Heritability of three condition surrogates in the yellow dung fly

Condition capture has been proposed as a general mechanism maintainingadditive genetic variation, V_a, in sexually selected traitsunder directional selection. It relies on two main assumptions:condition-dependent trait expression and V_a in condition. Althoughthere is evidence for the former, direct evidence that conditionis heritable is scarce, although this is a requirement of mostmodels of handicap sexual selection. We used a parent–offspring,full-sib, two-container laboratory breeding design in the yellowdung fly Scathophaga stercoraria to demonstrate the broad- andnarrow-sense heritability of three surrogates of condition commonlyused in sexual selection studies: lipid and glycogen reserves(i.e., physiological condition), body size, and fluctuatingasymmetry. All three measures are nutrition dependent and havebeen linked to sexual selection in free-living yellow dung flies.While lipid reserves and body size were heritable, asymmetryand glycogen reserves were not. Moreover, the evolvability ofphysiological condition was higher than that of the other twotraits. Of the three surrogates, physiological condition ismost akin to the original definition, but all have their limitations.We conclude that condition is a useful heuristic concept inevolutionary ecology, but its practical value may be limitedby the fact that it cannot be measured directly.     

Statistical Studies Using AIC Method to Decide the Question of "Break" or "Straight" in Arrhenius Plots of Water Proton NMR Relaxation Times in Chilling-Sensitive Vigna and Insensitive Pisum Seedlings

The question of "break" or "straight" in Arrhenius plots forthe temperature dependency of NMR relaxation times (T₁) of waterprotons in etiolated intact seedlings for chilling-sensitivetwo Vigna species and chilling-insensitive Pisum was statisticallystudied using the Akaike's Information Criterion (AIC), a versatileprocedure for statistical model identification. Among sevenmodels, the most appropriate was based on the following assumptions:individual k (preparation numbers) two-half lines connectingat the break point (TCB) and imposing no restrictions for thegradient and the break point (Model 7). The worst two modelswere one straight line or one TCB (Model 1 or 4). Thus, thedata obtained from replicated preparations should not be treatedas a whole but as individual in each sample case. Break pointsdetermined with Model 7 ranged around 11-5°C for V. radiataand 17-10°C for V. mungo. The implication of the occurrenceof "break" for Pisum clearly differed from Vigna judging bythe model fitness based on the AIC values. The question of "break"or "straight" in Arrhenius plots is therefore fairly dependenton the validity of the model selection in the statistical analysis,and the AIC method is a useful procedure for the resolutionof the problem of the "use" or "misuse" of Arrhenius plots inplant physiology. (Received November 2, 1988; Accepted January 17, 1989)     

Population Variation in Continuously Varying Traits as an Ecological Genetics Problem

The niche variation hypothesis is an adaptive explanation forvariation within populations and for, the differences in variationbetween populations in morphological, physiological or behavioraltraits. It has received only partial support from empiricaltests and has been criticized on theoretical grounds. Recentquantitative genetic models have made an advance by exploringthe effects of mutation, migration, mating pattern and selectionon phenotypic variance. These models are reviewed and theirmost important features are integrated in a new model. In thismodel population variation is in a state of balance betweenthe opposing forces of mutation and immigration, which tendto elevate variation, and selection and possibly genetic drifttending to decrease it. Populations exhibiting different levelsof variation are interpereted as having different equilibriumpoints, and it is the task of empirical studies to determinethe relative magnitudes of the opposing factors. An exampleis given from studies of Darwin's finches. Geospiza fortis variesmore than G. scandens on Isla Daphne Major, Galápagos,in several morphological traits including beak and body size.This is explained, assuming equal mutation rates in the twospecies, as the result of more frequent genetic input to theG. fortis population, through occasional hybridization withimmigrant G. fuliginosa, and relaxed stabilizing selection.Stabilizing selection is less intense on G.fortis than on G.scandens because the G. fortis population has a broader niche;there is both a within-phenotype and betweenphenotype componentto the broad niche of G. fortis. The success of theory in explainingpopulation variation is discussed, and it is concluded thatempirical studies lag far behind theory.     

The Net Assimilation Rates of Wild and Cultivated Beets

The net assimilation rate (E) of Kleinwanzleben sugar-beet wasthe same as that of three types of wild sea-beet (Beta vulgarissubsp. maritima) when the leaf-area index (L) was near to I.In a subsequent period, when mean L of sugar-beet and of theleafiest wild beet type was 2.5, there was an inverse relationbetween E and L of the three wild types, and E of sugar-beetwas then much greater than that of the wild type with equalL but was little different from that of the wild type with smallestL (about 1.5). It is concluded that the development of sugar-beetfrom its wild ancestors by selection and breeding has not affectedthe intrinsic photosynthetic efficiency of the leaves, but hasdiminished the effect of mutual-interference between leaves,so that E falls less rapidly as L increases, i.e. it has decreasedthe leaf-density dependence of E. This change may be relatedto the difference in form between sugar-beet and wild beet plants.     

Adaptive evolution of sperm bindin tracks egg incompatibility in neotropical sea urchins of the genus Echinometra

Bindin is a gamete recognition protein known to control species-specificsperm-egg adhesion and membrane fusion in sea urchins. Previousanalyses have shown that diversifying selection on bindin aminoacid sequence is found when gametically incompatible speciesare compared, but not when species are compatible. The presentstudy analyzes bindin polymorphism and divergence in the threeclosely related species of Echinometra in Central America: E.lucunter and E. viridis from the Caribbean, and E. vanbruntifrom the eastern Pacific. The eggs of E. lucunter have evolveda strong block to fertilization by sperm of its neotropicalcongeners, whereas those of the other two species have not.As in the Indo-West Pacific (IWP) Echinometra, the neotropicalspecies show high intraspecific bindin polymorphism in the samegene regions as in the IWP species. Maximum likelihood analysisshows that many of the polymorphic codon sites are under mildpositive selection. Of the fixed amino acid replacements, mosthave accumulated along the bindin lineage of E. lucunter. Weanalyzed the data with maximum likelihood models of variationin positive selection across lineages and codon sites, and withmodels that consider sites and lineages simultaneously. Ourresults show that positive selection is concentrated along theE. lucunter bindin lineage, and that codon sites with aminoacid replacements fixed in this species show by far the highestsignal of positive selection. Lineage-specific positive selectionparalleling egg incompatibility provides support that adaptiveevolution of sperm proteins acts to maintain recognition ofbindin by changing egg receptors. Because both egg incompatibilityand bindin divergence are greater between allopatric speciesthan between sympatric species, the hypothesis of selectionagainst hybridization (reinforcement) cannot explain why adaptiveevolution has been confined to a single lineage in the AmericanEchinometra. Instead, processes acting to varying degrees withinspecies (e.g., sperm competition, sexual selection, and sexualconflict) are more promising explanations for lineage-specificpositive selection on bindin.     

Intragenic Hill-Robertson interference influences selection intensity on synonymous mutations in Drosophila

Natural selection influences synonymous mutations and synonymouscodon usage in many eukaryotes to improve the efficiency oftranslation in highly expressed genes. Recent studies of genecomposition in eukaryotes have shown that codon usage also variesindependently of expression levels, both among genes and atthe intragenic level. Here, we investigate rates of evolution(Ks) and intensity of selection (_s) on synonymous mutationsin two groups of genes that differ greatly in the length oftheir exons, but with equivalent levels of gene expression andrates of crossing-over in Drosophila melanogaster. We estimate_s using patterns of divergence and polymorphism in 50 Drosophilagenes (100 kb of coding sequence) to take into account possiblevariation in mutation trends across the genome, among genesor among codons. We show that genes with long exons exhibithigher Ks and reduced _s compared to genes with short exons.We also show that Ks and _s vary significantly across long exons,with higher Ks and reduced _s in the central region comparedto flanking regions of the same exons, hence indicating thatthe difference between genes with short and long exons can bemostly attributed to the central region of these long exons.Although amino acid composition can also play a significantrole when estimating Ks and _s, our analyses show that the differencesin Ks and _s between genes with short and long exons and acrosslong exons cannot be explained by differences in protein composition.All these results are consistent with the Interference Selection(IS) model that proposes that the Hill-Robertson (HR) effectcaused by many weakly selected mutations has detectable evolutionaryconsequences at the intragenic level in genomes with recombination.Under the IS model, exon size and exon-intron structure influencethe effectiveness of selection, with long exons showing reducedeffectiveness of selection when compared to small exons andthe central region of long exons showing reduced intensity ofselection compared to flanking coding regions. Finally, ourresults further stress the need to consider selection on synonymousmutations and its variation—among and across genes andexons—in studies of protein evolution.     

The Determinants of Muscle Fiber Type During Embryonic Development

SYNOPSIS. Most vertebrate skeletal muscles consist of a heterogeneousarray of muscle fiber types that are distinguishable, in part,by differences in their contractile protein isoform content.It is often suggested that the information necessary for directingthe development of these fiber types is derived from interactionswith factors outside the muscle fibers themselves and, in particular,with innervating motoneurons. However, recent data from thisand other laboratories indicate that the emergence of fiberspecialization within developing muscle is not dependent oninnervation at all. These studies recognize two periods of embryonicfiber specialization. The first occurs during early embryonicdevelopment as individual muscles are formed from primary generationfibers expressing different myosin isoform types. The formationof these "early" muscle fiber types and their characteristicdistributions within and among different muscles are not dependenton interactions with innervating motoneurons. Furthermore, myoblastsisolated from "early" embryonic muscle tissue and cultured invitro display the same heterogeneity of myosin expression asthe primary generation fiber types in ovo, suggesting that thedifferences in expression among early muscle fiber types arepreprogrammed within their myoblasts. The second period occurs"late" in development after the major morphological events oflimb formation are complete and the initial pattern of fibertypes has been established. It is during this period that massivegrowth of most muscles occurs which is due, in part, to theformation of a secondary generation of muscle fibers. Thesesecondary generation fibers in ovo and the cultured myotubesderived from "late" embryonic myoblasts exhibit a single myosinphenotype (e.g., fast). The transition from "early" to "late"embryonic phases is accompanied by a change in fast myosin heavychain expression and is blocked by agents that disrupt neuromuscularcontacts.     

The influence of experimental scale on estimating the predation rate of Gammarus lacustris (Crustacea: Amphipoda) on Daphnia in an alpine lake

We examined the effect of experimental scale on the predationrate of Gammarus lacustris preying on Daphnia middendorffianain 20 l cubitainers, 2800 l mesocosms and diurnal whole-lakesurveys. The predation rate differed significantly among experimentalscales. It was highest in the 20 l cubitainers, intermediatein the 2800 l mesocosms and lowest in the lake. At all experimentalscales, the predation of G.lacustris on D.middendorffiana increasedas a linear function of prey density (Type I functional response).Very different predation rates were calculated for the wholelake depending on whether D.middendorffiana densities were estimatedfrom whole-water column hauls or stratified depth hauls. Thishighlights the importance of accurately determining the spatialdistribution of prey for estimating reliable in situ predationrates. We also determined prey selection by G.lacustris. Daphniamiddendorffiana was strongly selected over the calanoid copepodHesperodiaptomus arcticus. When presented with different sizedDaphnia, G.lacustris preyed size selectively on individuals2 mm. Our results show that the predation rate of small invertebratepredators is sensitive to a wide range of experimental conditionsand needs to be corroborated at a variety of scales. We concludethat the impact of G.lacustris on zooplankton communities wouldbe strongest in small fishless lakes or ponds.     

Characterization, Functional Reconstitution and Activation by Fusicoccin of a Ca2+-ATPase from Corydalis sempervirens Pers. Cell Suspension Cultures

Cell suspension cultures of Corydalis sempervirens have provenideal for the study of fusicoccin action [Schulz et al. (1990)Planta 183: 83] and express the fusicoccin-binding protein aswell as a plasma membrane H⁺-ATPase which is activated by thefungal toxin. Microsomal vesicles prepared from these cellsaccumulate Ca²⁺ in the presence of Mg-ATP. The protonophorecar-bonylcyanide m-chlorophenylhydrazone did not inhibit theMg-ATP dependent Ca²⁺-transport into the vesicles. This processis thus due to the activity of at least one primary active,ATP-driven, Ca²⁺-pump. The enzyme was characterized in detail.It has a pH optimum of 7.2, an apparent K_m of 0.3 mu (ATP),12pm (Ca²⁺), accepts ATP>ITP GTP>CTP UTP, and is strongly(Kⁱ, app 0.75 µmM) inhibited by erythrosine B but lessso (Kⁱ, app 95 µM) by or-thovanadate. These characteristicsare typical for the plasma membrane Ca²⁺-ATPase characterizedfrom differentiated tissues [Graf and Weiler (1990) Physiol.Plant. 75: 634]. Fusicoccin activates the erythrosine-sensitiveCa²⁺-pump by lowering its K_m for ATP, when added to living cellsprior to tissue homogenization. Thus, fusicoccin appears toactivate at least two ion-translocating ATPases in one and thesame tissue, suggesting that the toxin's mechanism of actionis complex and not restricted to activation of the H⁺-ATPase.FC has no effect when administered to microsomes. The microsomalenzyme was solubilized and reconstituted into asolec-tin liposomesin functional form. The reconstituted, erythrosine sensitiveCa²⁺-ATPase was insensitive to fusicoccin. Thus, componentsessential for toxin action are either lost or inactivated duringsubcellular fractionation. It is likely that FC action requiressoluble components. (Received April 22, 1991; Accepted July 24, 1991)     

Corbicula (Bivalvia: Sphaeriacea) vs. Indigenous Mussels (Bivalvia: Unionacea) in U.S. Rivers: A Hard Case for Interspecific Competition?

At a time when populations of indigenous river mussels havebeen dwindling and/or disappearing, the introduced Asian clam,Corbicula, has spread through many U.S. rivers from Californiato Florida. In the Arkansas River Navigation System, a heavilymanaged waterway, Corbicula presently has a different "competitive"presence than it does in the relatively unmanaged Buffalo Riverin Arkansas. Comparative studies of both Corbicula and indigenousbivalved mollusks reveal biological bases for the contrastingkinds of benthic faunal change. There are ecologically relevant,distinctive differences between the two kinds of animals: inmantle/shell and mantle/gill apparatus, in the reproductivecomplex and neuroanatomy, and in spawning and locomotor behaviors.It is argued that the conservative molluscan characteristicsof Corbicula enable it to function in an exclusive, "contradictory"role with indigenous bivalves in a heavily managed waterway,and in a "contrary" competitive role elsewhere. Rationale ispresented for incorporating organismic evaluation into studiesof competition between distantly related taxa.     

The Interaction of Ultraviolet-B Radiation and Water Deficit in Two Arabidopsis thaliana Genotypes

It has been demonstrated, in both herbaceous and woody species,that tissue hydration resulting from exposure to drought isless pronounced if plants are concurrently exposed to ultraviolet-Bradiation (UV-B). An explanation for the mechanisms underlyingthis phenomenon has been elusive. Arabidopsis thaliana(L.) Heynh.genotypes, defective in specific defences against UV-B exposure,may permit more insightful study of drought-UV-B interactionsthan is possible with genetically uniform plants. Arabidopsishas a rosette stature and has predominantly abaxial stomata.Thus, it is difficult to investigate its stomatal behaviourand gas exchange using conventional techniques and instrumentation.In this study, the relative abundance of¹³C and¹²C in leaf tissue(¹³C) was used as a means of determining water use efficiency(WUE) and the relative balance, at the site of carbon fixation,between CO₂supply and demand. UV-B insensitive (L er) and sensitive(fah1)Arabidopsis genotypes were raised in a growth chamberand exposed to 6 kJ m^-2 d^-1UV-B irradiation and subjected todrought. In both genotypes, leaf desiccation was less pronouncedthan that of control plants that were subjected to drought butnot exposed to UV-B. The relatively low (more negative) leaf¹³C values (indicating low WUE), but high dry matter productionof the UV-B exposed plants suggest that their higher leaf watercontent was not primarily due to stomatal closure. We proposethat the mechanisms underlying the maintenance of higher leafwater content involved UV-B and water stress induced biosynthesisof stress proteins and compatible osmolytes. Copyright 2000Annals of Botany Company Arabidopsis thaliana, ultraviolet-B, water deficit, stable carbon isotopes, ¹³C, stomatal opening, tissue dehydration, dehydrin     

Studies on the Role of Photosynthesis in the Photoperiodic Induction of Flowering in the Short-Day Plants Kalanchoe blossfeldiana Poellniz and Xanthium pensylvanicum Wallr: I. THE REQUIREMENT FOR CO2 DURING PHOTOPERIODIC INDUCTION

It has been established that Kalanchoe blossfeldiana and Xanthiumpensylvanicum require CO₂ during the light period of short daysfor successful photoperiodic induction of flowering, even ifall but the induced leaf are held in normal air. In X. pensylvanicumfloral induction in normal air was independent of the starchstatus of the leaves but when reserves were reduced, lack ofCO₂ in the light suppressed floral induction to an even greaterextent. Injection into the induced leaf (Kalanchoe) or leaftip feeding (Xanthium) of carbohydrates, organic and amino acidsor several other metabolites failed to substitute for the CO₂requirement for induction. A small response was produced by10 mg ml^–1 sucrose in X. pensylvanicum while in normalair 25 parts 10^–6 ATP reduced the time to flowering inK. blossfeldiana and 10^–4 M proline was inhibitory. Anexperiment on the light requirement established a need for redlight ( max 660 nm) during photoperiods but red light alonedid not facilitate maximal induction. It is concluded that someearly, possibly labile, product of photosynthetic CO₂ fixationis essential to floral induction in these species.     

不同杀虫剂选育对家蝇抗药性水平及kdr基因频率的影响

采用杀虫剂（溴氰菊酯和甲基嘧啶磷）筛选及不接触药物自然衰退的方法,研究了家蝇Musca domestica氯氟氰菊酯高抗品系(Cyh-R)对杀虫剂的抗性变化,探讨蝇类抗药性治理的方法。用点滴法测定氯氟氰菊酯对不同家蝇品系的毒力,比较抗药性的变化,结合特异性等位基因PCR扩增（PASA）技术检测了不同家蝇品系的kdr基因频率,探讨kdr基因频率与抗性水平之间的关系。结果表明:甲基嘧啶磷筛选后,氯氟氰菊酯对第2~8代Cyh-R品系的LD₅₀呈递减趋势,从F₀的2.8434 μg/蝇降为F₈的0.4404 μg/蝇,但第8~18代Cyh-R品系的LD₅₀呈逐代递增趋势;溴氰菊酯筛选后,氯氟氰菊酯对Cyh-R品系第2~16代的LD₅₀呈上升趋势,从F₀的2.8434 μg/蝇升至F₁₆的24.3249 μg/蝇;表明了施用有机磷杀虫剂可降低其对氯氟氰菊酯的抗药性,而施用拟除虫菊酯药剂则有助于其对氯氟氰菊酯抗药性的增长;不使用任何杀虫剂也能降低其对氯氟氰菊酯的抗药性,但下降速率低于甲基嘧啶磷。PASA技术检测表明Cyh-R品系的kdr抗性基因频率为88.8%,不经过任何药剂筛选其kdr抗性基因频率下降程度最大,达到69.7%;甲基嘧啶磷筛选后其结果降为78.8%,而经溴氰菊酯筛选后kdr抗性基因频率则明显升高,达到98.9%。通过对kdr抗性基因频率和抗性水平进行相关和回归分析表明kdr抗性基因频率与家蝇对氯氟氰菊酯的LD₅₀呈对数关系,即LD₅₀值高的品系其kdr抗性基因频率相应的也较高。建议在家蝇防治中考虑轮换用药。     

Patterns of Parental Investment and Sexual Selection in Teleost Fishes: Do They Support Bateman's Principles?

Bateman demonstrated differences in variance for fertility andmating success between the sexes, with males usually havinga greater variance than females. Thus in general, male reproductivesuccess increases with number of mates acquired. These resultshave been referred to as "Bateman's principles" and taken togetherwith other parameters (e.g., relative parental investment) havebeen proposed to estimate a component of sexual selection. Forthis review I examine patterns of parental care and sexual selectionin teleost fishes (substrate brooding and with internal fertilization).I present data for the pumpkinseed sunfish Lepomis gibbosus,in which I estimated cost of paternal care and compared directmeasures of the intensity of selection on possible sexuallyselected traits to measures of sexual selection based on Bateman'sprinciples. Despite high levels of paternal care in substrate brooding fishes,sexual selection tends to act more strongly on males than onfemales, which suggests that maternal investment is higher thanpaternal investment and that parental care does not limit thereproductive rate for males. In pumpkinseed sunfish, selectionfavors parents with high levels of defense that may excludepredators more effectively and, as suggested by Bateman's measures,alternative reproductive strategies may decrease the opportunityfor sexual selection within the parental strategy. In teleostfishes with internal fertilization, patterns of parental investmentand intensity of sexual selection seem to support Bateman'sprinciples, but further studies using these systems and thesemeasures of selection will improve the understanding of factorsaffecting the intensity of sexual selection and its relationto mating systems.     

CO2 chemosensitivity in Helix aspersa: three potassium currents mediate pH-sensitive neuronal spike timing

Elevated levels of carbon dioxide increase lung ventilation in Helix aspersa. The hypercapnic response originates from a discrete respiratory chemosensory region in the dorsal subesophageal ganglia that contains CO₂-sensitive neurons. We tested the hypothesis that pH-dependent inhibition of potassium channels in neurons in this region mediated the chemosensory response to CO₂. Cells isolated from the dorsal subesophageal ganglia retained CO₂ chemosensitivity and exhibited membrane depolarization and/or an increase in input resistance during an acid challenge. Isolated somata expressed two voltage-dependent potassium channels, an A-type and a delayed-rectifier-type channel (I_KA and I_KDR). Both conductances were inhibited during hypercapnia. The pattern of voltage dependence indicated that I_KA was affected by extracellular or intracellular pH, but the activity of I_KDR was modulated by extracellular pH only. Application of inhibitors of either channel mimicked many of the effects of acidification in isolated cells and neurons in situ. We also detected evidence of a pH-sensitive calcium-activated potassium channel (I_KCa) in neurons in situ. The results of these studies support the hypothesis that I_KA initiates the chemosensory response, and I_KDR and I_KCa prolong the period of activation of CO₂-sensitive neurons. Thus multiple potassium channels are inhibited by acidosis, and the combined effect of pH-dependent inhibition of these channels enhances neuronal excitability and mediates CO₂ chemosensory responses in H. aspersa. We did not find a single "chemosensory channel," and the chemosensitive channels that we did find were not unique in any way that we could detect. The protein "machinery" of CO₂ chemosensitivity is probably widespread among neurons, and the selection process whereby a neuron acts or does not act as a respiratory CO₂ chemosensor probably depends on the resting membrane potential and synaptic connectivity. carbon dioxide     

Cellulose Microfibril Orientation in Rubbery Wood

The fibre length L and average helical angle of microfibrilorientation in fibres from successive growth rings in both normaland ‘rubbery’ wood of stems of apple var. Lord Lambournehave been measured. It has been shown that the normal relationship,L = A+B cot , does not hold for ‘rubbery wood’.There is a tendency for the helix to remain flat, the angle fairly constant independently of fibre length. This, togetherwith abnormalities in the lignin chemistry, causes the rubberywood to have low tensile strength and high extensibility.     

Lipids in Cryptomonas CR-1. II. Biosynthesis of Betaine Lipids and Galactolipids

The biosynthesis of lipids in Cryptomonas strain CR-1 was studiedusing radioactive tracers. For studies of general aspects ofthe biosynthesis of lipids, the cells were labelled with [¹⁴C]NaHCO₃or with [l,3-¹⁴]glycerol. In both cases, monogalactosyl diacylglycerol(MGDG) was the most heavily labelled lipid. Phosphatidylcholineand the alanine lipid DGTA were not labelled to specific activitiescomparable to those of MGDG and DGDG. It is improbable thatthe so-called "eukaryotic pathway", which has been suggestedas the pathway for the synthesis of " eukaryotic" molecularspecies of MGDG from PC in higher plants, is operative in Cryptomonascells which contain typical "eukaryotic" MGDG. The homoserinelipid DGTS was labelled to a significant level only in its polargroup. The C-3 and C-4 atoms of methionine, as well as the methylcarbon of methionine, were incorporated into both DGTS and DGTA,whereas the C-l carbon of methionine was incorporated uniquelyinto DGTS. Results of pulse-chase experiments with [3,4-¹⁴C]methionineand [methyl.-^l4C]methionine suggest the conversion of DGTS toDGTA. (Received April 22, 1991; Accepted June 12, 1991)     

Mesh selection of copepodite and nauplius stages of four calanoid copepod species

High-speed plankton nets, using mesh sizes of 61, 90, 124,190and 270 µn, were deployed in the North Sea to catch Calanusspp., Pseudocalanus minutus, Paracalanus parvus and Temora longicomis.These species were identified to their nauplii, copepodite andadult stages, and the numbers caught in each stage were convertedto numbers m^–3 seawater filtered. The width and lengthof a representative sample of each stage was measured, and theproportion caught by the different mesh sizes is presented.The selection pattern was described by a mathematical model,which showed that a mesh size of 75% of the copepod carapacewidth catches 95% of the individuals of that size present inthe seawater. Some recommendations for mesh sizes required tosample copepods are given.     

Specific anosmia to l-carvone: the minty primary odour

Specific anosmia to l-carvone has been found in about 8% ofthe human population. Olfactory thresholds of 24 chemicals exhibitinga minty odour have been measured with panels of normal and specificallyanosraic subjects. The results show that this anosmia is mostlyassociated with l-carvone and compounds very closely relatedboth in molecular shape and configuration. It is suggested thatl-carvone represents the best example of the "minty" primaryodour, already proposed by Amoore in 1962 and that the inabilityto smell it corresponds with the absence of a specific receptorprotein.