The food of coral-reef Drupa (Gastropoda)

Eight species of the predatory gastropod Drupa are abundant in exposed habitats of Indo-Pacific coral reefs. The diets of seven species and two subspecies were investigated by gut content analysis of over 1400 specimens from a number of localities from the Red Sea to the western Pacific. Two species, D. grossularia and D. lobata, are sipunculan specialists, whilst D. morum and D. rubusidaeus mainly eat eunicid polychaetes. Drupa ricinus and probably D. elegans feed upon a wide variety of prey including crustacea, vermetid gastropods, chitons, polychaetes and sipunculans. The Red Sea subspecies D. ricinus hadari also eats small gobiid fish. Drupa clathrata clathrata, probably the least advanced species in the genus, has a diet of molluscs and barnacles, similar to that of other thaiid gastropods.     

DESCRIPTION OF A NEW SPECIES OF PHYLLIDIOPSIS BERGH (NUDIBRANCHIA: DORIDOIDEA: PHYLLIDIIDAE) FROM THE TROPICAL WESTERN PACIFIC, WITH COMMENTS ON THE ATLANTIC SPECIES

A new species of phyllidiid nudibranch, Phyllidiopsis shireenae,is described. The new species has a middorsal crest insteadof being flattened dorso-ventrally like most phyllidiids. Itsbody is a very pale shade of pink with black bands, and itsrhinophores are salmon pink. The anatomy of the alimentary systemand reproductive system are described. Characters originallyused by Bergh (1875) to differentiate the genus are supportedby this new species. Phyllidiopsis shi-reenae is presently knownfrom coral reef habitats in the extreme western Pacific Ocean.A review of the taxonomic status of the Atlantic specis of Phyllidiopsisis required. ^*Present address: Australian Biological and Environmental Survey.Australian National Parks and Wildlife Service, GPO Box 1383,Canberra. ACT 2601. Australia. (Received 15 August 1989; accepted 8 January 1990)     

PREY CAPTURE, PREFERENCE AND CONSUMPTION BYLINATELLA CAUDATA (GASTROPODA: TONNOIDEA: RANELLIDAE) IN HONG KONG

On sheltered rocky beaches in Hong Kong, Linatella caudata preysupon the lower-littoral and sub-littoral fringe fauna. Ascidiantests are cut with the radula, while the proboscis is insertedbetween the parted shell valves of bivalves. The salivary glandssecrete sulphuric acid that is not used in prey penetration,as in the Cassidae, but is more likely used in digestion ordefence. In preference experiments, prey were chosen in the sequence:Barbatia virescens (Bivalvia: Arcidae) > Styela plicata (Ascidiacea)/Saccostreacucullata (Bivalvia: Ostreidae) > Lunella coronata (Gastropoda:Turbinidae) > Balanus amphitrite (Crustacea: Cirripedia).52% of all attacks were upon Barbatia Lunella and Balanus wereattacked rarely. Prey preferences by individual gastropods werealso demonstrated. Calibration plots of total weight against wet and dry tissueweight of prey (Barbatia virescens) and, finally, the predatorwere obtained and used in estimations of consumption. On average,an adult Linatella caudata (10-15g) consumed three B. virescens.week^–1 The mean weight of B. virescens flesh consumed.week^–1 ranged between 0. 208–0.412g dry weight prey.gdry weight predator^–1, i.e., a mean of 28.2% of the predator'body weight.week^–1 or 4%.day^–1. Such a figure accordswell with estimates of consumption obtained for other adultpredatory gastropods from Hong Kong. (Received 4 September 1989; accepted 5 December 1989)     

Competition, predation and the relative abundances of two species of Daphnia

We investigated the factors controlling the relative abundancesof two Daphnia species, D.pulex and D.laevis, in a small Wisconsinpond. D.pulex was the dominant Daphnia species in fall 1977and summer-fall 1978; D.laevis was the only Daphnia speciespresent in summer 1979. The abundance of D.laevis was positivelycorrelated with the abundance of the notonectid, Buenoa confusa.In predation trials, notonectides exhibited a distinct preferencefor D.pulex over similarly-sized D.laevis, but Chaoborus larvaefed at similar rates on both Daphnia species. Behavioral observationsrevealed that Buenoa adults were much less efficient at capturingD.laevis than D.pulex. Quantitative results of these predationtrials were combined with estimates of predator and prey densityand distribution to evaluate the effect of predation on thedaphnid populations. The effect of predation varied throughtime and microhabitat, and only infrequently could predationaccount for total prey mortality. D.laevis was most abundantat times and in places where Buenoa predation was most intense.Competition experiments illustrated the competitive superiorityof D.pulex over D.laevis. D.pulex was able to competitivelyexclude D.laevis in long term experiments, and D.pulex's fecunditywas higher than that of D.laevis in shorter experiments. Inlong-term experiments, Chaoborus larvae at natural densitieswere able to keep both Daphnia species at low, constant levelsand neither species clearly dominated when Chaoborus was present.The relative abundances of D.pulex and D.laevis were controlledby a complex of biotic and abiotic factors. Pond depth and predatordensity determined the intensity of predation on daphnid populations.When notonectid predation was intense, D.laevis dominated; whenthe intensity of predation by notonectids was low, D.pulex dominateddue to its superior competitive abilities. At different timesselective predation or high resource levels promoted the co-existenceof these two species. ¹Current address of both authors: Department of Biological Sciences,University of California, Santa Barbara, CA 93106, USA     

THE DIET, PREY SIZE AND CONSUMPTION OF PHILINE ORIENTALIS (OPISTHOBRANCHIA: PHILINIDAE) IN HONG KONG

Philine orientalis occurs on Hong Kong's beaches for {smalltilde}2 months each year, in May and June when it breeds, laysegg capsules and dies. It is believed to have a life span ofone year. Hoi Sing Wan, a sandy beach in the New Territoriesof Hong Kong is dominated at lower levels by the venerid bivalveTapes philippinarum, the population of which in May and June,following spring recruitment, mostly comprises juveniles. P.orientalis, occurring at a density of {small tilde} 1.m^–2,feeds voraciously upon these juveniles consuming, in laboratoryexperiments, a mean of 25.day^–1. At Hoi Sing Wan, P. orientalisappears to be highly prey specific. It is, however, known tofeed on other prey items and probably has a catholic diet, duringits annual migration from deeper to shallower sediments, accordingto the prevailing fauna. In terms of wet weight, P. orientalis consumes a mean of {smalltilde}4.4% (2.2–6.7%) of its body weight day^–1.In terms of dry weight, however, this figure increases to amean of 35.5% and one figure of 208% has been recorded. Althoughthis is because of the large body fluid content of this, essentiallyshell-less, gastropod, using a hydrostatic skeleton to achieveburrowing, such figures further attest to the voracity of thebreeding adults. This study joins others in questioning ourpresent understanding of the scale of energy budgets on suchshores, i.e., are our estimates of loss to predation grosslyunderestimated? ^*Present address: Department of Biology, Baptist College, WaterlooRoad, Kowloon, Hong Kong. (Received 20 May 1989; accepted 3 July 1989)     

Dynamics of herbivorous grazing by the heterotrophic dinoflagellate oxyrrhis marina

In a series of batch experiments in the dark the heterotrophicdinoflagellate Oxyrrhis marina grazed three phytoplankton prey(Phaeodactylun tricornutum, Isochrysis galbana and Dunaliellateriolecta) with equal efficiency. Growth rates of the dinoflagellateranged between 0.8 and 1.3 day–1 Maximum observed ingestionrates on a cell basis varied according to the size of the preyfrom about 50 cells flagellate^–1 day^–1 when D.tertiolectawas the prey to 250–350 cells fiagellate^–1 day^–1when the other species were eaten. However, when compared ona nitrogen basis, ingestion rates were independent of prey type.Both ingestion and growth ceased when prey cell concentrationsfell below a threshold concentration of about 10⁵ cells ml^–1.Maximum specific clearance rates were 0.8x10⁴0ndash;5.7x10⁴it day which is considerably lower than that found for heterotrophicdinoflagellates in oceanic waters and may explain why O.marinagenerally thrives only in productive waters. The timing of NHregeneration was linked to the C:N ratio of the prey at thestart of grazing. Regeneration efficiencies for NH₄. never exceeded7%; during the exponential phase and were 45% well into thestationary phase. These results are comparable to those obtainedwith heterotrophic flagellates and demonstrate that the bioenergeticpatterns of grazing and nutrient cycling by different protozoaare very similar. Moreover, they support the notion that toachieve 90+% nutrient regeneration in the open ocean, as iscurrently believed, the microbial food loop must consist ofmultiple feeding steps. Alternatively, nutrient regenerationefficiencies may be considerably lower than 90%.     

COMPARATIVE MORPHOLOGY OF RADULAR TEETH IN CONUS: OBSERVATIONS WITH SCANNING ELECTRON MICROSCOPY

Radular teeth of 22 Indo-Pacific species of the genus Conus(Neogastropoda: Toxoglossa) were compared. On morphologicalfeatures all can be related to one of three known feeding modes:piscivorous, vermivorous and molluscivorous. Observations arereported on the radular teeth of six piscivores, thirteen vermivoresand three molluscivores. The radular teeth of piscivores areof two general types. In the first, two barbs and a posteriorly-directedprocess with a recurved tip are found at the anterior end. Inthe second, two barbs are located at the anterior end and theshaft is serrated for most of its length. An enlarged posteriorregion (terminal knob) is present in the first and absent inthe second. Molluscivores possess radular teeth with two anteriorbarbs and in some species a serrated shaft or terminal knob.The radular teeth of vermivores, which show much greater interspecificvariation than those of piscivores or molluscivores, are characterizedby one or two anterior barbs and in most species a serratedregion near the apex. A forwardly-projecting cone (basal spur)is usually located on the terminal knob. Piscivores and molluscivoreslack such basal spurs. The radular teeth of Conus are used toconvey a potent venom and hold prey firmly during feeding. Previouslyundescribed morphological features are noted on the teeth ofC. obscurus and C. lividus. Figured here for the first timeare the radular teeth of C. abbreviatus, C. aureus, C. catus,C. litoglyphus, C. pennaceus, C. rattus and C. sponsalis. ^*Present address: Department of Paleontology, University ofCalifornia, Berkeley, California 94720, U.S.A. (Received 2 April 1979;     

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)     

A PRELIMINARY INVESTIGATION INTO PREY SPECIES PREFERENCE BY THE TROPICAL GASTROPODS NATICA MACULOSA LAMARCK AND THAIS CARINIFERA (LAMARCK)

A preliminary assessment of the prey-species preference of theMalaysian intertidal mudflat gastropods Natica maculosa Lamarckand Thais carinifera (Lamarck) has been made using some commonpotential prey species. The results are assessed in terms ofthe likely benefits and costs of attacking particular prey speciesand, in the case of the two most important prey species, theassessment is supported by details of energy yield. For N. maculosaonly, a comparative assessment of growth when fed on differentprey species is presented. The consequences of observed preferencesfor previous estimates of potential energy flow from a populationof the bivalve Anadara granosa (L.) through populations of thetwo predators, are considered. ^*Present address: Welsh Water Authority, Tremains House, CoychurchRd, Bridgend, CF31 2AR (Received 3 February 1982;     

Comparative growth rates and yields of ciliates and heterotrophic dinoflagellates

Growth rates, ingestion rates and grazer yields (grazer volumeproduced/prey volume consumed) were measured for six protozoanspecies (ciliates: Favella sp., Strombidinopsis acuminatum,Uronema sp.; heterotrophic dinoflagellates: Amphidinium sp.,Gymnodinium sp., Noctiluca scintillans) in laboratory batchculture experiments. Comparative growth data indicate that theprymnesiophyte Isochrysis galbana, the prasinophyte Mantoniellasquamata, two cryptophyte species and several autotrophic dinoflagellatespecies were suitable foods for these grazers. When grown onoptimized diets at 13C, maximum ciliate growth rates (range0.77–1.01 day^–1 uniformly exceeded maximum heterotrophicdioflagellate growth rates (range 0.41–0.48 day^–1).A compilation of published data demonstrates that this growthrate difference persists across a range of ciliate and dinoflagellatetaxa and cell sizes. Comparison of volume-specific ingestionrates and yields for the six species studied here showed thatthere was no single explanation for this growth rate disparity.Heterotrophic dinoflagellates exhibited both low ingestion ratesand, in one case, low yields; ciliates were able to achievehigher growth rates via either higher ingestion rates or higheryields, depending on ciliate species. Volume yield increasedover time throughout the exponential growth phase in nearlyall experiments, suggesting variation in response to changingfood concentrations or long-term acclimation to culture conditions.Higher maximum ciliate growth rates mean that these grazershave the potential to exercise tighter control over incipientblooms of their prey than do heterotrophic dinoflagellates.     

PRELIMINARY INVESTIGATIONS OF THE ECOLOGY OF THE INTERTIDAL PREDATORY GASTROPOD LEPSIELLA VINOSA (LAMARCK) (GASTROPODA MURICIDAE)

Lepsiella vinosa\ (Lamarck), a common intertidal predatory gastropod,was studied in two zones on an exposed rocky shore in Victoria(Australia). Those from the Mussel Zone in the mid-shore primarilyate one species of mussel and had a faster rate of energy consumptionthan those from the Littorinid Zone in the high-shore, whichmainly ate one species of littorinid gastropod. Shell length,growth rate and size-specific body weight of L. vinosa wereall significantly greater in the Mussel Zone. Egg capsules ofL. vinosa from the Mussel Zone contained significantly moreeggs and more potential hatchlings per capsule than those fromthe Littorinid Zone although there were no significant differencesin the sizes of eggs or hatchlings between zones. These differencesbetween the two zones were correlated to the greater consumptionof energy by L. vinosa in the Mussel Zone and were discussedin relation to the absence of dispersive larvae in this species ¹Present address: Department of Zoology, Monash University,Clayton, Victoria, 3168, Australia ²Present address: School of Biological Sciences, Carslaw Building,F07, University of Sydney, N.S.W., 2006, Australia. Addresseefor reprints. (Received 2 June 1987;     

Predation impact of Cyclops vicinus on the rotifer community in Lake Constance in spring

The predation impact of Cyclops vicinus on rotifers was studiedunder near-natural conditions in small enclosures to evaluatewhether copepod predation is responsible for the decline ofrotifers in Lake Constance in spring. Cyclops vicinus fed selectivelyon Synchaeta spp.; Keratella and Polyarthra spp. were not selectedfor. Predation rates increased with prey density up to a maximumof 37 Synchueta day^–1 at a density of 1.6 x 10⁶ Synchaetam^–2, i.e. at -1200 Synchaeta l^–1. Calculation ofcropping rates suggests that Cyclops alone can control the abundanceof Synchaeta in spring, i.e. that mainly Cyclops is responsiblefor the decline of Synchaeta species in Lake Constance in May.     

LARVAL GROWTH AND THE INDUCTION OF METAMORPHOSIS OF A TROPICAL SPONGE-EATING NUDIBRANCH

The Hawaiian dorid nudibranch Hypselodoris infucata (Rppell& Leuckart, 1828) was reared to metamorphosis in the laboratory.Egg diameter averaged 88 µm and veligers hatched, afterabout 5 days at 25°C, with a coiled shell averaging 149µm in length. Larvae fed on phytoplankton grew to a maximumshell length of 306 µm in about 15 days. Larval growthwas affected by both quality and quantity of the algal diet.Some larvae were competent to metamorphose 16 days post-hatchingat 26°C, and competence could be retained for at least oneweek. Metamorphosis is complete within 24 hours of exposureto an inducer. At least three species of sponge, Halichondriacoerulea, Sig-modocia sp., and Tedania macrodactyla, in additionto the nudibranch's adult prey species, Dysidea sp., inducedmetamorphosis of competent larvae. Primary films grown on glassslides also induced metamorphosis in some larvae, as did 20µM excess potassium ions in seawater. These data suggestthat nonspecific induction of metamorphosis occurs in this specieseven though the adult nudibranchs are highly prey specific.This implies that in the field, H. infucata find Dysidea sp.after settlement and metamorphosis Present address: Dept of Genetics and Development, College ofPhysicians and Surgeons of Columbia Univeisity, 701 West 168thStreet, NewYork, 10032, USA (Received 22 June 1987; accepted 3 March 1988)     

The influence of zooplankton defenses on prey selection by young Chaoborus larvae

Prey exhibiting a variety of morphological and behavioral antipredatordefenses were examined for susceptibility to first through thirdinstar Chaoborus americanus larvae. Synchaeta sp. was highlyvulnerable to these predators due to high encounter rates, itsrelatively soft cuticle, and lack of a precontact defense. Keratellatestudo exhibited postcontact defenses and was more susceptibleto predators than were prey of comparable size that exhibitedprecontact escape behaviors (Hexarthra mira and Diaptomus birgeinauplii). Ontogenetic changes were observed in the escape responseof D.birgei and the foraging success of C.americanus larvae.Chaoborus was observed to prey on the protists Bursaria andVolvox. Precontact defenses were more effective than postcontactdefenses in the prey species examined; however, the relativeeffectiveness of prey defenses cannot be generalized by preygenus nor by the defensive tactics employed. Present address: Department of Entomology, University of California,Riverside, CA 92521, USA     

Prey size, prey nutrition, and food handling by shrews of different body sizes

We tested some predictions relating metabolic constraints offoraging behavior and prey selection by comparing food handlingand utilization in four sympatric shrew species: Sorex minutus(mean body mass = 3.0 g), S. araneus (8.0 g), Neomys anomalus(10.0 g), and N. fodiens (14.4 g). Live fly larvae, mealwormlarvae, and aquatic arthropods were offered to shrews as smallprey (body mass <0.1 g). Live earthworms, snails, and smallfish were offered as large prey (>0.3 g). The larvae werethe high-nutrition food (>8 kJ/g), and the other prey werethe low-nutrition food (<4 kJ/g). The smallest shrew, S.minutus, utilized (ate + hoarded) <30% of offered food,and the other species utilized >48% of food. The largerthe shrew, the more prey it ate per capita. However, highlyenergetic insect larvae composed 75% of food utilized by S.minutus and only >40% of the food utilized by the other species. Thus, inverse relationships appeared between shrewbody mass and mass-specific food mass utilization and betweenshrew body mass and mass-specific food energy utilization:the largest shrew, N. fodiens, utilized the least food massand the least energy quantity per 1 g of its body mass. Also,the proportion of food hoarded by shrews decreased with increase in size of shrew. With the exception of S. araneus, the sizeof prey hoarded by the shrews was significantly larger thanthe size of prey eaten. Tiny S. minutus hoarded and ate smallerprey items than the other shrews, and large N. fodiens hoardedlarger prey than the other shrews.     

Effects of visual conditions and prey density on feeding kinetics of paralarvae of Octopus vulgaris from a laboratory spawning

Consumption rate and feeding success of newly hatched paralarvaeof the cephalopod Octopus vulgaris preying on Artemia larvaewere investigated in relation to visual conditions and preydensity. Each paralarva was tested individually using a small-scaleexperimental setup; consumption over one day was measured at20°C. A factorial experiment was designed to investigatethe effects on the consumption rate of two predictor variables:illumination/background (three levels: 7.5 Wm^–2 whitelight + white background, 7.5 Wm^–2 white light +blue background, darkness) and prey density (four levels: 2.35,4.70, 9.40 and 14.10 Artemia metanauplii ml^–1). Consumptionrate varied significantly between different conditions of illuminationand prey density. Light enhanced consumption rate, but differentbackgrounds yielded similar rates. The maximal consumption rateunder illumination was close to 16 Artemia paralarva^–1day^–1, and it was around 5 Artemia paralarva^–1 day^–1for assays in darkness. The predatory efficiency, measured asthe proportion of prey consumed, was significantly affectedby prey density, pointing to a type III functional response.The number of nonfeeding paralarvae was significantly higherin darkness and at low prey density. (Received 14 February 2006; accepted 23 December 2006)     

Food partitioning and spatial subsidy in shelter‐limited fishes inhabiting patchy reefs of Patagonia

The diets of the most conspicuous reef‐fish species from northern Patagonia, the carnivorous species Pseudopercis semifasciata, Acanthistius patachonicus, Pinguipes brasilianus and Sebastes oculatus were studied. Pinguipes brasilianus had the narrowest diet and most specialized feeding strategy, preying mostly on reef‐dwelling organisms such as sea urchins, limpets, bivalves, crabs and polychaetes. The diet of A. patachonicus was characterized by the presence of reef and soft‐bottom benthic organisms, mainly polychaetes, crabs and fishes. Pseudopercis semifasciata showed the broadest spectrum of prey items, preying upon reef, soft‐bottom and transient organism (mainly fishes, cephalopods and crabs). All S. oculatus guts were empty, but stable‐isotope analyses suggested that this species consumed small fishes and crabs. In general, P. brasilianus depended on local prey populations and ate different reef‐dwelling prey than the other species. Pseudopercis semifasciata, A. patachonicus and probably S. oculatus, however, had overlapping trophic niches and consumed resources from adjacent environments. The latter probably reduces the importance of food as a limiting resource for these reef‐fish populations, facilitating their coexistence in spite of their high trophic overlap.     

Environmentally controlled Daphnia spring increase with implications for sockeye salmon fry in Lake Washington, USA

In Lake Washington, juvenile sockeye salmon (Oncorhynchus nerka)strongly prefer Daphnia over other prey, switching uniformlyto Daphnia when the threshold abundance of 0.4 Daphnia L^–1is achieved. Using long-term Lake Washington data (1978–2001)and fry trap data (1992–2001) from a major tributary,we examined the following: (i) factors that predict Daphniapulicaria and Daphnia thorata increase to this threshold "switching"abundance, (ii) trends in Daphnia dynamics that may affect sockeyeforaging and (iii) temporal correspondence of Daphnia increaseand fry arrival. The winter abundance of D. pulicaria, in combinationwith basic parameters of spring conditions, was an importantpredictor of the date of D. pulicaria spring increase, indicatinggreater reliance on pelagic population dynamics (versus diapausehatch) than D. thorata exhibited. In addition, D. pulicariawas a more consistent prey than D. thorata, the latter exhibitinglarger population fluctuations. Thus, recently increasing D.thorata prominence could decrease diet consistency for sockeyefry. Additionally, the timing of sockeye arrival to Lake Washingtonand Daphnia’s increase to the switching threshold hasbecome less concordant, so that fry in recent years have hadto rely upon less profitable prey for longer periods. Long-termtrends and species-specific differences in Daphnia phenologymay affect fry through altering diet composition, with additionalimplications for other zooplankton withstanding greater predationpressure in Daphnia’s absence. Recent decades of warmingin Lake Washington are consistent with the warming of lakesworldwide, and complex phenological responses such as thosereported here may be common as the climate continues to change.     

Feeding and metabolism of the siphonophore Sphaeronectes gracilis

The in situ predation rate of the siphonophore Sphaeronectesgracilis was estimated from gut content analysis of hand-collectedsiphonophores and from laboratory data on digestion rates ofprey organisms. At daytime prey densities of 0.25 copepods 1^–1,S. gracilis was estimated to consume 8.1 – 15.4 prey day^–1siphonophore^–1. From data on abundances of siphonophoresand copepods, S. gracilis was estimated to consume 2–4%of the copepods daily. In laboratory experiments, ingestionrates averaged 13.8 prey day^–1 siphonophore^–1 atprey densities of 5 copepods 1^–1 and 36.9 at 20 copeods1^–1. This was equivalent to a specific ingestion rate(for both carbon and nitrogen) of –17% day^–1 and45% day^–1, respectively, while specific ingestion in situwas only 2% day^–1. Ammonium excretion averaged 0.095 µg-atsiphonophore^–1 day^–1 at 5 prey 1^–1, and 0.162at 20 prey 1^–1. The specific respiration (carbon) andspecific excretion (nitrogen as ammonium) were calculated tobe 3% day^–1 at the lower experimental food level, and5% day^–1 at the higher food level. ¹Contribution from the Catalina Marine Science Center No. 66. ²Present address: Dept. of Biology, University of Victoria,Victoria, B.C., Canada V8W 2Y2.