METABOLIC RATES IN SPIDERS By JOHN FRANCIS ANDERSON A DISSERTATION PRESENTED TO THE GRADUATE COX.TNCIL OF THE UNrVTO^SITY OF FLORIDA IX PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPIIY UNIVERSITY OF FLORIDA 1968 ACKNOWLEDGEMENTS I am deeply indebted to Dr, James L. Nation, under whose direction the present research was conducted. Dr. Robert M. DeWitt must be thanked for his liberal support in providing the necessary supplies and equipment. Grateful acknowledgement is given to Dr. Frank G. Nordlie, Dr. Brian K. McNab, Dr. John D. McCrone, Dr. James L. Nation, and Mr. Thomas Krakauer who gave most generously of their time in evaluating some of my ideas. My thanks go to Dr. Martin H. Muma, Dr. John D. McCrone, and Mr. Cole Benton for supplying certain animals which otherwise would not have been available. For aid in solving various statistical problems, 1 am indebted to Miss Mary E. Glenn, Dr, Rodger Mitchell must be thanked for his assistance in conducting the histological studies. Financial support through appointment to research and teaching positions was provided by Dr. Frank G. Nordlie and Dr. Lewis Berner to whom 1 am grateful. Dr. Nation, Dr. Nordlie, and Dr. McCrone must again be thanked along with other members of my graduate supervisory committee, Dr. Thomas J, Walker and Dr. Howard K. Wallace, who not only critically reviewed the dissertation, but also provided support in solving the many small but important problems that occurred during my tenure as a graduate student. Finally thanks are also due to Mrs. Lillian ingenlath for typing the manuscr i pt. i i TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ii LIST OF TABLES iv LIST OF FIGURES v INTRODUCTION 1 MATERIALS AND METHODS 5 RESULTS ]k Weight Changes . 1^ Temporal Variation in Oxygen Consumption ]k Loss of Temporal Variation in Oxygen Consumption 19 Standard Metabolic Rates 20 Respiratory Q^uotient 23 Breathing Systems 23 Exoskeleton V/eight, Metabol i ca] 1 y Active Tissue Weight, and Total V/eight. , 23 Oxygen Consumption and Temperature 23 DISCUSSION . 37 LITERATURE CITED 6h BIOGRAPHICAL SKETCH 6? Ill LIST OF TABLES Table Page 6 1 LIST OF EXPERIMENTAL ANIMALS 2 WEIGHT CHANGES IN SPIDERS 1^ 20 3 AVERAGE OXYGEN CONSUMPTION OF ARACHNIDS AT 20 C k OXYGEN CONSUMPTION OF INDIVIDUAL ARACHNIDS AT 21 20 C. , . , 5 CALCULATED SLOPES AND INTERCEPTS OF THE EQUATION LOG METABOLISM = LOG K + n • LOG WT 22 6 RESPIRATORY GAS EXCHANGE SYSTEMS OF SPIDERS 2k 7 TOTAL WEIGHTS, EXOSKELETON WEIGHTS, AND ACTIVE TISSUE WEIGHTS 26 8 OXYGEN CONSUMPTION AT DIFFERENT TEMPERATURES 29 9 AVERAGE WEIGHT, METABOLIC RATE AND BOOK-LUNG SURFACE AREA IN ADULT SPIDERS 50 10 CALCULATED RELATIONSHIPS BET\/EEN EXOSKELETON WEIGHTS AND METABOLI CALLY ACTIVE TISSUE WEIGHTS TO TOTAL WEIGHTS 57 I V LIST OF FIGURES Figure Page 1 Oxygen consumption over 2h hours. Each point represents the mean of N determinations. The time interval indicated by the black stripe represents the 12 hour dark period. (a) J_, - = if lenta . N 6; (b) F. hibernal is , N 1 16 2 Oxygen consumption over 2k hours. Each point represents the mean of N determinations. The time interval indicated by the black stripe represents the 12 hour dark period. (a) _P. = = reqius . N 6; (b) T. ruf ipes . N 5; (c) A. tepidar jorum , H = 5 18 Oxygen consumption of _P. regi u s versus temperature. © 10 C acclimation; o 20 C acclimation; © 30 C acclimation. Acclimation time exposures are indicated in Table 8 31 Oxygen consumption at 30 C. Vertical lines represent 95% confidence intervals of the sample means. Spiders v^ere exposed to 20 C for three v;eeks prior to the start of this _P. experiment. (a) regi u s ; (b) F. h ibernal i s 3^ Oxygen consumption at 10 C. Vertical lines represent 95% confidence intervals of the sample means. Spiders viere exposed to 20 C for three v;eeks prior to the start of this experiment. (a) £. hibernal i s; (b) j.. lenta 36 Relationship between metabolic rate and weight. (a) pooled regression line for all arachnids; (b) theraphosid species (adults and immatures); (c) £. hi bcrna 1 i 5 (adults); (d) J., lent a (adults); (e) L. lenta (immatures); (f) P. rcjg^Ijjs (adults); (g) _P. r egi u s (immatures); T. r i s ( (h) uf pe (adults); i ) £. o tiosus (adults); (j) !• si syphoides (adult); (k) _E. bi loba tu s (adults) ) A. tep id (adults) ( 1 arioruni (adults); (m) _C. XLPJ.^Lyi. (n) U_. audoui ni (immature); (o) T. marqi nemaculata (adults); and (p) C.. hent zi (adults) ^1 Figure Page 7 Relationship betv/een metabolic rate and weight. (a) Hemmi ngsen' 5 (I96O) poikiJotherm line; (b) pooled arachnid line. Vertical lines represent 95% confidence intervals Wj 8 Relationship between book-lung surface area and oxygen consumption in spiders. (a) _L. i lenta ; (b) _P. regi us ; (c) F. hi bernal s ; (d) T. si syphoides ; (e) A. tepi dar iorum ; and (f) T. ruf i pes 52 9 Deviations of actual versus calculated values of oxygen consumption and respiratory surface area. Abscissa, surface area deviations. Ordinate, oxygen consumption deviations. (a) A. tepidar iorum ; (b) _L. lenta ; (c) _P. i regi us ; (d) T. si syphoides ; (e) T. ruf pes ; and (f) F. hi bernal i 5 55 10 Relationship between temperature and standard metabolism in P_. regi us and _F. hi bernal i s . (a) minimal required energy expenditure at 20 C; (b) minimal required energy expenditure at 30 C; (c) compensation at 30 C in _P. regi us 62 INTRODUCTION The diversity of spiders is well known in terms of anatomy, be- havior, and ecology. These aspects have been documented by Petrunke- vitch (1933), Gertsch (19^9), and Millot (19^9). Although Anderson (1966) studied the excreta of many different spiders, most other phys- iological studies have dealt with a relatively small number of species. This situation has resulted in a lack of information pertaining to physiological diversity and , as such, precluded a fuller understanding of the biology of these arachnids, 1 thought that respiration, as measured by oxygen consumption, would be the most productive variable to analyze in this regard, not only because of its ease of measurement, but because it reflects the total energy requirement for all the meta- bolic processes. This latter point was made by Benedict (1938), and is supported by the wealth of literature where specific physiological processes were studied using some aspect of respiration. The major aim of this study was to determine whether interspecific differences in oxygen consumption exist and, if so, to uncover some of the causative factors in order to explore the consequences of these differences in relation to the biology of spiders. Interspecific differences have been detected in a number of arachnids: they have been discovered in oribatid mites by Berthet (1963); in harvestnien by Phillipson (1962); and in scorpions by Oresco- Derouct (igC't). In regard to spiders, Oerouet {\353) found that a 2 caverni colous species had a lov-jer metabolic rate than one which nor- mally lives outside caves. A second aim of this study was to determine whether being a spider is reflected in an energetic sense by comparing the metabolic rates of spiders with those of other poi ki lotherms. There is some difficulty in making these corripari sons ; the weights of the groups being compared often differ, and the relationship betv;een weight and metabolism is not one of direct proper t i onal i cy . While larger animals have a greater total rate of metabolism than smaller ones, the converse is true when metabolism is put on a per unit weight basis. The relationship be- tween weight and metabolism has generally been represented by the following equations: . , , n , , . metabolism = k , weight or log metabolism = log k + n . log weight The logarithmic form of the equation is useful since most of the values of _n do not equal one, hence an arithmetic plot results in a curved line. A double logarithmic plot of the equation for any value of jn does give a straight line. Consequently, to compare metabolic rates, values of n and k are determined from experimental data. The equations represented by these constants can then be compared with one another as vjell as with standard curves. The latter have been constructed by pooling data obtained from a wide variety of organisms. Examples of such standards are Hemmingsen's (I96O) unicellular, poi ki 1 otherm, and homeotherm metabolism-weight regression lines. factors which might be i also thought it valuable to consider that responsible for the size of n^ and k. Hemmingsen (I96O) suggested 3 the differences betv-veen levels of metabolism of poi ki 1 othe rms and homeotherms, i.e., different values of J<, may be the result of an increase in respiratory surface area in the latter group, Tenney and Rammers (1963) demonstrated a relationship between lung surface area and metabolic rate in a group of mammals ranging from bats to whales. In poi ki lotherms , both Brown (1957) and Hemmingsen (I960) cite data Indicating that active fish have larger gill surface areas than sluggish fish of the same weight. Whitford and Hutchison (196?) demonstrated that above 15 C, lunged salamanders have a higher metabolic rate than lungless species of the same weights. These findings indicated the desirability of making interspecific comparisons of the relationship between surface areas of book-lungs and metabolic rates in spiders. In addition, 1 thought it of value to investigate metabolic rates of those arachnids having only book-lungs or only trachea. The Solifugae, as most insects, utilize only trachea while the Amblypygi utilize only book-lungs as breathing organs.