identical to the reference haplotypes reported from all over the world, and thus no specificity of the haplotype distribution in Japan was found. The T4 sub-genotype analysis using the 16S rRNA gene locus also revealed a clear sub-conformation within the T4 cluster, and lead to the recognition of a new sub-genotype T4i, in addition to the previously reported sub-genotypes T4a-T4h. Furthermore, 9 out of 23 strains in the T4 genotype were identified to a specific haplotype (AF479533), which seems to be a causal haplotype of AK. While heterozygous nuclear haplotypes were observed from 2 strains, the mitochondrial haplotypes were homozygous as T4 genotype in the both strains, and suggested a possibility of nuclear hybridization (mating reproduction) between different strains in Acanthamoeba. The nuclear 18S rRNA gene and mitochondrial 16S rRNA gene loci of Acanthamoeba spp. possess different unique characteristics usable for the genotyping analyses, and those specific features could contribute to the establishment of molecular taxonomy for the species complex of Acanthamoeba.

Phylogenetic position of Linguatula arctica and Linguatula serrata (Pentastomida) as inferred from the nuclear 18S rRNA gene and the mitochondrial cytochrome c oxidase subunit I gene

Genomic DNA was isolated from a Linguatula serrata female expelled from a dog imported to Norway from Romania and from four Linguatula arctica females collected from semi-domesticated reindeer from northern Norway and subjected to PCR amplification of the complete nuclear 18S rRNA gene and a 1,045-bp portion of the mitochondrial cytochrome c oxidase subunit I gene (cox1). The two species differed at two of 1,830 nucleotide positions (99.9% identity) of the complete 18S rRNA gene sequences and at 102 of 1,045 nucleotide positions (90.2% identity) of the partial cox1 sequences. The four isolates of L. arctica showed no genetic variation in either gene. The new cox1 primers may facilitate the diagnosis of various developmental stages of L. arctica and L. serrata in their hosts. In separate phylogenetic analyses using the maximum likelihood method on sequence data from either gene, L. arctica and L. serrata clustered with members of the order Cephalobaenida rather than with members of the order Porocephalida, in which the genus Linguatula is currently placed based on morphological characters. The phylogenetic relationship of L. arctica, L. serrata and other pentastomids to other metazoan groups could not be clearly resolved, but the pentastomids did not seem to have a sister relationship to crustaceans of the subclass Branchiura as found in other studies. A more extensive taxon sampling, including molecular characterisation of more pentastomid taxa across different genera, seems to be necessary in order to estimate the true relationship of the Pentastomida to other metazoan groups.

Phylogeography of the sand dollar genus Mellita: Cryptic speciation along the coasts of the Americas

Sand dollars of the genus Mellita are members of the sandy shallow-water fauna. The genus ranges in tropical and subtropical regions on the two coasts of the Americas. To reconstruct the phylogeography of the genus we sequenced parts of the mitochondrial cytochrome oxidase I and of 16S rRNA as well as part of the nuclear 28S rRNA gene from a total of 185 specimens of all ten described morphospecies from 31 localities. Our analyses revealed the presence of eleven species, including six cryptic species. Sequences of five morphospecies do not constitute monophyletic molecular units and thus probably represent ecophenotypic variants. The fossil-calibrated phylogeny showed that the ancestor of Mellita diverged into a Pacific lineage and an Atlantic+Pacific lineage close to the Miocene/Pliocene boundary. Atlantic M. tenuis, M. quinquiesperforata and two undescribed species of Mellita have non-overlapping distributions. Pacific Mellita consist of two highly divergent lineages that became established at different times, resulting in sympatric M. longifissa and M. notabilis. Judged by modern day ranges, not all divergence in this genus conforms to an allopatric speciation model. Only the separation of M. quinquiesperforata from M. notabilis is clearly due to vicariance as the result of the completion of the Isthmus of Panama. The molecular phylogeny calibrated on fossil evidence estimated this event as having occurred ∼3Ma, thus providing evidence that, contrary to a recent proposal, the central American Isthmus was not completed until this date.

Relationship Between Two Androgenetic Clam Species,Corbicula leanaandCorbicula fluminea, Inferred from Mitochondrial Cytochrome b and Nuclear 28S rRNA Markers

Two shell color types, yellow (type I) and brown (type II), of hermaphrodite Corbicula fluminea clams from Ritto, Shiga Prefecture, Japan, are sympatric with both male and hermaphrodite Corbicula leana. In the present study, the mitochondrial DNA (mtDNA) cytochrome b and nuclear 28S rRNA genes of C. fluminea were sequenced to construct a haplotype network in order to investigate the genetic relationship with C. leana. Ninety C. fluminea samples revealed only two cytb haplotypes; the majority (97.8%) were CB7, while the remainder were CB1. In C. leana, only CB1 was detected in hermaphrodites, but both CB1 and CB7 were detected in males. Nuclear 28S rRNA haplotypes of C. fluminea type I individuals were divergent from those of hermaphrodite C. leana. However, C. fluminea type I clams shared haplotypes with male C. leana individuals, whereas C. fluminea type II individuals shared haplotypes with both hermaphrodite and male C. leana samples. These results suggest that it may be difficult to define a clear genetic border between these species.

Systematic revision of the genusScaphander(Gastropoda, Cephalaspidea) in the Atlantic Ocean, with a molecular phylogenetic hypothesis

The genus Scaphander (Gastropoda, Cephalaspidea) is a group of predominantly deep-sea, soft-bottom snails with extant species distributed worldwide from the Arctic to the Antarctic. There are approximately 45 species described worldwide, of which about 18 are considered to be valid. The systematics of Scaphander has traditionally been shell-based, but shell characters often show high intraspecific variability, and this led to a high number of nominal names available of unclear taxonomic status. The main objectives of this article are to revise the systematics of the Atlantic species of Scaphander, and to produce an identification key and a molecular phylogeny to aid with species delimitation. The validity of species was assessed following an integrative approach combining the study of type material and original descriptions, shells, morpho-anatomical characters, and molecular phylogenetics. Anatomical structures were documented by drawings, macro-photography, and scanning electron microscopy (SEM). Two mitochondrial (COI and 16S rRNA) and one nuclear (28S rRNA) genes were sequenced, and Bayesian molecular phylogenetic hypotheses were produced. Representatives of the Cephalaspidean genera Bulla and Haminoea were included to test the monophyly of Scaphander. Eight species of Scaphander were recognized in the Atlantic Ocean. Three species are restricted to the western Atlantic (Scaphander clavus, Scaphander darius, and Scaphander watsoni), one is distributed only in the eastern Atlantic (Scaphander lignarius), one is endemic to the Azores (Scaphander gracilis; this species is only known from shells), and three have amphi-Atlantic distributions (Scaphander bathymophilus, Scaphander nobilis, and Scaphander punctostriatus). Shell characters and the morphology of the male reproductive system were found to be the best diagnostic characters for species recognition. The molecular phylogeny confirms the monophyly of Scaphander, and is largely congruent with species delimitation based on morpho-anatomical characters. © 2013 The Linnean Society of London

Phylogeny, biogeography and systematics of hydrothermal vent and methane seep Amphisamytha (Ampharetidae, Annelida), with descriptions of three new species

Amphisamytha has five currently recognized species. One of these, A. galapagensis has been reported from numerous hydrothermal vents and methane seeps across the Pacific Ocean. Here, a collection of Amphisamytha from a range of Pacific habitats, as well as Amathys lutzi from Atlantic hydrothermal vents, were studied using morphology and DNA sequences from mitochondrial (COI and 16S rRNA) and nuclear (18S rRNA) genes. Phylogenetic analyses revealed a deep-sea clade comprised of the previously recognized Amphisamytha species, and three lineages that are treated as new species. The morphologically distinct Amathys lutzi was nested within Amphisamytha and the monotypic Amathys is treated as a junior synonym of Amphisamytha, with a resulting name change to Amphisamytha lutzi comb. nov. A revision of the other Amphisamytha species, the description of three new species, and a key are provided. The geographic range of the ‘cosmopolitan’ A. galapagensis is restricted to hydrothermal vents of the East Pacific Rise and the Galápagos Ridge. Amphisamytha fauchaldi, previously only known from sedimented hydrothermal vents of the Guaymas Basin (Gulf of California, Mexico), is recorded from cold seeps off the coasts of Costa Rica and Oregon. Amphisamytha carldarei sp. nov. is described from hydrothermal vents of the northeast Pacific (Juan de Fuca), while A. jacksoni sp. nov. spans much of the East Pacific Rise and is sympatric with A. galapagensis for part of its range. Amphisamytha julianeae sp. nov. is found at western Pacific vent systems in sympatry with A. vanuatuensis. Relaxed molecular clock analyses were calibrated using the vicariant event involving the Farallon-Pacific Ridge in the northern Pacific Ocean. This provides mean dates for the origin of the deep-sea Amphisamytha clade at 44 or 55 million years ago, and the separation of the Pacific–Atlantic sister-species pair at 13 or 21 million years ago, depending on the tree used. http://www.zoobank.org/urn:lsid:zoobank.org:pub:502BC05E-FFB9-4FFB-B367-95F628AD6456

Molecular phylogeny of kinorhynchs

We reconstructed kinorhynch phylogeny using maximum-likelihood and Bayesian analyses of nuclear 18S and 28S rRNA gene sequences from 30 species in 13 genera (18S) and 23 species in 12 genera (28S), representing eight families and both orders (Cyclorhagida and Homalorhagida) currently recognized in the phylum. We analyzed the two genes individually (18S and 28S datasets) and in combination (18S+28S dataset). We detected four main clades (I–IV). Clade I consisted of family Echinoderidae. Clade II contained representatives of Zelinkaderidae, Antygomonidae, Semnoderidae, Centroderes, and Condyloderes, the latter two currently classified in Centroderidae; within Clade II, Zelinkaderidae, Antygomonidae, and Semnoderidae comprised a clade with strong nodal support. Clade III contained only two species in Campyloderes, also currently classified in the Centroderidae, indicating polyphyly for this family. Clades I–III, containing all representatives of Cyclorhagida included in the analysis except for Dracoderes abei, formed a clade with high nodal support in the 28S and 18S+28S trees. Clade IV, resolved in the 18S and 18S+28S trees with high nodal support, contained only species in order Homalorhagida, with the exception of the cyclorhagid Dracoderes abei. Order Cyclorhagida as it currently stands is thus polyphyletic, and order Homalorhagida paraphyletic. Our results indicate that Dracoderidae has been misplaced in Cyclorhagida based on homoplasious characters. Our analyses did not resolve the relationships among Clades I–III within Cyclorhagida. Neither gene alone nor the combined dataset resolved all nodes in trees, indicating that additional markers will be needed to reconstruct kinorhynch phylogeny.

DNA-barcoding contradicts morphology in quill mite species Torotrogla merulae and T. rubeculi (Prostigmata: Syringophilidae)

Torotrogla merulae Skoracki, Dabert et Ehrnsberger, 2000 and T. rubeculi Skoracki, 2004 have been considered as distinct steno- and monoxenous quill mite species (Acari: Prostigmata: Syringophilidae) parasitizing the thrushes of the genus Turdus Linnaeus and the European robin Erithacus rubecula (Linnaeus), respectively. Morphological and molecular studies on the taxonomical status of these two species provided contradictory results. Well defined differences in morphology were not supported by substantial genetic distance in nucleotide sequences of the DNA barcode (mitochondrial cytochrome c oxidase subunit I, COI, and D2 domain of the nuclear 28S rRNA gene), by the topology of the phylogenetic trees (neighbor-joining, maximum parsimony, maximum likelihood) and the network analyses of the COI haplotype genealogy (median-joining, statistical parsimony) that reveal rubeculi populations nested within merulae haplotypes. Since detected differences between T. merulae and T. rubeculi populations (1.6-2.4% for COI and 0.1% for D2) are comparable to the intraspecific level observed in majority of currently recognized European Torotrogla species and are much lower than the interspecific distances observed in the genus, we postulate their conspecificity. Because main morphological distinctions concern the structures used for feeding, we hypothesize that they are the result of phenotypic plasticity evoked by specific and different environmental conditions prevailing on the host bodies (thickness of the feather quill wall).

Morphology, 18S rRNA gene sequence and life history of a new Polydora species (Polychaeta: Spionidae) from northeastern Japan

A new species of spionid polychaete, Polydora onagawaensis, is described from mol- lusk shells in Pacific waters of northeastern Japan. Its nuclear 18S rRNA gene sequence as well as its morphology, reproductive features, life history and infestation characteristics are reported. Polydora onagawaensis sp. nov. belongs to the Polydora ciliata/websteri group and has a moder- ate size and variable black pigmentation on the palps and body. Up to 115 worms were found bor- ing in a single scallop shell from suspended cultures in Onagawa Bay, with significantly higher numbers in the right than in the left valve. Females repeatedly deposited a string of egg capsules from around October to June (seawater temperature was below 15°C). The larvae developed inside the egg capsules for 2 wk (10°C, laboratory conditions), until the 3-chaetiger stage, before being released as planktonic larvae. The main spawning occurred in December, recruitment onto the shells increased after January, and most large worms disappeared between July and October. Thus, the estimated life span is around 1.5 yr after settlement. Details on biology and gene infor- mation not only contribute to distinguishing the species from other polydorids similar in morpho - logy, but also allow control of polydorid infestation in mollusk aquaculture.

Morphology and molecular analysis of the 18S rRNA gene of oyster shell borers, Polydora species (Polychaeta: Spionidae), from Japan and Australia

Nuclear 18S rRNA gene sequences of oyster shell borers, Polydora websteri, P. calcarea and P. haswelli (Polychaeta: Spionidae), were determined for the first time. A wide range of morphological variation, particularly with regard to pigmentation, is observed among these three species. This variation was characterized at the species level. Black pigmentation pattern on the palps is suggested to be a key characteristic for species determination. Polydora websteri and P. haswelli were sister species. This is the first record of P. calcarea from Japan and Australia and P. haswelli from Japan.