The Dispersion and Activity of the Terrestrial Gastropod Allogona Ptychophora (A

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1966

The dispersion and activity of the terrestrial gastropod Allogona ptychophora (A. D. Brown) in relation to its micro-habitat

Polley McClure Illich The University of Montana

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Recommended Citation Illich, Polley McClure, "The dispersion and activity of the terrestrial gastropod Allogona ptychophora (A. D. Brown) in relation to its micro-habitat" (1966). Graduate Student Theses, Dissertations, & Professional Papers. 6740. https://scholarworks.umt.edu/etd/6740

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ALLOGONA PTYGHOPHORA (A. D. BROWN), IN RELATION

TO ITS MICRO-HABITAT

Polley McClure I llic h

B. A. The University of Texas, 1965

Presented in partial fulfillment of the requirements for

the degree of

Master of Arts

UNIVERSITY OF MONTANA 1966

Approved by :

Chairman, Board/of Examiners

/ / Dean, Graduate School

NOV : 1968 Date UMI Number: EP37541

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Page

Introduction 1

Acknowledgments

Materials and Methods . . . » , 3 Field Studies ...... 4 Sampling procedure. . • 4 Temperature . * . . . » 5 Relative humidity « » • 5 Soil and litter moisture 5 Soil reaction (pH). • . 6 Litter depth. « « . . . 6 Laboratory Studies. . . * . 6 Temperature preference. 6 Substrate preference. • 8

R e s u l t s...... 8 Dispersion. • • • , ...... 8 Vegetation type ...... 9 Soil reaction (pH). . . . 10 Seasonal variations . « . 10 A ctivity. « » • . . . » . . . 12 Temporal sequence of a c tiv ity sta te s. 13 Relative humidity ...... o 14 Substrate moisture...... 14 Substrate preference...... 14 Temperature ...... 14 Temperature preference...... 15 Population Structure...... 16 Observations...... « « « • « . . . » « « 18

Discussion. . o . o . . . o o . . o . o . . o a . . « 19 Dispersion...... « . . . « . . . . . « 19 Activity...... CO.. *....». 21 Population Structure...... 24 Appendix Ao Oxygen Consumption of Hibernating, Aestivating, and Active Allogona .o...... 26

Appendix B. Table of Data. 33

Appendix C. Tables, Figures, and Plates 52

Literature Cited...... 87

1 1 I l l TABLES

Table Page

1. Average number of A. ptychophora in regions of various pH...... 53

2. Locations and dates of captures and re captures of marked sn a ils. •...»• 53

3* Percentages of adults and immatures in the population in each of the time periods 54

4* Mortality indices for adults and immatures in each of the time periods, ...... 54

ILLUSTRATIONS

Figure Page

1. Index map of plots ...... 56

2* Distribution of temperatures in gradient . 58 3. Early spring density contours ...... 60

4. Mid-spring density contours ...... 62

5. Late spring density contours 64 6. Early summer density contours...... 66

7. Early spring mortality index map . . . . . 68

8. Mid-spring mortality index map • 70

9. Late spring mortality index map. 72

10, Early summer mortality index map 74

11 , Distribution of temperature and activity states on various plots. • » ...... 76

12. Frequencies of temperatures selected , 78

13. Population structure in all four periods , 80

14. Oxygen consumption of hibernating, aesti vating, and active Allogona ptychophora, . 82 IV

Plate Page

1. Photographs of favorable and unfavorable h a b ita t...... « • • • ...... • • Ô4

2. Photographs of Allogona ptychophora in f i e l d ...... 86 THE DISPERSION AND ACTIVITY OF THE TERRESTRIAL GASTROPOD,

ALLOGONA PTYCHOPHORA (A. D. BROWN), IN RELATION

TO ITS MICRO-HABITAT

INTRODUCTION

In view of the important roles as transformers and

herbivores which terrestrial gastropods play in the ecosys

tem, comprehensive studies of their relationships to their

environment are desirable. Several studies on the ecology

of terrestrial gastropods have been done, but few of these

include much quantitative detail. Even fewer have encom

passed more than one or two aspects of the animales envi

ronment. Blinn (1963) characterized the diel and seasonal

activity of Mesodon thyroidus and Allogona profunda. Al

though he found evidence to support the observations made

by Edelstam and Palmer (1950) of a late summer homing to

the area occupied for winter hibernation, he concluded that 2 the 50 meter quadrat which he used was too small for an

adequate study of th is phenomenon. He also observed that

winter mortality was apparently insignificant. Strandine

(1944) carried out a study of selected quadrats and analyzed

these for soil moisture, pH, and per cent organic matter.

He found Succinea ovalis on moist so il, though not where

excessive moisture was present, and noted that it was most

abundant in regions of high pH. Garrick (1941) found

Agriolimax agrestis inhabiting soils of a wide range of pH 2 but with populations distinctly more dense in regions with a high soil moisture holding capacity.

Chamberlin (1897) recommended the method of m ultiple working hypotheses as the most desirable philosophy for scientific investigations. In the present study this phi losophy is particularly applicable;

In developing the multiple hypotheses, the effort is to bring up into view every rational explanation of the phenomenon in hand and to develop every ten able hypothesis relative to its nature, cause or origin, and to give to all of these as impartially as possible a working form and a due place in the inves tig a tio n .

One of the superiorities of multiple hypotheses as a working mode lies just here. In following a single hypothesis the mind is biased by the presump tions of i t s method toward a single explanatory con ception. But an adequate explanation often involves the coordination of several causes. This is espe cially true when the research deals with a class of complicated phenomena naturally associated, but not necessarily of the same origin and nature. (empha sis mine)

This is the method that I have attempted to u tiliz e to answer the question: What factors are responsible for the spatial distribution and temporal sequence of activity states in the terrestrial gastropod, Allogona ptychophora?

This species (family, Polygyridae) is a common land sn ail of rip arian woodlands in B ritish Columbia and Montana west of the continental divide, the northwest half of Idaho,

Washington east of the Columbia River, and northwestern Ore gon (Pilsbry, 1939). The study area was a typical riparian woodland in a rath er unfrequented area in Greenough Park,

Missoula, Montana. ACKNOWLEDGMENTS

I wish to thank the following people for help with out which th is work would have been much more d iffic u lt and much less enlightening: For showing me how to do many things, my friend and fellow student David Murrish; for ad vice and critic ism . Dr. R. S. Hoffmann and the members of my advisory committee, Drs. R. B. Brunson, W. B. Rowan, 5. J.

Preece, and J. R* Templeton; for doing the photography and offering patience and encouragement, my husband Harold; for help in construction of the temperature gradient apparatus and thermister, Mr. Bill Morrelles, Patrick Carney, and the sta ff of the physical plant at the University of Montana; for enlightening discussions, my fellow students at the Uni v e rsity of Montana.

MATERIALS AND METHODS

Preliminary observations were made during the summer and fall of 1965 in the study area. Actual sampling was per formed between 23 March and 12 July, 1966. A colony of A. ptychophora was maintained in the laboratory during the en tire study and these animals were used for the laboratory studies. Observations were made of reproductive activity.

Animals which were observed in copulation were iso lated when the act was complete and observations were made of clutch size, gestation period, number of young hatched, and growth rate of the juveniles. Field Studies 2 Sampling procedure;-Randomly selected 1 meter quad

rats were searched for snails. Quadrats were selected by

projecting a grid on a map of the study area and selecting 2 an area 25 feet by consultation of a table of random num bers. When this large area was located in the field, a 2 small area of 1 meter was censused in the center of it.

Occasionally the region in the center was not suitable for

searching, because of very dense underbrush, deadfalls, or

a stream. In these instances I subjectively selected an

area within the large area which could be studied meaning

fully. This occurred approximately 3 times. The study

area and locations of the numbered plots is shown in fig . 1.

All living ^ . ptychophora were collected, note was

made of their state of activity, and they were returned to

the laboratory to be marked, weighed, and measured. Empty

shells were counted as adult or immature but were not meas

ured .

The collected snails were weighed to the nearest

milligram on a Mettler Balance. Measurements were made with

calipers of the greatest diameter and height to the nearest

0.1 mm. A number was placed on the shell of each adult and

large immature snail with a latex Tech-pen. The pressure

required for application of latex was great enough to damage

the shell of small snails so that Eternal ink was used

rather than the latex for small immature animals. This was 5 coated with clear nail lacquer to ensure permanence. Snails were considered adult if the lip of the aperture was re flected and immature if i t was not. After the lip becomes reflected in adult animals there is no further increase in diameter. All animals were returned to the point of their capture within one week, usually sooner.

Temperature t-Measurements were made with a 100,000 ohm thermister probe and Wheatstone bridge. The following five measurements were taken at each collection site: 1) a ir temperature 40 cm above the l i t t e r surface, 2) a ir tem perature 10 cm above the litter surface, 3) temperature of the surface of the litter, 4) temperature in the space be tween the unincorporated litter and the humus layer, and 5) the soil temperature 2 cm deep into the soil or humus, whichever was present at this depth. All measurements were made in the shade.

Relative humidity;-This was measured in the region

10-15 cm above the litter surface. This measurement was made with a Bendix Model 566 battery powered blower psy- chrometer. Humidity measurements nearer the litter surface and s u b - litte r space would have been more desirable, but no suitable instrument was available.

Soil and litter moisture :-Samples of soil and litter were collected separately with a spoon and placed in an a ir tight can or polyethylene bag. All litter covering an area approximately 10 cm square was collected. The soil collected 6 included that from the surface to a depth of about 2 cm. In the laboratory determinations of moisture as a percentage of the dry weight were made. The samples were dried at a tem perature of approximately 70*C to a constant weight.

Soil reaction (pH);-This was measured with an Helige soil reaction kit.

Litter depth:-This was determined by taking a series of measurements with a scale and estimating the average depth based on the areas covered.

All other factors (dominant vegetation and macro- environmental cover) were recorded qualitatively at the time of each census.

Laboratory Studies

Temperature preference;-Since in preliminary obser vations the dispersion and activity displayed by A. ptycho phora appeared to be related in some way to temperature as well as several other parameters, it seemed desirable to attempt to control experimentally all environmental vari ables except temperature.

The sn a ils, a ll adults, were maintained under lab oratory conditions of constant daylight and temperature

(approx. 20®C) from the time of th e ir collection in Greenough

Park in the fall of 1965 until these trials were made in the spring and summer of 1966.

A device for the production and maintenance of a graded series of temperatures was constructed. It was 7 similar to that described by Dainton (1954) except that a heating coil controlled by a variable transformer and a re frigerator cooling coil and thermostat were used rather than water for production of a more stable gradient. The animal chamber i t s e l f consisted of a trough made of galvanized sheet steel. A false floor made of hardware cloth was placed i inch from the bottom. The space below this false floor was kept filled to an approximate depth of h inch with tap water. Thus, the a ir in the chamber was kept nearly saturated (relative humidity, 95-100#).

The gradient temperatures ranged from 8®C to 30*C, and the gradient was steepest in the two terminal segments

(fig. 2). Temperatures at each thermometer varied less than

0.1*0 in the central segments and less than 0.5*0 at the terminal thermometers.

The false floor was covered by a strip of cello phane, with which the thermometers were in contact and upon which the snails were placed. The snails appeared to avoid contact with the metal sides of the chamber and most of them remained, unrestrained, on the cellophane surface. Occa sionally a snail would climb up a thermometer bulb and creep along the plexiglass top of the chamber. When this occurred, the animal was ignored and not included in the results be cause of the possibility of vertical thermal gradients not detectable by means of the stationary thermometers.

In each trial one snail was placed, aperture down, 8

as near as possible to each of the 7 thermometers. The ani mals were le f t in the chamber for a period of 24 hours after which they were returned to their terrarium. Another group

of snails was then introduced into the chamber. Upon termi

nation of the 24 hour trial, record was made of the number

of snails which were between each of the thermometers, in

the temperature classes, 30-25®C, 25-23*0, 23-21*0, 21-19*0,

19-16*0, and 16-8*0. A total of 143 animals were tested.

Substrate preference:-A series of trials were made

to determine whether individuals of A. ptychophora would

select a moist or a dry substrate.

The experimental chamber consisted of a 9 cm pyrex

petri dish. In the bottom of this dish were placed two

semi-circles of filter paper 2 mm apart. One semi-circle

was moist, but not wet, and the other was dry. The tempera

ture was approximately 20*0.

In these trials 42 adult snails from the laboratory

colony were used. They were placed one at a time on the

space between the two semi-circles of filter paper. After

30 minutes, the position and condition of the snail were

recorded. Aestivating or otherwise inactive snails were not used in the trials.

RESULTS

Dispersion

Quantitative work was conducted from 23 March, 1966 through 12 July, 1966. During the study 87 quadrats were

sampled and 1065 A. ptychophora were collected and marked.

The mean number of snails per square meter was 12.2; the median was 5; standard deviation, 15.7; variance, 246.9.

The frequencies per square meter were compared with a

Poisson distribution by means of chi square to test the null

hypothesis of randomness. A chi square value of 631.3 indi

cates less than 0.05 probability that the null hypothesis is

valid. Since the variance exceeds the mean, the snails were

super-dispersed or clumped.

Vegetation type:-The most dense populations of A.

ptychophora were found in areas where cow parsnip, Heracleum

lanatum. was the dominant herb. Occasionally a dense popu

lation was found in association with other dominant plant

types, and occasional plots of H. lanatum had only average

populations of A. ptychophora. On plots where H. lanatum

was present the average density of A * ptychophora was 25*5 ±

25*3 individuals/meter • On plots on which H. lanatum did

not grow, the average density of A. ptychophora was 7.2 t

12.7 individuals/m eter . When these means are compared by

means of Student’s T test, a T value of 3.4049 indicates a

probability of 0.993 that they are different. This estab

lishes that A. ptychophora was found in greater numbers in

regions where H. lanatum was present. This association was more consistent than that with any of the other environmen

tal factors studied. This correlation was evident after 10

1 May, 1966, since in early spring H. lanatum had not yet

appeared.

Soil reaction (pH):-Soil pH in the study area ranged

from 6.5 to 8.0. The higher pH values tended to be associ

ated with the various streams in the area. The lower values were usually found in association with the occasional stands

of ponderosa pine (Pinus ponderosa). The most dense popula

tions of A. ptychophora were in regions were the so il pH was

7*5* The mean densities/meter in regions with each of the

4 pH values were compared by means of Student*s T te s t and

all were significantly different at p > 0.90. The T values

and probabilities are given in Table 1. The snails are

slightly more dense in regions of soil pH 7.0 than 8,0.

Their density in regions of soil pH 6.5 is only half the

average density (12.2) for the area.

There was no consistent correlation between sub

stra te moisture or depth of l i t t e r and numbers of A, ptycho

phora (Appendix B). The average litter depth was 2.6 cm,

and varied from 0-10 cm. Soil moisture varied from 4-142#

of dry weight (mean, 61.7#) while l i t t e r moisture varied

from 8-278# (mean, 71.8#).

Seasonal variations t-Littie direct information on

seasonal movements was obtained since very few marked in d i viduals were recaptured due to the large number of unmarked

snails in the population. However, some in d irect informa tion was obtained from the seasonal records of distribution. 11

Figs. 3-6 show the spatial relationships of densities of A. ptychophora during the 4 time periods of the study. "Early spring" was arbitrarily considered to begin on 23 March,

1966 when most of the snow cover had disappeared, and to end on 12 April, 1966, 4 days after the last hibernating snail was found. This period probably also represents the winter distribution of the snail. "Mid-spring" was considered to extend from 13 April to 12 May, 1966. "Late spring" was be tween 13 May and 12 June, 1966 and "early summer" covers the time between 13 June and 12 July, 1966.

In early spring the highest densities are in close association with the system of streams which cuts through the long axis of the study area. The high densities in mid spring are less clearly tied to the stream system and in late spring the areas of higher density are much further from the central stream system. In early summer the data indicate a continuation of this decentralization, although the densities in the region just east of the stream system at the south end of the study area appear much as they did in early spring. Unfortunately this area was not sampled of ten enough in mid- and late spring, but perhaps the density shift is not so marked in this region as on the west side.

The scanty recapture data is summarized in table 2 and fig. 1 and substantiates the idea of an outward seasonal movement. The average distance traveled was 44 feet (range,

4O— 6 0) . 12

Further indirect evidence can be gained from a com parative study of the dispersions of empty shells and live animals. In early spring the plots in which live adult snails outnumber empty shells were closely associated with the stream system, whereas plots in which the empty shells outnumber the live snails were peripheral to the stream sys tem (fig. 7). The distributions of snails and empty shells in subsequent periods (figs. 8-10) show that plots in which the live snails outnumber the empty shells are progressively more peripheral to the stream system.

For example, on 18 April, 1966, plot 30 was sampled and 5 live sn ails and 72 empty shells were found. Inspec tion showed this same relationship in the area surrounding the plot. On 19 May, 1966 plot 57, which is immediately ad jacent to plot 30, was found to have 59 live snails and 67 empty shells. Inspection indicated similarity in the sur rounding area. Since the shells cannot move, and the sam ples were obtained randomly, the logical explanation for this shift in relationships is that the snails moved away from the stream system. Thus, both direct and indirect evi dence indicate seasonal patterns of movement in A. ptycho phora of a magnitude approaching 50 feet in linear extent.

A ctivity

Individuals of A. ptychophora have three character istic activity states. They undergo a period of hibernation between October and April of each year, characterized by a 13 thick white calcareous epiphragm, not seen at any other sea son. During unfavorable periods at other seasons snails enter aestivation, which is characterized by a thin, trans parent "mucous veil" closure of the aperture. When condi tions are favorable the snails are "active," _i ,, the body is extended from the shell and locomotor activity usually occurs. Occasionally a snail is found withdrawn into the shell with no aperture closure. For the purposes of this study, this condition is considered as "active."

Temporal sequence of a c tiv ity s t a te s ;-Figure 11 gives the proportions of all live animals encountered on the indicated plot which were in hibernation, aestivation and active. Initially the proportion of snails hibernating is high. As the season progresses, the proportion of non hibernating (aestivating and active) animals increases.

The proportion increased first in the immature animals and was followed after a lag by the adult animals. The non hibernating group gradually shifts from predominantly aesti vating animals to predominantly active animals. In almost every plot the proportion of immature snails which were in the active condition exceeded the proportion of adults which were active.

Since all collections were made during the daylight hours, usually in the afternoon, it is evident that A. pty chophora is at least not exclusively nocturnal but can and does remain in the active and foraging state during the day 14 when conditions are favorable.

Relative humidity;»There appeared to be no distinct

correlation between activity and any one range of relative humidity. The humidity 10 cm above the litter surface usu

ally remains between 40 and B0% (see Appendix B) although

occasionally it rose to or dropped as low as 20#.

Substrate moisture;-Activity did not appear to be

associated with any specific range of substrate moisture

content (Appendix B), There was a tendency for animals to

be more active when the litter moisture exceeded that of the

so il. On plots where the soil moisture exceeded that of the

l i t t e r , the average percentage of adults present which were

active was 32 i 37#, compared with 75 ± 36# on plots where

the litter moisture was greater than the soil moisture, A

Student’s T value of 6,8055 indicates p > 0,995 that the two

means are different.

Substrate preference!-Individuals of A, ptychophora

selected a moist substrate rather than a dry one in 31 of

the 42 trials, and in every case remained active at the end

of the trial. In 5 of the 42 trials, the snails chose a dry

substrate; 3 of these remained active and 2 became inactive.

In 6 cases, the snail remained on the space between the two

papers; 5 of these became inactive and only 1 remained ac tive .

Temperature;-Environmental temperatures are given in fig, 11, The temperatures in the upper three strata (40 cm, 15

10 cm, litter surface) were considerably more variable than those in the sub-litter space and soil. The majority of animals encountered in aestivation were in or under the lit ter layer. During periods of increased activity, most ani mals assumed foraging positions on the l i t t e r surface or they climbed appropriate vegetation. Thus, the key temper ature in consideration of activity appears to be that of the litter surface. When this temperature was in the range of

18*C the proportion of active and foraging adult snails was high. When the temperature of the litter surface increased much above 18°C the activity of the snails ceased, and they retreated to the cooler sub-litter space. Aestivation was particularly evident when the temperature of the sub-litter region also exceeded 18*C. Possibly the activity threshold of immature snails is d ifferen t from that of adults. One interesting occurrence involved plots 30 and 33 on 18 April,

1966. On this date air temperatures fell to nearly 0*C, but the litter surface and sub-litter temperatures remained at

10®C. Apparently this temperature was too cold for activity as a ll snails encountered were aestiv atin g .

Temperature preference:-The mean temperature selected by the snails placed in the temperature gradient box in the laboratory was approximately 18.4*0 (S.D.4*09). The modal class was 19-21°C. The median temperature selected was ap proximately 20*0. The frequencies of temperatures selected are shown in fig. 12. As indicated by the difference between 16 the mean and mode, the curve is skewed toward the cooler temperatures. The one temperature selected most frequently by the snails was 20®C, but more snails selected tempera tures cooler than this than selected warmer temperatures.

For this reason the mean seems to be a closer representa

tion of the idea of "preferred temperature."

Since temperature acclimation can affect temperature

preference, the results of this study can be applied only to

summer animals whose ambient temperature approximates 20®C,

the acclimation temperature of the snails in the laboratory.

Population Structure

The distribution of diameters of individual A. pty

chophora in each of the four periods of the study is shown

in fig. 13» Distributions of shell height and weight show

a similar pattern. It is not possible to construct a life

table in the usual sense from these data because several

necessary assumptions cannot be met. Deevey (1947) states

that life tables can be constructed from direct observations

of the age structure of the population. This assumes, how

ever, that the age structure is stable with respect to time.

As can be seen from fig. 13 this assumption was not met in

the present study. Another assumption is that the age of

the animal shows a direct relation to size or some other measurable character. While this is in general true for the

immature animals, they cease growth upon attainment of adult

s i z e . I know of no reliab le method for determining the age 17

of adult snails. Even with immature animals, size is only a

rough indication of the age of the animal because of the in

fluence of environmental and genetic growth factors. A mem ber of the population under study which has lived for one

calendar year, has probably been in the active and growing

state for less than 7 months. During November-March the

snails are in hibernation and thus can execute no active

growth. During April-October their growth is interrupted

frequently by periods of aestivation (fig. 11) during which

their mantle is retracted from the aperture of the shell.

I interpret fig. 13 to represent a population which

is composed of more adults than immature animals of any one

size class, but approximately equal numbers of adults and

to ta l immature animals. This could be the resu lt of the

adult animals living for more than one year, probably 2 or

more .

The population in early spring is composed of 40.5^

immature snails and 59*5^ adult animals (table 3). In mid

spring there is an increase in the proportion of immature

animals and decrease in the proportion of adult animals to

51•5% and 42.5^ respectively. This might be due to an in

crease in immatures through natality, but there is no evi

dence for this (fig. 13) and the adult mortality index

(table 4) is higher in this period than in any other, indi

cating that increased adult mortality is the cause. There

is a gradual increase in adults and decrease in immature 18 portions of the population during late spring and early sum mer. Mode B represents natality in late spring. Although natality increased, decreasing adult mortality at this time more than compensated for i t .

If mode A represents a single size class, then a

possible interpretation is that these animals hatched a few months before winter hibernation ensued in the f a ll, 196$.

Growth was suspended for the winter so the distribution in early spring represents the late fall distribution of sizes

as well. This size peak can be traced through subsequent

periods as indicated. This represents a growth rate of ap

proximately 2 mm per month. If this rate remains fairly

constant, these animals may become adult late in the fall,

1966 or early spring, 1967, and spring hatched snails will be represented in the diameter classes below 16.5 mm in the

early spring following their birth, 10 months before.

Observations ;-In the laboratory at least 23 days is required for oviposition and hatching of young snails once

copulation has occurred. If this length of time is required in the field then copulations must ensue within one month of

arousal from hibernation. The f i r s t copulation which 1 ob served in the spring was on 12 April, 1966. 1 also observed copulations as late as 28 June, 1966. In late June and early July egg masses were present in the soil on many plots.

Since copulations also occurred in the laboratory as late as

2 December, 196$, 1 fe e l that copulation can and does occur 19 whenever physical conditions of the environment are favor

able .

Animals maintained in the laboratory produced an

average clutch of 19 eggs (range, 12-32). Two snails which

copulated on 12 November, 196 5 subsequently produced 6

clutches apiece. The first clutch was deposited by each 5

days after copulation and subsequent clutches were deposited

at approximate 5 day intervals. An average period of 20

days after deposition was required for the young snails to

hatch.

DISCUSSION

Dispersion

Strandine (1944) and Garrick (1941) found a positive

correlation between densities of other terrestrial gastro

pods and soil moisture, but this relationship does not seem

to exist for A. ptychophora at the time of the study. The

dispersion of this species is closely tied to the stream

system in the interior of the study area in winter but

sh ifts in spring to areas in which j!. lanatum is the domi

nant herb and the pH is about 7*5. Lee (1952) found Steno-

trema hirsutum more dense in regions of soil pH 8.0. On the

west side of the stream system, these stands of jj. lanatum

are nearly 50 feet from the stream, necessitating a migra

tion to these areas. Whether the selection made by the

snails is based upon pH or vegetation type was not 20 determined. Foster (1936) noted that Polygyra thyroïdes was most dense in areas where the wood n e ttle was dominant.

Krull and Napes (1952) found Cionella lubrica associated with berry thickets and noted small scale seasonal shifts in distribution.

Since the snails use the leaves and stalks of H. lanatum. both alive and dead, for food and there are no such succulent plant types in the immediate region of the stream, the movement appears to have a trophic basis. However, the snails can and do consume the other plants, as well as lit ter, and probably fungi growing on it. There should, there fore, be some advantage incurred by moving into these regions of H. lanatum. since such a migration must represent an addi tional energy expenditure. Advantages might be gained if the food in these areas were of a higher u tiliz a b le energy con te n t, making growth and reproduction more economical or if the nature of the plant cover were important in mediating the macro-environment, thus decreasing mortality. As can be seen from plate 1 of suitable and unsuitable habitat, the form of this plant certainly would seem to afford more protection from the macro-environment. Advantage might also be incurred if the animals could obtain necessary moisture from H. lanatum which is a very succulent type of plant. Perhaps a combination of these factors explains the pattern of movement seen.

The terrain in the region of the stream system has 21 more micro-relief than that in the periphery. This affords a large number of the small depressions which were reported by Carney (1966) to be used as wintering habitat for this species. Moreover, moisture content of the soil in this re gion in fall should be greater due to its proximity to the

stream. This was not true in the spring because there was no water in the stream system until late spring. This soil moisture would increase the specific heat of the soil and thus buffer rapid temperature changes. If the snails were responding to a preferred temperature, then as the macro-

climate temperature fell, the region remaining longest at the preferred temperature would be these moist regions.

A ctivity

It has been shown that the snails tend to be more

active in the field when the temperature of the litter sur

face is close to 18®C. The mean temperature selected in the

temperature gradient study was 18.4®C. It appears that the

preferred temperature at least in part conditions the activ ity of the animals, and that they carry out their feeding activity when the temperature is near that which they prefer.

It also appears that they select against unfavorable litter surface temperatures by retiring into the cooler sub-litter space and assuming the condition of aestivation which pre sumably offers more resistance to the environment (see Ap pendix A) .

Van der Schalie and Getz (1963) demonstrated 22 temperature preferences (mean selected temperature) of 21® and 24*0 in Pomatiopsis Cincinnatiensis and P* lapidaria re spectively. However, since they failed to give the previous thermal history of the animals, any comparison with their results is impossible. Getz (1959) recorded preferred tem peratures for Arion circumscriptus and Deroceros reticulatum of 18*-24*C and D. laeve of 14*-26*C.

In view of the substrate selection results in the laboratory it is not surprising to see that in the field the animals are active primarily when the moisture content of the litter is greater than that of the soil. Since they have demonstrated the ability to select moist over dry sub strate and to remain active longer on the moist one, this is possibly the key to the periodic activity of the snails.

Dainton (1954) studied the humidity response of the slug,

Agriolimax agrestis, and found experimentally that relative humidity did not condition activity. In a series of similar experiments with A. ptychophora I have established that the same is true for this snail as well. Therefore the stimulus must be the actual moisture of the substrate or some other concurrent phenomenon. Van der Schalie and Getz (1962) found Pomatiopsis cincinnatiensis inhabiting regions along stream banks where the soil moisture approximated their pre ferred substrate as determined experimentally.

Wells (1943) demonstrated experimentally that Helix pomatia tends to be most active (although it still exhibits 23 activity-aestivation cycles) when it has both food and water present. Animals deprived of food are sluggish and those from which water was withheld tended to aestivate more.

These re su lts might help to explain my fie ld observations that A. ptychophora are more active when the litter is more moist than the soil. They feed rather extensively on the leaves of the litter. If by feeding on these when they are moist they obtain more water (the food is probably also easier to scrape off) then the proper state of body moisture and food content required for activity could be maintained.

This would not be the case with dry l i t t e r .

The conditions for maximum activity are met when the l i t t e r surface temperature is about 18°C, and more moist than the soil. These conditions might occur together fre quently after rainfall or at night or early morning. These are the times when numerous authors have reported intense gastropod activity. Perhaps the high moisture content of the litter and the resultant evaporative cooling serve to keep the temperature of the litter surface in the favorable range.

One might expect _a priori to find the snails concen trated in regions of high substrate moisture if they do tend to select moist over dry substrates. This is not evident because the individual snail indeed does not have the choice of all available substrates in the field. The snail is lim ited by its small size and relatively slow movement to the 24 moistures available in the immediate region which it occu

pies* Since there is relatively little variability in soil

and litter moisture content over the entire area, the snail

is limited in its day-to-day movements to excursions up and

down between litter and soil in its attempts to find suit

able areas for activity.

Population Structure

Foster (1936) studied the population structure of

Polygyra thyroides and found a very slow rate of growth in

immature snails in spring (less than 1 mm per 3 months in

least diameter) and a very rapid rate of growth in summer

(7-8 mm per 3 months). The growth rate of A, ptychophora

(2 mm per month) is greater and more uniform than this, al

though the snails are of similar size.

In this study it appears that young are produced

from May to August or September of the year, depending on

environmental conditions. These young may mature late in

their second summer or early their third spring. It appears

that they then live about 2 years as adults. More adults

appear to die in the spring, following arousal from winter hibernation, than the 17^ mortality found by Carney (1966)

during the winter. Carney’s snails had been moved from the

areas which they had selected for hibernation and placed in

an area which he selected. This could have caused increased mortality. Blinn (1963) and Foster (1936) both commented on low winter mortality, based on observations of untouched 25 animals. This, and the low mortality index of the early spring sampling period (representing winter, see table 4) seem to substantiate the idea that spring (April-May) is the time of greatest mortality for A. -ptychophora. I have also observed that it is much more difficult to maintain popula tions in the laboratory in spring if the animals are freshly caught from the field. 26

APPENDIX A

OXYGEN CONSUMPTION OF HIBERNATING, AESTIVATING,

AND ACTIVE ALLOGONA PTYCHOPHORA 27

OXYGEN CONSUMPTION OF HIBERNATING, AESTIVATING,

AND ACTIVE ALLOGONA PTYCHOPHORA

Introduction

The acclimation of respiration of molluscs to vari ous temperatures has been studied in some detail in recent years. Segal (1959) demonstrated that the slug, Limax fla v u s, had a higher rate of oxygen consumption at tempera tures of 10® and 20® when it had been acclimated to 10® than when i t had been acclimated to 20®C. Berg (1952, 1953, 1958) was unable to demonstrate this acclimation in various aquatic snails, and the limpet. His studies have, however, been with field-collected animals at various seasons, whereas Segal*s work has been mostly done with animals which were acclimated in the laboratory. While undertaking an ecological study of the dispersion and activity states of the terrestrial mol lusc, Allogona ptychophora. it became evident that the activ ity states of hibernation, aestivation, and activity might re fle c t d ifferen t physiological states aside from simple tem perature acclimation. A series of oxygen consumption deter minations was made in an attempt to determine this differ ence .

M aterials and Methods

Adult snails were collected in Greenough Park,

Missoula, Montana, in the fall of 1965 and maintained for the winter under laboratory conditions of 20®C temperature 28 and constant light. During this time they were kept in plastic shoe boxes with moist sand as a substrate and pro vided with moistened lettuce leaves, occasional carrots, and blackboard chalk for food.

A. Active Group. Active animals were fed for sev e ra l days, removed from food and placed in a moist glass container 24 hours prior to determinations. They were kept at temperatures of approximately 20*C under constant illumi nation .

B. Aestivating Group. Specimens of A. ptychophora were induced to aestivate by being dessicated with silica gel for 25 days; they had formed aestivation epiphragms after 24 hours and the silica gel was exhausted at this time. Temperature and light conditions were those described for active snails.

C. Hibernating Group. These animals were collected on 10 March, 1966. The ambient temperature was 6.4*0. They were all hibernating (that is, with a thick white epiphragm) when collected. I placed the animals in a dark paper bag and supported the bag on a tray above an ice bath for tran s port to the laboratory, where the paper bag with the snails was placed in a refrigerator at 5*0*0.

Oxygen consumption determinations were made with a micro-Scholander respirometer similar to that described by

Steen and Iversen (1965)* The apparatus was suspended in a water bath which maintained temperatures of 5*, 10°, and

15*0 within 0.2°. Because of the low rate of oxygen consump tion particularly by the hibernating group at low tempera tu res, three individuals were introduced into each chamber at a time. Active animals were placed in the chamber in such a way that much locomotor activity was impossible.

Readings were taken over a span of 1 hour at 5*0 and

J hour at the two higher temperatures. All animals were left at 5*0 initially for 3 hours. After the 1 hour trial, 29 the temperature was raised to 10*C at a rate of about 1® every 5 minutes* A period of 1 hour was allowed for animals and glassware to attain this temperature before trials were begun. This process was repeated for the 15*C trials.

There were two variables not controlled in these ex periments, humidity and temperature acclimation. Vapor pressure between the 2 chambers in the aestivating and h i bernating groups were kept equal by removing all water and water vapor with Drierite and Silica gel* CO^ was absorbed by dried Baralime* Vapor pressure was equalized in the ac tive group by maintaining the air saturated with moist fil ter paper in each chamber. CO^ was absorbed with Baralime.

Thus, the active animals were in a moist environment and the aestivating and hibernating animals were in a dry atmosphere

This was necessary because no way could be found to consis tently keep these snails active in dry air or hibernating and aestivating in moist air* While important physiologi cally perhaps, this is of minor significance ecologically.

The second uncontrolled variable was that of temperature acclimation. Active and aestivating animals were acclimated to laboratory temperatures while hibernating animals were acclimated to winter field temperatures near 0®C* This ef fect would have tended to reverse the differences which were observed, and so it can be neglected*

Results

As seen in fig . 14> oxygen consumed by active animals 30 was greater at all temperatures than aestivating and hiber nating snails. Aestivating animals consumed more oxygen at

5®C and 10*C than those hibernating which were lowest of a ll

at every temperature except 1$*C. At this temperature oxy

gen consumption of hibernating animals was greater than that

of aestivating animals. Average Q^^s were calculated for

the 5-15° range. The of hibernating animals was highest

of all at 6. Aestivating animals had the lowest of 2.

The of active animals was about 3* Thus the oxygen con

sumption of these snails is most independent of temperature

change when the animal is aestivating. Hibernating animals

can be induced to increase their metabolism 6X for a 10® in

crease in temperature.

Discussion

The rates of oxygen consumption and the metabolism which they reflect are seemingly adaptive to the existence

of A, ptychophora under conditions of severely cold winters

and relatively hot, dry summers in western Montana. This

snail undergoes a winter hibernation which la s ts from Octo ber until April of each year. In addition, aestivation is a state often found in the field and laboratory whenever conditions become unfavorable to the activity of the animals.

It appears that by ceasing activity and entering aestivation

A. ptychophora can reduce the rate of its body processes and conserve the energy which i t would have to expend in keeping its body in osmotic equilibrium in dry atmospheres. Its 31 oxygen consumption at 5® when hibernating is about i that at the same temperature when active. This, too, represents considerable energy savings for an animal whose major food sources are frozen and unavailable at this season. The high

of hibernating animals would allow them to respond read ily to slight increases in temperature in spring facilitat ing arousal.

These sn ails, then, have an altered physiological state which allows them to consume less oxygen when hiber nating in a cold environment or when aestivating in a warm one, than when warm and active. This is decidedly more ad vantageous in the climate to which they are exposed than simple temperature acclim ation, which would raise the level of oxygen consumption in winter animals* 32

Literature Cited

Berg, K, 1952. On the oxygen consumption of Ancylidae (Gas tropoda) from an ecological point of view. Hydro- biologica 4:225-267.

Berg, K. 1953* The problem of respiratory acclimatization illustrated by experiments with Ancylus fluviatilis (Gastropoda). Hydrobiologica 5:331-350,

Berg, K., and K. W. Ockelmann. 1958* The respiration of freshwater snails. J. Exp. Biol. 36:690-708.

Segal, E. 1959. Respiration and temperature acclimation in slugs. Anat. Record. 134:636.

Steen, J. B., and 0. Iverson. 1965. Modernized Scholander respirometer for small aquatic animals. Acta Physiol. Scand. 63:171-174* 33

APPENDIX B

TABLE OF DATA 34

Plot Number 1 2 3 4

Date of Census 23 Mar. 23 Mar. 23 Mar. 23 Mar. Time 10:30am 11:15am 12:00am 1:00pm

Temperature (®C) 1) 40 cm 1.6 2 .2 $.9 4.1 2) 10 cm 0.9 3.1 6.1 2.3 3) litter surface 2.4 - 10.1 2.1 4) sub-litter 2.1 1.3 6.4 -0.1 5) so il 1.2 1.3 3.8 -

Relative Humidity (%) - - - - pH 8.0 7.5 8,0 -

Soil Moisture (%) 113 69 108 frozen

Litter Moisture (%) 247 138 169 frozen

Depth of L itter (cm) 4.0 3.5 4.0 frozen

Dominant Vegetation 1 0 0 0

Emply Shells 7 3 55 Adult 1 1 31 - Immature 6 2 24 -

Live Snails 2 2 25 Adult 1 1 16 - Active 0 0 0 - Aestivating 0 0 4 - Hibernating 1 1 12 —

Immature 1 1 9 — Active 0 0 0 Aestivating 0 0 2 - Hibernating 1 1 7 -

Mortality Index Adult 50 50 66 - Immature 86 67 73 35

Plot______6______8______2______10______12

Date 24 Mar. 24 Mar. 24 Mar. 29 Mar. 30 Mar. Time 2:30p 2s00p 3:00p 7s00p 11:00a

Temp. 1) 12.3 11.6 11.9 10.9 14.7 2) 11.1 11.5 11.1 9.7 17.0 3) 7.3 12.0 8.5 8.1 23.2 4) 1.5 8.1 5.6 7.7 11.3 5) 2.2 6.0 4.1 6.7 7.3

R » H # •“ — — — — pH 7.0 8.0 8.0 7.0 7.0

SeM. 45 88 80 65 133

LeM, 180 111 156 - 46

D.L, 1 - 2.5 2.5 6.0

Dom.Veg. 0 0 1 0 0

Shells 0 16 59 15 10 Adult 0 10 56 14 9 Imm. 0 6 3 1 1

Snails 0 6 13 5 5 Adult 0 4 10 5 2 Act. 0 0 0 0 0 Aest. 0 0 0 0 0 Hib. 0 4 10 5 2

Imm. 0 2 3 0 3 Act. 0 0 0 0 0 Aest 0 0 1 0 0 Hib. 0 2 2 0 3

Mort.Index Adult - 71 85 74 82 1mm. - 75 50 100 25 36

Plot 13 - 1-4____ 15 _ - 16 17

Date 8 April 30 Mar. 30 Mar. 31 Mar. 31 Mar. Time 2:00p 10:00a 10:30a 9:00a 8 :30a

Temp. 1) 19.1 8.5 11.4 13.5 10.9 2) 19.2 8.5 13.0 13.2 10.4 3) 19.6 7.3 20.5 13.1 9.8 4) 11.1 4.4 6.5 7.2 6.8 5) 10.5 3.5 5.1 5.9 6.1

R.H. 32 - - - - pH 7.5 7.0 8.0 7.5 7.5

S .M. 84 94 57 80 78

L.M. 14 170 66 69 64

D 0 L « 1.5 2.0 2.5 3.5 3.0 Dom.Veg. 1 0 0 0 0

Shells 3 3 26 12 1 Adult 3 2 23 12 0 Imm. 0 1 3 0 1

Snails 13 1 2 25 2 Adult 7 0 0 15 2 A ct. 2 0 0 5 0 A est. 4 0 0 0 0 Hib. 1 0 0 10 2

Imm. 6 1 2 10 0 A ct. 6 0 0 7 0 Ae s t . 0 0 2 0 0 Hib. 0 1 0 3 0

Mort.Index Adult 30 100 100 44 0 Imm. 0 50 60 0 100 37

Plot 18 20 22 . 24 25

Date 31 Mar. 5 April 5 April 8 April 30 Mar. Time 8:00a 3:lOp 3:50p 2:45p 11:45a Temp. 1) 10.6 17.9 18.4 18.2 14.2 2) 10.0 17.5 18.4 18.0 14.5 3) 9.8 17.5 16.1 18.2 18.7 4) 8.7 9.6 8.5 12.5 8.7 5) 7.6 7.3 7.3 6.4 7.1

R.H. - - - 30 - pH 7.5 7.5 7.5 7.0 8.0

S «M. 54 82 77 70 93

L.M. 55 17 18 21 68

D.L. 4.5 3.5 5.5 1.5 2 .0

Dom.Veg. - - Oi 1 -

Shells 5 10 5 5 5 Adult 3 6 2 4 3 Imm. 2 4 3 1 2

Snails 3 7 14 5 6 Adult 2 5 2 3 1 Act. 1 0 0 2 0 A est. 0 2 0 0 1 Hib. 1 3 2 1 0

Imm. 1 2 12 2 5 Act. 1 2 6 2 0 Ae st • 0 0 5 0 4 Hib. 0 0 1 0 1

Mort.Index Adult 60 55 50 57 75 Imm. 67 67 20 33 29 38

Plot 26 27 28 31 30

Date 8 April 8 April 12 April 16 April 18 April Time 3 :45p 3:20p l:30p 11:30a 2;00p Temp. 1) 18.9 20.9 13.2 10.9 3.4 2) 18.9 20.6 11.8 11.0 3.3 3) 19.0 21.5 13.4 11.3 10.5 4) 11.0 11.4 9.5 10.8 10.5 5) 9.9 7.9 7.1 10.1 10.5

R.H. 23 32 60 60 33 pH 7.0 7.0 7.5 7.5 7.5

S.M. 60 106 142 115 73

L.M. 18 26 48 106 51

D.L. 3.0 5.0 9.5 5.5 1.5 Dom.Veg. 0 0 1 2 2

Shells 0 6 31 0 72 Adult 0 5 11 0 58 1mm. 0 1 20 0 14

Snails 0 4 57 5 5 Adult 0 2 39 4 3 Act • 0 1 39 4 0 Ae st • 0 1 0 0 3 Hib. 0 0 0 0 0

Imm. 0 2 18 1 2 Act. 0 0 18 1 0 A est. 0 2 0 0 2 Hib. 0 0 0 0 0

Mort.Index Adult — 71 22 0 95 Imm. 33 53 0 87 39

Plot 33 _ 29 _ 32 _ 34 35

Date 18 April 20 April 20 April 21 April 21 April Time 2:45p l:45p 2:20p 9:10a 9:40a Temp, 1) 3.4 10.8 10.8 10.2 10.6 2) 3.4 11.5 10.8 10.3 10.5 3) 10,4 13.4 13.0 10.6 10.9 4) 10.5 10.7 10.4 10.3 10.7 5) 10,4 10.2 10.2 10.2 10.3

R,H. 23 31 36 84 85 pH 7.5 7.5 6.5 7.5 8.0

S.M. 96 79 57 75 91

L.M. 15 24 20 120 163

D.L. 3.5 3.5 2.0 2.5 3.0

Dom.Veg. 0 0 3 2 4

Shells 1 4 4 8 43 Adult 1 4 4 5 39 Imm. 0 0 0 3 4

Snails 2 0 4 1 22 Adult 2 0 4 1 11 A ct. 0 0 0 0 6 A est. 2 0 4 1 5 Hib. 0 0 0 0 0

Imm. 0 0 0 0 11 Act • 0 0 0 0 10 Aest • 0 0 0 0 1 Hib. 0 0 0 0 0

Mort.Index Adult 33 100 50 83 78 Imm. 100 27 AO

Plot 36 37 38 39 40

Date 28 April 28 April 3 May 3 May 3 May Time 9:55a 9:30a 2:05p l:30p 2:30p

Temp. 1 3.1 4.5 31.9 29.8 30.6 2) 3.5 5.0 30.8 28.8 29.9 3) 4.5 8.9 29.9 29.8 28.9 4) 2.4 7.2 18.7 25.1 18.8 5) 10.8 6.9 14.4 14.8 16.1

R.H. 83 85 - - - pH 8.0 7.5 8.0 7.5 7.5

S.M. 131 54 88 71 98

L.M. 278 177 14 23 12

D.L. 3.5 1.5 3.0 3.5 3.0

Dom.Veg. -- 0 - 0

Shells 4 0 1 5 20 Adult 2 0 1 4 15 Imm. 2 0 0 1 5

Snails 15 0 1 4 5 Adult 4 0 1 1 3 A ct. 4 0 0 0 0 Aest • 0 0 1 1 3 Hib. 0 0 0 0 0

Imm. 11 0 0 3 2 Act. 11 0 0 3 1 Ae s t . 0 0 0 0 1 Hib. 0 0 0 0 0

Mort.Index Adult 33 - 50 80 83 Imm. 15 25 71 41

Plot 42 - 43 44 __ 45 46

Date 4 May 4 May 5 May 5 May 5 May Time 2:30p 3:10p 2:20p 2:50p 3:45p

Temp* 1) 29.4 28.0 27.9 28.0 32.3 2) 30.2 27.8 27.6 26.7 31.2 3) 35.0 27.2 26.7 25.3 25.1 4) 16.3 18.0 17.1 17.0 20.1 5) 13.4 16.1 12.0 14.5 17.3

R.H. 19 18 28 40 30 pH 7.0 8.0 8.0 6.5 7.5

S.M. 62 54 58 36 73

L.M. 10 15 15 8 10

D.L. 3.0 1.5 3.5 2.0 1.5

Dom.Veg. 5 3 3 3 4

Shells 16 6 6 20 37 Adult 10 5 3 3 20 Imm. 6 1 3 17 17

Snails 2 4 2 17 19 Adult 0 3 1 1 3 Act • 0 0 0 1 1 Aest • 0 3 1 0 2 Hib. 0 0 0 0 0

Imm. 2 1 1 16 16 A ct. 2 1 0 16 16 Ae s t . 0 0 1 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 100 63 75 75 84 Imm • 75 50 75 52 52 42

Plot 47 48 49 . 50 51

Date 9 May 9 May 9 May 11 May 11 May Time 2 : 0 5p 2:50p 3 :40p 2:15p 3;00p Temp. 1) 23.8 22.9 22.0 13.7 13.5 2) 22.5 22.5 22.1 13.9 12.8 3 ) 24.2 22.6 20.6 13.0 12.8 4) 18.2 19.3 17.0 12.9 11.6 5) 14.4 13.1 16.1 12.5 12.8

R.H. 49 45 45 52 50 pH 7.5 7.5 7.5 7.0 7.0

S.M. 44 98 61 68 60

L.M. 20 17 21 75 55

D.L. 1.5 5 . 0 0.5 0.5 1.5

Dom.Veg. 3 - 3 4 4

Shells 7 6 23 43 28 Adult 5 2 6 33 24 1mm. 2 4 17 10 4

Snails 3 7 4 26 21 Adult 0 3 0 10 14 Act. 0 0 0 10 14 A est. 0 3 0 0 0 Hib. 0 0 0 0 0

Imm. 3 7 4 16 7 Act • 3 5 4 16 7 Aest • 0 2 0 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 100 40 100 77 63 Imm. 40 36 81 38 36 43

Plot 52 53 54 _^5 56

Date 12 May 12 May 15 May 15 May 17 May Time 2:40p 3:30p 2:55p 3%55p 2;45p Temp. 1) 13.5 15.0 13.8 12.1 13.7 2) 13.4 15.0 13.0 13.0 12.7 3) 14.2 13.2 13.2 13.4 12.7 4) 9.8 10.6 11.5 11.4 5) 8.8 10.1 9.8 9.8

R.H. 39 48 45 41 70 pH 7.5 7.0 7.0 6.5 7.5

S.M. 51 109 67 27 48

L.M. 35 29 82 66 100

D.L. 2.0 3.5 2.5 3.0 2.5

Dom.Veg. 0 - - 2 -

Shells 10 13 4 31 9 Adult 7 10 1 19 2 Imm. 3 3 3 12 7

Snails 2 0 6 9 21 Adult 1 0 2 6 1 Act. 0 0 2 6 1 A est. 1 0 0 0 0 Hib. 0 0 0 0 0

Imm. 1 0 4 3 20 Act. I 0 4 3 20 Ae st • 0 0 0 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 88 100 33 76 67 Imm. 75 100 43 80 26 A4

Plot _37 _ 58 59 60 61

Date 19 May 23 May 23 May 24 May 24 May Time 3 : 0 5p l:45p 3 : 0 5p l:45p 3:20p Temp* 1) 19.9 2 3 . 6 18.5 20.6 20.8 2) 18.8 26.3 14.4 18.2 19.9 3) 18.3 26.1 12.0 17.6 18.3 4) 17.6 20.6 10.4 12.3 15.0 5) 11.8 25.1 10.4 10.9 11.0

R.H. 62 29 56 45 51 pH 7.5 7.0 7.5 7.5 8.0

S.M. 60 35 49 42 55

L.M. 71 18 73 38 28

D.L. 1.0 0.5 0.5 0.5 5.0

Dom.Veg. 4 4 4 4 2

Shells 67 34 8 42 3 Adult 49 32 8 30 3 Imm. 18 2 0 12 0

Snails 59 41 24 39 1 Adult 33 5 17 15 0 Act • 30 0 15 4 0 A est. 3 5 2 11 0 Hib. 0 0 0 0 0

Imm. 26 36 7 24 1 Act • 26 14 6 11 0 Aest • 0 22 1 13 1 Hib. 0 0 0 0 0

Mort .Index Adult 60 86 32 67 100 Imm. 41 5 0 33 0 45

Plot 62 63 64 65 66

Date 25 May 25 May 26 May 26 May 26 May Time l:00p 1 :40p 2;25p 3:15p 3:45p Temp. 1) 25.0 30.1 28.5 26.6 26.8 2) 24.5 29.1 25.1 25.1 26.6 3) 23.5 28.6 23.8 20.9 25.5 4) 21.0 19.5 21.1 17.7 17.4 5) 13.9 11.2 13.0 14.9 16.8

R.H. 29 36 45 56 36 pH 6.5 7.5 7.5 7.0 7.0

S.M. 9 48 31 31 4 L.M. 10 21 18 18 11

D.L. 1.5 3.0 1.5 1.0 3.0

Dom.Veg. 4 4 4 1 5

Shells 4 32 40 10 2 Adult 1 17 8 5 1 Imm. 3 15 32 5 1

Snails 2 116 10 0 2 Adult 1 60 1 0 0 Act • 0 3 0 0 0 Aest • 1 57 1 0 0 Hib. 0 0 0 0 0

Imm. 1 56 9 0 2 Act « 0 12 1 0 0 Ae s t . 1 44 8 0 2 Hib. 0 0 0 0 0

Mort.Index Adult 25 22 89 100 100 Imm. 50 21 78 100 33 46

Plot 67 68 69 70 71

Date 1 June 1 June 6 June 6 June 6 June Time 2:25p 3:20p 1 ;30p 2:15p 3:00p Temp. 1) 21.2 20.9 19.9 23.2 18.4 2) 19.3 19.8 19.6 23.6 16.6 3) 16 .3 19.0 15.4 19.3 14.1 4) 16.0 15.9 11.5 16.6 12.1 5) 13.1 14.5 11.0 13.0 10.4

R.H. 69 50 52 51 76 pH 6.5 7.5 7.5 6.5 6.5

S.M. 41 50 40 28 60

L.M. 65 50 137 126 215

D.L. 2.5 1.5 1.0 3.0 0.5

Dom.Veg. - 4 1 5 3

Shells 5 32 25 2 2 Adult 4 24 12 1 1 I mm. 1 8 13 1 1

Snails 4 16 11 1 3 Adult 3 8 2 0 2 Act. 3 8 2 0 2 A est. 0 0 0 0 0 Hib. 0 0 0 0 0

I mm. 1 8 9 1 1 A ct. 1 7 9 1 1 A est. 0 1 0 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 57 75 86 100 33 Imm. 50 50 59 50 50 47

Plot 72 73 74 75 76

Date 21 June 21 June 23 June 23 June 23 June Time 2 :15p 3:20p 2:25p 3:25p 4 ;00p Temp. 1) 18.7 16.4 15.6 16.4 15.1 2) 17.6 16.8 15.0 15.1 14.6 3) 17.6 15.4 14.8 13.8 14.3 4) 14.4 14.4 13.4 14.1 13.9 5) 13.5 13.6 12.6 12 .3 12.6

R.H. 78 83 72 83 88 pH 7.5 7.5 7.5 6.5 7.5

S.M. 78 61 22 46 61

L.M. 123 128 102 123 184

D.L. 1.5 2.5 4.5 2.5 5.0

Dom.Veg. 4 3 2 4 3

Shells 26 5 1 23 3 Adult 23 4 1 13 2 Imm. 3 1 0 10 1

Snails 47 7 11 3 5 Adult 39 5 7 1 3 A ct. 39 5 7 1 3 A est. 0 0 0 0 0 Hib. 0 0 0 0 0

Imm. 8 2 4 2 2 A ct. 8 2 4 1 2 A est. 0 0 0 1 0 Hib. 0 0 0 0 0

Mort.Index Adult 37 44 13 93 40 Imm. 27 33 0 83 33 48

Plot 77 78 79 80 81

Date 25 June 25 June 28 June 28 June 28 June Time 2 :05p 2 :50p 1 ; 40p 2:20p 4 :00p Temp, l) 17.8 17.3 26.6 29.7 23.8 2) 17.7 16.9 25.5 31.3 23.1 3) 15.5 15.7 25.0 29.4 20.2 4) 13.9 12.7 17.0 18.1 19.2 5) 11.2 12.2 14.4 17.2 16.9

R.H. 49 54 63 36 64 pH 8.0 8.0 7.5 7.5 7.5

S.M. 48 55 44 35 56

L.M, 17 11 38 20 69

D.L. 3.5 1.5 3.0 1.0 0

Dom.Veg * 1 - 1 5 4

Shells 4 9 2 9 3 Adult 2 6 1 1 2 Imm. 2 3 1 8 1

Snails 16 3 2 16 10 Adult 10 1 0 1 6 A ct, 9 1 0 1 5 Ae st • 1 0 0 0 1 Hib. 0 0 0 0 0

Imm. 6 2 2 15 4 A ct. 6 2 1 15 4 Aest • 0 0 1 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 17 86 100 50 25 Imm. 25 60 33 35 20 4 9

Plot 82 83 84 85 86

Date 30 June 30 June 30 June 30 June 1 July Time l:25p 2:15p 3 :20p 4:30p 2:35p Temp. 1) 23.7 20.9 21.5 21.0 21.1 2) 21.1 20.5 20.4 20.3 19.9 3) 20.2 20,5 16.3 18.8 17.3 4) 17.2 18.7 14.5 17.7 16.2 5) 15.6 15.9 13.9 14.3 13.5 R.H. 60 64 67 64 85 pH 7.0 7.0 7.0 7.5 8.0

S.M. 21 18 31 30 58

L.M. 111 146 86 43 121

D.L. 1.5 5.0 1.0 1.0 0.5

Dom.Veg. 5 1 4 3 4

Shells 31 3 7 21 21 Adult 15 3 4 5 18 Imm. 16 0 3 16 3

Snails 33 1 22 1 12 Adult 20 0 15 1 9 A ct. 20 0 15 1 9 A est. 0 0 0 0 0 Hib. 0 0 0 0 0

Imm. 13 1 7 0 3 A ct. 13 1 7 0 3 A est. 0 0 0 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 43 100 21 83 67 Imm. 55 0 30 100 50 50

Plot 87 88 89 90 91

Date 1 July 4 July 4 July 5 July 5 July Time 3 s40p 12:45p l:15p 2 ;45p 3;30p Temp • 1) 23.1 18.1 17.8 25.6 22.8 2) 22.9 18.0 15.4 23.4 22.5 3) 20.7 17.1 15.4 22.4 22.2 4) 18.6 15.1 14.5 20.0 18.8 5) 13.8 12.4 12.4 15.5 15.5

R.H. 66 67 78 74 68 pH 6.5 7.5 8.0 7.5 7.5

S .M, 67 36 80 29 26 L.M. 98 158 142 80 106

D.L. 3.0 5.0 2.0 1.0 4.0

Dom.Veg. 3 0 3 4 2

Shells 3 15 5 6 22 Adult 2 3 1 5 5 Imm. 1 12 4 1 17

Snails 12 0 0 21 73 Adult 3 0 0 15 14 Act • 3 0 0 15 13 Aest • 0 0 0 0 1 Hib. 0 0 0 0 0

Imm. 9 0 0 6 59 Act • 9 0 0 6 59 A est. 0 0 0 0 0 Hib. 0 0 0 0 0

Mort.Index Adult 40 100 100 25 26 Imm. 10 100 100 14 22 51

Plot______22______22______94 95

Date 8 July 8 July 9 July 9 July Time 2s30p 3s50p 11:40a 12:05a

Temp. 1) 25.8 24.7 23.8 22.5 2) 25.3 24.0 22.7 21.8 3) 25.1 23.3 21.9 21.4 4) 20.6 20.7 17.1 20.0 5) 18.0 17.5 14.5 18.1

R.H. 61 71 73 67 pH 7.5 7.0 7.0 7.5

S.M. 57 50 19 36

L.M. 26 24 29 32

D.L. 1.5 0.5 10.0 0.5

Dom.Veg. 4 4 5 3

Shells 6 5 1 6 Adult 5 4 1 6 Imm. 1 1 0 0

Snails 20 18 0 0 Adult 8 6 0 0 Act. 1 5 0 0 Aest. 7 1 0 0 Hib. 0 0 0 0

Imm. 12 12 0 0 Act . 6 4 0 0 Aest. 6 8 0 0 Hib. 0 0 0 0

Mort.Index Adult 38 40 100 100 I mm. 8 8 — — 52

APPENDIX C

TABLES, FIGURES, AND PLATES 53 Table 1. Average number of A. ptychophora per meter 2 in regions of various pH.

Mean Density ± S.D. m „ pH (per meter2) ^ Value

6.5 6.1 i 5.4 t=lo26 (p > .90) 7.0 9.6 i 12.5 t=2,59 (p > .99) 7.5 l 6 .8 ± 24.0 t=2.29 (p > .975) 8.0 8.2 ± 12.2

Table 2. Locations and dates of captures and recaptures of marked sn ails.

Snai 1 Original Capture Re-capture N umber Plot No. Date Plot No. Date

273 60 24 May 57 5 July 87 28 12 April 63 25 May 118 28 12 April 63 25 May 92 28 12 April 63 1 June 80 28 12 April 63 6 June 54 Table 3* Percentages of adults and immatures in the population in each of the time periods.

Adult Immature Period Total # %T

Early spring 116 59.5 79 40.5 195 Mid-spring 74 42.5 100 57.5 174 Late spring 154 43.1 203 56.9 357 Early summer 162 48.2 174 51.8 336

Table 4» Mortality indices for adults and immatures in each of the time periods.

Pe riod Adults Immature s

Early spring 60.0 52.0 Mid-spring 71.9 54.5 Late spring 67.1 42.7 Early summer 57.8 38.5 55

Figure 1. Locations of numbered plots. The area vithin the stippled border is the region of the study. The study area shown is located in the northeast cor ner of Greenough Park, Missoula, Montana. The arrows indicate distances and directions traveled by recaptured animals (see table 2). Rotflesnake Creek

picnic orea

INDEX MAP OF PLOTS 100 feet 1 57

Figure 2* Distributions of temperatures in the gradient for preferred temperature determinations. X^s indi cate positions of thermometers. 5B

4 0 r

I- 20 ÛC CL

2 6 10 14 18 22 XXX

POSITION IN CHAMBER (in.) 59

Figure 3* Distributions of densities in early spring (23 March-12 April, 1966). Density contours were plotted by connecting areas of similar density without inclusion of any unlike den s i t y . Rattlesnake Creek

picnic ADULT DENSITY

26+

16-25

EARLY SPRING 100 feet

o 61

Figure 4* Distributions of densities in mid-spring (13 April-12 May, 1966). Rattlesnake Cree

picnic

ADULT DENSITY

16 -2 5

6-15 MID-SPRING >00 feet k ------I 63

Figure 5* Distribution of densities in late spring (13 May-12 June, 1966). KattiesnoKe Creek

path

ooo

picnic

ADULT DENSITY

16-25

.V .1 6-1 5 LATE SPRING 100 fe e t H ------4 - 5 6 5

Figure 6. Distributions of densities in early summer (13 June-12 July , 1966). Rattlesnake Creek

picnic x::Xx area ADULT DENSITY

EA RLY SUMMER 100 feet

ON ON 6 7

Figure ?. Early spring (23 March-12 April). Cross-hatched areas represent contours of plots in which the adult mortality index was less than 50 (the alive adult snails outnumbered the empty shells). Rattlesnake Creek

OOO q O

path

O o o

picnic area

EARLY SPRING 100 feet

lo CO 6 9

Figure 8. Mid-spring (13 April-12 May). Cross-hatched areas represent contours of plots in which the adult mortality index is less than 50 (the alive adult snails outnumber the empty shells). Rattiesnoke Creek

Oo OOO

path

OOO O o o

picnic oO! area pO

100 feet

o 71

Figure 9* Late spring (13 May-12 June, 1966). Cross- hatched areas represent contours of plots in which the adult mortality index is less than 50 (the alive adult snails outnumber the empty s h e l l s ) • Rattlesnake Creek

ooo OO

path

OOO O o o

picnic orea qOj

LATE SPRING toofeet 73

Figure 10* Early summer (13 June-12 July)* Cross-hatched areas represent contours of plots in which the adult mortality index is less than $0 (the alive adult snails outnumber the empty shells)* Rattlesnake Creek

picnic area

EARLY SUMMER 100 feet >■ « 7 5

Figure 11. Distributions of activity states in adults and immature ^ . ptychophora and temperature measure ments in the 5 strata. Preferred temperature (Tp) as determined in the laboratory is shaded. On plot 63 the 55 immature snails extend into the column of adult animals. Of these 55 * 44 are aestivating and 12 are active. There were 57 aestivating adults as indicated by the top of the column. Plot 91 contained 59 active immatures and 14 adults (l aestivating, 13 a c t i v e )• 76

hibernating __ litter surface ______su b -litter soil ac tiv e

TEMPERATURE ACTIVITY

20-0

K) 12 13 W 15 25 16 17 18 20 22 2 3 26 27 28 31 30 , 33 29 32 34 35 36 37 38 39 40 42 43 44 45 46 47 48 49 50 51 52 53 54 55 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 7 7

Figure 12. Frequencies of selection of various temperatures by A. ptychophora in preferred temperature de terminations. X is the mean, or preferred tem perature of 18.4®C. FREQUENCY OF SELECTION

m m"O 30 > c 30 :1 P ^ n

,A,-.

-J cn 7 9

Figure 13* Frequencies of greatest diameters of ptycho phora in each of the four periods.

I is early spring (23 March-12 April, 1966) II is mid-spring (13 April-12 May, 1966) III is late spring (13 May-12 June, 1966) IV is early summer (13 June-12 July, 1966) 8 0

4 0

4 01

>- V zUJ 8 (KUJ u_ 40

1 917 DIAMETER (mm.) 81

Figure 14* Oxygen consumption of hibernating * aestivating^ and active Allogona ptychophorao 16

ACTIVE 14

z 9 H CL 10 S => (/) z c O o I Q» 8 z AESTIVATING w o > oX 6

HIBERNATING 4

5 TEMPERATURE (®C) 15

OXYGEN CONSUMPTION OF HIBERNATING, AESTIVATING, and a c t iv e ALLOGONA PTYCHOPHORA 83

Plate 1* Photographs of favorable and unfavorable habitat*

a* Unfavorable habitat (density of A* ptychophora 0-5/m2). “

b. Favorable habitat (density > 5/m^). The plant with large leaves is Heracleum lanatum, cow parsnip* I 8 5

Plate 2. Photographs of Allogona ptychophora in field.

a. Snals climbing the stalk of H. lanatum. Often the snails will be found aestivating at the same height above ground in the morning.

b. Snail foraging on leaf of H. lanatum.

c. Snails foraging on leaf litter. ; Tr; mm »

w 8 7

LITERATURE CITED

Blinn, Walter C. 1963. Ecology of the land snails. Mesodon thyroidus and Allogona profunda. Ecol. 44(3)s498- 508.

Garrick, R. 1942. The grey field slug, Agriollmax agre stis, and its environment. Ann. Appl. Biol. 29:43-55.

Carney, W* Patrick. 1966. Mortality and apertural orienta tion in Allogona ptychophora during winter hiberna tion in Montana. Nautilus 79(4):135-136.

Chamberlin, T. C. 1897. The method of m ultiple working hy potheses. Jour. Geol. 5:837-848,

Dainton, Barbara H. 1954 # The activity of slugs 1. The in duction of activity by changing temperatures. Jour. Exp. Biol. 31(2) :165-187.

Deevey, Edward S. 1947. Life tables for natural populations of animals. Quart. Rev. Biol. 22:283-314»

Edelstam, Carl and Carina Palmer. 1950. Homing behavior in Gastropods. Oikos 2 (2 ):259-270.

Foster, T. D. 1936. The biology of the land snail, Polygyra thyroidus. unpubl. Ph.D. thesis at University of I l l i n o i s •

Getz, L. L. 1959. Notes on the ecology of the slugs, Arion circumscriptus. Deroceros reticulatus. and ^ . laeve. Am. Midi. Nat. 61:485-498.

K rull, Wendell H. and Cortland R. Mapes. 1952. Studies on the biology of Dicrocoelium dendriticum (Rudolph!, 1819) Loos, 189'9 (Trematoda:Dicrocoeliidae ) , includ ing its relation to the intermediate host, Cionella lubrica (Muller) VI. Observations on the life cycle and biology of _C. lubri c a. Cornell Vet. 42(4) "464- 489. Lee, C. Bruce. 1952. Ecological aspects of Stenotrema hirsutum in the region of Ann Arbor, Michigan. Amer. Midi. Nat. 47(l):55-60.

Pilsbry, Henry A. 1939. Land Mollusc a of North America. The Academy of Natural Sciences of Philadelphia.

Strandine, E. J. 1944. A quantitative study of a snail popu lation. Ecol. 22(l):86-91. 8 8

Van der Schalie, Henry and Lowell L. Getz* 1962. The d i s t r i bution and natural history of the snail Pomatiopsis cincinnatiensis. Am. Midi. Nat. 68(l)s203-231«

Van der Schalie, Henry and Lowell L. Getz. 1963. A compari son of temperature and moisture responses of the snail genera Pomatiopsis and Oncomelania. Ecol. 44(1):73-83. Wells, G. P. 1943. The water relations of snails and slugs III. Factors determining activity in Helix pomatia L. Jour. Exp. Biol. 20 :79-87.