The Life Cycle of Three Species of Portia (Salticidae, Spartaeinae)
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THE CYCLE OF THREE SPECIES PORTIA. SALTIer ,SPARTAEINAE) SUSAN E A. HALLAS A thesis submitted in fulfillment of the for the Doctor of Phil in the University of Unive ty of 7 Ii , II i CONTENTS i/I I (I ~~' l page List of Tables iv List of Figures v Abstract 1 CHAPTER 1: INTRODUCTION 3 THE SALTICIDAE 3 PORTIA, AN ABERRANT SALTICID 3 CENTRAL QUESTIONS 5 PHYLOGENETIC STATUS OF PORTIA'S PECULIARITIES 5 PLAN OF THE THESIS 10 CHAPTER 2: HATCHING AND EARLY POST-EMBRYONIC DEVELOPMENT IN THE SALTICIDAE 12 INTRODUCTION 12 METHODS 13 TERMINOLOGY 14 RESULTS 15 ECLOSION 15 POST-HATCHING DEVELOPMENT 19 DEVELOPMENTAL TIMING 21 DISCUSSION 21 CHAPTER 3: LIFE HISTORY IN THE LABORATORY OF THREE SPECIES OF PORTIA, WEB-BUILDING ~UMPING SPIDERS (SALTICIDAE, ARANEAE) 25 INTRODUCTION 25 METHODS 26 RESULTS 27 APPEARANCE 27 MOULTING 28 AGE-SPECIFIC MORTALITY 31 SURVIVAL TO MATURITY 34 NUMBER OF INSTARS 34 INSTAR DURATION 34 MATURATION TIME 36 ADULT LONGEVITY 36 INTItASPECIFIC VARIATION IN GROWTH INCREMENT 36 ii INTERSPECIFIC VARIATION IN GROWTH INCREMENT 41 MORPHOLOGICAL INDICES OF SPECIES' GROWTH PATTERNS 43 DISCUSSION 43 MOULTING SURVIVAL AND MORTALITY 44 NUMBER OF INS TARS AND MATURATION TIME 46 INSTAR DURATION 48 ADULT LONGEVITY 48 GROWTH 50 CONCLUDING REMARKS 55 CHAPTER 4: OVIPOSITION BIOLOGY OF PORTIA, WEB-BUILDING JUMPING SPIDERS (ARANEAE, SALTICIDAE) 56 INTRODUCTION 56 METHODS 57 RESULTS 59 INTERSPECIFIC DIFFERENCES IN BATCH SIZE 59 ABDOMEN SIZE AND DISTENSION 61 VARIATION IN EGG SIZE 61 DIFFERENCES IN BATCH SIZE BETWEEN SEQUENTIAL BATCHES 65 TIMING OF OVIPOSITION 66 FERTILITY OF BATCHES 66 DISCUSSION 67 THE AFFECT OF LATITUDE 67 THE AFFECT OF FEMALE SIZE 69 THE AFFECT OF FORAGING STRATEGY 71 CONCLUSION 72 CHAPTER 5: THE ONTOGENY OF BEHAVIOUR IN PORTIA FIMBRIATA, P. LABIATA AND P. SCHULTZI, WEB-BUILDING JUMPING SPIDERS (ARANEAE, SALTICIDAE) 74 INTRODUCTION 74 METHODS 75 GENERAL 75 NORMATIVE ASSESSMENT 76 EXPERIMENTAL MANIPULATIONS 78 l:Prior Experience with Web-spider Prey 78 2:Prior Experience with Salticid Prey 78 3:Prior Experience with Insects in Alien Webs & Spider Eggs 78 RESULTS 78 PREDATORY BEHAVIOUR 78 WEB-BUILDING BEHAVIOUR 79 DEFENSIVE BEHAVIOUR 81 INTRASPECIFIC INTERACTIONS 81 EXPERIMENTAL MANIPULATIONS 82 iii DISCUSSION 82 CHAPTER 6: THE ORIGINS AND EVOLUTION OF PREDATORY BEHAVIOUR IN PORTIA (SALTICIDAE, SPARTAEINAE), ARANEOPHAGIC JUMPING SPIDERS 85 INTRODUCTION 85 METHODS 86 SUMMARY OF INTERSPECIFIC (PREDATORY) DISPLAYS AND INTRASPECIFIC DISPLAYS 87 VIBRATORY BEHAVIOURS 87 CRYPTIC STALKING 89 INTRASPECIFIC DISPLAYS 90 RESULTS 90 GROOMING BEHAVIOURS 90 Grooming of the Palps 91 Grooming of the Legs 92 STARTLE RESPONSES 92 DISCUSSION 94 GROOMING BEHAVIOURS AS ANTECEDENTS OF VIBRATORY BEHAVIOURS 94 ORIGINS OF FLUTTERING 95 ORIGINS OF PLUCKING 96 ORIGINS OF STRIKING 97 ORIGINS OF CRYPTIC STALKING 97 CONCLUSIONS 98 CHAPTER 7: GENERAL DISCUSSION 100 THE LIFE CYCLE OF PORTIA 100 IS THE LIFE CYCLE OF PORTIA ABERRANT? 102 THE PHYLOGENETIC STATUS OF AN ABERRANT LIFE CYCLE 102 ACKNOWLEDGEMENTS 107 REFERENCES 108 APPENDICES 117 1: SALTICIDS STUDIED AND SALIENT FEATURES OF THEIR NATURAL HISTORIES 117 2: MEAN DIMENSIONS AND COEFFICIENTS OF VARIATION OF 5 CARAPACE MEASURES (SEE FIG. 1) FOR THREE SPECIES OF PORTIA 1.18 iv LIST OF TABLES table chapter no. page 2 1 Medians and ranges (days) for time from oviposition for events of salticid post embryonic development, and their duration. 16 2 2 Traits specific to post-embryonic larvae of 9 species of salticids. 17 3 1 Summary of life history data for 3 species of laboratory-reared Portia. 32 3 2 Test-statistics for pairwise comparisons of life history data of 3 species of Portia. 32 3 3 Survival to maturity, as a percentage of first instars, for 3 species Portia. 34 3 4 Chi-square values for tests for differences in ins tar in which maturation occurs for 3 species of Portia. 36 3 5 F-statistics of two-way ANOVA's performed on growth indices (see Fig.l) for the effect of moult number and survival class of 3 Portia species. 40 3 6 F-statistics of two-way ANOVA's performed on ~rowth indices (see Fig.l) for the effect of moult number and sex of 3 Portia species. 41 3 7 Summary of results for two-way ANOVA's for the effect of sex class and moult type on growth indices (see Fig.l) of 3 species of Portia. 42 3 8 Principal component analysis of growth indices (see Fig.l) of 3 species of Portia at selected moults. 45 3 9 Instar of maturity of 15' species of spiders (males and females) from the literature. 47 3 10 Species in which females live longer than males, from the literature. 49 4 1 Salticids investigated and the nature of oviposition data collected from each species. 58 4 2 Maximum and mean batch sizes of 24 species of salticids, ranked by increasing maximum batch size. 59 v 4 3 Abdomen distension data on females of 5 species of Salticidae. 62 4 4 Mean egg volumes for 17 species of salticids. 63 5 1 Arthropods used in maintenance, rearing and tests for behaviour in Portia. 77 LIST OF FIGURES figure chapter no. page 2 1 Salticid egg with air spaces surrounding 18 appendages, with egg teeth and stress wrinkles. 2 2 Chorion and vitelline membrane partially shed during the first phase of eclosion, exposing a first prelarva. 18 2 3 Second prelarva of salticid post-embryonic development resulting from combined eclosion and first ecdysis. 18 2 4 Larval stage of salticid post-embryonic development, resulting from second ecdysis. 18 2 5 Ventral view of elongated fang found in the larval stage of Cyrba. 20 2 6 Ventral view of pointed, elongated fang found in the larval stage of Portia. 20 3 1 Carapace of Portia sp. Bars indicate measure ments recorded for size and growth. 27 3 2 Second instar of P. fimbriata. 29 3 3 Fourth instar of P. fimhriata. 29 3 4 Second instar of P. labiata. 29 3 5 Fourth instar of P. labiata. 29 3 6 Sixth instar of P. labiata, subadult male. 30 3 7 Second instar of P. schultzi. 30 3 8 Fourth instar of P. schultzi. 30 3 9 Survivorship values (Ix) for 3 species of Portia for successive instars. 33 vi 3 10 Percentage of adult males and females which matured in various instars for 3 species of Portia. 35 3 11 Mean growth increments and standard errors for juvenile instars of P. fimbriata. 37 3 12 Mean growth increments and standard errors for juvenile instars of P. labiata. 38 3 13 Mean growth increments and standard errors for juvenile instars of P. schultzi. 39 3 14 Growth increments of juveniles of 4 species salticids, taken from the literature. 51 4 1 Regression lines for mean batch size and for maximum batch size against female body size. 60 4 2 Regression line for mean egg size against female body size. 64 4 3 Regression lines for batch size against batch number for 3 species of Portia. 65 5 1 Regression line for area of Type 1 web against instar number. 80 5 2 Regression line for volume of Type 2 web against instar number. 80 6 1 Portia with palps held in frontal position. 88 6 2 Portia holding 1 palp between chelicerae prior to palp chewing behaviour. 88 6 3 Portia with palps held in forward-frontal position. 88 6 4 Palp swipe behaviour of Portia. 88 6 5 Palp rubbing behaviour qf Portia. 88 6 6 Cryptic rest posture of Portia. 90 Abstract The life cycle of the araneophagic, web-building, and therefore unusual salticid Portia (Spartaeinae) was investigated through labor atory studies of three species: P. fimbriata (Queensland, Australia), P. labiata (Sri Lanka), and P. schultzi (Kenya). The sequence and nature of morphological changes associated with the three stages of early post-embryonic development (prelarva 1, prelarva 2 and larva) were similar between the species. Several traits character istic of active instars of typical salticids appeared in the larval stage of Portia, most notably prey consumption and silk spinning. Virtually the complete repertoire of the species-specific behaviours of Portia was present in first instars, including web-building, web invasion, silk vibratory behaviours, and cryptic stalking. Leaf-raising behaviour appeared in instars 3-4, and in males disappeared, as did web building. Five new grooming behaviours were described in Portia: palp chew; palp swipe; palp brush; leg chew; leg brush. The routes by which these and other behaviours may have become ritualised into silk vibratory and cryptic stalking behaviours were considered. Portia moulted every 2-3 weeks, maturing in instars 5-10 (varying between species, sexes, and individuals). The period of peak mortality varied between species but c. 24% of first instars of each species reached maturity. Adult female Portia lived two to three times longer than males (i.e., males had mean longevities of 61-172 days). The growth rates of Portia fluctuated during development (means: 0.24 lengthwise; 0.19 widthwise), but always decreased in the final moult to maturity. Batch and egg sizes of Portia species varied with volumetric measures of female size (e.g., cubed body length, abdomen volume) and latitude of origin. Of the developmental traits of Portia, four were unusual for a salticid: precocial appearance of certain traits in the larval stage of post-embryonic development of Portia; moulting in a large three dimensional web rather than inside an enclosing silk nest; lengthwise growth rates comparable to those of web-builders of other families; and fluctuating rather than progressively increasing instar durations. None of these aberrant traits of the life cycle seem to clarify our under standing of Portia's position in salticid evolution.