A NEW SPECIES OF THE AEOLID GENUS FLABELLINA (NUDIBRANCHIA) FROM THE STRAIT OF GIBRALTAR

A new species of nudibranch, Flabellina insolita, is describedfrom specimens from the Strait of Gibraltar. The new speciesis assigned to the genus Flabellina on the basis of the jaws,radula and reproductive system, despite the shape of the rhinophoresand oral tentacles and the presence of small papillae flankingthe pericardium and small laminar enlargements on the dorsalsurface of the body. These features separate this species fromother aeolids. (Received 14 June 1988; accepted 19 August 1988)     

Computer-based 3-dimensional reconstruction of major organ systems of a new aeolid nudibranch subspecies, Flabellina engeli lucianae, from Brazil (Gastropoda: Opisthobranchia)

Obtaining accurate and comprehensive anatomical informationfrom small opisthobranch specimens has been a major problem.Computer-based 3-dimensional reconstruction from serial histologicalslides applying AMIRA (TGS Graphics) software is shown to bean efficient and fully reproducible way to analyse tiny andcomplex organ systems in their true relative positions and proportions;this method is herein applied to nudibranchs for the first time.We used Flabellina engeli lucianae n. subsp., a small aeolid(up to 8 mm body preserved length) from subtropical southernBrazil, to illustrate all major organ systems including nervoussystems, and discuss them comparatively. Flabellina engeli lucianaediffers externally from congeners by having a translucent bodywith opaque white and iridescent blue spots, orange ceratalbands, and by the special branching of cerata forming distinctgroups on common peduncles. External and internal differencesfrom the apparently geographically and hydrographically separatedCaribbean specimens of F. engeli engeli Marcus & Marcus,1968 are discussed in detail. (Received 9 January 2006; accepted 10 July 2007)     

EASTERN MEDITERRANEAN OPISTHOBRANCHIA: DOTIDAE (DENDRONOTOIDEA), ARMINIDAE AND MADRELLIDAE (ARMINOIDEA)

An account is given of Doto, Armina and Madrella species collectedon diving and dredging expeditions to the Ligurian, Tyrrhenian,Adriatic, Ionian and Aegean Seas during the period 1973–1988,supplemented by material collected around Naples (southern Italy)and Banyuls (French Côte Vermeille). In all, 5 speciesof Doto, 3 of Armina and 1 of Madrella were investigated, yielding5 new records for the eastern Mediterranean Sea and one speciesnew to science, Armina tricuspidata from the Tyrrhenian Sea.The common arminid on the American coast from North Carolinato Texas is not A. tigrina as claimed by Abbott(1954) and byEyster (1981), but is a new species, for which we propose thename Armina abbotti. Consideration of world-wide records of Madrella leads to theconclusion that the senior Madrella sanguinea Angas, 1864, embracesM. ferruginosa Alder & Hancock, 1864, M. aurantiace Vayssière,1903 and M. granularis Baba, 1949 (but not the Japanese M. gloriosaBaba, 1949, which is probably distinct). ^*T.E. Thompson died in a car accident 1 January 1990. (Received 2 May 1989; accepted 4 November 1989)     

PROTECTIVE-COMMENSAL MUTUALISM BETWEEN THE QUEEN SCALLOP CHLAMYS OPERCULARIS(LINNAEUS) AND THE ENCRUSTING SPONGE SUBERITES

The relationship between the two encrusting sponges, Suberitesrubrus (Sole-cava & Thorpe, 1986) and Sub-erites luridus(Sole-cava & Thorpe, 1986) and the pectinid bivalve molluscChlamys opercularis (Linnaeus) was shown to be a protective-commensalmutualism. The sponge protected the scallop from asteroid predation(Asterias rubens, L.) probably by reducing their tube-feet adhesionand also by excluding the settlement of other taxa likely tohinder the scallop's mobility. The sponge benefited in turnby protection from predation by the nudibranch Archidoris pseudoargus(Pallas) and more generally from transport to favourable locations. Both Asterias and Archidoris were frequently observed movingdirectly towards their prey, possibly indicating chemotaxicmechanisms. Yet, the sponges did not appear to confer any chemicalprotection to the scallop from asteroid attack. Similarly theliving scallop conferred no chemical protection to the sponge. (Received 12 December 1990; accepted 24 September 1991)     

MORPHOLOGY OF THE MATURE SPERMATOZOON OF PHYSA ACUTA (DRAPARNAUD, 1801) (GASTROPODA: PHYSIDAE)

The morphology of the spermatozoon of Physa acuta (Draparnaud,1801) was examined using TEM. It was found to be of the modified-type,sharing characteristic features of other basommatophoran species.However, differences were noted in some cases, for example,in P. acuta the nucleus was torpedo-shaped with two helicalkeels, the midpiece possessed a maximum of three glycogen helices,the end piece was long and tapered and the total length of thespermatozoon was 365 µm. No identical spermatozoa havebeen found in other basommatophoran gastropods studied so far.If spermatozoon morphology is unique for individual specieswithin the genus Physa, it may provide a useful taxonomic toolin helping to clarify the uncertainty that surrounds the systematicsof this genus. (Received 26 February 1990; accepted 28 June 1990)     

THE BIOLOGY AND FUNCTIONAL MORPHOLOGY OF MYTILOPSIS SALLEI (RECLUZ) (BIVALVIA: DREISSENACEA) FOULING VISAKHAPATNAM HARBOUR, ANDHRA PRADESH, INDIA

Mytilopsis sallei (Récluz) (Dreissenacea) has been introducedinto Visakhapatnam harbour, India. The normal distribution ofthe species is Central America and it is here contended thatthe species has been introduced into the Indo-Pacific via thePanama canal (opened in 1915) attached to the hulls of ships.M. allyneana (Hertlein & Hanna) with a distribution restrictedto Fiji is considered synonymous with M. sallei. The literature on M. sallei is reviewed and it is shown thatthe species has wide temperature, salinity and oxygen tolerancesand thus transport across a variety of water masses is entirelyfeasible. The species also possesses a fast rate of growth,a high fecundity and matures early. It is an opportunistic specieswhich free from the restraints that normally hold it in checkin its natural environment, poses a serious fouling threat toharbours throughout the Indo-Pacific and to the endemic fauna. The morphological adaptations of M. sallei are also describedand compared with those of Dreissena polymorpha (Pallas) inparticular and other fouling bivalves in general. The speciesis ideally adapted to life in turbid estuaries experiencingwide variations in temperature, salinity, oxygen and turbulence.A warning against further introductions is given. (Received 14 December 1979;     

ALLOZYME VARIATION IN SOME POPULATIONS OF THE FRESHWATER SNAILS LYMNAEA PEREGRA, L. AURICULARIA AND L. STAGNALIS (GASTROPODA: PULMONATA)

Three species of the genus Lymnaea (Gastropoda, Pulmonata, Basommatophora)were examined for genetic variation at 11 enzymatic loci insamples collected in Brittany (North-Western France). Variabilitywas greatest in L. percgra, but the limited area of samplingdid not allow specific inferences. The UPGMA clustering of unbiasedgenetic distances (Nei, 1978) isolated first L. auriculariasamples, and secondly the single L. stagnalis sample from theL. peregra set. This scheme of relationships was opposed tothe identification of alleles shared by the three species atthe studied loci Analysis of L. peregra population structure by F-statistics(Weir & Cockerham, 1984) suggested high inbreeding and raisedthe possible role of self-fertilization. The contradiction betweenhigh variability and high homozygosity is discussed. Furthermore,population differentiation was rather weak (although statisticallysignificant), despite some remarkable differences among loci.Nm estimates using Wright's (1951) and Slatkin's (1985) methodsrevealed a gene flow unable to prevent the effect of geneticdrift among populations. The relative homogeneity of populationswith weak genetic exchange is discussed (Received 24 May 1993; accepted 21 March 1994)     

EASTERN MEDITERRANEAN OPISTHOBRANCHIA: OXYNOIDAE, POLYBRANCHHDAE, STILIGERIDAE (SACOGLOSSA)

An account is given of the ceratiform sacoglossans collectedon diving expeditions to the Mediterranean shores of Yugoslaviaand Greece during the period 1978–86. Six species aredescribed, two of which, Cyerce graeca and Hermaea (Placida)saronica, are new to science; four of the six represent additionsor new records for the eastern Mediterranean (Received 20 July 1987;     

EASTERN MEDITERRANEAN OPISTHOBRANCHIA: ELYSIIDAE (SACOGLOSSA = ASCOGLOSSA)

An account is given of the elysiid sacoglossans collected ondiving expeditions to the eastern Mediterranean shores of Yugoslaviaand Greece during the period 1978–1986, supplemented bymaterial collected around Naples and some preserved specimensfrom other Mediterranean localities. In all, 6 species of Elysiaand 1 of Bosellia were investigated, including one new to science,E. gordanae from the Yugoslav Istrian Peninsula. The enigmaticElysia translucens Pruvot-Fol, 1957 was found in the easternbasin for the first time. The presence of the Bermudan, CanaryIslands and Jamaican E. flava Verrill, 1901 was confirmed inthe Greek Ionian and Aegean Seas, as well as in the Gulf ofCorinth. The geographical ranges of the other species were extendedby these collections from the eastern basin. The 7 elysiid specieswere illustrated from life and the radulae compared; great differencesin the size, shape and denticulation of the teeth of the differentspecies were evident (Received 8 May 1987;     

REVISION OF THE GENUS NAPAEUS ALBERS, 1850 (GASTROPODA PULMONATA: ENIDAE). THE PROBLEM OF NAPAEUS (NAPAEINUS) NANODES (SHUTTLEWORTH, 1852) AND DESCRIPTION OF FIVE NEW SPECIES FROM ITS CONCHOLOGICAL GROUP

With this paper we initiate a taxonomic review of the genusNapaeus from the Canary Islands, indicating the statisticalmethodology used therein. We discuss the taxonomic problem ofNapaeus (Napaeinus) nanodes (Shuttleworth, 1852), designateits lectotype and describe five new species: Napaeus (Napaeinus)doliolum Henríquez, Napaeus (Napaeinus) bechi Alonso& Ibáñez, Napaeus (Napaeus) taguluchensisHenríquez, Napaeus (Napaeus) pygmaeus Ibáñez& Alonso and Napaeus (Napaeus) tagamichensis Henríquez,the first two from Tenerife; and the other three from La Gomera.Furthermore, we discuss the general relationships of the genusand its two sub-genera, whose original diagnoses are deficient;because of this, we think that in the future a broad reviewof the subfamily Eninae will be necessary in order to clarifythe actual position of this subfamily in the Canary Islands. (Received 11 March 1991; accepted 22 September 1992)     

PAGODATROCHUS, A NEW GENUS FOR MINOLIA VARIABILIS H. ADAMS, 1873 (GASTROPODA: TROCHIDAE)

Nomenclaturel confusion surrounding the name Minolia variabilisH. Adams, 1873 is clarified. Joint consideration of overallshell morphology and radula structure indicates previous subfamilialand generic referral of the taxon to be incorrect. This necessitatesthe proposal of Pagodatrochus gen. nov. which is provisionallyplaced in the Gibbulinae. Trochus mariei Fischer, 1886, andMinolia eutyches Melvill, 1918, are shown to be synonyms. Lectotypesof the following species are designated and figured: M. eutyches,Gibbula holdsworthana G. & H. Nevill, 1871, and Vanitrochustragema (Melvill & Standen, 1896); the holotype of Trochusmariei is also figured. Minolia charmosyne Melvill, 1918, issynonymised with Gibbula holdsworthana G. & H. Nevill, 1871. (Received 24 April 1988; accepted 26 May 1988)     

Phylogeography of the Wabash pigtoe, Fusconaia flava (Rafinesque, 1820) (Bivalvia: Unionidae)

Reconstructing the phylogeographic patterns of widely distributedand common freshwater mussel species (Bivalvia: Unionidae) mayprovide insight into unionid evolution and speciation. The Wabashpigtoe, Fusconaia flava, is currently recognized as a single,polytypic species that is widely distributed and common throughoutthe Mississippi River drainage and parts of the Canadian Interior,Great Lakes and Gulf Coast drainages. Sequence analysis of themitochondrial COI gene revealed two divergent (3.43%) clades.Clade A consisted of specimens located throughout the upperand lower Mississippi River drainage and in the Red River (Canada)and Lake Erie drainages and all F. cerina specimens. All haplotypeswithin clade A differed by three (0.55%) or fewer nucleotidesubstitutions from the most widely distributed and abundanthaplotype, F1. Clade B, consisting of specimens located in thefar western portion of the species' range, may comprise an undescribedspecies. There was no evidence of genetic differentiation amongF. flava inhabiting headwater and intermediate-sized river localitiesof the Muskingum River system and large river localities ofthe nearby Ohio River. The divergence among F. flava haplotypescomprising clade A (0.18–1.10%) was similar to the divergencebetween the F. cerina haplotypes and the F. flava haplotypescomprising clade A (0–1.10%). This study illustrates theimportance of accessing genetic diversity across the distributionof a polytypic species. Additional analyses based on a combinationof morphology and genetics are needed to determine the taxonomicstatus of clade B and to strengthen our understanding of therelationship between F. flava and F. cerina. (Received 28 May 2007; accepted 13 August 2007)     

SPERMOGENESIS AND SPERM STRUCTURE IN THREE SPECIES OF PATELLOIDA AND ONE SPECIES OF NIPPONACMAEA (PATELLOGASTROPODA: ACMAEOIDEA)

The spermatozoa of Patelloida profunda albonotata, P. saccharina,P. pygmaea and Nipponacmaea schrenkii (Lottiidae) are describedby transmission electron microscopy. All have ect-aquasperm,typical of invertebrates using external fertilization. The spermof all four species have a cylindrical nucleus (length: breadth> 4: 1 in P. p. albonotata and P. saccharina; <4: 1 inP. pygmaea and N. schrenkii) which tapers towards the roundedanterior end. All have an acrosome with a posterior acrosomallobe which extends into the centre of the subacrosomal space.In P. p. albonotata and P. saccharina the acrosomal contentsare undifferentiated and the posterior lobe extends to the nucleus,being separated from it by flocculent material. In P. pygmaeathe acrosomal contents are differentiated, the lobe is relativelyshort and the subacrosomal space is filled with material witha fibrous appearance. The acrosome of N. schrenkii is undifferentiatedand the posterior lobe is no more than a bulge. The sperm ofP. p. albonotata and N. sacchrina have a small (0.25 µmlong) cytoplasmic collar which surrounds the axoneme anteriorlywhereas in P. pygmaea and N. schrenkii the cytoplasmic collaris longer (1 µm) and is swollen by an electron-dense vesicle.The composition and function of this vesicle is unknown. Thespermatozoa of Patelloida and Nipponacmaea have structural featureswhich are similar to sperm of the Lottiidae providing some supportfor the placement of these genera in the Lottiidae as proposedby Lindberg & Hedegaard (1996) and Sasaki & Okutani(1993) respectively. The similarities of the sperm of P. pygmaeato N.schrenkii raise some doubts about the tax-onomic statusof the former species. Spermiogenesis in all four species issimilar to that described for other Acmaeoidea and Patelloidea.In P. pygmaea and N. schrenkii, however, in addition to theacrosomal vesicle, the Golgi body produces a number of electron-densevesicles which fuse and eventually form a single vesicle inthe collar of the mid-piece. (Received 24 October 1996; accepted 10 February 1997)     

SPERM ULTRASTRUCTURE IN THE AUSTRALIAN OYSTER SACCOSTREA COMMERCIALIS (IREDALE & ROUGHLEY) (BIVALVIA: OSTREOIDEA)

Sperm ultrastructurc is investigated in the economically importantAustralian oyster Saccostrea commercialis (Iredale & Roughley).Mature spermatozoa consist of a broad, cap-shaped acrosomalvesicle, sub-acrosomal material (axial rod embedded in a granularmatrix), a round nucleus (deeply invaginated anteriorly), twotriplet substructure centrioles surrounded by four sphericalmitochondria, and a flagellum anchored via satellite fibresto the distal centriole and plasma membrane. Spermatozoa ofS. commercialis closely resemble those of other investigatedostreids, with the exception that the anterior region of theacrosomal vesicle is transversely banded. Differences in acrosomalsubstructure correlate with the known inability of Saccostreaand Crassostrea gametes to interact. Potential exists for useof sperm morphology in the resolution of taxonomic problemswithin the Ostreoidea. (Received 23 April 1990; accepted 28 June 1990)