CALCIUM PHOSPHATE GRANULES IN THE HEPATOPANCREAS OF THE BLUE CRAB CALLINECTES SAPIDUS

The hepatopancreas of the adult male blue crab Callinectes sapidus in intermolt was found to contain substantial amounts of calcium, magnesium, and inorganic phosphorus, averaging about 260, 20, and 250 µg-atoms per g wet tissue, respectively, accounting for over 10% of the tissue dry weight. Electron microscopy of the intact tissue showed three qualitatively different granular structures having electron densities suggestive of high mineral content. After fractionation of the tissue using centrifugal techniques, almost 95% of the total mineral was found to reside in a heavy, nonmitochondrial particulate fraction(s). The bulk of the low-speed pellet consisted of relatively dense, roughly spherical granules 1–5 µm in diameter, which could be considerably purified by repeated suspension in water and low-speed sedimentation. In the electron microscope the isolated granules appeared basically similar to one of the three characteristic types of electron-dense granules seen in the intact tissue. Although the freshly isolated granules lost approximately 50% of their wet weight when dried at 105°C, only 10% more was lost upon dry ashing at 450°C, suggesting a fairly low content of organic material. Chemical analysis revealed calcium, magnesium, and inorganic phosphate at 5.7, 2.1, and 4.4 µg-atoms per mg dried granules, respectively, accounting for 69% of the dry weight of the fraction. By specific enzymatic assays, the freshly isolated granules were found to contain ATP, ADP, and AMP at levels of 0.13, 0.03, and 0.01 µmol/mg, or 8% of their total dry weight. The remainder of the total phosphorus contributed an additional 3%, whereas carbonate, citrate, oxalate, and protein each constituted no more than 1%. The mineral granules of the crab hepatopancreas appear to function as storage forms of calcium and phosphate during the intermolt period. This tissue appears promising as a model for study of the cellular events associated with biological calcification, since conventional biochemical techniques can be employed. Furthermore, the major mineralized component of the tissue can be obtained in large amounts for direct study by a simple fractionation procedure.     

ONTOGENY OF THE PSEUDOHERMAPHRODITIC REPRODUCTIVE SYSTEM IN NASSARIUS VIBEX (GASTROPODA: BUCCINIDAE: NASSARIINAE)

Pseudohermaphroditism or imposex is an abnormality of the gastropodreproductive system caused by the effects of an environmentalpollutant, tributyltin, in which parts of the male reproductivetract develop in females. In this study, the post-larval developmentof the reproductive system in pseudohermaphroditic male andfemale Nassarius vibex was investigated relative to normal developmentto determine how and when the abnormalities associated withpseudohermaphroditism develop. Two populations of N. vibex were compared:one exhibiting normal development, and one in which the animalswere effected by pseudohermaphroditism. In the affected N. vibexpopulation, a penis and anterior spermiduct developed very earlyin ontogeny in both males and females. Normal reproductive systemdevelopment was affected in some females, evidenced by fusion ofthe induced spermiduct and anterior oviduct, or by abnormaloviduct development. Several males displayed precocious maturationof the gonad in addition to early development of the anteriorspermiduct and penis. (Received 25 April 2000; accepted 1 July 2000)     

THE STRUCTURE OF THE SECONDARY GILLS OF SIPHONARIA CAPENSIS (GASTROPODA: PULMONATA)

The secondary gill of the pulmonate limpet Siphonaria capensisis located in the dorsal portion of the mantle cavity. Eachlamella of the gill is triangular in shape and bears ciliarytufts which have a density of about 400/mm². The free ends ofsome of the cilia are enlarged biconcave discs. Each gill lamellais covered by a single layer of cuboidal (4x4 µm) epitheliumon each side, separated by a central haemocoelic space. Ciliatedand mucus secreting cells are interspersed amongst the epithelialcells. The haemocoelic space is spanned at intervals by trabeculaecontaining longitudinal and transverse muscle fibres. (Received 29 August 1986;     

A REVIEW OF LARVAL DEVELOPMENT IN THE INTERTIDAL LIMPET GENUS SIPHONARIA (GASTROPODA: PULMONATA)

A compilation of distributional and life-history data relatingto mode of larval development is presented for 26 species ofSiphonana, a genus of intertidal pulmonates. Most species depositgelatinous benthic egg masses with two species releasing pelagicegg masses. Fifteen species hatch as planktonic-developing larvae,nine hatch as direct-developing juveniles, and in a furthertwo larvae hatch with both the swimming velar apparatus (associatedwith plank-tonic development) and a crawling foot (associatedwith direct development). Data on mode of larval developmentare interpreted with respect to some adaptive models. Despiteimportant exceptions, there is support for adaptive models basedupon egg capsule size (direct developers hatch from larger eggcapsules) and intertidal distribution (direct developers generallyoccur higher on the shore than planktonic developers). Worldwide,planktonic developers are more widespread than direct-developingspecies, and individual planktonic species have a greater meanlatitudinal range. The evidence for adaptive models relatinglatitudinal distribution to developmental mode is equivocal.There appears to be no clear relationship between body sizeand developmental mode in the genus, although the smallest specieshas direct development and the largest has planktonic development.In most siphonariid subgenera, developmental mode appears tobe constant, but two subgenera contain a mixture of developmentaltypes (Received 1 November 1993; accepted 15 April 1994)     

GEOGRAPHICAL PATTERNS OF GENETIC DIFFERENTIATION IN THE LANDSNAIL HELIX ASPERSA MuLLER (GASTROPODA: PULMONATA)

In order to investigate the initial processes responsible forthe geographical distribution of the Mediterranean landsnailHelix aspersa, populations from 64 locations in Maghreb andin Europe were studied at 17 enzyme loci by both starch andpolyacrylamide gel electrophoresis. Allele frequencies and genotypedistributions were analysed to provide information on populationstructure and genetic differentiation among populations. Valuesof Nei's unbiased (D) and Rogers (R) genetic distances led tothe formation of two main groups, namely Europe-west Algeriaand east Maghreb (average D = 0.182). Such splitting supportedthe pattern of anatomical variation recently described. Twosamples from Morocco were excluded from these groups becauseof an average D = 0.224. Within this Moroccan entity, geneticdivergences did not distinguish the ‘giant’ snailsH. a.maxima from the brownsnails H. a. aspersa. Such biochemicalsimilarities among morphological heterogeneity throws the subspecificstatus of H. a. maxima into question. Values of fixation indicesindicated that the greatest differentiation between samplesoccurred on the Maghreb territory ( = 0.393). The patterns of population differentiation are discussed inrelation to past geological and historical events. Thus, threescenarios, not mutually exclusive, are considered: the disjunctionof populations by plate tectonics during the Tertiary, the formationof geographically isolated populations during the Pleistoceneglacial/interglacial cycle and the possibility of human introductionas early as the Neolithic period. (Received 9 December 1992; accepted 11 November 1993)     

ANALYSIS OF REPRODUCTIVE SYSTEM ONTOGENY AND HOMOLOGY IN NASSARIUS VIBEX (GASTROPODA: BUCCINIDAE: NASSARIINAE)

The post-larval development of the reproductive system in Nassariusvibex was investigated using a histological approach, to establishthe sequence of organogenesis and the contribution of differentorganogenetic components to the adult system. This researchis part of a broader investigation with two primary objectives.The first is to provide a detailed analysis of reproductivesystem development that can be used to re-evaluate existingcharacter sets and generate new characters for reconstructing gastropodphylogenies. The reproductive tract has always been a promisingbut problematic system to work with in phylogenetic research,because of the uncertain homology of many parts of the system.Most of the reproductive system itself develops during post-larvalontogeny, a phase of gastropod development that has been investigatedin very few taxa; thus this line of research has the potentialto provide a wealth of new information. The second objective isto establish comparable organogenetic series for representative gastropodtaxa that can be used to investigate the significance of heterochronicprocesses in the evolution of gastropod organ systems. The reproductive system in Nassarius vibex develops very latein ontogeny from two ontogenetic components in the male andthree in the female. Development and differentiation of theorgan system is not completed until near maturity. In both sexes,ductal components develop first and fuse to form the rudimentaryreproductive tract. Gonads and accessory reproductive structuresdevelop after the ductal components are fused, and glandulartissues do not appear until near maturity. The penis does notdevelop until near maturity. The capsule and albumen glandsin this species are broadly conjoined, unlike the situationin other members of Nassarius. The ingesting gland developsbetween them as a dorsal outgrowth of the glandular lumen. (Received 25 April 2000; accepted 1 July 2000)     

A NEW SPECIES OF OXYCHILUS FROM THE LIGURIAN APENNINES (ITALY) (PULMONATA: ZONITIDAE)

A new species of Oxychilus Fitzinger from the Ligurian Apennines(Italy) is described. The new species is particularly characterizedby its penial complex which has a very slender proximal peniswith variable inner sculpture and a widened distal penis. Theproximal penis inner structure consists of a series of longitudinalpleats which may often be crenulated, undulated or fragmentedto form rows of papillae, providing new evidence to supportthe opinion that this is not a valid diagnostic character forseparating Oxychilus into the nominal subgenus and OrtiziusForcart. Consequently Ortizius is herein proposed as a juniorsynonym of Oxychilus s. str. (Received 5 July 1990; accepted 4 March 1991)     

WATER-CONTENT OF SLUGS (GASTROPODA:PULMONATA) MAINTAINED IN STANDARDISED CULTURE CONDITIONS

A culture method for mass-rearing slugs is described and thewater-contents of 11 species of slug raised under these conditionsare analysed. The conclusion is drawn that, supplied with anappropriate environment, slugs showed no obvious rhythmic fluctuationsin hydration but exhibited water-contents relatively stablewithin species and presumably maintained by behavioural mechanisms. ^*Present address: Department of Zoology, East Mailing ResearchStation, Maidstone, Kent ME19 6BJ (Received 12 May 1981;     

POPULATION GENETICS OF LYMNAEA PEREGRA (MULLER) (GASTROPODA: PULMONATA) IN LAKE GENEVA

Using gel electrophoresis, a study was made of genetic exchangeamongst populations of Lymnaea peregra in Lake Geneva. Geneticvariability is high. A within-population heterozygote deficiencyis shown and the role of null alleles as an explanation of thisdeficiency is discussed. High values of gene flow show thatthe inter-population structure is weak. Exchange between populationspropably occurs by both active and passive means. (Received 9 January 1989; accepted 15 August 1989)     

EVOLUTION, DURING DIGESTION, OF THE BACTERIAL FLORA IN THE ALIMENTARY SYSTEM OF HELIX ASPERSA (GASTROPODA: PULMONATA): A SCANNING ELECTRON MICROSCOPE STUDY

The use of scanning electron microscopy (SEM) allowed a studyof the distribution of bacteria in the various digestive organsof the snail Helix aspersa Müller. The bacteria are enclosedby mucous secretions (mucous film or mucous grains) and sometimesattached on the cilia of some of the digestive walls. Accordingto the food that was given to the snails, different morphologicaltypes appeared, two of which dominated. Adult snails were fasted for 4 days, given a dehydrated artificialfood and then sacrificed at different times during digestion.The presence of bacteria may be related to the time of digestion.In fact, bacteria seem to accompany the food mass; they developmostly in the stomach and in the intestine where they may helpdigest the food. Fasting or hibernating snails do not possess bacteria in thealimentary lumen or on the digestive walls. However, the residualfaeces localized in the distal, intestinal lumen, lodge greatquantities of bacteria. From these results, the endogenous or/and exogenous existenceof the bacterial flora in alimentary system of Helix aspersais discussed. (Received 26 June 1989; accepted 16 October 1989)     

THE INFLUENCE OF INGESTIVE CONDITIONING ON FOOD CHOICES IN THE LAND SNAIL HELIX ASPERSAMULLER (GASTROPODA: PULMONATA: STYLOMMATOPHORA)

An experiment of food choice in one-day-old naïve landsnail Helix aspersa Müller was carried out, involving threephases. First, a training period on a monophagous diet of leafdiscs of Taraxacum officinale or Urtica dioica was given for1, 5, 10, 15 or 30 days. The area of leaf discs consumed byeach snail during this stage was assessed. In the intermediatephase, the animals were not fed for 24hours. Finally, food choicewas tested over 24 hours, when animals could eat leaf discsof each species of plant usedfor training. A coefficient offood preference for Urtica dioica was calculated (UPC = areaof Vrtica leaf disc consumed/area of Urtica and Taraxacum discsof leaves consumed for 24 hours). The length of the training phase did not reduce the percentageof individuals preferring the plant previously consumed. Onthe contrary, after 15 days of monophagous diet, animals formerlyfed on Urtica showed a coefficient of food preference for Urticasignificantly higher than Taraxacum fed animals, and after 30days of training this phenomenon was more pronounced. Thus,during the choice test, snails ate more of the previously eatenplant leaf. Our experiment highlighted the feeding behaviourplasticity of H. aspersa. The significant correlation betweenthe area of Urtica eaten during the training phase and the coefficientof food preference for Urtica is discussed. (Received 10 April 1994; accepted 10 January 1995)     

THE ROLE OF LYMNAEA AURICULARIA (LINNAEUS) AND LYMNAEA PEREGRA (MULLER) (GASTROPODA: PULMONATA) IN THE TRANSMISSION OF LARVAL DIGENEANS IN THE LOWER THAMES VALLEY

Eleven species of larval digeneans are reported for the firsttime in the UK from the freshwater snail Lymnaea (Radix) auricularia.The latter replaced its congener L. peregra in a gravel pitnear Wraysbury, Berkshire in the Lower Thames Valley and hostedan assemblage of larval digeneans similar to that previouslytransmitted by L peregra. The larval digeneans of L. peregrain small bodies of water in the area were also similar to thosefound in L. auriculania in the gravel pit. This replacementin the role of the host is explained on the basis of morphological,physiological and ecological similarities of the two lymnaeidspecies. (Received 19 February 1992; accepted 27 April 1992)     

STARVATION, DESICCATION AND USE OF ALLOSPERM IN THE HERMAPHRODITE FRESHWATER SNAIL BIOMPHALARIA GLABRATA (GASTROPODA: PULMONATA)

Pairs of albino and pigmented snails were used to test the hypothesisthat the hermaphrodite freshwater gastropod Biomphalaria glabratawas able to conserve and use allosperm, despite periods of desiccationand starvation. In laboratory experiments, lots of twenty snailswere subject to 0, 5, 10, 15 AND 20 days starvation; similarlots of 20 snails were subjected to 0, 2, 4, 6, 8, 10 weeksof desiccation at R.H. 100%. After all periods of starvationand desiccation, albino parents were still producing significantnumbers of pigmented offspring, suggesting preferential cross-fertilizationusing stored allosperm. (Received 30 September 1993; accepted 23 December 1993)     

THE ONCHIDIACEA (GASTROPODA, PULMONATA) OF HONG KONG WITH A WORLDWIDE REVIEW OF THE GENERA

The Onchidiacea are a superfamily of mainly marine intertidal,slug-like pulmonates. Twelve genera are recognizable, and theseare redefined. Four of these genera are represented in HongKong, each by a single species, and these are recorded herein.Two of these are new; a third has not been seen since it wasoriginally figured in 1850. ^*Present address: Palmers Sixth-Form College, Grays, Essex. (Received 18 August 1983;     

RELATIVE IMPORTANCE OF AIRBORNE ODOURS AND TRAILS IN THE GROUP HOMING OF LIMACUS FLAVUS (LINNAEUS) (GASTROPODA, PULMONATA)

The relative importance of airborne odours and con-specifictrails in the group homing of Limacus flavus has been studiedin the laboratory using an Y-olfac-tometer and trail followingtests. The slugs showed positive anemotaxis along air flowspassing through shelters inhabited or recently inhabited byconspecifics. In the choice between single and group shelters,the animals headed preferentially towards the latter ones. L.flavus is able to discriminate between conspecific and heterospecific(Limax maximus) shelters. Trail following tests failed to showsignificant trail superimposition, but did show a significantdeflection of the test slug path towards the marker after crossing.In direct comparison, distant chemoreception prevailed overtrail following in the orientation towards conspecifics (Received 10 August 1987;     

INFLUENCE OF THE QUINOLIZIDINE ALKALOID CONTENT OF LUPINUS ALBUS (FABACEAE) ON THE FEEDING CHOICE OF HELIX ASPERSA (GASTROPODA: PULMONATA)

Adult Helix aspersa snails were maintained individually forone week in plastic cages with 9 living Lupinus albus plantsas their only food. Among these 9 plants, 3 chemotypes bitter,intermediate and sweet which differed in their alkaloid contentwere equally represented. Each day, the leaf surface grazed and the number of leaves attackedby the snails were recorded for each chemotype and each snail.A consumption/ attack (C/A) ratio was calculated by dividing thesurface grazed (C) by the number of attacks (A). The numberof attacks and the grazed area were positively correlated foreach chemotype during the whole experiment, and the snails atesimilar quantities of lupin each day. After 4 and 6 days ofexperiment, we noticed a rejection of the bitter chemotype infavor of the intermediate and sweet ones respectively. Afterthe 6th day, the surface grazed per attack was significantlyhigher on the sweet chemotype than on the bitter plants. Wehypothesize that rejection of the bitter chemotype might berelated to (i) an alkaloids reaction threshold associated withan increase in the amount of alkaloids in the wounded plantsand/or (ii) aversive ingestive conditioning. (Received ; accepted 16 April 1999)     

THE REPRODUCTIVE BIOLOGY OF COLUS JEFFREYSIANUS (GASTROPODA: PROSOBRANCHIA) FROM 2200 m IN THE N.E. ATLANTIC

The reproductive biology of Colus jeffreysianus, collected aspart of a time-series sampling programme at 2200 m in the NorthernRockall Trough, is described. The gross morphology of the reproductiveorgans of this deep-water species does not differ significantlyfrom confamilial species in shallow water. Gametogenesis inboth females and males is a continuous process with no apparentchange in the proportion of the various developmental stagesin relation to the time of year. No post-spawning individualswere found. Maximum oocyte diameter was 170 µM, suggestinglecithotrophic development. In the testis polymorphic spermatozoawere found. The reproductive pattern observed is discussed inrelation to feeding strategy and developmental type. (Received 22 April 1985;