Discovery and anatomy of the arenophilic system of cuspidariid clams (Bivalvia: Anomalodesmata)

The arenophilic system of anomalodesmatan clams comprises multicellular glands, muscular papillae, and radial lines of adhesive secretion, which glue sand grains and other extraneous particles to the external surface of the shell. The presence and morphology of these organs have been established in an increasing number of taxa, but arenophilic glands were not previously known to occur in the deep‐sea, carnivorous family Cuspidariidae. Dissections, histological sections and ultrastructural examination of members of the cuspidariid genera Cuspidaria and Cardiomya revealed a functional arenophilic system positioned around the siphonal apparatus. Glands are contained in muscular papillae at the posterior tip of the siphonal sheath, from where they deposit their adhesive secretion onto the shell rostrum. Discovery of an arenophilic system in cuspidariid clams adds support to the idea that the glands are a synapomorphy of Anomalodesmata, secondarily absent in only one of the major component branches (the clade joining Thraciidae, Cleidothaeridae, and Myochamidae). Moreover, similarity between the arenophilic papillae we observed on the siphonal sheath of Cuspidaria, Cardiomya, and Myonera, and literature reports on the crown of tentacles of Multitentacula is puzzling and highlights the need for further studies of the latter genus. J. Morphol. 275:9–16, 2014. © 2013 Wiley Periodicals, Inc.     

Deep-water bivalves from the oxygen minimum zone area off the western Peninsula of Baja California,Mexico

ABSTRACT

Eighteen species of deep-sea bivalves were collected below the Oxygen Minimum Zone (OMZ) core off western Mexico. This material was obtained during the research cruises XVI, XVIB (off the northwestern Peninsula of Baja California), and VIII (Gulf of California) of the TALUD project aboard the R/V El Puma. The samples were taken with an epibenthic sledge (710–2077?m deep) and with a box corer (750–2600?m). The species belong to 10 families: Solemyidae, Nuculanidae, Malletiidae, Tindariidae, Limopsidae, Propeamussiidae, Tellinidae, Periplomatidae, Poromyidae and Lyonsiellidae. Environmental parameters (oxygen, salinity, sediments composition and temperature) are given for each sampling station. Tolerance to oxygen depletion is analysed for all deep-water species collected by the TALUD survey off the Baja California Peninsula. The additional file includes shell characteristics and distributional information for each species.     

Principles of systematics and the system of bivalves

The systems of the class Bivalvia accepted in recent manuals are discussed. The system proposed by L.A. Nevesskaja, O.A. Skarlato, Ya.I. Starobogatov, and A.G. Eberzin (1971) is substantiated and updated. Morphological characters important for the establishment of taxa of different ranks are listed. Three superorders and 17 orders are established; two orders, which are restricted to the Cambrian and the beginning of the Ordovician, are placed outside the accepted superorders.     

Developmental stability is not disrupted by extensive hybridization and introgression among populations of the marine bivalve molluscs Mytilus edulis (L.) and M. galloprovincialis (Lmk.) from south-west England

The effects of hybridization and introzgression were assessed among two naturally hybridizing bivalve molluscs (the mussels Mytilus edulis and M. galloprovincialis) from western Europe to estimate how disruptive these processes are to developmental stability (measured in terms of morphological variability). Ten shell traits were measured for 392 mussels from four allopatric populations (two each of At. edulis and At. galloprovincialis) and two hybrid populations. An index of variability (defined as Z_i= |y_i–y_i where y_; is the population mean of the length-standardized trait, and y_i is the individualcar;s length-standardized trait value) was constructed for each trait, and for the sum of the traits. The hybrid populations did not exhibit greater mean variability than the allopatric populations for any of the indices. Upon pooling, the hybrid populations had significantly lower variability than the pooled M. edulis populations and the pooled M. galloprovincialis populations in two analyses, and had similar means in the remaining nine analyses. Where significant differences existed, the pooled M. galloprovincialis had lower levels of mean trait variability than the pooled M. edulis. Among the two hybrid populations, the putative Fl hybrids and backcross individuals exhibited means of trait variability which were similar to those of the parental types. Thus, extensive hybridization and introgression do not adversely affect developmental stability among these mussel populations. There was a strong significant correlation between the ranking of indices (based on the amount of variability) across all six populations, indicating that a large genetic component determines the measured morphological variability. It is concluded that the genes or gene complexes which control morphological development in M. edulis and M. galloprovincialis arc very similar, providing further evidence of the close evolutionary relatedness of these mussel taxa.     

The Ramonalinids: a new family of mound‐building bivalves of the Early Middle Triassic

Abstract: Ramonalina n. gen. is a large thick‐shelled bivalve abundant in mounds preserved in the Gevanim Formation (late Anisian, Middle Triassic) of southern Israel. This bivalve was an edgewise‐recliner with a flattened anteroventral (functionally basal) surface and partially fused valves. It is the basis of a new family, the Ramonalinidae, which is descended from the myalinids through adaptation to edgewise positioning. Ligamental attachment was inadequate to hold valves together on large adults, resulting in valve displacement followed by shell secretion in the apical area that fused valves together and caused irregular growth on abapical areas. The ramonalinids formed large, nearly monospecific mounds on firm mud substrates in shallow marine waters. These are the largest Middle Triassic bivalve mounds known.     

Taphonomy in the light of intrinsic shell properties and life habits: Marine bivalves from the Eemian of northern Russia

A taphonomic analysis of the bivalvesArctica islandica (Arcticidae),Astarte borealis (Astartidae),Mytilus edulis (Mytilidae), andSpisula elliptica (Mactridae) from shallow-marine last interglacial Sediments exposed along the Pyoza river, Arkhangelsk region, shows that they differ in preservation, probably because of differences in shell shape, shell structures, and life habits. The Shells indicate that the temporal sequence of taphonomic processes was as follows: (1) pre-mortem bioerosion and dissolution; (2) post-mortem bioerosion; (3) abrasion, disarticulation, and fragmentation; and (4) dissolution. A new graphic Illustration, the taphonomic constituent diagram (TCD), is proposed to illustrate the sequences of taphonomic processes. It is inspired by the ichnofabric constituent diagram used in ichnology and integrates the shell surface coverage of different taphonomic features by graphically plotting them against relative time. The taphonomic constituent diagram may display differences in the Chronologie order of paleoenvironmental processes. Also, the diagram enables a combination of both microscopic and macroscopic taphonomic features, and eases comparative studies of fossil assemblages.      

Cretaceous opine bivalves from the Pacific slope of North America and palaeobiogeography of subfamily Opinae Chavan, 1969

Abstract: Opines constitute a small subfamily of Mesozoic astartid bivalves that lived mostly in the Tethys Sea region. They first appeared in western Europe during the Middle Triassic, became most widespread during the Jurassic and had their first undoubted appearance in the New World during the Late Jurassic. Their Pacific slope of North America record is studied in detail for the first time. The earliest of the Pacific slope opines is Opis californica Stanton of Early Cretaceous (Hauterivian or Barremian) age. The other six opine species in the study area are of Late Cretaceous age (collectively Middle Turonian – early Late Maastrichtian), have hinges bearing two strong cardinal teeth in each valve, and are placed in the new subgenus Hesperopsis, which is the first astartid to have a partially internal ligament. These six species comprise two morphological lineages inferred to have evolved from O. (H.) popenoei sp. nov. The ‘holzana’ lineage includes O. (H.) holzana sp. nov. and O. (H.) rosarioensis Anderson and Hanna. The ‘anae’ lineage includes O. (H.) anae sp. nov., O. (H.) vancouverensis Whiteaves and O. (H.) triangulata (Cooper). Hesperopis lived in warm temperate waters in offshore shelfal areas. It had a vertical commissure and probably lived as an edgewise recliner. Through time, the species of both lineages became larger and either broader or more elongate. Neither Opis shastalis Anderson, of Aptian age, nor Opis virginalis Waring, of late Palaeocene age, are opines. A junior secondary homonym of Opis trigonalis (Sowerby) was detected and is renamed here as Opis tamurai nom nov.     

Profiles of trace elements and stable isotopes derived from giant long-lived Tridacna gigas bivalves: Potential applications in paleoclimate studies

This study investigates the environmental and biological controls on trace element partitioning and stable isotope composition of modern giant long-lived bivalves (Tridacna gigas) with the aim to use these archives for paleoclimatic reconstructions. Firstly, the intra-shell variability is studied by measuring time equivalent profiles in the different shell layers characterised by different growth rates. Secondly, the inter-site variability is studied by comparing profiles derived from three modern specimens collected in sites across the Indo-Pacific region characterised by different ranges of temperature and productivity.These results show that δ¹⁸O profiles are highly reproducible across the shell regardless of significantly different growth rates. Shell δ¹⁸O is primarily controlled by water δ¹⁸O and temperature. Comparison of intra shell Mg/Ca profiles shows a clear and systematic partitioning where inner layer Mg/Ca values are a least 2–3 times higher than outer layer and hinge areas. Inner layer Mg/Ca shows seasonal oscillations but superimposed on an ontogenetic trend with increasing values and increasing amplitude Mg/Ca oscillations with age. The Sr/Ca profiles do not show clear reproducible seasonal trends in the different shell zones. It is concluded that Mg/Ca and Sr/Ca profiles appear to reflect a combination of biological and environmental controls that will need to be disentangled before using these proxies in paleoclimatic studies.Finally, intra shell Ba/Ca profiles are reproducible in great detail for all modern specimens studied. Inter-site comparison shows that the amplitude and the timing of the Ba/Ca peaks appear to reflect the timing and the amplitude of the chlorophyll peaks associated with phytoplankton blooms at each locality making this tracer a potential paleoproductivity indicator.     

Revisiting the chlamydial type III protein secretion system: clues to the origin of type III protein secretion

The bacterial type III secretion pathway delivers effector proteins into eukaryotic cells. Analysis of the type III system and flagellar export genes in the obligate parasites of the family Chlamydiales suggests that the type III system arose from the flagellar export system in chlamydiae or related bacteria.     

New lucinid bivalves from shallow and deeper water of the Indian and West Pacific Oceans (Mollusca,Bivalvia, Lucinidae)

Four new species and a new genus of lucinid bivalves are described from shallow and deeper waters in the Indian and West Pacific Oceans. The new genus Scabrilucina (subfamily Lucininae) includes the little-known Scabrilucina victorialis (Melvill, 1899) from the Arabian Sea and Scabrilucina vitrea (Deshayes, 1844) from the Andaman Sea as well as a new species Scabrilucina melvilli from the Torres Strait off northeastern Australia. Ferrocina brunei new species (Lucininae) was recovered from 60 m near oil drilling activities off Borneo; its anatomy confirmed the presence of symbiotic bacteria. Two unusual deeper water species of Leucosphaerinae are described, both species included in on-going molecular analyses; Gonimyrtea ferruginea from 400–650 m in the southwest Pacific and Myrtina reflexa from 200–825 m off Zanzibar and Madagascar.     

The locomotion system of Mesozoic Coleoidea (Cephalopoda) and its phylogenetic significance

A morphological comparison of shell‐muscle contacts in coleoid cephalopods mainly from the Early Jurassic (Toarcian) Posidonia Shales of Holzmaden (Germany), the Middle Jurassic (Callovian) Oxford Clay of Christian Malford (UK), Late Jurassic (Kimmeridgian‐Tithonian) plattenkalks of Solnhofen (Germany), and the Late Cretaceous (Cenomanian) of Hâdjoula and Hâkel (Lebanon) provides new and meaningful insights into their locomotion systems. The study shows that both pro‐ostracum‐ and gladius‐bearing coleoids are typified by a marginal mantle attachment and by distinctly separated fins, which usually insert (indirectly via the shell sac and basal fin cartilages) to posterior shell parts. While absent in gladius‐bearing forms, mantle‐locking cartilages might have existed already in pro‐ostracum‐bearing belemnoids. Similar to ectocochleate ancestors, funnel‐ and cephalic retractors are generally attached to the internal (ventral) shell surface. A comparison of Mesozoic and Recent gladius‐bearing coleoids shows that the locomotion system (most significantly the dorsal mantle configuration, and the presence of nuchal‐ and funnel‐locking cartilages) is fundamentally different. This does not support the concept of ‘fossil teuthids’, but suggests, owing to similarities with Recent Vampyroteuthis, placement of Mesozoic gladius‐bearing coleoids within the Octobrachia (Octopoda + Vampyromorpha). Classification of Mesozoic gladius‐bearing coleoids as octobrachians implies that: (1) unambiguous teuthids are still unknown in the fossil record and (2) the similarity between Recent and some fossil gladiuses represents a matter of homoplasy.     

Bioprocessing of polluted suspended matter from the water column by the zebra mussel (Dreissena polymorpha Pallas)

Measurements of pseudofaeces production of Dreissena polymorpha were carried out with the aim of developing a biological filter at the freshwater inlet of Lake Volkerak-Zoommeer, the Netherlands. Bioprocessing of polluted suspended matter by suspended cultures of D. polymorpha occurs by filtration and sedimentation of the suspended matter as pseudofaeces. The measurements were conducted under semi-natural conditions.Pseudofaeces production was mainly determined by the dry matter content of the water; the relation is linear. Temperature was of much less importance. This agrees with earlier investigations of the filtration rate of D. polymorpha. Even at the lowest temperature measured during the experiments (6.4 °C) no large decrease in activity was observed. The relation of pseudofaeces production with shell length was sigmoid in shape, in accordance with measurements of the filtration rate.The pseudofaeces produced was slightly more polluted than suspended matter, partly due to a finer grainsize. D. polymorpha from Lake IJsselmeer exposed for 217 days at the intended location of the filter showed bioaccumulation of toxicants, especially organic pollutants and Polycyclic Aromatic Hydrocarbons (up to 10-fold accumulation). The required number of D. polymorpha in the biological filter to treat the waterflow of 14 m³ s^–1 entering Lake Volkerak-Zoommeer is 1.24 * 10⁹. The purification efficiency of the filter, the reduction of the amount of toxicants, partly depends on the binding properties of the toxicants and is highest for those strongly bound to suspended matter.     

Phylogeny of cardiid bivalves(cockles and giant clams): revision of the Cardiinae and the importanceof fossils in explaining disjunct biogeographical distributions

Despite being the type subfamily of the Cardiidae, theCardiinae has received relatively little attention from systematists.Recent investigations of the phylogenetic relationships betweenand within various subtaxa of cockles and giant clams have incorporatedseveral cardiine representatives. These studies have implied thatCardiinae as usually construed is a paraphyletic group. The presentstudy, a cladistic analysis that includes exemplars of the 18 generallyaccepted genera and subgenera of Cardiinae, as well as exemplarsfrom two notable lineages heretofore not assigned to any genus‐leveltaxon, also indicate cardiine paraphyly. Cardiinae is restrictedto Cardium, Bucardium, Vepricardium, Dinocardium, Planicardium, Chesacardium, Acanthocardias.s., A. (Rudicardium) and Schedocardia. Theclosest relatives of Cardiinae are the Eocene Sawkinsia anda clade (the ‘CFTL lineage’) containing Plagiocardium, Maoricardium,Clinocardiinae, Fraginae, Lymnocardiinae and Tridacninae (giantclams). The remaining taxa that have usually been placed in Cardiinaeform a monophyletic group that is the sister taxon to Sawkinsia +Cardiinae + CFTL; the new subfamily Orthocardiinae is erectedfor this group. Orthocardiinae contains the taxa Orthocardium, Loxocardium, Europicardium, Hedecardiums.s., H. (Titanocardium), H. ( Iheringicardium ) subgen.nov ., Agnocardia, Afrocardium and Freneixicardia gen.nov .; only Afrocardium (nine species) and Europicardium (onespecies) are extant. Hedecardium s.l. was not restrictedto New Zealand as usually argued but was present in Myanmar andAustralia, as well as being represented in South America by H. (Iheringicardium).Renewed studies of the long‐ignored marine invertebrate Cenozoicfaunas of South America may yield additional examples of taxa longthought to be endemic to New Zealand. The only other orthocardiinewith representatives in the Americas is the extinct Agnocardia. Agnocardia’sclosest relative, Afrocardium, long misconstrued as a memberof Fraginae, is known only from Pleistocene and Recent faunas, usuallyfrom the Indian Ocean. This disjunct biogeographical distributionis found to be a function of a century of misidentification of fossiland Recent species, for species attributable to Agnocardia occurin the Palaeogene of Europe and Africa; likewise, species attributableto Afrocardium occur from the Eocene to Pliocene of Europeand Africa. A greater awareness of modern taxonomy of both fossiland Recent forms is necessary to avoid constructing erroneous biogeographicaldistributions and phylogenetic hypotheses. Discrepancies betweenthe results of (1) rigorous character analysis and phylogenetichypotheses and (2) published stratigraphic and palaeobiogeographicaldistributions of fossils, are not necessarily the results of aninadequate fossil record. Instead, stratigraphic and palaeobiogeographicalanomalies may be the result of inadequate attention paid to theactual fossils by taxonomists. © 2002 The LinneanSociety of London. Zoological Journal of the Linnean Society,2002, 136 , 321?369     

Seven clues to the origin and structure of class-I ribonucleotide reductase intermediate X

Class-I ribonucleotide reductases (RNRs) are aerobic enzymes that catalyze the reduction of ribonucleotides to deoxyribonucleotides providing the required building blocks for DNA replication and repair. These ribonucleotide-to-deoxyribonucleotide reactions occur by a long range radical (or proton-coupled-electron-transfer) propagation mechanism initiated by a fairly stable tyrosine radical ("the pilot light"). When this pilot light goes out, the tyrosine radical is regenerated by a high-oxidation-state enzyme intermediate, called X. The active site of class-I RNR-X has been recognized as a spin coupled Fe(III)Fe(IV) center with S(total)=1/2 ground state. Although several clues have been obtained from M?ssbauer, (57)Fe, (1)H, (17)O(2), and H(2)(17)O ENDOR (electron-nuclear double resonance), EXAFS (extended X-ray absorption fine structure), and MCD (magnetic circular dichroism) experiments, the detailed structure of the intermediate X is still unknown. In the past three years, we have been studying the properties of a set of model clusters for RNR-X using broken-symmetry density functional theory (DFT), and have compared them with the available experimental results. Based on the detailed analysis and comparisons, we have proposed a definite form for the active site structure of class-I RNR intermediate X. The puzzle is now set: can you find any flaws in the argument or evidence? Can you add anything further to the current experimental picture? The argument is formulated from seven experimental clues with associated calculations and models.     

Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae)

Zhang, G. and Weirauch, C. 2011. Sticky predators: a comparative study of sticky glands in harpactorine assassin bugs (Insecta: Hemiptera: Reduviidae). —Acta Zoologica (Stockholm) 00 : 1–10. For more than 50 years, specialized dermal glands that secrete sticky substances and specialized setae have been known from the legs of New World assassin bugs in the genus Zelus Fabricius (Reduviidae: Harpactorinae). The gland secretions and specialized ‘sundew setae’ are involved in enhancing predation success. We here refer to this predation strategy as ‘sticky trap predation’ and the specialized dermal glands as ‘sticky glands’. To determine how widespread sticky trap predation is among Reduviidae, we investigated taxonomic distribution of sticky glands and sundew setae using compound light microscopical and scanning electron microscopical techniques and sampling 67 species of Reduviidae that represent 50 genera of Harpactorini. We found sticky glands in 12 genera of Harpactorini and thus show that sticky trap predation is much more widespread than previously suspected. The sticky glands vary in shape, size and density, but are always located in a dorsolateral position on the fore tibia. Sundew setae are present in all taxa with sticky glands with the exception of Heza that instead possesses unique lamellate setae. The sticky trap predation taxa are restricted to the New World, suggesting a New World origin of this unique predation strategy.     

Secretory structures in plants: Lessons from the Plumbaginaceae on their origin,evolution and roles in stress tolerance

The Plumbaginaceae (non-core Caryophyllales) is a family well known for species adapted to a wide range of arid and saline habitats. Of its salt-tolerant species, at least 45 are in the genus Limonium; two in each of Aegialitis, Limoniastrum and Myriolimon, and one each in Psylliostachys, Armeria, Ceratostigma, Goniolimon and Plumbago. All the halophytic members of the family have salt glands and salt glands are also common in the closely related Tamaricaceae and Frankeniaceae. The halophytic species of the three families can secrete a range of ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃⁻, SO₄^2-) and other elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn). Salt glands are, however, absent in salt-tolerant members of the sister family Polygonaceae. We describe the structure of the salt glands in the three families and consider whether glands might have arisen as a means to avoid the toxicity of Na⁺ and/or Cl⁻ or to regulate Ca²⁺ concentrations with the leaves. We conclude that the establishment of lineages with salt glands took place after the split between the Polygonaceae and its sister group the Plumbaginaceae.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

New clues on the origin of the Friedreich ataxia expanded alleles from the analysis of new polymorphisms closely linked to the mutation

Friedreichs ataxia (FRDA) is an autosomal recessive neurodegenerative disorder commonly caused by large expansions of a GAA repeat in the first intron of the frataxin gene, FRDA. The expansion of the triplet repeat is localized within an Alu sequence. FRDA GAA-repeat alleles can be divided into three classes depending on their lengths: short normal alleles (SN), long normal alleles (LN) and expanded pathological alleles (E). We made an accurate analysis of the Alu sequence containing the GAA repeat. We found a new single-nucleotide polymorphism (SNP) that is the closest one to the GAA repeat. We studied this new SNP and the polymorphic polyA region contiguous to the GAA triplets in two populations with different frequencies of FRDA. We found that, while both E and LN alleles seem to be genetically homogeneous and likely related, SN represents a more heterogeneous class of alleles. Indeed, one SNP variation (T) was more frequently associated with (GAA)₈ alleles, whereas the other one (C) with (GAA)₉ repeat(s). The long normal and expanded alleles presented the C haplotype. The same correlation was described for polyA-tract polymorphisms. Thus, 14A was commonly associated with (GAA)₈ alleles and 17A with (GAA)₉ alleles. The long normal alleles more frequently showed the 17A haplotype. Our data seem to suggest that all the E alleles come from LN alleles, while LN alleles come from a defined subclass of SN alleles.