VARIATIONS IN INFESTATIONS OF SIPHONARIA CAPENSIS AND S. CONCINNA(PULMONATA) BY LARVAL TREMATODES IN SOUTHERN AFRICA

The prevalence of digenean trematode parasites in Siphonariacapensis (Pulmonata) was examined in populations from 24 sites,and in S. concinna from 10 sites along the coast of southernAfrica from 1989 to 1991. Sporocysts containing cercariae werefound in the digestive gland of both species. To date, two typesof cercaria have been isolated from S. capensis and one typefrom S. concinna, these types possibly representing three distinctspecies of trematode. In approximately 30% of parasitized S.capensis and 10% of parasitized S. concinna the digestive glandwas completely destroyed. In both species of Siphonaria therewas considerable temporal and spatial variation in parasiteprevalence. At some locations up to 40% of S. capensis wereinfected whereas at others, no parasites were found. Prevalenceof trema-todes in S. concinna rarely exceeded 12%. At severalsites the prevalence of infestation within the limpets increasedwith increasing host size. (Received 8 June 1992; accepted 6 July 1992)     

MONOPHASIC AND DIPHASIC DIGESTIVE CYCLES IN VENERUPIS DECUSSATA AND CHLAMYS VARIA

Feeding and digestive cycles in Chlamys varia and Venerupisdecussata are identified and shown to relate to a tidal cycle.The processes of digestion within the diverticula of the twospecies are very different. The tubules of Venerupis are synchronizedand exhibit a monophasic cycle completed within a twelve-hourperiod, facilitating feeding at the next cycle of the tide.The digestive process of Chlamys requires twenty-four hoursand to accommodate feeding at each twelve-hour tidal cycle thetubules within the diverticula exhibit two different digestivephases simultaneously so that a diaphasic cycle is apparent.The pH of the mantle cavity and regions of the digestive tractand the formation and dissolution of the crystalline style areshown to be related to the tidal cycle. ^*Department of Brewing and Biological Sciences, Heriot-WattUniversity, Chambers Street, Edinburgh, EH1 1HX. (Received 22 March 1978;     

Effects of diet and starvation on digestive enzyme activity and feeding behavior of the marine copepod Calanus pacificus

In this paper we look at the response of Calanus pacificus overa period of several weeks to both starvation and diet as reflectedby survival rates, feeding rates and digestive enzyme activities.Phytoplankton species used as food were the diatom Thalassiosiraweissflogii, two dinoflagellates, Gymnodinium simplex and Scrippsiellatrochoidea, and the chlorophyte Dunaliella tertiolecta. In general,C.pacificus appeared to be resistant to starvation for periodsup to 1 week. Survival remained high for at least 6 days ofstarvation, while maximum feeding rates remained constant forseveral days and then declined by 50% after a week of starvation.When initial digestive enzyme activities were low, they didnot change appreciably during the experiments. However, activitylevels dropped rapidly during starvation experiments in whichthey were initially high. Other evidence indicates that starvationmay induce changes in the digestive system before it affectsingestion rates or survival. In general, long-term changes indigestive enzyme activity under different dietary regimes weregradual. An exception to this pattern was S. trochoidea, whosepresence in the diet induced a precipitous, though reversible,decline in digestive enzyme activity, a phenomena possibly relatedto the toxic reaction to this species reported by other researchers.A positive induction of digestive enzymes occurred over a time-scaleof 1–5 days in response to a change in diet. The absenceof laminarin in the diet of C.pacificus for nearly 3 weeks (whenfeeding on G.simplex), during which time laminarinase activitydeclined by {small tilde}50%, did not adversely affect subsequentassimilation of a laminarin-rich food (T. weissflogii).     

DISTRIBUTION OF DIGESTIVE TUBULES AND FINE STRUCTURE OF DIGESTIVE CELLS OF APLYSIA PUNCTATA (CUVIER, 1803)

The distribution of digestive tubules of Aplysia punctatahas been studied in animals under experimental feeding conditions.Histological analysis of the digestive gland has revealed twotypes of tubules, called tubules A and B. Tubules of type Awere composed of basiphilic cells (calcium, excretory and thincells) and tubules of type B were lined by large digestive cellsand basiphilic cells. The latter occur in small groups, usuallyin the corners of the tubules. Type A tubules are involved inion metabolism and show a diphasic cycle (absorptive and reconstitutive)according to the height and the stage of calcium cells. TypeB tubules are involved in digestive processes and display atetraphasic cycle (holding, absorption, fragmentative and reconstitutive)depending upon the height and the stage of the digestive cells.The tetraphasic cycle was compared with the four categoriesof tubules in bivalves. It is proposed that digestive processesmay be continuous in digestive cells of A. punctata. (Received 16 November 1999; accepted 1 October 2000)     

Comparison of diurnal feeding rhythms in Temora longicornis and Centropages hamatus with digestive enzyme activity

Zooplankton samples were collected in St. George's Bay In theGulf of St. Lawrence, during July, 1981. The level of chlorophyllplus phaeopigment was measured for Centropages hamatus and Temoralongicornis collected at three depths every 4–6 h fora 36 h sampling period. The results showed that these speciesfeed predominantly at night. Measurements were also made ofthe levels of digestive protease, laminarinase and amylase,in samples of animals with either full or empty guts. No significantdifferences in digestive enzyme acthities could be found suggestingthat digestive enzyme levels are not directly related to instantaneousdigestion rates. Nevertheless it is likely that feeding ratesand digestive enzyme levels are closely linked and a mechanismis proposed here which would explain this apparent inconsistency.     

FEEDING PATTERNS OF FISSURELLA SPECIES ON ISLA DE MARGARITA, VENEZUELA: USE OF RADULAE AND FOOD PASSAGE RATES

Structural differences and functional wear of the radula inthree species of the gastropod Fissurella from Isla de Margarita,Venezuela, were examined using light and electron microscopy.Wear patterns indicate between 6 and 9 transverse rows of teethare comonly used during feeding. Mechanical wear was most noticeableon the cusps of the outer lateral tooth; this wear varied fromrounding (F. nimbosa) to blunting (F. barbadensis) to squaring(F. nodosa) of the cusps. Morphological changes were additionallycharacterized by a significant decrease in the cusp length ofmarginal cusps in F. nodosa and breakage of the central toothand inner lateral teeth in F. barbadensis. Interspecific differencesin wear patterns suggest that the rhipidoglossate radula maybe used differently by congeneric Fissurella. Despite considerable variation, rasping rates while feedingon the same substrate were comparable among species; however,food passage rates through the digestive system differed amongspecies studied. Fissurella barbadensis requires 12 hours topass its food through the digestive tract, taking almost twiceas much time as F. nodosa and F. nimbosa. These data highlightdifferences in the feeding ecology of Fissurella species andcorrelate well with individual activity patterns and grazinghabits. ^*Present address: La Salle University, Department of Biology,20th Street at Olney Avenue, Philadelphia, PA 19141, USA. (Received 4 October 1988; accepted 16 February 1989)     

The Ultrastructure of the Digestive Glands in Pinguicula vulgaris L. (Lentibulariaceae) Relative to their Function. II. The Changes on Stimulation

The secretory cells of the digestive glands remain highly activeduring the entire period of prey digestion and absorption ofnutrients. They appear to play a major role in gland activity.A model of the digestive gland's activity on stimulation isproposed. It is very similar to that suggested earlier for Dionaeamuscipula. After the digestion and absorption cycle, destructiveprocesses are initiated in the glands. These appear similarto those observed in the glands of the ageing, unstimulatedleaf and are not associated with feeding. Pinguicula vulgaris L. carnivorous plant, digestive glands, ultrastructure, protein secretion absorption, senescence     

FOOD-RELATED CONDITIONING AND NEURONAL CORRELATES IN THE FRESHWATER SNAIL LYMNAEA STAGNALIS

The feeding response of Lymnaea stagnalis shows robust appetitiveconditioning to a novel chemostim-ulus (amyl acetate), whichis retained for more than 4 days. In scrru-isolated centralnervous system (CNS)-hp preparations taken from conditionedsnails, application of amyl acetate to lip tissue led to theonset of fictive feeding in 5/17 individuals, and excitationof an identified cerebral-buccal feeding intemeuron, CV1_a. ina further 8. Control group snails showed no response to amylacetate. Attempts were made to aversively condition L. stagnalis usinga food stimulus (sucrose) as the conditioned stimulus and eitheran electric shock or mechanical stimulus as the unconditionedstimulus. No conditioned response to sucrose (i.e. withdrawal)was seen following training. However, trained snails exhibiteda reduction in responsiveness which was manifest as inhibitionof the feeding response to sucrose and an increase in the timetaken to emerge from the shell following handling. This reducedresponsiveness was seen at 1 hr but was lost by 24 hr aftertraining, and was not observed in control group snails. Semi-isolatedCNS-hp preparations from experimental snails recorded 1-3 hrafter training exhibited either inhibition of fictive feedingor no response following application of sucrose. Control groupsnails showed the normal excitatory response to sucrose includinginduction of feeding motor output Differences in food-related learning between Lymnaea and othergastropod species are discussed in relation to lifestyle andfeeding strategies (Received 14 January 1996; accepted 3 May 1996)     

Ingestion and incorporation of freshwater diatoms by Daphnia pulicaria: do morphology and oxylipin production matter?

In order to explain differences in the growth and reproductionof Daphnia pulicaria fed various freshwater diatoms, we measuredingestion rates and carbon incorporation for six cultured diatomspecies: the single-celled Stephanodiscus hantzschii, Stephanodiscusminutulus and Cyclotella meneghiniana, and the colony-formingAsterionella formosa, Fragilaria capucina and Fragilaria sp.Two of the colony-forming species, when damaged, produced polyunsaturatedaldehydes (oxylipins) that have been found to impair the reproductionof marine copepods. We tested two hypotheses: (i) feeding andincorporation rates are affected by diatom morphology; and (ii)polyunsaturated aldehydes act as feeding deterrents. Daphniabody length versus ingestion rate regressions differed for single-celledand colony-forming diatoms. Ingestion rates for single-celleddiatoms showed clear size dependencies and high correlationcoefficients, while the dependency was weak for colony-formingdiatoms and individual variability was high. This differencewas not observed for carbon incorporation rates, which showedlow variability for all diatoms. Asterionella formosa yieldedthe lowest incorporation rates due to low incorporation efficiency,while all other diatoms were incorporated at similar rates.Thus, morphological differences of the diatoms had no effecton carbon uptake by Daphnia. The presence or absence of polyunsaturatedaldehydes did not cause different ingestion rates; hence thealdehydes are not feeding deterrents.     

Heat tolerance in Mediterranean land snails: histopathology after exposure to different temperature regimes

The physiological and biochemical adaptation mechanisms of heat-tolerantsnail species are poorly known. We investigated cellular adaptationsto heat stress in four heat-exposed snail populations (two ofXeropicta derbentina, one each of Cernuella virgata and Thebapisana). Snails were exposed to different temperature regimes(25, 33, 38, 40, 43, 45, 48, 50 and 52°C) in the laboratoryfor 8 h. After exposure, immobility rates were determined anda qualitative and semi-quantitative histopathological analysisof the digestive gland (calcium and digestive cells) and mucocytesin the foot was conducted. In addition, the coloration of theshells was densitometrically determined. The shells of T. pisanawere significantly darker than the shells of the other populations.The immobility rates and histopathological examinations showedthat X. derbentina (both populations) was slightly better adaptedto heat than C. virgata, and much better adapted than T. pisana.The observed differences in heat tolerance seemed to be connectedto the ability for rapid and extreme proliferation of calciumcells in the digestive gland. (Received 26 November 2007; accepted 25 July 2008)     

Toxic and inhibitory effects of the blue-green alga Microcystis aeruginosa on herbivorous zooplankton

Blooms of blue-green algae are often associated with declinesin populations of large-bodied cladocerans and increased importanceof small cladocerans, copepods, and rotifers. We conducted toxicityand herbivory experiments, using a wide range of herbivore taxa,to test the hypothesis that the blue-green alga Microcystisaeruginosa most strongly inhibits large cladocerans. For a varietyof herbivore taxa, M. aeruginosa was toxic or non-nutritious,and inhibited feeding on co-occurring nutritious food. The rotiferBrachionus calyciflorus was unique in several respects: it wasunaffected by M. aeruginosa toxins, it showed some ability togrow and reproduce on a diet of M. aeruginosa, and it maintainedhigh feeding rates on co-occurring nutritious food in the presenceof bloom densities of M. aeruginosa. There was a strong relationbetween the toxicity of M. aeruginosa and its inhibitory effecton herbivore feeding rates. Copepods strongly avoided consumingM. aeruginosa, but all cladocerans and rotifers tested filteredunicellular M. aeruginosa at rates similar to or higher thannutritious Chlamydomonas reinhardi. Our results indicate thatthere are a variety of mechanisms whereby herbivorous zooplanktoncan coexist with blooms of M. aeruginosa, including resistanceto toxic chemicals (B. calyciflorus), and avoidance of consumptionof M. aeruginosa by chemosensory means (copepods), or by theinability to consume large colonies (some small cladocerans). ¹Present Address: Department of Biology, George Mason University,4400 University Drive, Fairfax, VA 22030, USA     

FURTHER STUDIES ON THE TAXONOMY AND BIOLOGY OF THE OCTOCORAL-FEEDING GENUS PHYLLODESMIUM EHRENBERG, 1831 (NUDIBRANCHIA: AEOLIDOIDEA)

The aeolid nudibranch genus Phyllodesmium (Mollusca: Gastropoda)is reviewed, three new species are described and further informationon the biology, anatomy and distribution on the eight previouslyknown species is reported. The genus Ennoia Bergh, 1896 is considereda synonym of Phyllodesmium and the type species Ennoia briareusredescribed. The genus Phyllodesmium is unique amongst the aeolidsin feeding on octocoral cnidarians. This has led to the evolutionof nudibranch- zooxanthellae symbioses, zooanthellae being obtainedfrom the octocoral prey. The adaptations developed throughoutthe genus are described and possible relationships between thespecies proposed. (Received 6 January 1990; accepted 20 May 1990)     

Glutamine Synthetase Isoenzymes of Striga hermonthica and other Angiosperm Root Parasites

The occurrence of multiple forms of glutamine synthetase inStriga hermonthica and other angiosperm root parasites was investigated.The facultative chlorophyllous parasite Melampyrum arvense exhibitedtwo isoenzymes in leaf tissue, the cytosolic component (GS₁)comprised less than 30% of total glutamine synthetase. In contrastGS₁ was the major component (<70%) in photosynthetic tissueof Striga hermonthica and S. gesnerioides. Only a single isoenzyme(GS₁) was detectable in the achlorophyllous root parasites Orobancheand Lathraea and in non-photosynthetic tissue of S. gesnerioides.The kinetic and physical properties of GS₁ and GS₂ of theseangiosperm parasites were similar to those of the isoenzymesin other non-parasitic angiosperms. Key words: Glutamine synthetase, Angiosperms, Root parasites     

Using "Mighty Mouse" to understand masticatory plasticity: myostatin-deficient mice and musculoskeletal function

Knockout mice lacking myostatin (Mstn), a negative regulatorof the growth of skeletal muscle, develop significant increasesin the relative mass of masticatory muscles as well as the abilityto generate higher maximal muscle forces. Wild-type and Mstn-deficientmice were compared to investigate the postnatal influence ofelevated masticatory loads due to increased jaw-adductor andbite forces on the biomineralization of mandibular articularand cortical bone, the internal structure of the jaw joints,and the composition of temporomandibular joint (TMJ) articularcartilage. To provide an interspecific perspective on the long-termresponses of mammalian jaw joints to altered loading conditions,the findings on mice were compared to similar data for growingrabbits subjected to long-term dietary manipulation. Statisticallysignificant differences in joint proportions and bone mineraldensity between normal and Mstn-deficient mice, which are similarto those observed between rabbit loading cohorts, underscorethe need for a comprehensive analysis of masticatory tissueplasticity vis-à-vis altered mechanical loads, one inwhich variation in external and internal structure are considered.Differences in the expression of proteoglycans and type-II collagenin TMJ articular cartilage between the mouse and rabbit comparisonssuggest that the duration and magnitude of the loading stimuluswill significantly affect patterns of adaptive and degradativeresponses. These data on mammals subjected to long-term loadingconditions offer novel insights regarding variation in ontogeny,life history, and the ecomorphology of the feeding apparatus.     

Structural analysis of the digestive gland of the queen conch Strombus gigas Linnaeus, 1758 and its intracellular parasites

This study describes the structure of the digestive gland ofStrombus gigas in individuals from Guadeloupe and discussesthe function of its cell types and their relationship with intracellularApicomplexa-like parasites. Three cellular types were foundin the epithelium of the blind-ending tubules of the digestivegland according to histological and transmission electron microscopy(TEM) observations; these were: digestive cells, pyramidal cryptcells and vacuolated cells. Columnar digestive cells were characterizedby large Alcian blue-positive granules, which have not beenpreviously described in digestive cells of other caenogastropods.Such granules contain large quantities of proteoglycans thatare exported to the stomach through the physiological destructionof the digestive cells, which undergo a holocrine secretion.Their cytoplasm appears vacuolar due to lipid extraction bysolvents used for tissue preparation. Vacuolated cells alsoappear to be lipid-storage cells. Small triangular-shaped cryptcells, on the other hand, appear to be metabolically activeas suggested by a strong positive in situ hybridization of eukaryoticribosomes, which was confirmed by their large content of ribosomesand rough endoplasmic reticulum compared to the other cell types.These observations suggest that crypt cells may be immaturecells that are involved in the replacement of eliminated digestivecells. However, their spherocrystal inclusions indicate thatthey may be excretory cells or calcium cells. Large brown inclusionswere frequently observed in vacuolated cells; these were identifiedas parasitic protozoans and were present in the digestive glandof all sampled specimens. These protozoans have previously beendescribed from a queen conch population in the San Andres Archipelago(Colombia). Several life cycle stages of the parasite were identifiedby scanning electron microscopy and TEM; trophozoites were characterizedby their conoid-like structure, sporocysts by their thick walls,and gamonts by their thin walls. These observations suggestthat this parasite completes its entire life cycle within thesame host and type of tissue. Although previous investigationsplace this parasite within the Apicomplexa group, further investigationsare necessary in order to confirm the identification of theparasite. (Received 13 May 2008; accepted 3 October 2008)     

PROTAEOLIDIELLA ATRA BABA, 1955 AND PLEUROLIDIA JULIAE BURN, 1966; ONE SPECIES, TWO FAMILIES (NUDIBRANCHIA)

The aeolid nudiberanch species Protaeolidiella atra Baba, 1955and Pleurolidia juliae Burn, 1966, sole species of the familiesProtaeolidiellidae and pleurolidiidae respectively, are shownto be conspecific. The apparent ‘primitive’ featuresof their morphology are re-examined and reinterpreted and itis suggested that the species is a member of the Fomily Aeolidiidae.Unlike other members of the family, which all feed on anthozoans,this species is highly specialised for feeding on the hydroidSolanderia fusca. The single species is shown to have a wideIndo-west Pacific distribution. Functional extra-ceratal lobesof the digestive gland are reported for the first time, froman aeolid without zooxanthellae symbiosis. (Received 4 October 1989; accepted 23 December 1989)     

12a-羟基鱼藤酮对斜纹夜蛾生殖力的影响及其作用机理

为探讨12a-羟基鱼藤酮对斜纹夜蛾Prodenia litura (Fabricius)生殖力的影响及其作用机理, 本文测定了该虫取食12a-羟基鱼藤酮后的产卵量。在用高效液相色谱仪确定其卵巢组织中存在12a-羟基鱼藤酮后, 通过MTT法测定该化合物对斜纹夜蛾卵巢细胞（PL细胞）的细胞毒性,并利用流式细胞仪检测该化合物对PL细胞细胞周期、膜电位、胞内钙离子浓度、线粒体膜电位的影响。结果表明:斜纹夜蛾幼虫取食12a-羟基鱼藤酮后产卵量下降80％以上, 并从卵巢组织中检测出该化合物。12a-羟基鱼藤酮对PL细胞增殖具有抑制活性, 其IC₅₀为6.6 mg/L。该化合物将PL细胞周期阻滞于S期, 导致PL细胞膜电位、线粒体膜电位和细胞内游离钙离子浓度均显著升高。该化合物导致斜纹夜蛾繁殖力降低。12a-羟基鱼藤酮将PL细胞增殖阻滞于细胞周期的S期。同时, 该化合物对卵巢细胞具有较弱的毒杀活性, 导致一些卵巢细胞死亡。由于上述原因, 卵巢细胞数量逐渐减少而导致卵巢管萎缩。卵巢管的萎缩使卵巢管内的卵母细胞不能发育成卵细胞, 故其生殖力下降。     

N-Glycosylation in trypanosomatid protozoa

Trypanosomatid protozoa are parasites of considerable medicaland economic importance in developing countries. The pathwayleading to N-glycosylation in these micro-organisms is characterizedby the following features: (i) dolichols are composed of only10–13 isoprene units; (ii) oligosaccharides transferredin N-glycosylation have the compositions Man_{(6, 7, 9)}GlcNAc₂,depending on the species; (iii) trypanosomatids are unable tosynthesize dolichol-P-Glc and, in addition, some species lackcertain dolichol-P-Man-dependent mannosyltransferases; (iv)the oligosaccharyl-transferase does not require the presenceof glucose units in the oligosaccharide in order to catalysean efficient transfer reaction; (v) trypanosomatids have a glucosidaseII-like enzyme, but lack glucosidase I; (vi) glucosidase IIis required for deglucosylation of oligosaccharides glucosylatedby the UDP-Glc: glycoprotein glucosyltransferase, an activityfirst detected in those parasites; (vii) the structures of polymannose-typecompounds in these protozoa have no significant differenceswith those of their mammallan counterparts except for the presence,in certain species, of oligosaccharides having galactofuranoseunits linked to external mannose residues; (viii) biantennarycomplex-type oligosaccharides having in some cases terminal     

Lipids in Acanthodiaptomus denticomis during starvation and fed on three different algae

Variations in the levels of triglycerides, wax esters and polarlipids were determined in adults of the calanoid copepod Acanthodiaptomusdenticornis when freshly caught, starved or fed on the followingalgae: Anabaena spiroides, Cyclotella pseudostelligera and Pediastrumduplex. Over 7 days starvation, triglycerides and wax esterswere almost entirely used up by the copepods. Subsequent feedingover 20 days partially restored triglycerides but restored onlya relatively small fraction (<20%) of wax esters in the animals.Differences in the lipid restoration were found: the restoredtriglyceride level was higher in animals feeding on Cyclotellapseudostelligera or Pediastrum duplex than in those feedingon Anabaena spiroides. Fatty acid composition of neutral lipidswas closely linked to fatty acid composition of algae. The resultssuggest that lipid and fatty acid contents of Acanthodiaptomusdenticornis are good indices of the copepod's nutritional statusand short-term (0–20 days) feeding history.     

Predaceous feeding habits of Limnocalanus macrurus

Limnocalanus macrurus, a large, glacial-relict copepod, hasbeen assumed an omnivore or a herbivore; predaceous habits ofthe species are unknown. The predaceous feeding habits of Limnocalanusfrom Lake Michigan were studied in the laboratory using naturalprey. Predation rates were highest on copepod nauplii. Copepoditesof Diaptomus spp. and Cyclops spp. were preyed upon at lowerrates. Limnocalanus preyed selectively upon nauplii <300µm. Small cyclopoid copepodites (<–750 µm)were also selected over large copepodites. Experiments usingtwo prey types showed that nauplii were selected over all copepodites,and that no selectivity existed for either diaptomid or cyclopoidcopepodites. Predaceous feeding habits began in the fourth copepoditestage of Limnocalanus. Predaceous feeding rates of Limnocalanuschanged seasonally being highest in late spring and autumn andlowest in summer and early winter. Since Limnocalanus also feedson net-phytoplankton, predation rate changes may be relatedto changes in the relative abundance of large phytoplanktonand naupliar prey in nature. Limnocalanus predation may be animportant factor in structuring the zooplankton community. Present address: Great Lakes Research Division, University Michigan,Ann Arbor, MI 48109, USA