Distinguishing between Stage I and Stage II nauplii of the copepods Metridia and Pseudocalanus from the Bering Sea

Stage I nauplii of Metridia pacifica, Stage I and II naupliiof Metridia lucens, and the equivalent stages of Pseudocalanusmimus were reared from eggs to find morphological charactersfor separating the genera at these stages. Differences in naupliarbody shape and caudal armature permit the differentiation ofStage I and II Metridia from Pseudocalanus in southeastern BeringSea plankton.     

繁殖寄主对赤眼蜂羧酸酯酶和乙酰胆碱酯酶的影响

通过测定赤眼蜂Trichogramma羧酸酯酶和乙酰胆碱酯酶的活性、对底物的亲和力以及对抑制剂的敏感度研究了繁殖寄主对松毛虫赤眼蜂T.dendrolimi和螟黄赤眼蜂T.chilonis的影响。柞蚕卵和米蛾卵繁殖的赤眼蜂羧酸酯酶对底物的亲和力有不同程度的影响,柞蚕卵繁殖的赤眼蜂羧酸酯酶对α-乙酸萘酯或β-乙酸萘酯的亲和力最高是米蛾卵的2倍以上。繁殖寄主对乙酰胆碱酯酶对底物亲和力没有明显的影响。米蛾卵繁殖的松毛虫赤眼蜂羧酸酯酶活性明显高于柞蚕卵繁殖的种群,而米蛾卵繁殖的螟黄赤眼蜂种群羧酸酯酶的活性明显低于柞蚕卵繁殖的种群。用柞蚕卵繁殖的松毛虫赤眼蜂种群对对氧磷的敏感度明显低于米蛾卵繁殖的种群,而增效磷则正好相反。繁殖寄主对松毛虫赤眼蜂吉林种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度没有明显的影响,而在松毛虫赤眼蜂广东种群和螟黄赤眼蜂中,柞蚕卵繁殖的种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度明显低于米蛾卵繁殖的种群。     

粘虫的年龄—发育期结构生命表

在23℃下用玉米嫩叶饲养幼虫,组建了粘虫的年龄-发育期结构生命表。这种生命表考虑到种群内个体发育进度的差异并包括雄性成虫。根据生命表资料计算的粘虫种群主要参数是：净繁殖率R_O= l55.88,内禀增长率r_m=0.1120,平均世代长度T=45.08天。讨论了年龄-发育期结沟生命表方法和传绕生命表方法的主要差别及各自的优缺点,比较了用这两种方法得到的粘虫种群的主要参数值。     

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;     

GROWTH AND REPRODUCTION OF THE SLUG LIMAX VALENTIANUS FIRUSSAC IN EXPERIMENTAL CONDITIONS

Growth and reproduction of batches and isolated Limax valentianus Férussacslugs reared under long-day photoperiods were compared with thosereared under short-day photoperiods combined with higher temperaturesduring the dark period. Weight increase in L. valentianus occurredin three distinct phases: an initial phase of rapid growth (infantilephase), followed by a phase with a smaller increase in weight(juvenile phase) and finally a phase with minimal growth, duringwhich reproduction occurred (adult phase). This phase ended witha weight decrease, due to senescence. Short days associatedwith an increase in temperature during the night reduced thereproductive rate, but did not affect growth. Long days werefavourable for reproduction. Growth rate was fastest in isolatedindividuals reared under long days and warm nights, while reproductionwas greatest in isolated individuals reared under long daysand cool nights. Fertility generally decreased with age, butegg production of slug batches evolved through a maximum, occurringbefore mean life span. High slug density reduced reproductiverate and longevity. (Received 22 December 2000; accepted 10 October 2000)     

Ontogeny of the Behavior of Strombus maculatus (Gastropoda: Strombidae)

The ontogeny of strombid behavior was studied by observing thebehavior of Strombus maculatus veligers collected from the planktonand reared past metamorphosis to adults, and by observing juvenilestrombids collected in the field. Complete adult modal actionpatterns (MAP's) associated with locomotion, feeding, and rightingof overturned shells are performed by S. maculatus juvenilesimmediately after metamorphosis. There are changes in the frequencyof the use of certain MAP's which are associated with variationsin shell shape and size. The unique strombid escape response to molluscivorous gastropods(Conns spp.) is not released until juvenile S. maculatus arethree weeks past metamorphosis and two millimeters in shelllength. At that stage, the complete response is released uponthe first encounter with a predator. Experience with a predatordoes not seem to lower the age or size criteria. During ontogeny there is a trend toward an increasing complexityof behavior which is paralleled by an increasing complexityof neural structure and general morphology. There are majorsteps in the ontogeny of strombid behavior which probably coincidewith neural and morphological stages.     

Growth, development and condition of Dendraster excentricus (Eschscholtz) larvae reared on natural and laboratory diets

Feeding invertebrate larvae may be food limited while developingin the ocean. If they are, then their time in the plankton isprolonged, which likely increases mortality. Food limitationcould be due to the quantity and/or quality of the food available.In an effort to answer how food type influences larval nutrition,we compared growth, development and lipid deposition for Dendrasterexcentricus larvae reared in natural seawater from two depths(1 and 20 m) and in filtered seawater on a monoculture laboratorydiet of 6 cells µL^–1 of the green alga Dunaliellatertiolecta (Butcher). Five days post-fertilization, larvaereared on the laboratory diet had developed to the latest stage,were the largest and had lipid deposits. Larvae reared on naturalsurface water were intermediate in size and developmental stage,and larvae reared in the water from 20 m depth were the smallestand developed the slowest. This trend continued at 8 days post-fertilizationwhen surface water diet larvae were similar in size to laboratorydiet larvae, but their juvenile rudiments were significantlysmaller. To assess food availability in each food treatment,we compared the concentration of chlorophyll (Chl) a, b andc in natural seawater from each depth and in D. tertiolectaculture in filtered seawater. Natural seawater collected fromthe surface had the highest concentration of Chl a and c, whereasChl b was not significantly different between treatments. IncreasedChl concentrations in the surface water are likely due to higherconcentrations of diatoms and dinoflagellates, which are typicallynot high-quality food items for echinoid larvae. Our resultssupport a hypothesis that echinoid larvae in the water columnmay be limited by food quality.     

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)     

REVIEW OF THE GENUS DENDRODORIS EHRENBERG, 1831 (GASTROPODA: NUDIBRANCHIA) IN THE ATLANTIC OCEAN

Six valid species of the nudibranch genus Dendrodons Ehrenberg,1831 inhabit the Atlantic Ocean, including the Mediterraneanand Caribbean Seas. Dendrodons lumbata (Cuvier, 1804), Dendrodonsgrandiflora (Rapp, 1827), Dendrodons nigra (Stimpson, 1855)(immigrant from the Red Sea), Dendrodons krebsu (Mörch,1863), Dendrodoru senegalensis Bouchet, 1975 and Dendrodonswarta Marcus & Gallagher, 1976. Additional data about thebiology and geographical distribution of these species are presented.New evidence suggests that other species assigned to the genusDendrodons, Dendrodons racemosa Pruvot-Fol, 1951 and Dendrodonsminima Pruvot-Fol, 1951, must be included in the genus DoriopsillaBergh, 1880. Three new species of Dendrodoris are describedfrom the Northeastern Atlantic and West Africa;Dendrodons angolensis,Dendrodoris guineana and Dendrodons herytra. The variable external morphology makes species recognition difficult.Instead, the diagnostic characters utilised to separate speciesare the shape of the male cirrus hooks, the structure of thereproductive system and features of the egg-mass. (Received 25 April 1995; accepted 1 August 1995)     

FRESHWATER SNAILS OF THE BULINUS TRUNCATUS/TROPICUS COMPLEX IN KENYA: TETRAPLOID SPECIES

Studies in recent years on chromosome number in freshwater snailsbelonging to the Bulinus truncatus/tropicus complex demonstratedthe occurrence in Kenya of one diploid species, B. tropicus,and 2 tetraploid species, B. truncatus and B. permembranaceus.Further observations are now described on the morphologies ofthe tetraploid species, and their distributions. Observations were made on B. truncatus from 26 localities (11newly reported) and B. permembranaceus from 26 localities (7newly reported), in respect of chromosome number, egg proteins,enzymes (5 systems), shell (10 variables measured), male genitalsystem (normal or aphallic) and radula (1st lateral tooth, sizeand mesocone shape). B. permembranaceus differs most clearly from B. truncatus inegg proteins, enzyme-loci and in lacking aphallic individuals.Mesocone shape is generally less angular in B. permembranaceus.The shell of B. permembranaceus grows larger, has the columellamore commonly concave and its spire is proportionally higherand more acute. To distinguish these tetraploid species fromthe partly sympatric B. tropicus, observations on chromosomenumber and biochemical characters are necessary. The tetraploids are allopatric, B. truncatus being found rarelyas high as 1900 m altitude, whereas B. permembranaceus occupiesthe altitude range 1940–2760 m. B. truncatus may be expandingits distribution in Kenya in man-made waterbodies, while B.permembranaceus possibly is restricted by adaptation to coolconditions and by interaction with B. tropicus. Differencesbetween B. truncatus and B. permembranaceus, both morphologicaland biochemical, indicate their origins lie in independent episodesof tetraploidy. ^*Member of External Scientific staff, Medical Research Council (Received 31 October 1988; accepted 6 December 1988)     

TRANSFER EXPERIMENT SUGGESTS ENVIRONMENTAL EFFECTS ON THE RADULA OF LITTORARIA FLAVA (GASTROPODA: LITTORINIDAE)

Phenotypic variation in radulae has been studied in severallittorinid species because of this organ's intrinsic relationshipwith diet and, consequently, with the environment. In this work,we compared the radulae of the Brazilian species Littorariaflava found in mangroves and on rocky shores. Individuals ofL. flava showed marked differences in the shape of the cuspsamong samples from rocky shore and mangrove. In a transfer experiment,the shape of the radula changed within 40 days. A differentresponse was observed in individuals transferred to mangrove,where two different phenotypes were found, suggesting eitherintrapopulational variation in the responses to change of environmentalconditions, or that some snails showed a slow reaction to theenvironmental changes. The alterations could be attributed toecophenotypic plasticity. Analysis of variance showed that thelength of the radula in L. flava was strongly influenced bythe substrate (F_6,22=17.13, P<0.000), but apparently notby the transfer experiment. (Received 3 May 2005; accepted 18 July 2005)     

NORTH ATLANTIC SPURILLID NUDIBRANCHS, WITH A DESCRIPTION OF A NEW SPECIES, SPURILLA COLUMBINA, FROM THE ANDALUSIAN COAST OF SPAIN

The new species Spurilla columbina differs from its Europeancongeners in coloration and the shape of its cerata. Comparativedata derived from S. norvegica (Odhner, 1939), S. coerulescens(Laurillard, 1830) and S. verrucicornis (Costa, 1864) are tabulated. ^* T. E. Thompson died in a car accident 1 January 1990 (Received 10 January 1989; accepted 4 July 1989)     

THE OPERCULA OF NERITOPSID GASTROPODS AND THEIR PHYLOGENETIC IMPORTANCE

The fossil record of neritopsid opercula and shells shows thatthe shell shape typical for Neritopsidae and Neritidae appearedin the Triassic. The ancestors of Neritimorpha were most probablyforms similar to Naticopsis. The operculum of Recent Neritopsisis composed of two calcitic parts secreted from inside and anaragonitic callus deposited from outside. Similar neritopsidopercula were already present in the Late Triassic. The firstopercula with asymmetrically situated muscle scars, possiblyancestral for neritids, also appeared at that time. (Received 27 May 2004; accepted 8 December 2004)     

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)     

ELECTROPHORETIC AND MORPHOMETRIC CHARACTERS IN POPULATION DIFERENTIATION OF THE PEARL OYSTER, PINCTADA RADIATA (LEACH), FROM AROUND BAHRAIN

Variation at the leucine aminopeptidase (Lap), glucose phosphateisomerase (Gpi) and tetrazolium oxidase (To) loci was investigatedin samples of three populations, Al-Mayana (MAY), Shigita (SH)and Mina Salman (MS), of Pinctada radiata from pearl oysterbeds around Bahrain. The To locus was monomor-phic. SignificantLap and Gpi heterozygote deficiencies were evident and it issuggested that these were generated by selection. The MS population,to the East of Bahrain, differed significantly in Gpi allelefrequencies from both Northern populations (MAY, SH) and Nei'sgenetic identity indicates a close relationship between theNorthern populations. Measurements of shell morphometrics were used both as ratiosof one dimension to another, and as regressions of one dimensionon another to examine relatedness between populations. Boththese mor-phometric approaches gave different results from eachother and also differed from the electrophoretic data. It isconcluded that estimates of relatedness in pearl oysters basedon electrophoretic data will be more reliable than those basedon shell shape. (Received 20 November 1990; accepted 12 April 1991)     

Induction of helmet development by a Chaoborus factor in Daphnia ambigua during juvenile stages

Daphnia ambigua juveniles developed spike-like helmets inducedby a water-soluble factor from Chaoborus, when reared in Chaoborusflavicans-conditioned medium. A study was made of the time atwhich the Chaoborus factor affects helmet development. Juvenilesdeveloped the helmets when individuals were exposed to the Chaoborusfactor after being born, but did not develop the helmets whenthe individuals were exposed to the factor only in the egg orembryo stages. These results indicate that D.ambigua respondsto the Chaoborus factor during the juvenile stages.     

THE EGG MASS OF LITTORINA OBTUSATA AND LACUNA PALLIDULA (GASTROPODA : PROSOBRANCHIA)

The egg masses of Littorina obtusata and of Lacuna pallidulahave been compared with regard to size, shape, egg number, eggsize and substratum. The structure and histochemistry of thespawn of the two species has been investigated and observationson the laying process in L. obtusata are also recorded. ^* Present address: Portway School, Penpole Lane, Shirehampion,Bristol, BS11 0EB. (Received 12 October 1977;     

THE GENUS TRICOLIA IN THE EASTERN ATLANTIC AND THE MEDITERRANEAN

The genus Tricolia(Phasianellidae) in the Eastern Atlantic andMediterranean is reviewed on the bases of radular morphology,shell characters and polychromatism. The taxa included within the T. pullus (L.) group are not clearlyseparable and are treated as geographical subspecies:T. pulluspullus (L.), T. pullus picta (da Costa), T. pullus azorica (Dautzenberg),T. pullus canarica Nordsieck. The case of T. tenuis (Michaud)is problematic since it is clearly separable from sympatricT. pullus pullus in most parts of the Mediterranean but transitionalto T. pullus picta, towards the Atlantic. Other taxa are considered as having specific status since theyare consistently separable when found in sympatric populations.These include T. speciosa (Muhlfeldt), T. miniata (Monterosato),T. tingitana n.sp., T. petiti (Craven), T. nordsiecki (Talavera)and T. algoidea (Pallary). The last two species are stated forthe first time as belonging to the Phasianellidae. The genusEpheriella Pallary, based on T. algoidea, is synonymized withTricolia. (Received 6 April 1981;