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Contents �i–ÚŽŸ�j

Abstracts ..............................................................1

Aknowledgements ........................................................4

Contents ...............................................................6

1. General Introduction ................................................9

2. Description of Study Site in the Ogasawara Islands Outline of OgasawaraIslands ..................................11

�@�@Distribution of Achatina fulica in Ogasawara Islands..........13

�@�@Description of study sites....................................13

3. Growth Pattern and Protandry of Achatina fulica

�@�@Introduction ..................................................18

�@�@Materials and methods.........................................19

�@�@�@�@Dissection of reproductive system

�@�@�@�@Growth pattern trace by mark-recapture experiment

�@�@�@�@Comparison of genital system between adults and subadults

�@�@Results.......................................................21

�@�@Morphology and function of genital system.............21

�@�@�@�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

�@�@Relationship between shell growth and peristome thickness........24

�@�@Comparison of genital system between subadults and adults...26

�@�@Discussion....................................................27

�@�@�@�@Self-fertilization

�@�@�@�@Maturation of A.fulica

�@�@�@�@Protandry

�@�@�@�@Reproductive cycle of land snail

4. Oviposition and Characteristics of Egg Clutches in Achatina fulica

�@�@Introduction..................................................41

�@�@Materials and Methods.........................................42

�@�@�@�@Observation of oviposition and hatching

�@�@�@�@Dissection of pregrant snails

�@�@Results.......................................................43

�@�@�@�@Oviposition and hatching of A.fulica in laboratory

�@�@�@�@Observation clutch size and egg volume

�@�@Discussion....................................................46

�@�@�@�@Variation of clutch size and egg volume in A.fulica

�@�@�@�@Ecology of egg laying in pulmonate land snails

5. Activity patterns of Achatina fulica

�@�@Introduction..................................................55

�@�@Materials and methods.........................................56

�@�@�@�@Study site

�@�@�@�@Radio-transmitters

�@�@�@�@Radio-taggeing for determination of snail age

�@�@�@�@Detection of radio-tagged animals

�@�@�@�@Activity analysis by means actogram

�@�@Results.......................................................59

�@�@�@�@Shell growth in radio-tagged snails

�@�@�@�@Activity pattern of the snail

�@�@�@�@Long distance movement traced by radio-tracking

�@�@Discussion....................................................62

6. Daily movements of Achatina fulica around Resting Sites

�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

7. Homing Behabior of Achatina fulica

�@�@Introduction..................................................84

�@�@Materials and methods.........................................85

�@�@�@�@Study site

�@�@�@�@Observations on locomotive activity at night

�@�@�@�@Snail movements examined by removal and transplanting

�@�@Results.......................................................86

�@�@�@�@Movement pattern at night

�@�@�@�@Mark-recapture experiment

�@�@�@�@Transplantation of snails

�@Discussion....................................................88

�@�@�@�@Homing behavior of A.fulica

�@�@�@�@Adaptive significance of homing in Pulmonates

�@�@�@�@Orientation mechanisms

8. Mating behavior in Achatina fulica

�@�@Introduction..................................................97

�@�@Materials and Methods.........................................97

�@�@�@�@Observation site

�@�@�@�@Hourly change in number of copulating pairs

�@�@�@�@Observations on courtship behavior and duration of copulation

�@�@�@�@Repeating ability of copulation in an individual

�@�@�@�@Characteristics of mates chosen in copulation

�@�@Results.......................................................99

�@�@�@�@Mating activity

�@�@�@�@Courtship behavior

�@�@�@�@Duration of copulation

�@�@�@�@Repeating ability of copulation in an individual

�@�@Discussion...................................................103

9.�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

10.�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

11.�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

12.�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

13.�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

14. General Discussion ...............................................216

�@�@�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–�–

Summary..............................................................224

Referance ............................................................227

Japanese Abstracts ...................................................247

Plates ...............................................................248