A new poecilogonous species of sea slug (Opisthobranchia: Sacoglossa) from California: comparison with the planktotrophic congener Alderia modesta (Loven, 1844)

Cryptic species are increasingly recognized as commonplace amongmarine gastropods, especially in taxa such as shell-less opisthobranchsthat lack many discrete taxonomic characters. Most cases ofpoecilogony, the presence of variable larval development withina single species, have historically turned out to representcryptic species, with each possessing a single canalized typeof development. One well-characterized example of poecilogonywas attributed to the sacoglossan opisthobranch Alderia modesta;in southern California, slugs resembling this member of a monotypicgenus produce both long-lived, planktotrophic and short-lived,lecithotrophic larvae. Paradoxically, however, A. modesta isexclusively planktotrophic everywhere else in the northern Pacificand Atlantic Oceans. A recently completed molecular study foundthat slugs from poecilogonous populations south of Bodega Harbor,California, comprise an evolutionarily distinct lineage separatefrom northern, strictly planktotrophic slugs. We now describethe southern species as A. willowi n. sp., based on differencesin morphology of the dorsum and radula, characteristics of theegg mass, larval development mode and nuclear and mitochondrialgenetic markers. A DNA barcode is provided, based on 27 fixeddifferences in the cytochrome c oxidase subunit I gene thatcan reliably differentiate Pacific specimens of Alderia species.Genetic and morphological data are concordant with developmentalevidence, confirming that A. willowi is a true case of poecilogony.An improved understanding of the ecological differences betweenthese sister taxa may shed light on the selective pressuresthat drove the evolution of lecithotrophy in the southern species. (Received 1 November 2005; accepted 20 September 2006)     

A novel role for dpp in the shaping of bivalve shells revealed in a conserved molluscan developmental program

During the molluscan evolution leading to the bivalves, the single dorsal shell was doubled. To elucidate the molecular developmental basis underlying this prominent morphological transition, we described the cell cleavage and expression patterns of three genes, brachyury, engrailed, and dpp in the Japanese spiny oyster Saccostrea kegaki, and examined the function of dpp in this species. The cleavage pattern of the S. kegaki embryo was nearly the same as the previously described pattern of other bivalve species, suggesting that the pattern itself is highly important for the establishment or the maintenance of the bivalve body plan. The expression pattern of a brachyury homolog in S. kegaki (SkBra) was similar to the pattern in gastopods even at the single cell level despite the deep divergence of gastropods and bivalves. Engrailed and dpp were previously found to be expressed around the shell anlagen in gastropods. Like that of gastropods, an engrailed homolog in S. kegaki (SkEn) was found to be expressed around the shell anlagen. However, the dpp homolog in S. kegaki (SkDpp) was expressed only in the cells along the dorsal midline. ZfBMP4 treatment experiments revealed the importance of dpp in establishing the characteristic shape of the bivalve shell anlagen.     

ALLOZYME COMPARISON OF LITTORINA SPECIES FROM THE NORTHWESTERN PACIFIC

Three unknown Littorina species were revealed by allozyme studyof snails from the northwestern Pacific. One of them was foundin Kasatka Bay (Pacific coast of Iturup Island, south KurileIslands) together with L. sitkana, which it resembled in anatomicalfeatures, but the genetic distance between these species wasD=0.622. The second one was found in Tauiskaya Inlet (northernpart of Okhotsk Sea) and was again similar to L. sitkana inmorphological and anatomical features, but D=1.160. The thirdspecies was found in Egvekinot Inlet (Anadyrskiy Gulf, BeringSea) in sympatry with L. natica, to which was close genetically(D=0.256) although it differed in shell shape. (Received 4 April 2005; accepted 26 August 2005)     

Multigene Phylogeography of Bactrocera caudata (Insecta: Tephritidae): Distinct Genetic Lineages in Northern and Southern Hemispheres

Bactrocera caudata is a pest of pumpkin flower. Specimens of B. caudata from the northern hemisphere (mainland Asia) and southern hemisphere (Indonesia) were analysed using the partial DNA sequences of the nuclear 28S rRNA and internal transcribed spacer region 2 (ITS-2) genes, and the mitochondrial cytochrome c oxidase subunit I (COI), cytochrome c oxidase subunit II (COII) and 16S rRNA genes. The COI, COII, 16S rDNA and concatenated COI+COII+16S and COI+COII+16S+28S+ITS-2 nucleotide sequences revealed that B. caudata from the northern hemisphere (Peninsular Malaysia, East Malaysia, Thailand) was distinctly different from the southern hemisphere (Indonesia: Java, Bali and Lombok), without common haplotype between them. Phylogenetic analysis revealed two distinct clades (northern and southern hemispheres), indicating distinct genetic lineage. The uncorrected ‘p’ distance for the concatenated COI+COII+16S nucleotide sequences between the taxa from the northern and southern hemispheres (‘p’ = 4.46-4.94%) was several folds higher than the ‘p’ distance for the taxa in the northern hemisphere (‘p’ = 0.00-0.77%) and the southern hemisphere (‘p’ = 0.00%). This distinct difference was also reflected by concatenated COI+COII+16S+28S+ITS-2 nucleotide sequences with an uncorrected ''p'' distance of 2.34-2.69% between the taxa of northern and southern hemispheres. In accordance with the type locality the Indonesian taxa belong to the nominal species. Thus the taxa from the northern hemisphere, if they were to constitute a cryptic species of the B. caudata species complex based on molecular data, need to be formally described as a new species. The Thailand and Malaysian B. caudata populations in the northern hemisphere showed distinct genetic structure and phylogeographic pattern.     

Daphnia populations in three interconnected lakes with roach as the principal planktivore

Data on two co-existing Daphnia species, D.cucullata (G.O.Sars)and D.hyalina (Leydig), from three neighboring and interconnectedlakes in northern Poland, revealed an extremely confined rangeof population density fluctuations throughout summer in eachof the two species in each of the three lakes, with D.cucullatabeing an order of magnitude more abundant than D.hyalina (meanof 11.5 ind. l^–1 for D.cucullata and 1.1 ind. l^–1for D.hyalina with 95% confidence limits of ±2.5 and±0.5 ind. l^–1, respectively), in spite of markedlychanging fecundity. There was no apparent phase of decline orincrease that could be related to the distinct phases of lowor high fecundity resulting from different food levels. Analysisof the gut contents of roach (Rutilus rutilus), the dominantplanktivore in the three lakes, revealed identical selectivityfor each of the two Daphnia species, suggesting that the lowerdensity of the D.hyalina population was compensated for by thegreater conspicuousness of individuals of this species. It isconcluded that the population density of these Daphnia speciesremains far below the carrying capacity of the habitat and doesnot depend on food levels. Food availability merely sets therate of population increase, while the actual population densityin the lakes studied reflects the species' vulnerability topredation by planktivorous fish.     

Significant correlation of Cd,Cu, Pb and Zn in sediments and oysters (Saccostrea cucullata) collected from Qeshm Island,Persian Gulf,Iran

Abstract

The relationships are evaluated between the heavy metal species in sediments and the accumulation by the soft tissues of Saccostrea cucullata collected from the northern and southern coasts of Qeshm Island, Persian Gulf. The sequential extraction technique was employed to fractionate the sediment into non resistant and resistant fractions. Data from sequential extractions indicated that the metals were mainly associated with the residual fraction at the north coast and with non residual fractions at the south coast. The results showed that the best correlations were observed between heavy metals concentrations in soft tissues and the fractions in the southern sediment. Note that the bioavailability of trace metals is influenced by the chemical characteristics and properties of the sediment. Therefore, the present results generally supported the use of soft tissues of S. cucullata as a more accurate biomonitoring organism for Cu, Pb and Cd in sediments from the southern coast of Qeshm Island, Persian Gulf.     

THE SYSTEMATIC POSITION OF LAROCHEA FINLAY, 1927, AND INTRODUCTION OF A NEW GENUS AND TWO NEW SPECIES (GASTROPODA: SCISSURELLIDAE)

Species of the gastropod genus Larochea Finlay, 1927 are shownto be scissurellids without an anal shell slit or foramen. TheNew Zealand species, L. miranda Finlay, 1927 and L. secundaPowell, 1937, brood their young in the right subpallial cavityagainst a modified inner lip that is set well behind the aperturalplane. Larochea scitula n.sp. is based on shells from WanganellaBank, southern Norfolk Ridge. Larocheopsis n. gen. is introducedfor a minute species from off northern New Zealand that lacksa shell brood chamber. Larochea miranda and Larocheopsis amplexan.sp. are either gonochoristic with smaller males or consecutivehermaphrodites, while Larochea secunda and L. scitula are evidentlygonochoristic, having mature males and females of similar size. (Received 23 July 1992; accepted 10 December 1992)     

Daphnia invasion: population dynamics of Daphnia assemblages in two eutrophic lakes with particular reference to the introduced alien Daphnia ambigua

The population dynamics of Daphnia species (D.cucullata, D.ambigua,D.galeata) in two small, productive lakes were studied and experimentswith field enclosures were carried out to elucidate the ecologicalniches of the introduced, alien species D.ambigua. Daphnia ambiguocoexisted temporally with the similarly sized D.cucullata, butlived in deeper water. Although both species had the same clutchsizes, similar proportions of ovigerous females, and death rates.D.cucullata was nurnerically dominant over D.ambigua. This suggeststhat the observed difference in abundance is simply a resultof the slower population growth rates of D.ambigua at lowertemperatures in greater depths. The experiments with field enclosuresshowed that when D.culcullata and D.ambigua were forced to livein the same layer of water, D.ambigua was numerically dominantover D.culullata both in the enclosures with and without fish.As the difference between the abundances of the two speciesdecreased in the enclosure with fish, D.cucullata seems to bebetter protected against fish predation than D.ambigua. In theenclosures without fish, D.ambigua and D.cucullata were numericallysurpassed by the larger species D.galeara. The present resultsimply that in some productive lakes with a high fish stock,D.mbigua invaded the niche of D.galeara and that the speciescan become an important component of the native zooplankton.The results also support the opinion that co-existing Daphniacan have very similar dynamics and niches. ¹ Present address: Zoologisches Institut, Christian-Albrechts-UniversitätKiel, Olshausenstrasse 40, D-24098 Kiel, FRG     

Resource depression in Daphnia galeata, Daphnia cucullata and their interspecific hybrid: life history consequences

In this study, the effect of the food concentration on severallife history parameters of Daphnia galeata, Daphnia cucullataand the hybrid between these two species was examined. The foodconcentration had a significant effect on both growth and reproductionof all three taxa. Mortality was highly species specific, andto a lesser extent dependent on the food concentration. Changesin life history parameters resulted in changes in the intrinsicrate of population increase (r). The food dependence of thedifferent species was found to be different. Daphnia cucullatahad a relatively constant and low r. The r values for the hybridvaried most, with low values compared with the parental specieswhen grown at low food levels and relatively high values athigher food concentrations. Our results suggest that when foodconcentrations are high the hybrid will have a selective advantageover both parental species, but that at lower food levels D.galeatawill have an advantage over both D.cucullata and the hybrid.     

Sphagnum divinum (sp. nov.) and S. medium Limpr. and their relationship to S. magellanicum Brid.

Sphagnum magellanicum has been viewed as being a predominantly circumpolar species in the northern hemisphere, but it occurs in the southern hemisphere and was originally described from the southern parts of Chile. It is an ecologically important species in mire ecosystems and has been extensively used as a model to study processes of growth, carbon sequestration and peat decomposition. Molecular and experimental studies have, however, revealed genetic structure within S. magellanicum, and morphological differences associated with these genetic groups. Here we describe Sphagnum divinum in Sphagnum subgenus Sphagnum (Sphagnaceae, Bryophyta) as a new species, based on molecular and morphological evidence. Sphagnum medium is reinstated as a distinct species and is epitypified. Consequently, a new species concept of S. magellanicum is presented including an epitypification. Important morphological characters to separate these three species in the field and under the microscope are presented. Ecology and distribution differ among the species; S. divinium has a wide habitat range including mire margin, forested peatlands and moist heaths, and a circumpolar distribution around the northern hemisphere. Sphagnum medium seems to be more restricted to ombrotrophic mire expanse habitats and shows an amphi-Atlantic distribution in the northern hemisphere. Sphagnum magellanicum has a very broad ecological niche in peatlands and is found in most mire habitats in Tierra del Fuego on the southern tip of South America.     

Electrophoretic analysis of populations of the southern hemisphere lampreys Geotria australis and Mordacia mordax

Electrophoretic data for 15 enzymes encoded by 18 loci were analysed in samples of larval lampreys from two southern hemisphere species (Geotria australis and Mordacia mordax). Low values for Nei genetic distance coefficients for all loci in populations of G. australis from Western Australia, Tasmania and New Zealand (0.0013 to 0.0058) suggest that adults may intermix over distances greater than 4000 km. The average heterozygosity for four populations of G. australis (0.086) was much greater than for two populations of the far less widely distributed M. mordax (0.021).     

Amphitropical disjunctive species in the complex thalloid liverworts (Marchantiidae)

Plant disjunctions between the temperate regions of the northern and southern hemisphere, commonly called amphitropical or bipolar disjunctions, have been discussed by numerous authors but very little attention has been paid to the occurrence of such disjunctive ranges in the complex thalloids (Marchantiidae). A perusal of the literature revealed 20 species of Marchantiidae with amphitropical ranges, in eight genera (Asterella, Clevea, Corsinia, Cryptomitrium, Oxymitra, Riccia, Riella and Sphaerocarpos). These amphitropical species are distributed in subtropical and Mediterranean regions of the northern and southern hemisphere but not, or rarely, in the tropics. The majority are disjunctive between North America and southern South America and between Eurasia and South Africa. Long-distance dispersal of spores via birds is considered the most plausible natural cause of these amphitropical ranges. About two-third of the species have bisexual spores, which should be advantageous to long-distance dispersal. Extinction due to past climatic fluctuations may also have played a role but fossil evidence is lacking. A few species have attained their amphitropical range by human-mediated introduction: Riccia warnstorfii Limpr. and Sphaerocarpos texanus Austin were presumably introduced in the southern hemisphere whereas S. stipitatus Bisch. ex Lindenb. from Central Chile and South Africa is adventive in the northern hemisphere. The amphitropical ranges exhibited by a number of complex thalloid species are solely based on morphological, floristic and ecological evidence and have not been tested by molecular analysis. Careful comparisons of the northern and southern populations based on an integrated molecular-phylogenetic, morphological-anatomical and chemical approach should be carried out.     

Gymnomitrion crenulatum und Verwandte

Abstract

All the southern hemisphere records of the European species of Gymnomitrion are rejected. Crenarion, sect.nov., is proposed. It is restricted to the northern hemisphere and comprises G. crenulatum (temperate eu-Atlantic coast of Europe), G. sinense (Yunnan, Nepal) and G. pacificum, sp.nov. (boreal Pacific coast of North America, central Japan). These three species are figured and described in detail. Gymnomitrion verrucosum is transferred to Marsupella.     

Instar-dependent mortality rates of coexisting Daphnia species in Lake Vechten, The Netherlands

In Lake Vechten, population parameters were determined for twocoexisting Daphnia species, D.hyalina and D.cucullata, fromApril 23 to December 10, 1986. Daphnia hyalina is dominant inspring and D.cucullata in summer and autumn. Size frequencydistributions were converted into instar frequency distributionsby using experimental growth curves and field measurements onnewborn size and the size at first reproduction. A discreteevent computer model was used to calculate the instar mortalityrates. Relative importances of instar mortality rates for thepopulation mortality rate were calculated and discussed. Themortality of the juvenile stages was found to be more importantthan adult mortality during most of the sampling season, despiteegg mortality when egg-bearing females are killed. Only in Septemberand October was the mortality of adult instars more important.Correlation coefficients between differences in the rates ofincrease and differences in mean brood size and instar mortalitiesshow that the former are caused mainly by differences in juvenilemortality, the main factor determining the replacement of D.hyalinaby D.cucullata during early summer.     

THE ANATOMY AND RELATIONSHIPS OF A MARINE VALVATOIDEAN (GASTROPODA: HETEROBRANCHIA)

The anatomy of Cornirostra (new genus) pellucida (Laseron),a marine Indo-West Pacific gastropod, is described and is shownto be similar to that of the northern hemisphere, freshwaterValvatidae. There are, however, several differences betweenCornirostra and valvatids, notably in details of the anatomyof the reproductive system, the morphology of the head-foot,the spawn and in radular characters that warrant family-levelseparation for Cornirostra. Tomura bicaudata (Pilsbry and McGinty) from Florida is alsoa member of the family. (Received 9 September 1989; accepted 30 December 1989)     

Shell growth, reproduction and mortality of Ovula ovum in southern Kyushu, Japan

Seasonal shell growth, reproduction and mortality of the eggcowry Ovula ovum were studied from May 2004 to October 2006in southern Kyushu, Japan, an area at the northern margin ofits geographic distribution. Rapid shell growth was observedduring the period of warmer ocean temperature (May–October).Average shell growth rate of small cowries was 2.84 mm/week.Reproductive activities were observed during most of the yearexcept during the coldest period (March–April). Egg cowriesreach maturity at approximately 7 cm in shell length, and at1 year of age. Average shell length of brooding females andcopulating pairs (female and male) were 8.14 ± 0.40,8.17 ± 0.49 and 8.08 ± 0.43 cm (mean ±SE), respectively. High mortality rates (average 67.5%) wereobserved from December to May. The maximum numbers of emptyshells in the field (April 2005, May 2006) were seen duringthe period of the lowest ocean temperatures (March 24, 2005;March 7, 2006). This suggests that ocean temperature may bean important factor for egg cowry populations at the northernmargins of their geographical distribution, and that O. ovummay increase fitness with rapid shell growth and early age ofmaturation. (Received 11 January 2008; accepted 22 August 2008)     

Repartition des Appendiculaires au large des cotes de Californie

Twenty-seven taxa of appendicularians have been identified fromthe cruise CALCOFI n° 7202 and their distribution has beenstudied by various numerical methods, with the purpose of definingsimultaneously the groups of associated species and the groupsof stations possessing similar characteristics. Two large recurrentgroups have been defined by the method of Fager and McGowan,corresponding approximatively to the major water masses present:central Pacific waters and equatorial Pacific waters. The methodof Williams and Lambert permits the separation of 11 southernstations and a northern group divided into 2 subgroups dependingon the presence or absence of O. dioica. The rank correlationsgive results very similar to those obtained with point correlations.Finally, principal component analysis allow good separationof the northern and southern zones by the factorial plan 1–3,while representation of the stations by the factorial plan 2–3separates the two northern subgroups depending on the presenceor absence of O. dioica. The results obtained by the differentmethods are therefore very much alike, but it is difficult toconclude they are a result of the specific cruise, or whetherthey represent a general phenomenon.     

Atebbania Bernasconii, a New Genus and Species from Subterranean Waters of the Tiznit Plain, Southern Morocco (Gastropoda: Hydrobiidae)

The new genus Atebbania is described for a new hydrobiid species,A. bernasconii, which lives in groundwaters of southern Morocco.Of the Hydrobiidae genera with known shell and anatomy Moitessieriais the closest to Atebbania. The two share the following characters:shell elongate; teleoconch surface with evident microsculpture;seminal receptacle absent. Atebbania is distinguished from Moitessieriaby: shell ovate; penis with a) apical stylet, b) one lobe bentdownward on left (inner) side and c) penial duct running nearthe right (outer) side; posterior end of foot indented. Atebbaniabernasconii n. sp., lives in a limited area, the Tiznit plainin southern Morocco. Other stygobiont hydrobiids from otherareas of Morocco are currently being studied. None of them appearsto be closely related to A. bernasconii or to the species ofMoitessieria (Received 10 February 1998; accepted 30 April 1998)     

THE OCCURRENCE OF THE UPPER JURASSIC BIVALVE MALAYOMAORICA MALAYOMAORICA (KRUMBECK) ON THE ORVILLE COAST, ANTARCTICA

Malayomaorica malayomaorica is an important Upper Jurassic bivalvein the southern hemisphere: widely distributed in strata ofEarly - Middle Kimmeridgian age, it is a zone fossil of considerablepotential for regional biostratigraphic correlations. Its commonoccurrence in the Latady Formation of the Orville Coast, Antarctica,indicates that at least part of this stratigraphic unit hasa Kimmeridgian age. Although its precise taxonomic status remainsin some doubt, it would appear to be the earliest buchiid-likebivalve so far recorded from the southern hemisphere. Its verywide distribution around the margins of Gondwana is similarto that established for species of the Late Jurassic bivalvegenera Retroceramus, Buchia and Anopaea (Received 13 April 1981;