A Review of Size at Maturity in Male Tanner (Chionoecetes bairdi) and King (Paralithodes camtschaticus) Crabs and the Methods Used to Determine Maturity

This paper reviews existing studies on the size of sexual maturityfor male Tanner or snow crab (Chionoecetes bairdi), a brachyuran,and the anomuran red king crab (Paralithodes camtschaticus).In this report the term sexual maturity is denned as the abilityto reproduce. A variety of indirect and direct methods thathave been used to determine maturity are reviewed. Examiningthe vas deferens for the presence of spermatophores was usefulin determining the size at which males first become mature.Breeding experiments in the laboratory demonstrated that mostmales, from both species, that produced spermatophores couldbreed with soft-shelled mates. Males of both species can breedat smaller sizes than do females. Morphometric techniques basedon reproductive tract weights and chela morphometry overestimatedthe sizes at which males mature in both species. Previous experimentsfor Tanner crab, which have internal fertilization, suggestsmall mature males can fertilize two to five females. Breedingexperiments showed recently matured red king crab do not appearto be able to fertilize more than one female per breeding season,while males nearing harvestable size can fertilize more thanone female. Breeding experiments and in situ observations of grasping pairsappear to be the most feasible methods for identifying malesize at maturity for these species. The value of morphometricestimations for determining when males mature is questionable.     

Reproductive skew among males in a female-dominated mammalian society

The purpose of this study was to document patterns of reproductiveskew among male spotted hyenas (Crocuta crocuta), a speciesin which many normal mammalian sex roles are reversed. We usedpaternity determined from 12 microsatellite markers togetherwith demographic and behavioral data collected over 10 yearsfrom a free-living population to document relationships among reproductive success (RS), social rank, and dispersal statusof male hyenas. Our data suggest that dispersal status andlength of residence are the strongest determinants of RS. Natalmales comprise over 20% of the adult male population, yet theysire only 3% of cubs, whereas immigrants sire 97%. This reproductiveadvantage to immigrants accrues despite the fact that immigrants are socially subordinate to all adult natal males, and it providesa compelling ultimate explanation for primary dispersal inthis species. High-ranking immigrants do not monopolize reproduction,and tenure accounts for more of the variance in male reproductivesuccess than does social rank. Immigrant male hyenas rarelyfight among themselves, so combat between rivals may be a relativelyineffectual mode of sexual selection in this species. Instead,female choice of mates appears to play an important role in determining patterns of paternity in Crocuta. Our data supporta "limited control" model of reproductive skew in this species,in which female choice may play a more important role in limitingcontrol by dominant males than do power struggles among males.     

Sexual selection and mating patterns in a mammal with female-biased sexual size dimorphism

In mammals, species with highly male-biased sexual size dimorphismtend to have high variance in male reproductive success. However,little information is available on patterns of sexual selection,variation in male and female reproductive success, and bodysize and mating success in species with female-biased size dimorphism.We used parentage data from microsatellite DNA loci to examinethese issues in the yellow-pine chipmunk (Tamias amoenus), asmall ground squirrel with female-biased sexual size dimorphism.Chipmunks were monitored over 3 years in the Kananaskis Valley,Alberta, Canada. We found evidence of high levels of multiplepaternity within litters. Variation in male and female reproductivesuccess was equal, and the opportunity for sexual selectionwas only marginally higher in males than females. Male and femalereproductive success both depended on mating success. We foundno evidence that the number of genetic mates a male had dependedon body size. Our results are consistent with a promiscuousmating system in which males and female mate with multiple partners.Low variation in male reproductive success may be a generalfeature of mammalian species in which females are larger thanmales.     

Does courtship behavior contribute to species-level reproductive isolation in field crickets?

Reproductive behavior influences gene flow within and amongspecies; thus, sexual selection may be a major contributor tothe maintenance of species, and possibly their formation. HereI experimentally manipulate the courtship interactions of thefield crickets Gryllus rubens and G. texensis to examine thepotential of close-range courtship interactions to limit interspecificgene flow. Responses of males to females and of females to malecourtship song and males per se were examined for four pairedsympatric and allopatric populations. Male G. rubens were morelikely to court conspecific females, but male G. texensis courtedfemales of both species equally. If paired with conspecificmales, female G. rubens and G. texensis both preferred conspecificcourtship song. In none of these comparisons were the responsesof males or females from allopatry different from those in sympatry.There was an asymmetry of courtship response across both sexand species: male G. rubens were more discriminating than maleG. texensis, whereas female G. texensis were more discriminatingthan female G. rubens. Despite significant preferences for conspecifics,the net effect of courtship interactions would appear to limitinterspecific gene flow only weakly. These results are consistentwith courtship behavior evolving under the influence of sexualselection and only indirectly promoting species integrity.     

Sexual selection and condition dependence of courtship display in three species of horned dung beetles

Sexual selection has traditionally been divided into competitionover mates and mate choice. Currently, models of sexual selectionpredict that sexual traits are expressed in proportion to thecondition of their bearer. In horned beetles, male contestcompetition is well established, but studies on female preferencesare scarce. Here I present data on male mating success and condition dependence of courtship rate in three species of horn-dimorphicdung beetles, Onthophagus taurus, Onthophagus binodis, andOnthophagus australis. I found that in the absence of malecontest competition, mating success of O. taurus and O. australiswas unrelated to their horn length and body size, whereas inO. binodis horn size had a negative effect but body size hada positive effect on male mating success. Overall, in O. binodismajor morph males had greater mating success than minor morphmales. In all three species male mating success was affectedby courtship rate, and the courtship rate was condition dependent such that when males were manipulated to be in poor conditionthey had lower courtship rates than males that were manipulatedto be in good condition. My findings provide new insight intothe mating systems of horned dung beetles and support an importantassumption in indicator models of sexual selection.     

Preference polymorphism for coloration but no speciation in a population of Lake Victoria cichlids

Female mating preference based on male nuptial coloration hasbeen suggested to be an important source of diversifying selectionin the radiation of Lake Victoria cichlid fish. Initial variationin female preference is a prerequisite for diversifying selection;however, it is rarely studied in natural populations. In clearwater areas of Lake Victoria, the sibling species Pundamiliapundamilia with blue males and Pundamilia nyererei with redmales coexist, intermediate phenotypes are rare, and most femaleshave species-assortative mating preferences. Here, we studya population of Pundamilia that inhabits turbid water wheremale coloration is variable from reddish to blue with most malesintermediate. We investigated male phenotype distribution andfemale mating preferences. Male phenotype was unimodally distributedwith a mode on intermediate color in 1 year and more blue-shiftedin 2 other years. In mate choice experiments with females ofthe turbid water population and males from a clearer water population,we found females with a significant and consistent preferencefor P. pundamilia (blue) males, females with such preferencesfor P. nyererei (red) males, and many females without a preference.Hence, female mating preferences in this population could causedisruptive selection on male coloration that is probably constrainedby the low signal transduction of the turbid water environment.We suggest that if environmental signal transduction was improvedand the preference/color polymorphism was stabilized by negativefrequency-dependent selection, divergent sexual selection mightseparate the 2 morphs into reproductively isolated species resemblingthe clear water species P. pundamilia and P. nyererei.     

Color patterns and species recognition in four closely related species of Lake Malawi cichlid

We examined interspecific female mating preferences in fourclosely related species of cichlid belonging to the Pseudotropheuszebra species complex of Lake Malawi. These species differin coloration but are similar in other respects, suggestingthat male color patterns may be important to female mate choicein species recognition. To test this hypothesis, we presented females from each species with a choice of four males, one ofher own species and three others that were each of a differentspecies. We also gave each female a choice between the threeheterospecific males only. In all four species, females showeda significant preference for conspecific males in the four-waychoice and chose the male with the most similar color patternto the conspecific male in the three-way choice. These resultsare discussed with reference to the theory of sexual selectionon color patterns as a means of sympatric speciation in cichlids.     

Sexual cannibalism, competition, and size dimorphism in the orb-weaving spider Nephila plumipes Latreille (Araneae: Araneoidea)

The degree and direction of sexual dimorphism varies widely,but in several taxa of orb-weaving spiders, including Nephila,males may be less than one-tenth the size of females. This differenceis commonly attributed to selection through precopulation sexualcannibalism: females may either fail to detect very small males,or ignore them as potential prey items. However, there is oftenthe potential for male-male competition in these species becauseseveral males can be found on the web of a single female. Weinvestigated experimentally the effects of sexual cannibalismand male-male competition on male body size and hence sexualdimorphism in the Australian golden orb-weaver (Nephila plumipes).Small males were less likely to be detected and cannibalizedthan larger males. However, larger males excluded small malesfrom the central hub of the web, where mating takes place. Theconflicting effects of sexual cannibalism and male-male competitionmay be responsible for the relatively large variation in malebody size in this species.     

Studies on nucleic acids in chloroplasts isolated from Chlorella protothecoides

1. 1. Subcellular fractions of Chlorella protothecoides were separatedby fractional centrifugation of the algal cell homogenate inmixtures of cyclohexane and CCl₄. The base composition, meltingprofiles and IRC-50 column chromatographic patterns of DNA preparationsfrom the chloroplast and non-chloroplast fractions were examined.It was shown that the algal chloroplast contains at least oneDNA species which is different from the nuclear DNA.
2. 2. RNApreparations from the subcellular fractions were subjectedtoMAK column chromatography, sucrose density gradient centrifugationand analysis for base composition. It was demonstrated thatthe chloroplast contains ribosomal RNA and soluble RNA. Twocomponents of the chloroplast ribosomal RNA were found to havethe same patterns as those of the E. coli ribosomal RNA in MAKcolumn chromatography and zone centrifugation. The major componentof the chloroplast ribosomal RNA was distinctly different fromthat of the non-chloroplastic (cytoplasmic) ribosomal RNA inall properties examined.

¹This work was partly reported at the Symposium on Mitochondriaand Chloroplasts as Self-duplicating Units sponsored by theBotanical Society of Japan in August, 1966, and at the Symposiumon Biogenesis of Subcellular Particles, the 7th Internatl. Congressof Biochemistry, Tokyo, 1967.     

Mating system, sexual dimorphism, and the opportunity for sexual selection in a territorial ungulate

In mammals, species with high sexual size dimorphism tend tohave highly polygynous mating systems associated with high variancein male lifetime reproductive success (LRS), leading to a highopportunity for sexual selection. However, little informationis available for species with weak sexual size dimorphism. Ina long-term study population, we used parentage analysis basedon 21 microsatellite markers to describe, for the first time,variance in male lifetime breeding success (LBS) of roe deer,a territorial ungulate where males weigh less than 10% morethan females. LBS ranged from 0 to 14 (mean = 4.54, variance= 15.5), and its distribution was highly skewed, with only afew males obtaining high LBS and many males failing to breedor siring only one fawn. As predicted for polygynous specieswith low sexual size dimorphism, the standardized variance inmale LBS was low (I_m = 0.75) and was only slightly higher thanthe standardized variance in female LRS (I_f = 0.53), suggestinga low opportunity for sexual selection. The I_m value reportedhere for roe deer is much lower than values reported for highlydimorphic ungulates such as red deer (I_m > 3). We suggestthat, along a continuum of opportunity for sexual selection,roe deer occupy a position closer to monogamous and monomorphicterritorial ungulates than to highly polygynous, sexually dimorphicungulates with dominance rank–based mating systems suchas harems or roving mating systems.     

Fitness correlates of male coloration in a Lake Victoria cichlid fish

Sexual selection by female choice has contributed to the rapidevolution of phenotypic diversity in the cichlid fish speciesflocks of East Africa. Yet, very little is known about the ecologicalmechanisms that drive the evolution of female mating preferences.We studied fitness correlates of male nuptial coloration ina member of a diverse Lake Victoria cichlid lineage, Pundamilianyererei. In this species, male red coloration is subject tointraspecific sexual selection by female mate choice. Male nuptialcoloration plays a critical role also in reproductive isolationbetween this species and the closely related sympatric speciesP. pundamilia. Here, we show that P. nyererei male colorationis carotenoid based, illustrating the potential for honest signalingof individual quality. In a wild population, we found that variationin male coloration was not associated with variation in a setof strongly intercorrelated indicators of male dominance: malesize, territory size, and territory location. Instead, the 2male characters that predominantly determine female choice,territory size and red coloration, may be independent predictorsof male quality: males with bright red coloration and largeterritories had lower parasite infestation rates. As a result,female preferences tended to select against heavily parasitizedmales. Consistent with parasite-mediated sexual selection, maleshad higher and more variable parasite loads than females.     

Microbiological Synthesis of Fat: PRELIMINARY SURVEY OF THE FAT-PRODUCING MOULDS

1. A survey of potential fat-producing moulds has shown that atleast 40 strains from 10 species are of interest.
2. These havebeen grown on five different media and A. nidulans,P. spinu-losum,P. javanicum, P. piscarium, P. flavo-cinereum,P. oxalicum,A. flavus, A. flavipes have shown the most promise.
3. The fatcontent on felt weight was maximal at 39?7 per cent,with A.flavipes and 34?6 per cent, with F. lini, and on usedsugarwas maximal at 9?3 per cent, with A. flavipes and 6?7per cent,with A. nidulans.
4. The potential value of micro-organisms asfat producers is discussedwith reference to the moulds.

     

Evolution of female mating preferences in stalk-eyed flies

Sensory exploitation predicts that female mate preferences existbefore the evolution of exaggerated male ornaments. We testedthis prediction by estimating female preference functions, rematingintervals, and copulation durations for three species of stalk-eyedflies. Two species, Cyrtodiopsis whitei and C dalmanni, exhibitextreme sexual dimorphism in eye span, with eye stalks exceedingbody length in large males. In contrast, C quinqucguttata ofboth sexes possess short eye stalks. Maximum parsimony analysisof 437 basepairs of the 16S mitochondrial ribosomal RNA genefrom 6 Malaysian diopsids reveals that short, sexually monomorphiceye stalks are plesiomorphic in Cyrtodiopsis. Observations ofmultiple copulations by females in paired-choice mating chambersindicated that female C whitei and C. dalmanni exhibit relativepreferences for longer eye stalks such that preference intensityincreases linearly with the difference in eye stalk length betweenmales. Females from the sexually monomorphic species showedno detectable preference for male eye stalk length. Female matingpreferences of bodi sexually dimorphic species exhibited significantrepeatability, as expected if genetic variation underlies thepreference. In addition, female C whitei and C. dalmanni exhibitedshorter copulations, mated more frequently, and rejected fewermating attempts than female C quinqueguttata. Thus, opportunitiesfor sperm competition have increased with acquisition of femalepreferences. We conclude that female sensory bias for maleswith long eye span did not exist in a common ancestor to thesespecies. Instead, female preference and remating propensityeither coevolved with eye span dimorphism or evolved after maleeye stalks elongated.     

COMPARISONS OF LIFE-HISTORY TRAITS AND SEXUAL DIMORPHISM BETWEEN ASSIMINEA JAPONICA AND ANGUSTASSIMINEA CASTANEA (GASTROPODA: ASSIMINEIDAE)

Life histories of two sympatric assimineid gastropods, Assimineajaponica and Angustassiminea castanea, were investigated ata reed marsh in northern Japan. Size frequency distributionsrevealed that growth curves of females and males differed inboth species resulting in sexual dimorphisms in shell size.In A. japonica, the shell height of females was larger thanthat of males, whereas in A. castanea males attained a biggershell than females. Mating behaviour of A. japonica was observedmainly from February to June, while that of A. castanea wasobserved from May to August. The diameter of deposited eggsof A. japonica was 200 to 250 mm, whereas that of A. castaneawas 125 to 150 mm. The length of the veliger larva of A. japonicaat hatching was approximately 200 mm, whereas that of A. castaneawas approximately 125 mm. Longevity, age at sexual maturityand opportunities for reproduction during life time were estimatedin the field. For A. japonica, sexual maturity was establishedby the age of 17 months and longevity was about three years.Opportunities for reproduction of A. japonica occurred twiceduring a lifetime. For A. castanea, sexual maturity was establishedby the age of 10 months and longevity was almost five years.Opportunities for reproduction of A. castanea occurred fivetimes during a lifetime. The differences of life-history traitsand sexual dimorphism between species and possible explanationsof evolutionary factors are discussed. To whom correspondence should be addressed. (Received 21 January 1999; accepted 8 September 1999)     

Mate sampling and the sexual conflict over mating in seaweed flies

The order in which females encounter, or sample, males in apopulation may have important consequences for mate choice,with the information gathered about males influencing boththe preference function and degree of choosiness of females.Sexual selection may be affected as a result. Sampling of particularsubsets of males may be a crucial component of individual variation in mate preferences within populations. However, the sequencein which males are sampled may also be important in specieswithout traditional, active mate choice, such as when sexualselection involves sexual conflict over mating. This wouldoccur if the likelihood of a female mating with a male of acertain phenotype changes as a result of previous encounters.We examined the effects of encountering males differing inbody size, a sexually selected phenotype, in the seaweed flyCoelopa frigida. Sexual selection occurs in this species asa result of a sexual conflict over mating. We show that theoutcome of the sexual conflict is independent of the orderin which males are encountered by female seaweed flies, withthe overall mating advantage to large males being unaffected.In addition, we explored female preference functions and evaluatethe heterogeneity in female willingness to mate. We suggestthat consideration of mate sampling theory is valuable whenexamining mate choice in species in which sexual selectionis driven by sexual conflict.     

Sexual harassment in live-bearing fishes (Poeciliidae): comparing courting and noncourting species

Sexual harassment by males has been reported from several live-bearingfishes (Poeciliidae) and has been shown to inflict costs onfemales. For example, poeciliid females have reduced feedingopportunities when accompanied by a male because females dedicateattention to avoiding male copulation attempts. Poeciliid speciesdiffer considerably in male mating behavior, such as the presenceor absence of courtship. Courting males display in front ofthe females, but males attempting to sneak-copulate approachfemales from behind, that is, in the blind portion of theirvisual field, and force copulations, which can be viewed asa male persistence trait. We predicted that poeciliid femalesneed to be more vigilant in the presence of noncourting males,and costs of harassment by noncourting males might be stronger.In a comparative approach we examined the costs of male sexualharassment for females as reduced feeding time in 9 speciesof live-bearing fishes, including courting (Poecilia latipinna,Poecilia reticulata, Xiphophorus cortezi, Xiphophorus variatus)and noncourting species (Poecilia mexicana [surface- and cave-dwellingform], Poecilia orri, Gambusia affinis, Gambusia geiseri, Heterandriaformosa). In all species examined except for the cave form ofP. mexicana, focal females spent significantly less time feedingin the presence of a male than when together with another female.The time females spent feeding was found to significantly declinewith increasing male mating activity (sum of all sexual behaviors),but there was no support for the idea that females would spendmore time feeding in the presence of courting males comparedwith noncourting ones.     

Sexual selection in a moth: effect of symmetry on male mating success in the wild

Sexual selection is generally caused by female choice and male–malecompetition. In female choice process, female preference isfavored indirectly and/or directly by sexual selection. In indirectselection, females expressing the preference might gain indirectgenetic benefits. In direct selection, females expressing thepreference might gain direct benefits or avoid male-imposedcosts. The white-tailed zygaenid moth Elcysma westwoodii ismonandrous, and males often gather around a female to mate withher, suggesting a high opportunity for sexual selection on maletraits. We quantified phenotypic selection on male morphologyin this species in the field. The morphological characters analyzedincluded body weight, antenna length, forewing length, hindwing length, hind wing tail length, genital clasper length,and the fluctuating asymmetry (FA) of these bilateral traits.In E. westwoodii, selection favored males with more symmetricgenital claspers, as well as longer and more symmetrical hindwings and antennae. Negative correlations between FA and sizewere also detected in the clasper and the antenna. Our resultssuggest that FAs of male traits, in particular the genital clasper,may have indirect and direct influences on mating success. Duringa copulatory attempt, an E. westwoodii male will try to graspthe female's abdominal tip with his claspers but often failto do so because of the female's reluctance to mate. The femaleabdominal tips are smooth and strongly sclerotized and couldthus be difficult for males to grasp. We hypothesize that moresymmetrical male claspers are more efficient in overcoming femalereluctance.     

THE DISTRIBUTION OF FORMYLTETRAHYDROFOLATE SYNTHETASE IN PLANTS, AND THE PURIFICATION AND PROPERTIES OF THE ENZYME FROM PEA SEEDLINGS

1. Formyltetrahydrofolate synthetase (E. C. 6. 3. 4. 3) was foundto be widely distributed in higher plants and the high enzymeactivity was observed in green leaves of Brassica and Alliumspecies, spinach, and in pea seedlings. In pea seedlings, theenzyme activity changed during the course of germination, andmost of the enzyme activity was located in a soluble fractionof the cytoplasm.
2. The enzyme was labile and lost the activityrapidly, even whenstored at 5 in the presence of 0.1 M mercaptoethanol.It was,however, found that ammonium sulfate was very effectivein stabilizingthe enzyme activity.
3. The enzyme has been purifiedapproximately 500-fold from extractsof pea seedlings by treatmentswith ammonium sulfate, protaminesulfate, hydroxylapatite, calciumphosphate gel, and DEAE-cellulosecolumn chromatography.
4. Thepurified enzyme was specific for formate, ATP and FAH₄,andthe Michaelis constants for these reactants were 2.1 10^–2M, 5.1 10^–4 M, and 5.6 10^–3 M, respectively.
5. The optimum pH was found to be 8.0, and the optimal temperaturewas observed at 37. Both NH₄^$ and a divalent cation (Mg^SS orMn^SS) were required for the optimal activity.

¹ Studies on the Enzymatic Synthesis and Metabolism of FolateCoenzymes in Plants. II. (For the previous paper see reference(8)) A part of this paper was presented at the Meeting of theKansai Division of the Agricultural Chemical Society of Japan,Kyoto, January 29, 1966.     

Same sexual system but variable sociobiology: evolution of protandric simultaneous hermaphroditism in Lysmata shrimps

The sexual system of the decapod (caridean) shrimp Lysmata isprotandric simultaneous hermaphroditism (PSH). Individuals firstmature as males (male phase = MP) and then when older (larger)change to the external phenotype of female carideans (femalephase = FP). However, unlike purely protandric carideans, LysmataFPs retain reduced male gonadal tissues and ducts, and are ableto mate nonreciprocally as males as well as to reproduce asfemales. Thus, FPs of Lysmata species are functional simultaneoushermaphrodites although most reproductive effort is devotedto embryo production and incubation. The question explored hereis, given the propensity of carideans to protandry, the apparentlow cost, and high reproductive advantage of PSH, why has notPSH evolved more frequently? The mating systems and sexual selectionof caridean shrimps, the original sex of protandric individuals,the cost of maleness, and sex allocation theory are discussedin relation to protandry and PSH. None of these factors adequatelyexplains the evolution of PSH of Lysmata species. Lysmata hasat least 2 species groups with very different sociobiologies;these groups do not appear to share current selective pressuresthat would explain PSH in both. A historical contingency hypothesis,testable in part with a phylogenetic analysis, may explain theevolution of PSH in Lysmata.     

Allometry and proximate mechanisms of sexual selection in photinus fireflies, and some other beetles

Ever since Darwin identified it as the force responsible forthe evolution of exaggerated male characters, sexual selectionhas been the focus of research aimed at understanding the mostbizarre and intriguing morphologies and behaviors in Nature.Two congeneric species in the firefly genus Photinus, P. pyralisand P. macdermotti, afford a unique opportunity to examine theinteraction between sexual and countervailing natural selectionthat act to shape the evolution of mating behavior and bodysize in closely related species with very different courtshipstrategies. Photinus pyralis males emit very bright flashesduring their extended patrolling flights and form ‘loveknots’ of competing suitors, while P. macdermotti males,whose courtships seldom exceed two competing males, produceweaker flashes during a shorter patrolling period. Possibly as a consequence of their scramble competition andlong flights, not only is there an extremely wide range of bodysizes in P. pyralis males, but they also exhibit wing allometricslopes greater than one, and lantern allometries less than one.In contrast, P. macdermotti males do not have allometric slopessignificantly different from one. Small males, when tested inan artificial scramble situation move faster than large males,an advantage in the intense competition that ensues once a femaleis located. Females answer several males in alternation andfail to respond to all male flashes, with the evident consequencethat love knots frequently develop around such fickle females.Allometric relationships in two non-luminescent beetle specieswith non-visual courtship protocols are compared. Visual, sexuallyselected characters showed positive allometric slopes, whilenon-visual characters showed isometry or negative slopes. Datapresented here support the existence of distinct patterns inmodality-specific sexual selection.