Studies on the eggs of the grasshopper species Aulocara elliotti Thos. by George R Roemhild A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology at Montana State College Montana State University © Copyright by George R Roemhild (1961) Abstract: Various aspects of the biology and physiology of the egg of the grasshopper species, Aulocara elliotti Thos., have been investigated. Eggs from three different populations were used for these studies. Mean weight for all the eggs was 15.4 milligrams. Mean weights for the eggs from the three populations were 16.0, 14.5 and 14.2 milligrams. The mean number of eggs per pod was 8.1 for all pods collected. The mean number of eggs per pod for the three populations were 8.9, 8.3 and 7.1 There was a significant difference in the weights of the eggs from the three populations when adjustments were made for the number of eggs per pod. Respiration of eggs from the three different populations was studied in relation to effects of moisture and temperature. It was found that eggs of this species respire through the entire cuticle. Isolated embryos and yolk respired at a higher rate than did the egg from which they came if the egg was in diapause but respired at a lower rate than the egg from which they came if the egg was not in diapause. The respiration rate of eggs was measured from 5°C to 45°C and characteristic responses to temperature were noted. Reducing materials were measured in the egg during development and were shown to be higher during diapause than during other periods of development. Physiological characteristics of diapause eggs were studied and related to structures within the egg. Studies on respiration show that neither an inhibitor nor lack of water are likely to be factors in maintaining or terminating diapause in this species. STUDIES ON THE EGGS OF THE GRASSHOPPER SPECIES AULOCAfeA ELLIOTTI THOS. by George Roemhild 4 A THESIS Submitted to the Graduate Faculty in. ' partial fulfillment of the requirements for the degree of Doctor of Philosophy in Entomology at Montana State College Approved* Dean, Gradual©/Division Bozeman, Montana June, 1961 ACKNOWLEDGMENT Acknowledgment and thanks are extended to the following < ' • ' for ideas and manuscript help in this studys Dr0 James H 0 Pepper Professor Ellsworth Hastings, Dr0 Donald J0 Reed and D r 0 Graeme Baker, all of Montana State College, and to my wife Mary, for aid in the preparation and typing of the manuscript* , -4- TABLE OF CONTENTS ' ' LIST OF ,TABLES, k...,...;... .. V. 5 LIST OF FIGURES........o.....................y..................... 6 ABSTRACT.. ..;........ ..................................... 8 INTRODUCTION............... ............ ........... 9 PROCEDURE AND RESULTS 17 Egg development. 17 Collection and handling of e g g s . ^ . 18 .Egg. weights and numbers.................. 19 • Egg viability......................... 25 Egg weight changes............................. .. 30 , Respiration of eggs...................... t,........ 34 Method of measuring respiration. 34 Respiration through the cuticle,. 48 E m b r y o rospirstionooeeeoo***#*00000*999**09999990@ 9 #9000000*91 50 Temperature effects on respiration#* *.... .poooeoooo9o0ooio9o9oo 55 Developmental respiration.IOOOOOOOOOOO69OOOO»OOOOO»OOOOOOO0OOO«O 62 Reducing material in egg s * * * * * * *# .* o*************************** 65 A m m o n 1 trbgeri in eggsooo*oo*oooooooooooeo9 oo**oo**ooooo9 *o*oo 67 DiapaUSe99O0OO*9O9O9OO9OOOOOOO9OOO9OOOOO999O9OOO99**99OO99999O 70 DISCUSSION AND CONCLUSIONS 83 LITERATURE CITED*,, O O . 0000900000 *0 0900*0 9' 9**0 O 0009 O O^OObOOOOOOi 89 -5 - • LIST OF TABLES TABLE I Weights of the eggs of A.elliotti from different areas......i..... 24 TABLE II Effect of moisture on egg development and hatching................ 27 TABLE III Respiration rates of A.elliotti eggs before and after covering parts' of them with gas impervious materials....................... 4.9 TABLE. IV Respiration rates of eggs and parts of eggs of A.elliotti^........ 53 — 6- LIST OF FIGURES FIGURE !......Balance constructed for weighing eggs of A.elliotti.... 21 FIGURE 2,.... Calibration of the qudrtz balance shown in Figure I.... 22 FIGURE 3..... Distribution of the weights of eggs of A.elliotti;..... 26 FIGURE 4 Relation between average weights of eggs of A.elliotti and the number of eggs in the .pods from which they came .................................. 28 FIGURE 5 Weight change in viable and nonviable eggs of elliottii..........O..*.. ooee»eoeeeoeeoo 0900000009 FIGURE 6 Weight change in' viable and nonviablh eggs of A.elliotti................................. 33 FIGURE 7 Weight change in eggs of A^elliotti due to water absorption or loss. 0000000000900000001 0000009909 FIGURE 8.. ....Cartesian diver respirometer used to measure respi­ ration of eggs and parts of eggs of A.elliotti......... 38 FIGURE 9 .... .Detail of flotation tube and respirometer vessel used for respiration studies of eggs of A.elliotti. ^ . 41 FIGURE 10.. .. .,Sample sheet to show results of respiration measure­ ments of eggs.......................................... 44 FIGURE 11.. ...Change in respiratory gas pressures in closed tubes containing eggs of A.elliotti. ^ . 47 FIGURE 12.. ...Respiration rates of eggs of A.elliotti at different ■ temperatures.. 56 FIGURE 13.. ...Respiration rates of eggs of A.elliotti at different temperatures ....... ................. 57 FIGURE 14.. ...Respiratiop rates of eggs of A.elliotti at different temperatures .... ........... 58 FIGURE 15.. ...Effect of temperature on eggs of A.elliotti............ 60 FIGURE 16.. ...Determination of the point atjwhich respiration ceases in eggs of . ...o............ .....o.......... 61 ■ i I -7 -- FIGURE 17.,.V.Oxygen consumption of developing post-diapause eggs ' of?A,eliiotti,..,,.;....,:...:....;,;....;.^:i..,,.... 63 FIGURE 18.....Oxygen consumption of developing pbst-diapaUse eggs of' A.eliibtti.............................'...... 64 FIGURE 19.....Reducing materials in the eggs of A.eliiotti during eniloryonic development.68 FIGURE 20.....Amipo nitrogen content of developing eggs of AoelJjliOttl e ........ .....oo.......... o...o.o.a. ........ 69 FIGURE 21.....Relationship of the embryo and membranes of acridid eggs in the diapause state....o....................... 71 FIGURE 22.....Micrpphotograph of hydropylar end of egg of A.elliotti........Q..................a................ 74 FIGURE 23.....Accumulated oxygen consumption of eggs of A.eliiotti and combinations of embryos and yolk-fluid............ 78 FIGURE 24.....Respiration rates of diapause eggs, parts of eggs and parts with w a f e r ..............o........... 81. - 8 - ABSTRACT Various aspects of the biology and physiology of the ggg of the \ grasshopper species0 .Auiocara- eiIiotti Thps., have been investigated; Eggs from three; different populations were used for these studies-. Mean weight for all the eggs'was 15.4;milligrams. Mean weights for the eggs from the three populations_wer.e 16.0, 14.5 and 14.2 milli­ grams. The mean number of eggs per pod was 8.I for all pods collected. The mean number of eggs per pod for„the three populations were 8.9, .8.3 and 7;I There was a significant differ­ ence in the weights of the eggs from the three populations when adjustments were made for the number of eggs per pod. Respiration of eggs from the three different populations was studied in relation to effects of moisture and temperature. It was. found ..that eggs . of this species respire through the entire cuticle. Isolated embryos and yolk respired at a higher rate than did the egg from which they came if.the egg was in diapause but respired at a lower rate than the egg from which they came if the egg Was not.ip diapause. The respiration rate of eggs was measured from 5°C to 459C and characteristic responses to temperature were noted. Reducing materials were measured in the egg during development and were shown to be higher during diapause than during other periods of development. Physiological characteristics of diapause eggs were, studied and related to structures within the egg. Studies on.respiration show that neither an inhibitor nor lack of water are likely to be factors in maintaining or terminating diapause in this species. INTBODUQnON , , The big-headed grasshopper, Aulocara elliotti Thos.', is one of the most abundant grasshoppers on Montana rangelands and is non-migratory in habit. The distribution and food habits of this species have been described by Pfadt (1949), Griddle (1933), and Apderson and .Wright (1952); There are no published studies concerning the egg stage of A.elliotti. The studies reported in this paper had as their objective the elucidation of various aspects of the biology of the egg stage of this species. It was desirable to obtain information on the physical characteristics of the eggs such as size, weight, apd number of eggs per pod. It was likewisejdesirAble tb study the.physiological charac­ teristics tif' the egg stage such as respiratory activity during develop- , ment, characteristics of diapause, and water absorptioh, Three populations were used fpr comparison to determine the extent of variation in the factors measured. Most of the studies concerned with grasshopper eggs have beep confined to single physiological systems and have beep carried out on species which do pot Undergo an obligatory diapause as does A.elliotti. Tuck and Smith (1939) have described the chorionic sculpturing of the eggs of forty-eight species of mid-western