Biochemical composition and trophic strategies of the amphipod Eurythenes gryllus at hadal depths (Atacama Trench,South Pacific)

Amphipods Eurythenes gryllus were collected at 7800?m depth in the Atacama Trench (South Pacific) for studying their biochemical composition (in terms of proteins, lipids and carbohydrates and fatty acid content) and to gather information on bioenergetic strategies and trophic habits of organisms living in this extreme environment. The effect of long-term formalin storage on the biochemical determinations was also determined. Proteins were the dominant biochemical class of organic compounds (39–53%D.W.), whereas carbohydrates accounted for a very small fraction (1–2%D.W.). Lipid concentrations of E. gryllus accounted for 7–18%D.W. and were much lower than those reported for other deep-sea amphipods. These differences are likely to be more dependent upon food availability in the Atacama Trench rather than upon temperature. Lipid composition of E. gryllus revealed the dominance of monounsaturated fatty acids with polyunsaturated fatty acids accounting for a very small fraction, suggesting that hadal amphipods are higher dependent upon lipid reserves than amphipods inhabiting at shallow depths. The ratio of C18:1Δ⁹ to C18:1Δ¹¹ was >11 confirming the necrophagous trophic habits of this hadal amphipod.     

Genetic population structure and gene flow among deep-sea amphipods,Abyssorchomene spp., from six California Continental Borderland basins

Studies of geographic population variation needed to estimate gene flow are lacking in deep-sea biology. Using allozyme electrophoresis, I have studied population-level geographic variation among scavenging lysianassoid amphipod populations (Abyssorchomene spp.) inhabiting deep-water basins of the Southern California Continental Borderland. Samples were collected from November 1987 to November 1990, using baited traps, from six basins whose bottom depths ranged from ca. 1000 to 2100 m. Five basins (San Diego Trough, Santa Catalina, San Nicolas, Santa Cruz, Tanner Basins) could be grouped together as shallow-sill basins, with physical conditions distinctly different from a single deepsill basin (San Clemente Basin). Amphipods tentatively identified asAbyssorchomene sp. 1 collected from the shallow-sill basins were morphologically discriminated from those collected in the San Clemente Basin, which were identified asAbyssorchomene sp. 2. Results from eight enzyme loci revealed significant genetic differentiation [Nei's genetic distance (D)>0.155] of deep-sill basin-dwellingAbyssorchomene sp. 2 vsAbyssorchomene sp. 1 from the shallow-sill basins and low levels of gene flow (migration rate, <1). Comparisons of benthic fauna suggest the presence of an abyssal-related assemblage in the deep-sill basin isolated from the northern shallow-sill basins. Genetic distances among the five shallow-sill basin populations ofAbyssorchomene sp. 1 were very low (D < 0.003). Estimates of gene flow among these populations were very high ( > 24 to 170) and suggested weak isolation by distance.     

九株染料脱色菌的脱色特性及其质粒与基因分析

对9株染料脱色菌的脱色特性及其质粒的携带情况进行初步的研究,测定和比较了这9株细菌的16SrDNA序列,并对其进行分子鉴定和分类,经检测的9株细菌均属于肠杆菌科,其中脱色能力较广谱的5株细菌均未检测到质粒的存在,它们在系统分类地位上基本上聚为一类,与埃希氏菌属的大肠埃希氏菌具有较高的同源性。而另外4株脱色能力单一、仅对三苯基甲烷类染料有较强脱色能力的菌株除一株以外,其它3株均携带有大分子量的质粒,在系统分类地位上也基本聚为另一类。     

Clostridia dominate 16S rRNA gene libraries prepared from the hindgut of temperate marine herbivorous fishes

Bacterial diversity in the microbial communities of posterior gut sections of three temperate marine herbivorous fish species from New Zealand was characterised using Amplified Ribosomal DNA Restriction Analysis, and 16S rRNA gene amplification and sequencing methods. The fish were collected in 1999–2000 in the Hauraki Gulf, New Zealand (35°54’–36°24’S, 174°48’–175°25’E). The gastrointestinal bacterial communities of Kyphosus sydneyanus (Günther, 1886) (F. Kyphosidae), Odax pullus (Forster in Bloch and Schneider, 1801) (F. Labridae) and Aplodactylus arctidens Richardson, 1839 (F. Aplodactylidae) were dominated by five clades of bacteria, four of which belong to recognized clostridial clusters. The clone libraries of K. sydneyanus and O. pullus contained sequences from most of these clades, but were dominated by members of clostridial clusters XI and XIVa, respectively. The clone library of A. arctidens was dominated by members of clostridial cluster XIVb and an unassigned cluster containing Eubacterium desmolans and Papillibacter cinnaminovorans. The finding that strains of Firmicutes dominated the gastrointestinal microbial communities of all three fish species is consistent with the results of similar studies on terrestrial vertebrate herbivores. This work thus contributes to the view that gastrointestinal symbionts in some marine herbivorous fishes may play a similar role to those in terrestrial vertebrate herbivores studied to date.     

利用16S-23S rDNA RFLP及16S rRNA基因序列分析方法对湖北省饭豆(Vigna umbellata L.)根瘤菌系统发育的研究

采用16S-23S rDNA间隔区段(IGS)PCR-RFLP与16S rRNA基因部分序列分析的方法对饭豆根瘤菌进行了遗传多样性及系统发育分析.由16S-23S rDNA IGS PCR-RFLP分析可知,所有菌株在52%的相似性水平上聚在一起,形成了慢生型菌群与快生型菌群这两大菌群.群Ⅰ中,在79%相似性的水平上分为ⅠA与ⅠB两个分支.群Ⅱ中,在62%相似性的水平上分为ⅡA与ⅡB两个分支,分支ⅡA在72%的相似性水平上进一步分为ⅡA1、ⅡA2和ⅡA3三簇;分支ⅡB中的饭豆根瘤菌与标准菌株USDA205T聚在一起,表现的差异并不大.由16SrRNA基因部分序列分析结果可知,供试的4个代表菌株分别位于不同的系统发育分支中.CYR4243与Sinorhizobium fredii的模式菌株USDA205T的序列相似性达到了99.87%.HCY1101与Rhizobium leguminosarum中的三叶草生物型(bv.trifolii)和豌豆生物型(bv.viceae)这两个生物型的参比菌株亲缘关系最近,序列相似性为100%.HCY5202与R.galegae亲缘关系最近,序列相似性为99.86%.CYY3302与Bradyrhizobium elkanii的参比菌株USDA86有最近的亲缘关系,序列相似性近似于100%.图4表1参13     

Differing distributions of potentially competing amphipods,copepods and gastropods among specimens of the intertidal alga Pelvetia fastigiata

Possible competitive interactions are inferred from the distributions and abundances of species within three invertebrate groups (Hyale spp., Ampithoe spp. and thallusdwelling species) among unmanipulated and experimental specimens of the brown alga Pelvetia fastigiata collected between 1974 and 1976, inclusive, at La Jolla, California, USA. During the fall, when the vagile amphipods Hyale grandicornis and H. frequens were relatively abundant, they were found mostly on specimens of P. fastigiata at upper mid-intertidal and mid-tide levels, respectively. H. grandicornis often dispersed to mid-tide levels, but the two species cooccurred on few plants. Although H. frequens infrequently occupied P. fastigiata in the spring, H. grandicornis still generally sheltered in upper mid-intertidal plants, in part, because the net reproduction rates of H. grandicornis were low when space was available. The tubiculous amphipod A. tea usually was the only Ampithoe species on P. fastigiata; however, A. lindbergii and A. pollex sometimes dispersed to and released broods on this alga, particularly during the early summer when abundances of A. tea were relatively low. Similarly, net immigration rates of other thallus-dwelling copepods were relatively high when abundances of Scutellidium lamellipes were low. Moreover, several copepods were most abundant on different specimens of small isolated plants, and thallus-dwelling gastropods on larger plants at sites with relatively low densities of S. lamellipes on P. fastigiata; such copepods and gastropods generally were not abundant on aggregated plants sheltering large numbers of S. lamellipes. Such differences suggest that competition for food or space is among the factors causing negative correlations in the densities of Ampithoe spp. and thallusdwelling species on P. fastigiata.     

Molecular data from the 16S rRNA gene for the phylogeny of Veneridae (Mollusca: Bivalvia)

Veneridae, a cosmopolitan and ubiquitous family in world-wide littoral environments, lists more than 500 species, many of which are often subject to intensive commercial exploitation due to their numerical dominance in benthic communities. Historically, the family has been divided into 12 subfamilies by M. Keen and, even though this taxonomical arrangement was adopted for convenience and does not necessarily reflect genetic relationships, as suggested by Keen herself, this classification is still accepted. To contribute to clarify the systematics and phylogeny of Veneridae, the portion of the nucleotide sequence corresponding to domains IV and V of the gene encoding the large subunit of mitochondrial ribosomal RNA was analysed in 14 species representative of 10 genera belonging to 6 different subfamilies. The results obtained using the maximum-parsimony and neighbour-joining methods indicate that the current placement of the genera into subfamilies does not always reflect a natural subdivision. In addition, the six species of Tapetinae studied, though confirmed to be a monophyletic clade, do not exhibit a correct attribution at the genus level.     

Phylogenetic relationship among several genera of Dictyotaceae (Dictyotales, Phaeophyceae) based on 18S rRNA and partial rbcL gene sequences

The partial sequences of the 18S rRNA gene and the rbcL gene, RuBisCo spacer region of representatives of the Dictyotaceae were determined and compared to resolve their phylogenetic relationships. A total of 1,861 base pairs of 18S rDNA sequences were aligned and examined. There was a high similarity of nucleotide sequences within the tribe Dictyoteae (99.4-99.6%) and the tribe Zonarieae (92.8-99.8%). The largest intergeneric divergence within the Dictyotaceae was 7.31%, between Dilophus and Zonaria. The aligned 422 bases of partial rbcL gene sequences gave a similar phylogenetic relationship among taxa to those of the 18S rDNA sequences, although our alignment covered less than 30% of the whole gene. All genera of Dictyotales consisted of several clades forming a polychotomy in MP trees based on partial rbcL gene sequences and on 18S rDNA sequences. The genera within the tribe Dictyoteae formed a clade, a Dictyota-Phacydictyon-Dilophus clade, while genera of the tribe Zonarieae formed four clades: Padina; Distromium-Lobophora-Zonaria; Spatoglossum-Lobospira; and Dictyopteris-Spatoglossum. All genera of the Dictyotaceae included in these sequence analyses are classified into five groups, which have little phylogenetic resolution among them. The genera classified in the tribe Zonarieae according to Womersley's criteria do not appear to be monophyletic, based on our analyses. Although not all genera of Dictyotaceae were analysed, our data suggest that the status of the meristem cells should not be a criterion for separating tribes within the family Dictyotaceae and that other hierarchical systems should be adopted to properly reflect phylogenetic relationships.     

Population structure and reproductive patterns of the NW Mediterranean deep-sea macrourid Trachyrincus scabrus (Rafinesque, 1810)

Macrourid fish are one of the most abundant marine species on continental margins worldwide. Although they play an important role in the ecosystem, little is known about their overall biology. We report here a large data set of the most abundant macrourid in Mediterranean waters, Trachyrincus scabrus, showing the main population and reproductive characteristics. The study was based on 3,239 specimens collected between 300 and 1,500 m depth on the northwestern Mediterranean in 2003–2004 and 2008–2009. The population showed a depth-related structure with the largest individuals at 1,100 m depth and the smallest (i.e., immature) at shallower depths. Macroscopic and microscopic analyses of the gonads showed that T. scabrus has a highly seasonal reproductive pattern. Spawning females were found during winter when the organic matter fluxes were highest on the continental slope. T. scabrus is a batch spawner with group-synchronous oocyte development and present low average fecundity of 14,191 oocytes.     

Temporal patterns in diversity and species composition of deep-sea benthic copepods in bathyal Sagami Bay,central Japan

Little is known about temporal changes in the diversity and species composition of deep-sea metazoan meiofauna and their relationships with changes in the food supply. Those changes were studied for benthic copepod assemblages based on 2-year time-series data at a bathyal site in Sagami Bay (1430 m depth), central Japan, where annual fluctuation in the abundance of benthic foraminiferans was previously observed. Species diversity of benthic copepods at the site was as high as, or slightly higher than, that observed at other deep-sea sites, but did not fluctuate temporally through the study period. Multivariate analyses did not reveal any clear seasonal or directional change occurring over the longer term in their species composition, although there was some consistent pattern. These results indicate a lack of, or only weak, seasonality in the diversity and species structure of the deep-sea benthic copepod assemblages, even though the fresh organic food supply fluctuates seasonally. They also suggest that there are differences between copepods and foraminiferans in the response to changes in environmental factors, and that spatial differences in the composition of copepod communities are greater than temporal ones at this deep-sea site.Communicated by T. Ikeda, Hakodate     

Evolutionary divergence among lineages of the ocean sunfish family,Molidae (Tetraodontiformes)

Ocean sunfish, family Molidae, are enigmatic members of the epipelagic fauna of all tropical and temperate oceans. A study, begun in 1998, initially focused on the population genetics of Mola mola Linnaeus 1758 immediately indicated high levels of genetic divergence in the d-loop and cytochrome b mitochondrial genes. This preliminary effort was expanded to include Masturus lanceolatus Liénard 1840, Ranzania laevis Pennant 1776, and representative sequences of other Tetraodontiformes. Analysis of the sequence data confirms that there are two species in the genus Mola, Mola mola and M. ramsayi Giglioli 1883, with the latter presumed to be limited to the southern hemisphere. There is an indication of inter-ocean subdivision within both species originating 0.05–0.32 and 1.55–4.10 million years ago, respectively. Given limited sample sizes, however, the divergence estimates are minimums and the isolating mechanisms remain speculative. The systematic analysis provided strong support for the sister taxa relationship between genera Masturus and Mola and the basal position of the genus Ranzania within the family, as well as the sister group relationship of the Tetraodontiform families Tetraodontidae + Diodontidae to the Molidae.     

Geographic patterns of non-carpeted floor dust loading in Syracuse, New York (USA) homes

Residential floor dust loading was measured on the smooth floor surface of 488 houses in Syracuse, New York, during the summers of 2003 and 2004. Using U.S. Environmental Protection Agency (EPA) wipe methods, pre-weighed Ghost Wipes, Lead Wipes, or Whatman Filters were employed to collect duplicate samples from (predominantly) kitchens. The collection efficiency of the various media was determined from multiple wipe tests and side-by-side comparisons. The results were normalized and aggregated at the census tract level to determine whether spatial patterns of dust loading could be observed. Loading was found to be log-normally distributed, with a geometric mean value of 0.311 g m⁻² (29 mg of dust per square foot of floor); 95% of the observations fell in the range of 0.042–2.330 g m⁻² (4–216 mg foot⁻²). The sampling for floor dust loading shows some bias for day of the week in which visits to the residential properties were made. After a first-order correction for this effect, results were aggregated by census tract and mapped in a geographic information system (GIS); strong spatial patterns can be identified in an inverse distance weighted mapping. The geographic patterns exhibit a strong correlation with socio-economic/demographic covariates extracted from the 2000 census summaries. Dust mass on the floors is positively correlated with renter-occupied properties and family size; it is negatively correlated with measures of household income.     

Latitudinal and bathymetric trends in body size of the deep-sea gastropod<Emphasis Type="Italic"> Troschelia berniciensis</Emphasis> (King)

Body size is a fundamental topic in ecology with important implications for community structure and biodiversity. Although there are numerous studies addressing patterns of geographic variation of body size in deep-sea benthos, results are conflicting. Thus geographic patterns of body size in deep-sea organisms remain poorly described. We analysed depth and latitudinal trends of body size in a species of gastropod, Troschelia berniciensis (King, 1846) from the eastern North Atlantic. We tested the hypotheses that (1) body size increases linearly with latitude and (2) body size increases with depth. Results partially supported the predictions. Firstly, there was a significant linear increase of body size with latitude, but this trend was weak. Secondly, body size decreased with depth. Environmental gradients that cause large-scale patterns of body-size variation in surface environments would have little effect on communities living at great depths. Latitudinal and depth clines may be produced by independent mechanisms that operate on different scales of time and space.Communicated by J.P. Thorpe, Port Erin     

Cytogenetic analysis of Epinephelus marginatus (Pisces: Serranidae), with the chromosome localization of the 18S and 5S rRNA genes and of the (TTAGGG)n telomeric sequence

 A cytogenetic analysis was carried out on specimens of Epinephelus marginatus (Lowe, 1834) from three localities in the Mediterranean Sea, to deepen knowledge of the chromosome complement of the species and identify any possible population-specific cytogenetic markers. All specimens had a 2n = 48 acrocentric karyotype with two Ag-, chromomycin A₃- and C-positive NORs (nucleolar organizer regions) in the subcentromeric region of the smallest chromosome pair. The constitutive heterochromatin was distributed centromerically. Except for NORs, neither eu- nor heterochromatin show fluorescence after fluorochrome staining, i.e. there is no localized increase of AT- or GC-rich DNA. In all populations, the (TTAGGG) _n telomeric sequences are restricted to the telomeres, and the 18S and the 5S rDNA clusters are located on different chromosome pairs. In specimens from Sardinia, additional signals after C-banding, Ag-staining and FISH (fluorescence in situ hybridization) with 18S rDNA can be observed in the telomeric region of one or two large-sized chromosomes, classified as No. 2. This suggests that additional and variable NORs could be detected in the species in addition to those on the genus-specific, NOR-bearing Chromosome Pair 24. Received: 20 October 1999 / Accepted: 14 April 2000     

Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores

We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton. Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within this range, colors are well-adapted to the particular environment which the species inhabit. Received: 27 April 1998 / Accepted: 27 October 1998     

The role of isopods and amphipods in the initial fragmentation of eelgrass detritus in Nova Scotia,Canada

Daytime observations on the isopods Idotea phosphorea and I. baltica and the amphipod Gammarus oceanicus held in laboratory microcosms showed that I. phosphorea and G. oceanicus spent 45% and 30% respectively, of their active time feeding on dead, intact eelgrass leaves which had been recently released from plants. I. baltica spent 41% of its active time consuming intact green leaves. The shredding of intact dead leaves by I. phosphorea and G. oceanicus resulted in production of small detrital particles which were liberated from the faeces of the invertebrates and this type of feeding led to the breakdown of whole leaves. Field experiments which separated the effects of shredding by invertebrates and grinding by waves and ice on the loss of weight from leaf packs showed that relative to controls isopods significantly increased weight loss from dead leaves. Loss of weight from leaf packs exposed to both biotic and physical shredding forces was not significantly different from that found on those exposed only to shredding by isopods. However, trends in the data indicated that fragmentation of whole, dead leaves in the field probably is a result of the synergistic effects of shredding by invertebrates and physical factors, particularly ice grinding. The role played by invertebrates in fragmenting intact, dead leaves is discussed in the light of energy flow and nutrient cycling within seagrass systems.     

Geographic structure of pollinator communities, reproductive assurance, and the evolution of self-pollination

Reproductive assurance is often invoked as an explanation for the evolution of self-fertilization in plants. However, key aspects of this hypothesis have received little empirical support. In this study, I use geographic surveys of pollinator communities along with functional studies of floral trait variation to examine the role of pollination ecology in mating system differentiation among populations and subspecies of the annual plant Clarkia xantiana. A greenhouse experiment involving 30 populations from throughout the species' range indicated that variation in two floral traits, herkogamy and protandry, was closely related to levels of autofertility and that trait variation was partitioned mainly among populations. Emasculation experiments in the field showed that autonomous selfing confers reproductive assurance by elevating fruit and seed production. Surveys of pollinator communities across the geographic range of the species revealed that bee pollinator abundance and community composition differed dramatically between populations of the outcrossing subspecies xantiana and the selfing subspecies parviflora despite their close proximity. Specialist bee pollinators of Clarkia were absent from selfing populations, but they were the most frequent visitors to outcrossing populations. Moreover, within the outcrossing subspecies xantiana, there was a close correspondence between specialist abundance and population differentiation in herkogamy, a key mating system trait. This spatial covariation arose, in part, because geographically peripheral populations had reduced herkogamy, higher autofertility, and lower pollinator abundance compared to central populations of xantiana. Finally, I detected strong spatial structure to bee communities both across the range of the species and within the outcrossing subspecies. In both cases, spatial structure was stronger for specialist bees compared to generalist bees, and pollinator communities varied in parallel with population variation in herkogamy. These results provide evidence that mating system differentiation parallels spatial variation in pollinator abundance and community composition at both broad and more restricted spatial scales, consistent with the hypothesis that pollinator abundance and reproductive assurance are important drivers of plant mating system evolution.     

Geographic,population, and seasonal patterns in the reproductive parameters of the sea urchin <Emphasis Type="Italic">Paracentrotus lividus</Emphasis>

Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body size do not seem to influence greatly gonad growth.     

Sequence divergence of mitochondrial DNA indicates cryptic biodiversity in Octopus vulgaris and supports the taxonomic distinctiveness of Octopus mimus (Cephalopoda: Octopodidae)

DNA sequence diversity of octopods was investigated using the mitochondrial cytochrome oxidase III gene (mtCOIII). DNA was obtained from ethanol- or formalin-fixed tissue of 15 specimens belonging to Octopus mimus Gould, 1852, Octopus vulgaris Cuvier, 1797 and Scaeurgus unicirrhus d'Orbigny, 1840, from coastal waters of the Mediterranean (France), the southwestern Atlantic (Brazil), the Caribbean (Costa Rica) and the southeastern/tropical Pacific (north Chile/Costa Rica). A 612 bp fragment of the mtCOIII gene was sequenced and aligned to the orthologous sequences available from northeastern Pacific Octopus species. Possible phylogenetic relationships were reconstructed. The mtCOIII gene tree revealed two main clusters, one comprised O. rubescens, O. dofleini and O. californicus, while the other included all O. vulgaris specimens, O. bimaculatus, O. bimaculoides and O. mimus. With one exception all South American haplotypes including O. bimaculatus and O. bimaculoides appeared as the sister group of the Mediterranean haplotype of O. vulgaris, indicating that most of the South American O. vulgaris specimens investigated would not belong to the recently redescribed species O. vulgaris restricted to the Mediterranean and eastern Atlantic. The treatment of O. mimus as a species distinct from Mediterranean O. vulgaris is supported by a high nucleotide divergence of 12.7%. Based on the mtCOIII gene tree the existence of cryptic species among O. vulgaris-like octopods is suggested. Received: 15 January 1999 / Accepted: 15 October 1999     

Phylogenetics of American scallops (Bivalvia: Pectinidae) based on partial 16S and 12S ribosomal RNA gene sequences

Pectinids constitute one of the most conspicuous groups of marine bivalves, and include some of the most important species from the point of view of fisheries and aquaculture. In spite of this, their systematics and evolution are not well understood. Only two molecular phylogenetic analyses based on relatively wide taxonomic samplings have been published. These studies largely neglected American species, some of which are central for testing current models of pectinid evolution and diversification, or are commercially valuable. We have sequenced 820 nucleotide base pairs of the 12S and 16S ribosomal RNA genes in nine species of pectinids belonging to six genera living along American coasts. Sequences from homologous regions of 19 other species were gathered from public databases. We constructed phylogenetic maximum-parsimony and maximum-likelihood trees of this set of 28 taxa. Our phylogenetic analysis indicates that Crassadoma is polyphyletic, and cementation to the substrate as a life habit could have appeared independently in two geographic chlamydinid lineages. Nodipecten is placed in the subfamily Pectininae, and the suspected close relationship of Amusium, Euvola and Pecten within this subfamily is also supported. Zygochlamys patagonica appears in the Chlamydinae subfamily, as expected. The existence of a separate subfamily Palliolinae is suggested but not supported statistically. The position of Argopecten, Aequipecten and Flexopecten within the subfamily Pectinidae, suggested by a recent study, could not be confirmed, and we argue that it could be due to a combination of long branch attraction and incomplete sequencing.