THE INFLUENCE OF AN ALTERNATIVE FOOD ON THE EFFECTIVENESS OF PROPRIETARY MOLLUSCICIDAL PELLETS AGAINST TWO SPECIES OF SLUGS

The effectiveness of three types of molluscicidal pellets againstDeroceras reticulatum (Müller) and Arion hortensis (Férussac)was assessed in the presence and absence of potato leaf discs.Pellets containing methi-ocarb were significantly more effectiveagainst both of the slug species than either of the metaldehydeformulations, in the absence of leaf discs. When leaf discswere present, methiocarb was no more effective against D. reticulatumthan were the metaldehyde formulations. Leaf discs did not interferewith the effectiveness of methiocarb against A. hortensis. Theresults are discussed in relation to past work and more recentfield studies. (Received 24 March 1986;     

MORPHOLOGICAL AND CHEMICAL CAMOUFLAGE OF THE MEDITERRANEAN NUDIBRANCH DISCODORIS INDECORA ON THE SPONGES IRCINIA VARIABILIS AND IRCINIA FASCICULATA

The nudibranch Discodoris indecora shows a perfect camouflageon its prey, the dictyoceratid sponge Ircinia variabilis. Shapeand colour of the nudibranch are remarkably similar to thatof the sponge which is widespread in the shallow waters of theMediterranean Sea. The metabolite pattern of I. variabilis isdominated by unusual molecules, the sesterter-penoids palinurinand variabilin, containing 25 carbons and displaying at theends a ß-substituted furan ring and a tetronic acid.However, a chemical polymorphism has been recently describedfor I. variabilis. Some specimens contain either palinurin orvariabilin whereas others possess a mixture of both sestertepenoids.During the study of Mediterranean sponges, a linear sesterterpenoidrelated to palinurin and variabilin was found in Ircinia fasciculata,that from a taxonomic point of view is closely relatedto Irciniavariabilis. Discodoris indecora shows a typical defence behaviourwhen it is disturbed, secreting a copious white slime that containslarge amounts of palinurin and variabilin. Most likely the animalis able to transfer the sponge metabolites from the digestiveglands to mantle glands. Electron micrographs of the nudibranchmantle showed the presence of unicellular glands characterizedby a cylindrical vacuole with a big nucleus on the basis. Theglands were concentrated in the most conspicuous tubercles ofthe dorsal mantle. Probably, the sponge metabolites are storedin these glands. Comparative chemical analysis of mucous secretions, dorsal tubercles,mantle, foot, digestive glands and hepatopancreas of D. indecoraconfirmed this hypothesis. Palinurin and fasciculation were,of course, present in the digestive glands but they were alsofound in the mucus and in the mantle sections enriched by theabove described unicellular glands. The defensive role of palinurinand variabilin, strongly suggested by their anatomical location,was supported by recording the induction of feeding-deterrencein the fresh-water fish Carassius auratus and in the marinefish Chromis chromis and Sparus auratus. (Received 15 March 1996; accepted 27 January 1997)     

INVESTIGATIONS OF THE ROLE OF MUCUS AND FAECES IN INTERSPECIFIC INTERACTIONS OF TWO LAND SNAILS

A previous report (Smallridge & Kirby, 1988) showed interspecificcompetition between the two land snails Theba pisana and Cernuellavirgata and suggested the mechanism of competition may be thatheterospecific mucus and excrement inhibits activity. We describea series of experiments in which we could find no consistentevidence for any short-term inhibition of activity in the presenceof heterospecific mucus. Furthermore snails did not consistentlyavoid mucus-treated surfaces or mucus-coated food. Cernuellastopped at and fed from snail faeces (both conspecific and heterospecific)more than did Theba. This suggests an alternate mechanism forinterspecific competition. (Received 9 April 1992; accepted 9 June 1992)     

THE IMPORTANCE OF MUCUS AS A DEFENCE AGAINST CARABID BEETLES BY THE SLUGS ARION FASCIATUS AND DEROCERAS RETICULATUM

The effect of mucus exudation on the survival of Arion fasciatusand Deroceras reticulatum was studied by exposing mechanicallystimulated and control slugs to Carabidae beetles for 24 hours.A light stimulation, lasting three minutes, exhausted the copiousflow of mucus for one day. A generalist, Pterostichus niger,significantly preferred stressed D. reticulatum over controlones. Similarly, P. niger exclusively ate stressed individualsof A. fasciatus. Two beetles which specialize in gastropods,Cychrus caraboides and Carabus violaceus, consumed an equalnumber of stressed and control D. reticulatum and A. fasciatus.The susceptibility of the slug species to predation was different:for each beetle species, the proportion of available D. reticulatumpreyed upon was significantly higher than that of A. fasciatus.The differences in the behaviour of A. fasciatus and D. reticulatumin defending themselves against attacks is described. The mainreason why specialist beetles are able to hunt slugs successfullyis their ability to prevent the slugs from exuding large amountsof mucus. This may succeed by different means: C. violaceustargeted their killing strokes against the posterior part ofthe mantle while C. caraboides hit the head of the slug. Inboth case the strokes seemed to paralyze the slugs. (Received 31 March 1993; accepted 1 October 1993)     

SLUG DAMAGE AND NUMBERS OF SLUGS IN OILSEED RAPE BORDERING ON GRASS STRIPS

In 1995, slug damage and numbers of slugs were estimated intwo grass strips and adjacent rape fields. Investigations beganas soon as rape seedlings emerged and lasted for five weeks.Slug damage to rape plants 1 m from the grass strips was significantlyhigher than at greater distances from the strips. Derocerasreticulatum was the most abundant slug species recorded in bothgrass strips and adjacent rape fields. Arion lusitanicus andArion fasciatus were much less abundant than D. reticulatum.In one field, D. reticulatum declined steadily with increasingdistance from the grass strips and therefore appeared to havecaused the majority of severe damage to rape plants close tothe strips. This finding was surprising because until now severeslug damage in oilseed rape beside semi-natural habitats hasbeen observed only where A. lusitanicus was abundant. (Received 12 November 1997; accepted 26 January 1998)     

Effects of metaldehyde and methiocarb on feeding preferences and survival of a slug predator (Pterostichus melanarius (F.): Carabidae,Pterostichini)

The potential for reducing slug populations in crops through predation by generalist carabid beetles is well documented. However, few studies have considered interactions between biological and chemical control agents of slugs. Laboratory assays supported previous findings that the consumption of metaldehyde by slugs (Deroceras reticulatum) leads to increased duration of feeding bouts by carabid beetles (such as Pterostichini) on sub‐lethally affected individuals. However, a similar effect was not found for Pterostichus melanarius exposed to slugs fed on the other widely applied pelleted molluscicide formulation (methiocarb). Examination of beetle survival after consumption of slugs containing molluscicides demonstrated the strong biocidal properties of methiocarb, whereas metaldehyde consumption (ingested through slug predation) did not differ from control slugs killed by freezing. Beetle avoidance of slugs containing a more toxic molluscicide compound and the interaction between slug mucus production and beetle attack rates are discussed.     

THE INFLUENCE OF FOOD DEPRIVATION ON THE LOCOMOTOR ACTIVITY OF SLUGS

Experimental animals used in studies of feeding behaviour areusually starved prior to observation, although little is knownof the behavioural effects of such pre-experimental treatment.This study investigated the effect of food deprivation on thelocomotor activity of two species of slugs, Deroceras reticulatumand Milax budapestensis. Locomotor activity was measured bythe quantitative assessment of mucus trails. The more surfaceactiveD. reticulatum showed a marked increase in its locomotoractivity when deprived of food, whereas the locomotor activityof M. budapestensis decreased. The implications of the resultsare discussed in relation to the ‘life-styles’ ofthe two species and the possible implications for the controlof slugs in the potato crop. ^*Present address: 59 Valley Park Drive, Clanfield, Hants. PO80PL. (Received 24 May 1986;     

MUCUS PRODUCTION AND PHYSIOLOGICAL ENERGETICS IN PATELLA VULGATA L.

Most energy budgets for marine gastropods lack a measured mucusterm. This is a major omission since mucus is widespread inmolluscan physiological processes. In this paper we outlinemethods for estimating mucus production in the intertidal gastropod,Patella vulgata L. This species uses mucus primarily for adhesionand locomotion. Pedal mucus production rates were measured inaerial environments of 70% relative humidity (RH) and 100% RHand in seawater. Animals in 70% RH did not move, while thosein 100% RH and seawater were mobile. Animals in 100% RH showedthe highest mucus production rate. Those in seawater secretedabout 75% of the mucus produced in 100% RH and those in 70%RH only about 40% of that produced in 100% RH. Significant logarithmicrelationships between mucus production rate and whole dry weightof animal, and mucus production rate and shell length were foundin all cases. The mucus term in the energy budget was calculated as 23% ofingestion both for individuals and for a specific population.This is much higher than the estimate of 4% of Wright &Hartnoll (1981). We have recalculated an energy budget for Patellavulgata to include the substantial mucus term. The recalculatedbudget is structurally different from the original budget. Thissuggests conclusions drawn from budgets not including a measuredmucus term should be regarded with caution. (Received 12 September 1989; accepted 13 December 1989)     

GROWTH, MORTALITY, AND FEEDING RATES OF THE SNAIL HELIX ASPERSA AT DIFFERENT POPULATION DENSITIES IN THE LABORATORY, AND THE DEPRESSION OF ACTIVITY OF HELICID SNAILS BY OTHER INDIVIDUALS, OR THEIR MUCUS

When reared at high densities, young Helix aspersa show lessshell growth, even if waste products are removed. They alsofeed less, and show increased mortality. It is suggested thatthese effects are linked to reduced activity. Juveniles showreduced activity in the presence of adults or their mucus. Mucusof adult Cepaca nemoralis also depresses the activity of bothadult and young Helix and Cepaea. ^* Present Address: Unit Zoologi, Universiti Kebangsaan Malaysia,Jalan Pantai Baru, Kuala Lumpur, West Malaysia. (Received 12 May 1981;     

辛硫磷和溴氰菊酯混剂对家蝇抗性发展的影响

以家蝇(Musca domestica vicina Macquart)为试虫,用辛硫磷溴氰菊酯单剂及不同配比的混剂进行汰选试验。所有混剂选育的家蝇抗性发展都很缓慢,而单剂抗性发展都很快。增效试验表明,辛硫磷与溴氰菊酯混配有明显增效作用,特别是对抗性品系。生化分析结果表明,对澳氰菊酯的抗性发展与酯酶的酶活升高有关。对辛硫磷抗性发展与多功能氧化酶的酶活升高和乙酰胆碱酯酶敏感性降低有关。混剂选育的家蝇其对单剂的敏感性的变化及酶系的变化,随着混剂的配比而变化。     

BIOCHEMICAL COMPOSITION OF HELIX SNAILS: INFLUENCE OF GENETIC AND PHYSIOLOGICAL FACTORS

This paper describes the biochemical composition of differentspecies (Helix lucorum, Helix pomatia) and sub-species of snails(Helix aspersa aspersa, Helix aspersa maxima) reared in thesame conditions with a feed (‘Helixal’) speciallydesigned for edible snails. In addition, the composition ofwild H. pomatia and H. lucorum is presented to allow comparisonbetween snails of different origins. Analyses determined thepercentages of proteins, lipids and minerals. They reveal bothsimilarities and differences in composition according to thespecies and the part analysed (whole body, pedal mass, and visceralmass). H. pomatia contains the highest percentage of mineralmatter and the lowest percentage of lipids. Surprisingly, proteincontents are slightly different between artificially rearedH. aspersa maxima of 3 months old and wild H. pomatia. The resultsmake it possible to evaluate nutritional quality of snails withthe composition of the body of four edible snail species. (Received 16 September 1996; accepted 24 May 1997)     

COMPARISONS OF THE BIOLOGY OF THE INTERTIDAL SUBANTARCTIC LIMPETS NACELLA CONCINNA AND KERGUELENELLA LATERALIS

Two limpet species occur intertidally on subantarctic SouthGeorgia, the patellid Nacella concinna and the siphonarlid Kerguelenellalateralis. N. concinna is confined to the lower shore closeto LWS; K. lateralis occurs in middle shore pools, so theirdistributions do not overlap. N. concinna has a much narrowerthermal niche (–12.9°C to +15.6°C) than K. lateralis(–17.8°C to +31.8°C). Environmental data are presentedto show that the upper lethal temperature of N. concinna islow enough to prevent the limpet living higher on the shore.Both limpet species are slow-moving, but K. lateralis showsincreasing speed with rising temperature, peaking at 15–20°C.In contrast, N. concinna moves actively down to –1.9°C(when sea water freezes), but there is a steady decrease inspeed of locomotion above +2°C. Locomotion ceases at 14°Cin N. concinna (c.f. 30°C in K. lateralis). Both speciesexhibit very low tenacities, but in N. concinna tenacity decreaseswith increasing shell length. In K. lateralis there is no effectof temperature on tenacity. Both species show a positive allometricrelationship between foot area and shell length. N. concinnafeeds upon microbial films and microepiflora, but K. lateraliseats colonial diatoms and Enteromorpha bulbosa. Observationson shell middens of the kelp gull Larus dominicanus showed thatthe gulls did not eat K. lateralis, though they ate great quantitiesof the less accessible N. concinna. Gulls ate N. concinna assmall as 11 mm shell length (within the size range of K. lateralis).Experiments on gulls demonstrated an unwillingness to eat K.lateralis, probably because the siphonariid extrudes a viscidwhite mucus when the foot is touched. (Received 9 May 1996; accepted 8 July 1996)     

SLUG FEEDING BEHAVIOUR IN RELATION TO CONTROL WITH MOLLUSCICIDAL BAITS

The feeding behaviour of Deroceras reticulatam (Müller)presented with molluscicidal baits in laboratory and terrariatrials is described and discussed in relation to pest slug control.Both metaldehyde and Methiocarb appears to be more effectivein wet conditions and less repellent to slugs allowing moreactive ingredient to be consumed before termination of feeding (Received 16 November 1987; accepted 15 February 1988)     

SEASONAL CYCLE AND POPULATION DYNAMICS OF THE SEA HARE APLYSIA OCULIFERA IN THE NORTHERN GULF OF EILAT (AQABA), RED SEA

Populations of the sea hare, Aplysia oculifera (Adams &Reeve, 1850) (Gastropoda: Opistho-branchia), were studied inthe northern coast of the Gulf of Eilat (Aqaba) between April1988 and March 1992. Recruitment occurred from December to February,synchronized with the blooming of green algae (Enteromorphaintestinalis and Ulva sp.). A single recruitment event occurredeach year, while a secondary recruitment was rarely, observedand was related to acute catastrophic disturbance of the habitat.Adult sea hares inhabited the inter- and subtidal zones fromDecember-January to April-June, feeding on E. intestinalis andUlva sp. Populations disappeared in April-June which coincidedwith disappearance of these green algae. Mean maximum body livemass of adult sea hares (MMBLM, that is the highest mean bodymass recorded at specific site within the season) ranged from0.77 to 33 g MMBLM, varied significantly among populations inhabitingthe various study sites, and was significantly and inverselycorrelated with water movement intensity. Abundance of sea haresvaried among sites and among years and was related to the amountof green algae during the recruitment season. ²Present address: Department of Biology, University of Haifaat Oranim, Tivon 36006, Israel. E-mail: plaut{at}research.haifa.ac.il (Received 29 April 1997; accepted 26 July 1997)     

ON THE GUSTATORY EFFECTS OF MIRACULIN AND GYMNEMIC ACID IN THE MONKEY

The summated response from the chorda tympani proper nerve of9 monkeys was recorded during stimulation with solutions ofacetic and citric acids, sodium chloride, quinine sulfate, sucrose,glucose and fructose before and after application of extractsof Synsepalum dulcificum-miraculin- and Gymnema sylvestre-gymnemicacid-on the tongue. It was observed that (a) miraculin enhancedthe response to all acids used (b) miraculin had no significanteffect on the response of the other taste stimuli (c) its effectlasts for more than h and was not removed by rubbing of thetongue (d) gymnemic acid had no significant effect on the responseto any of the stimuli used if miraculin had not been appliedbeforehand (e) gymnemic acid applied after miraculin diminishedthe response to acid, then miraculin enhanced the response toacid again. It was concluded that these electrophysiologicalfindings in monkey parallel the psychophysical observationsin man with regard to the effect of miraculin and gymnemic acidon the response to acids, but that they differ with regard tothe effect of gymnemic acid on the response to sugars. ^* On leave from Dept. of Psychology, University of New Hampshire,U.S.A. ^** On leave from Dept. of Oral Physiology, Osaka University,Japan.     

DISTRIBUTION AND ABUNDANCE OF GYMNOSOMATA (GASTROPODA: OPISTHOBRANCHIA) IN THE SOUTHWEST ATLANTIC

The distribution and abundance of gymnosome gastropods in theArgentine Sea and Brazil—Malvinas Confluence during 1978–1979and 1988 were studied. The collections analyzed included 768quantitative samples obtained between 48°W and the coast,and from 35°S to 55°S. Two species were found. Spongiobranchaeaaustralis was the most frequent and abundant (up to 730 per1000 m3); its presence in the area was associated with the coreof the Malvinas Current. Clione antarctica was less abundant(maximum abundance: 230 per 1000 m³) and was also associatedwith the Malvinas Current. The geographic ranges of both speciesin the area are wider than previously described. Since the rangeof S. australis in the area extends far from the range of itsprey Clio, it is not clear whether S. australis can feed onthe thecosomatous pteropod Limacina (and not only on Clio, asdescribed in the bibliography) or it starves in that area. Duringthe 1978–1979 annual cycle, the abundance of both speciesfollowed neither the abundance patterns of their prey nor ofthe total zooplankton, and differed from each other. The residencetime of swarms of both gymnosomes were shorter than one month.As a general pattern, the aggregates are rapidly transportednorthward by the Malvinas Current and also penetrate the outershelf water, but they remain there only during a short periodand cannot preclude the final expatriation. So, the abundanceof gymnosomes in the area depends on passive migration morethan intrinsic population factors. (Received 9 July 1997; accepted 15 December 1997)     

TAXONOMY AND OCCURRENCE OF DENDRODORIS NIGRA AND DENDRODORIS FUMATA (NUDIBRANCHIA: DENDRODORIDIDAE) IN THE INDO-WEST PACIFIC REGION

The nudibranch Dendrodoris nigra (Stimpson, 1855) has hithertobeen considered as a single, highly poly-chromic species. Ourinvestigations of external morphology, anatomy and colour variationhave revealed more than one species exists. This conclusiongives credibility to the previous discovery of differing developmentalpatterns within D. nigra. Besides D. nigra, we recognise Dendrodorisfumata (Rüppell & Leuckart, 1830) which has three distinguishablecolour forms. The occurrence of D. nigra is confirmed to beextensive, however, the species was not found to be circum-Australianas previously reported. The presence of D. fumata in Australiais confirmed and the species is also reported from Hong Kongand Fiji for the first time. The clear separation of these twospecies and recognition of the different colour forms will permita more accurate picture of their distribution. (Received 15 November 1994; accepted 2 January 1997)     

高温对小地老虎和东方粘虫精子发生和形成的影响

小地老虎和东方粘虫精子发生之后,开始分化出真核精子和无核精子。当温度超过32℃时,出现大量的畸形精细胞囊,精子形成受阻,核与鞭毛明显缩短,鞭毛中微管所受影响最大。但32℃温度以下不影响真核到无核精子的发生和二叉发生的转换。由此可见,小地老虎和粘虫夏季由南向北迁飞也是一种回避高温的适应性行为。     

PHYSIOLOGICAL ACTIVITIES OF HELMINTHOSPOROL AND HELMINTHOSPORIC ACID: I. EFFECTS ON GROWTH OF INTACT PLANTS

Helminthosporol (H-ol) and helminthosporic acid (H-acid) wereeffective in promoting elongation of leaf sheaths of rice, Japanesebarnyard grass and dwarf maize (d-2 and d-5) and of hypocotylsof taisai (Brassica chinensis), but inactive in leaf sheathsof oat and wheat, hypocotyls of sesame and morning glory (Pharbitisnil) and epicotyls of Pharbitis and dwarf and tall peas. Onthe elongation of the leaf sheath of maize d-1, H-ol was promotivebut the activity of H-acid was doubtful. On hypocotyls of lettuceand daikon (Raphanus sativus), only H-acid was active. Multiplicationrate and size of fronds of Lemna perpusila were not affectedby either of the substances. Compared with gibberellic acid for the effect on the shoot growth,H-ol and H-acid were weak in activity and narrower in the scopeof plants that responded. H-ol and H-acid characteristicallypromoted the elongation of the primary root. Comparative effectivenessof H-ol and H-acid varied with plant species or parts examined. ¹ This study was supported in part by grant-in aid of the Ministryof Education (No. 0417). The results reported here were presentedat the Annual Meeting of the Botanical Society of Japan at Kanazawain 1964 (S).     

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)