Molluscs in the marine curio and souvenir trade in NE Brazil: species composition and implications for their conservation and management

Marine molluscs are sold all over the world as curios and souvenirs. This market encompasses about 5,000 species of molluscs (bivalves and gastropods) worldwide, but the mollusc species involved in this trade are undocumented in all but a very small number of countries. The present study provides a baseline assessment of the mollusc species used in the manufacture of crafts, marine curiosities and souvenirs in northeastern Brazil. A total of 126 species (41 bivalves and 85 gastropods) were found to be sold individually as decorative pieces or incorporated into utilitarian objects. Overall, the families most represented were Veneridae bivalves (9 species) and the gastropods Conidae and Strombidae (8 species each). Large gastropod shells were observed in all of the localities surveyed (mainly as part of table lamps). The main species used were the King helmet Cassis tuberosa, the Hebrew volute Voluta ebraea, and the Goliath conch Eustrombus goliath. The majority of the species involved are harvested from the Atlantic Ocean (68%), but many are imported from Indo-Pacific countries, such as cowries Monetaria moneta. Among the species harvested in the Atlantic Ocean, 11.2% are endemic to Brazil as, for example, the Brazilian chank (Turbinella laevigata). The majority of the species sold in northeastern Brazil tend to inhabit shallow habitats, which facilitates their capture. As there are no official statistics available concerning the marine curio and souvenir trade in Brazil, some species may be endangered. Harvesting regulations should include minimum capture sizes, capture quotas, specific periods for harvesting, and the use of non-destructive techniques.     

Patterns of DNA Barcode Variation in Canadian Marine Molluscs

Background

Molluscs are the most diverse marine phylum and this high diversity has resulted in considerable taxonomic problems. Because the number of species in Canadian oceans remains uncertain, there is a need to incorporate molecular methods into species identifications. A 648 base pair segment of the cytochrome c oxidase subunit I gene has proven useful for the identification and discovery of species in many animal lineages. While the utility of DNA barcoding in molluscs has been demonstrated in other studies, this is the first effort to construct a DNA barcode registry for marine molluscs across such a large geographic area.

Methodology/Principal Findings

This study examines patterns of DNA barcode variation in 227 species of Canadian marine molluscs. Intraspecific sequence divergences ranged from 0–26.4% and a barcode gap existed for most taxa. Eleven cases of relatively deep (>2%) intraspecific divergence were detected, suggesting the possible presence of overlooked species. Structural variation was detected in COI with indels found in 37 species, mostly bivalves. Some indels were present in divergent lineages, primarily in the region of the first external loop, suggesting certain areas are hotspots for change. Lastly, mean GC content varied substantially among orders (24.5%–46.5%), and showed a significant positive correlation with nearest neighbour distances.

Conclusions/Significance

DNA barcoding is an effective tool for the identification of Canadian marine molluscs and for revealing possible cases of overlooked species. Some species with deep intraspecific divergence showed a biogeographic partition between lineages on the Atlantic, Arctic and Pacific coasts, suggesting the role of Pleistocene glaciations in the subdivision of their populations. Indels were prevalent in the barcode region of the COI gene in bivalves and gastropods. This study highlights the efficacy of DNA barcoding for providing insights into sequence variation across a broad taxonomic group on a large geographic scale.     

Separation of marine seston and density determination of marine diatoms by density gradient centrifugation

An attempt has been made to separate constituents of marineseston samples: inorganic material, detritus and the algal species,by density gradient centrifugation, without affecting the physiologicalstate of the algae. A relatively inert gradient material, consistingof Percoll, salt and sucrose, was composed. Since the densitiesof detritus and algae as well as those of different algal speciesoften overlapped, only 10 of the 100 samples processed in thecourse of the year showed a reasonable separation. However,an enrichment with respect to one or more species was oftenachieved. Densities of eleven species of marine diatoms andof one dinoflagellate have been determined at different timesof the year. For eight diatom species and for the dinoflagellatethe following specific density ranges were established: Bidduiphiaaurita: 1.18–1.23 g cm^–3, Biddulphia sinensis: 1.03–1.08g cm^–3, Cerataulina bergonii: 1.03–1.06 g cm^–3,Ditylum brightwellii: 1.07–1.13 g cm^–3, Rhizosoleniadelicatula: 1.04–1.09 g cm^–3, Skeletonema costatum:1.12–1.17 g cm^–3, Streptotheca thamensis: 1.04–1.10g cm^–3 , Thalassiosira rotula: 1.05–1.10 g cm^–3,Peridinium sp.: 1.08–1.12 g cm^–3. No seasonal variationin density was demonstrated. Gradients of different compositiondid not influence density measurements.     

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)     

Effect of Water Potential and Temperature on the Germination of Four Species of African Savanna Trees

The germination responses of seeds from the African tree speciesColophospermum mopane, Combretum apiculatum, Acacia tortilisand Acacia karroo under varying regimes of temperature and waterstress (induced by incubation in PEG 8000) are reported Withthe exception of Combretum (at –0.14 and –0.29 MPa)and Colophospermum (at –0.29 MPa), incubation in PEG decreasedthe maximum achieved germination percentage (90–100% forall species), but did not extend the germination lag (exceptin Combretum) or affect the time required to reach maximum germinationCombretum and Colophospermum were found to germinate under thewidest range of temperatures and water potentials, for example,as strongly negative as –1.0 MPa at 20 and 30 °C,respectively These seeds also showed greater or equivalent hypocotylelongation in PEG solutions creating potentials of –0.14,–0.29 or –0.51 MPa when compared with seeds germinatedin water, indicating an additional stress adaptation Acaciaspecies showed progressive reduction in germination rates andradicle elongation in response to decreasing water potentialExperiments giving pre-imbibition treatments in water priorto transfer to PEG solutions showed that both Acacia speciesgerminated at approximately 90% if given such pre-treatmentand less than 10% if transferred directly to PEG It is concludedthat the most stress-adapted species studied are Colophospermummopane and Combretum apiculatum, a finding generally correlatedwith the growth habit of these trees Colophospermum mopane, Combretum apiculatum, Acacia tortilis, Acacia karroo, germination, water stress, Zimbabwe     

Growth of harmful marine algae in multispecies cultures

Mixtures of harmful and harmless algae were grown in discontinuouslydiluted batch cultures under ammonium, nitrate and phosphatelimitation, and at different irradiances (20–500 µjnolquanta m^–2 s^–1). The species used were Chrysochromulinapolylepis, Emiliania huxleyi type B, Rhodomonas sp., the dinoflagellalesFibrocapsa japonica, Gymnodinium simplex, Gyrodinium aure-olum,Heterocapsa triquetra, Heterosigma carterae, Prorocentrum micansand Alexandrium tamarense, the diatoms Chaetoceros socialis,Cymatosira belgica, Ditylum brightwellii, Laudcria borealis,Odon-telta aunla, Pseudonitzschia pungens, Streptotheca tamesis,and the cyanobacterium Synechococcus. Their growth responsein the mixed algal cultures is discussed in relation to theirabundance in different natural habitats. In comparison withthe other non-diatoms, the mixotrophic C.polylepis grew fastunder all tested nutrient and light limitations.Emiliania huxleyigrew well under nitrogen (N) limitation (with nitrate as N source)and at irradiance levels from 15 up to 500 µmol quantam^–2 s^–1. No growth of calcifying cells could bedetected under N limitation when ammonium was used as N source.Rhodomonas grew reasonably well under ammonium-N limitationand grew fast at the highest irradi-ance. The dinoflagellateswere poor competitors compared to the Prymnesiophyceae. Theenvironmental fitness of the Prymnesiophyceae appears to beclosely related to the reproductive capacity of the vegetativestage, whereas the natural distribution of dinoflagellates seemsmore closely dependent on the generative reproduction-relatedspecific life cycle characteristics of the individual species.The marine diatoms include a mixture of both types of species.Some marine diatom species clearly have the capability to outcompetenon-diatoms under different types of nutrient and light limitationswhen silicate is in excess. Other diatoms seem to be poor competitors.     

Leaf-like Structure in the Photosynthetic, Succulent Stems of Cacti

This research examined the hypothesis that as cacti evolve tothe leafless condition, the stem epidermis and cortex becomemore leaflike and more compatible with a photosynthetic role.All cacti in the relict genus Pereskia have non-succulent stemsand broad, thin leaves. All members of the derived subfamilyCactoideae are ‘leafless’, having an expanded cortexthat is the plant's only photosynthetic tissue. In Pereskia,leaves have a high stomatal density (mean: 50.7 stomata mm^–2in the lower epidermis, 38.1 mm^–2 in the upper epidermis),but stems have low stomatal densities (mean: 11.3 mm ₂, threeof the species have none). Stems of Cactoideae have a high stomataldensity (mean: 31.1 mm^–2, all species have stomata). Theouter cortex cells of stems of Cactoideae occur in columns,forming a palisade cortex similar to a leaf palisade parenchyma.In this palisade cortex, the fraction of tissue volume availablefor gas diffusion has a mean volume of 12.9%, which is identicalto that of Pereskia leaf palisade parenchyma. Pereskia stemcortex is much less aerenchymatous (mean: 5.3% of cortex volume).Cactoideae palisade cortex has a high internal surface density(0.0207 cm₂ cm^–2 which is higher than in Pereskia stemcortex (0.0150 cm₂ cm^–3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm₂ cm^–3). Pereskia stem cortexhas no cortical bundles, but Cactoideae cortexes have extensivenetworks of collateral vascular bundles that resemble leaf veins. Cactaceae, cactus, intercellular space, stomatal density, internal surface/volume, evolution     

INTRA- AND INTERSPECIFIC VARIATIONS IN CALCIUM CONTENT OF FRESHWATER MOLLUSCA IN RELATION TO CALCIUM CONTENT OF THE WATER

Analyses of calcium content of molluscs collected from 53 freshwaterhabitats on a naturally occurring calcium gradient between theCanadian Shield and limestone formations in southern Ontarioshowed both intraspecific and interspecific variations in relationto pH, total alkalinity, total hardness and calcium hardnessof the water. The calcium content of individuals is relatedto the calcium concentration of the water for only about halfof the species analysed. Two species (Sphaerium rhomboideumand Sphaerium simile) showed negative correlations, while six(Cincinnatia cincinnatiensis, Pisidium casertanum, Pisidiumcompressum, Sphaerium striatinum, Anodonta grandis grandis,and Elliptio complanata showed positive correlations beteencalcium content of individuals and environmental calcium content.In general, species associated with the sediments (e.g. bivalves)showed better calcium concentrations than did species associatedwith macrophytes (e.g. gastropods). (Received 12 July 1982;     

Distribution and species-specific egg production of Pseudocalanus in the Gulf of Alaska

Pseudocalanus species are important contributors to the secondaryproduction of the northern hemisphere mid- to high-latitudeoceans. In the coastal Gulf of Alaska, Pseudocalanus are presentyear round and are represented by three species. In 2001, Pseudocalanusmimus was the dominant Pseudocalanus species on the shelf duringspring and summer, comprising 30–100% of the total, whilePseudocalanus newmani dominated in Prince William Sound (10–90%).Pseudocalanus minutus were only abundant in Prince William Soundduring early spring. Egg production (by number and volume) wasa function of female prosome length and decreased from springto summer; however, significant variability was attributableto regional influences that were independent of size. For thesame sized female, P. newmani produced more eggs per clutchthan P. mimus. Pseudocalanus mimus, however, tended to havea larger mean egg size than P. newmani. Consequently, clutchvolumes of the two species were indistinguishable. Pseudocalanusegg production rates (EPRs) (eggs female^–1 day^–1)were lower in July and August (ca. 2–4) than April andMay (ca. 1–9), but total egg production by the population(eggs day^–1) was nearly equivalent for the two time periodsdue to higher female concentrations in summer.     

Differential Effects of the Substituted Pyridazinone Herbicide Sandoz 9785 on Lipid Composition and Biosynthesis in Photosynthetic and Non-Photosynthetic Marine Microalgae: II. FATTY ACID COMPOSITION

The effect of the substituted pyridazinone, 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone(Sandoz 9785), on fatty acid synthesis in two photosyntheticspecies (Chroomonas salina and Nannochloropsis oculata) andone non-photosynthetic species (Crypthecodiniun cohnii) of marinemicroalgae were examined. Effects were more obvious in C. salinathan in C. cohnii or N. oculata. In C. cohnii the relative distributionamongst polyunsaturated fatty acids (PUFA) of radioactivityincorporated from ¹⁴C-acetate was not influenced by the herbicideto any great extent and no major changes in the fatty acid compositionof lipid fractions were observed. In C. salina, Sandoz 9785reduced the proportions of radioactivity recovered in 20: 5(n–3) and 22: 6 (n–3) of the phospholipid fraction.The distribution pattern of radioactivity in the fatty acidsof monogalactosyldiacylglycerol (MGDG) in this species was notgreatly affected by the herbicide whereas its presence significantlyreduced the proportions recovered in 18: 4 and 20: 1 in digalactosyldiacylglycerol(DGDG). The level of 20: 5 (n–3) in DGDG of C. salinawas increased from 4.0 to 19.8% by growing the algae in thepresence of Sandoz 9785. The only notable effect of the herbicideon the synthesis of PUFA in N. oculata was a reduction from18.3% to 11.3% of the proportion of radioactivity recoveredin 20: 5 in phospholipids. The herbicide had no effect on thedistribution of radioactivity in PUFA of galactolipids or onthe fatty acid composition of lipid fractions. The results arediscussed in relation to the potential role of galactolipidsand phospholipids as substrates for desaturations involved inthe formation of long chain PUFA in marine microalgae. Key words: Microalgae, herbicide, fatty acids     

THE BIOLOGY OF THE NORTHEASTERN PACIFIC TURRIDAE II. OENOPOTA

The habitat, diet, some reproductive and mortality factors forseveral shallow-water species of the boreal turrid genus Oenopotafrom the Puget Sound region were determined. All fed exclusivelyon tubicolous polychaetes. Oenopota fidicula was a dietary andhabitat generalise Oenopota elegans eats Schistocomus hiltoniand lives in areas of shell fragments. Oenopota excunata eatsTharyx multifilis and is a habitat generalist. Oenopota tabulataappears to be a dietary generalist, but lives only on or nearrocks. The widely-distributed species, O. levidensis, eats spionidpolychaetes, primarily Polydora species, or Owenia fusiformis,and is a habitat generalist. Feeding frequencies are low asare population densities; although O. levidensis sometimes exceeds15 animals m^–2. Crabs are major predators upon turridsin some areas, but mortality causes are generally obscure. Spawningwas observed in four species, but only O. elegans and O. levidensishad viable larvae. Development takes 13–15 weeks, 6–7weeks in a capsule and 6–7 weeks as planktonic veligers.There are no nurse eggs. Settling was not observed. ^*Present mailing address: Bamfield Marine Station Bamfield,B.C. VOR 1B0 CANADA (Received 30 May 1982;     

Feeding of Sagitta enflata and vertical distribution of chaetognaths in relation to low oxygen concentrations

Zooplankton samples were collected in Mejillones Bay, northernChile (23°00'15'S, 70°26'43'W ). Sampling was conductedat 4 h intervals, for 24 h during three seasons, austral spring(October 2000), summer ( January 2001) and winter (August 2001)at three different strata (0–25, 25–50 and 50–100m). Five species of chaetognaths were collected. Sagitta enflatawas the most abundant species, representing up to 65% of allchaetognaths in total numbers, followed by Sagitta bierii, makingup 34% of the total abundance of chaetognaths. S. enflata wasdistributed mainly above the Oxygen Minimum Zone, while S. bieriiremained below this zone. Feeding rates were relatively constantwithin the upper layer (0–25 m depth), for each samplingdate, averaging 1.2 prey S. enflata day^–1, and decreasingwith depth. Gut content analyses demonstrated that predationwas principally focused on small copepods (<1500 µm),with greatest feeding activity occurring at night. The dailypredation impact on the total standing stock of small copepodsvaried seasonally between 6% in spring and 0.4% in winter. Thispercentage may represent a negligible impact on the entire copepodcommunity, but it is relevant at the species or genus level,since S. enflata removed more than 20% of the standing stockof Centropages brachiatus and Corycaeus sp. Thus, during someperiods of the year, chaetognaths may strongly influence theabundance and size distribution of copepods in coastal upwellingecosystems.     

Photosynthesis in Panicum milioides, a Species with Reduced Photorespiration

The capacity for C₄ photosynthesis in Panicum milioides, a specieshaving reduced levels of photorespiration, was investigatedby examining the activity of certain key enzymes of the C₄ pathwayand by pulse-chase experiments with ¹⁴CO₂. The ATP$P₁ dependentactivity of pyruvate,P₁ dikinase in the species was extremelylow (0.14–0.18 µmol mg chlorophyll^–1 min^–1).Low activity of the enzyme was also found in Panicum decipiensand Panicum hians (related species with reduced photorespiration)and in Panicum laxum (a C₃ species). The antibody to pyruvate,P₁dikinase caused about 70% inhibition of the ATP$P₁ dependentactivity of the enzyme in P. milioides. The activity of NAD-malicenzyme and NADP-malic enzyme in ^P. ^milioides was equally low(approximately 0.1–0.2 µmol mg chlorophyll^–1min^–1) and similar to the activity in P. decipiens, P.hians and P. laxum. Photosynthetic pulse-chase experiments underatmospheric conditions showed a typical C₃-like pattern of carbonassimilation including the labelling of glycine and serine asexpected during photorespiration. During the pulse with ¹⁴CO₂only about 1% of the labelled products appeared in malate and2–3% in aspartate. During a chase in atmospheric levelsof CO₂ for up to 6 min there was a slight increase in labellingin the C₄ acids. The amount of label in carbon 4 of aspartatedid not change during the chase, indicating little or no turnoverof the C₄ acid via decarboxylation. The results indicate thatunder atmospheric conditions P. milioides assimilates carbondirectly through the C₃ pathway. Photorespiration as indicatedby the CO₂ compensation point may be repressed in the speciesby a more efficient recycling of photorespired CO₂. (Received June 8, 1982; Accepted July 22, 1982)     

Evolution of a Molluscan Cardioregulatory Neuropeptide

SYNOPSIS. The cardioexcitatory neuropeptide FMRFamide was firstidentified from a clam, but has now been demonstrated in severalother molluscs. It is probably present throughout the molluscanphylum though co-existing with related peptides in some species.For example, I report here the finding of the peptide phenylalanyl-leucyl-arginyl-phenylalanineamide (FLRFamide) in the mesogastropod Pomacea paludosa whereit accounts for 10–20% of the total FMRFamide-like activity.This peptide may be a minor component of the FMRFamide-likeactivity in other species as well. The pulmonate snails haveseveral, closely-related, heptapeptide analogs of FLRFamidethat are unique to them, such as pyroglutamyl-aspartyl-prolyl-phenylalanyl-leucyl-arginyl-phenylalanineamide (pQDPFLRFamide) which was isolated from Helix aspersa.Two additional pulmonate heptapeptides that have been isolatedprobably differ from pQDPFLRFamide only in their N-terminalamino acid residues. The heptapeptides account for most of theFMRFamidelike activity in the species in which they occur. Though the tetrapeptides FMRFamide and FLRFamide have virtuallyidentical activities on various molluscan tissues, the heptapeptideshave activity that is distinct from the tetrapeptides on somepulmonate muscles. 1 have attempted to explain the evolutionof this diversity of peptide structure and function found inthe modern pulmonates by postulating a gene duplication in thegastropod line leading to them.     

Photoinhibition of Seed Germination in Mediterranean Maritime Plants

Photoinhibition of seed germination was shown for Allium staticiforme,Brassica tournefortii, Cakile maritima and Otanthus maritimus,all plant species inhabiting sandy coasts of the MediterraneanSea. Germination of A. staticiforme was found to be typicallyMediterranean in regard to its temperature range (>0–20°C), while B. tournefortii germinated optimally at intermediatetemperatures (15–25 °C). Light sensitivity was morepronounced in the latter species and 50 % inhibition of seedgermination was obtained with photon flux densities of approximately0.1 and 0.015 mol m^–2 d^–1 in A. staticiforme andB. tournefortii, respectively. However, the slopes of the regressionlines of germination plotted against the logarithm of whitelight flux density are similar in both species. From monthlyexperiments performed under fluctuating conditions of temperatureand light, simulating the elimate of Athens throughout the year,optimal germination response peaked in ‘winter’conditions for A. staticiforme, while a bimodal pattern wasobserved for B. tournefortii (maxima at the warm ends of therainy season). In contrast to the other plants, a fifth speciestested, Crithmum maritimum, showed an absolute light requirement,probably related to the rocky habitats of the species; the optimumgermination period coincided with the rainy season. Pot experimentswith seeds of the five species buried at various depths confirmedthat maximum emergence is favoured by shallow depths (0.5–1cm). It is concluded that seed germination in maritime plantsof the Mediterranean rim is mediated by a photoinhibition mechanismwhich can be considered an adaptation strategy against surfaceseedling establishment at the harsh, sandy or shingle, sea coasthabitats. Allium staticiforme, Brassica tournefortii, Cakile maritima, sea rocket, Crithmum maritimum, rock samphire, Otanthus maritimus, ton-weed, seed germination, light, photoinhibition, phytochrome, seedling emergence     

An Ecological Imbalance Induced by a Non-Native Species: The Manila Clam in the Venice Lagoon

Among the 19 non-native species of marine invertebrates which have invaded the Venice Lagoon and have established populations, Ruditapes philippinarum, deliberately introduced in 1983, is surely the most successful species. According to the hypothesis that alien species invasion could be favoured by an altered ecological, chemical or physical state of the system induced by anthropogenic disturbance, R. philippinarum turned out to be ‘the right species at the right moment’. By comparing historical data (1968, 1985, 1990) with 1999 data, changes in macrobenthic community, in particular bivalve molluscs, of the lagoon induced by R. philippinarum introduction and subsequent clam exploiting activity were assessed. It has been possible to describe a sharp reduction, both in terms of distribution area and density, of all other filter feeder bivalves. Moreover, by using the clearance rate of the most abundant bivalve species in 1990 and 1999 (Cerastoderma glaucum and R. philippinarum, respectively), it was possible to estimate that the filtration capacity, expressed as l h⁻¹ m⁻², has more than doubled. This has altered the functioning of the ecosystem, resulting in a stronger benthic–pelagic coupling. In this context, R. philippinarum attains control of the system. Considering all this, it is possible to state that the Venice Lagoon ecosystem has entered into a new state, probably more resistant but less resilient, with implications for future management choices.     

Limnocalanus macrurus (Copepoda: Calanoida) retains a marine arctic lipid and life cycle strategy in Lake Michigan

Limnocalanus macrurus, an omnivorous calanoid copepod with strongcarnivorous tendencies that invaded fresh water during the Pleistoceneglaciation, retains a marine arctic lipid and life cycle strategyin the hypolimnion of Lake Michigan. Its maximum lipid concentrationof 67% of dry mass—consisting largely of wax esters—isthe highest reported for freshwater zooplankton and is amongthe highest reported for marine polar species. The high lipidconcentration of L.macrurus runs counter to the paradigm thathigh wax ester concentrations are found in herbivorous, butnot in carnivorous, polar species. Lipids are drawn down toextremely low levels (10% of dry mass) during the reproductiveperiod, November–May. Reproduction in this univoltinespecies appears to be timed so that the new generation developsduring the high abundance of prey (crustacean microzooplanktonand net phytoplankton) in spring. A high wax ester content mayallow egg production to start in winter when the prey concentrationis low. In contrast to many polar species, the new generationmoves through all copepodid stages to adult without diapausing.Copepodid 5 females have a low lipid concentration, and lipidsare slowly built up in new generation adults during summer andfail before reproduction commences. This lipid and life cyclestrategy may have given L.macrurus an advantage over potentialfreshwater competitors, such as the arctic freshwater cyclopoidcopepod Cyclops scutifer, in the hypolimnia of glaciated lakes.     

Trophic Dynamics and Niches of Salt Marsh Foraminifera

Energetic considerations of the growth of three species of littoralbenthic foraminifera, Allogromia laticollaris, Rosalina leei,and Spiroloculina hyalina, have been made on laboratory-grownpopulations. Under optimum laboratory conditions A. laticollarishas the greatest intrinsic rate of increase (r = 2.533 org/day);S. hyalina (r = 1.472 org/day), and R. leei (r = 0.272 org/day)being less fecund. The respiration rates of the three specieswere similar (0.5–4.5 µ1/mg body wt/hr) within thetemperature range (15–35 C) tested. The species studiedare selective feeders. Only 4-5 of 28 species of algae testedwere consumed in significant quantities (40-150 x 10⁸ g/foram/day).Although great numbers of bacteria were eaten, their biomasswas negligible when compared to the algae. The ecological growthefficiency (E_e) of the three species tested is highest in freshcultures (5-20%) and declines rapidly. Evidence suggests thatthe species studied are well adapted for the rapid changes inthe microbial community structure which take place throughoutthe summer, and that community stability and high rate of productivityare achieved through diversity.     

The effects of food deprivation, prey density and volume on clearance rates and ingestion rates of Diacyclops thomasi

The ingestion rates of the copepod, Diacyclops thomasi, on thesoft-bodied rotifer, Synchaeta pectinata, increased 10-fold(0.07–0.77 Synchaeta h^–1) over the range 50–250prey l^–1. The saturating functional response curve appearedsigmoid but was statistically indistinguishable from a parabola.The response curve was more linear and 10 times lower over thesame range of density when Diacyclops was offered Kerarellacochleans, a species having a stiffened lorica. Diacyclops maximizedits ingestion rate on Synchaeta as a function of the availablegut space. Predation effort, measured as clearance rates, waslinked tentatively to changes in swimming speed of Diacyclopsand was a function of hunger level. Diacyclops, which were starvedfor varying periods of time, increased their ingestion rateson Synchaeta up to a maximum (-3.0 h^–1) after 7–10h of food deprivation. The gut passage time of Diacyclops wasestimated to be 7–8 h. Therefore, ingestion rates (andclearance rates) appeared to be strongly correlated to the volumeof food in the gut.