ASPECTS OF THE REPRODUCTION AND ACTIVITY OF TWO
SYMPATRIC MASTUS (BECK, 1837) SPECIES IN CRETE
(GASTROPODA: PULMONATA: BULIMINIDAE)
A. PARMAKELIS 1 , 2 AND M. MYLONAS
1,2
1
Natural History Museum of Crete, University of Crete, Irakleio, P.O. Box 2208, 71409 Greece, and 2Department of Biology, University of Crete, Irakleio, Greece
(Received 4 July 2001; accepted 15 January 2002)
ABSTRACT
The present study reports an investigation into the reproductive biology and ecology of two sympatric
species of Mastus endemic to the island of Crete (southern Greece). The study lasted 6 months, from
September 1997 to March 1998, and involved field observations on single and copulating individuals,
and the study of the spermatophores within the genital tract. The two species have different aestivation habits and emergence times. Mastus olivaceus, which aestivates closer to the surface of the soil or
in the litter, emerges soon after the first rains, while Mastus cretensis emerges later. Additionally, M. olivaceus starts aestivating over a month earlier than M. cretensis. M. olivaceus reproduces from late
September till early January, while M. cretensis starts in early November and ends in early March. The
bursa-like diverticulum of M. cretensis bears only one spermatophore, but in M. olivaceus from one to
three spermatophores were found. The 91 spermatophores of M. olivaceus examined indicate intrapopulation variability in the number of transverse ridges and number of spines in the ornamentation
of its distal part. These types of difference in spermatophore morphology should not, therefore, be
considered species-specific.
INTRODUCTION
There have been numerous studies on the reproductive cycles
of land snails from a diverse array of habitats and regimes (for
reviews see Duncan, 1975; Peake, 1978; Tompa, 1984). However, the biology and ecology of the Greek land snails have not
generally been adequately studied. Some helicid species of
northern Greece have been studied (Staikou, LazaridouDimitriadou & Farmakis, 1988; Staikou, Lazaridou-Dimitriadou,
1990; Staikou, 1998), while some data concerning the genera
Codringtonia and Albinaria are presented by Hadjicharalambous
(1996) and Giokas (1996), respectively. Some information
regarding the land snails of the Cyclades islands is given in
Mylonas (1982).
One Mediterranean region very close to Greece that has
been adequately studied is Israel. There are many papers
regarding the reproductive cycles and the ecology of the land
snail species of Israel (Heller, 1975, 1982, 1987; Heller & Ittiel,
1990; Heller & Dolev, 1994; Jones & Shachak 1994; Heller,
Sivan & Hodgson 1997). According to Heller et al. (1997) the
vast majority of Israeli land snail species studied to date, are
active in autumn and early winter. During that period the snails
reproduce, feed, and grow. There are a few exceptions to this
rule, such as Lauria cylindracea (Heller et al., 1997), which remain
active during the whole year and reproduce whenever the conditions are favourable. On the other hand, in Greece, although
the majority of land snails reproduce within the autumn–
winter period, some land snails species also reproduce during
early spring to late summer (Mylonas, 1982; Staikou et al., 1988;
Hadjicharalambous, 1996; Staikou, 1998).
The present study reports an investigation into the reproductive biology and ecology of two sympatric species of Mastus
(Buliminidae). The study took place in the island of Crete,
southern Greece.
Mastus has a circum-Mediterranean distribution, except for
the eastern and southeastern regions. Thirty-two species of
Mastus have been recognized by various authors and 27 of these
Correspondence: A. Parmakelis; e-mail: [email protected]
J. Moll. Stud. (2002) 68: 225–233
have been reported in the Aegean area. Data regarding the
biology of reproduction, and the ecology of Buliminidae and
Mastus in particular, are very limited (Heller, 1975; Mylonas,
1982; Livshits, 1983; Jones & Shachak, 1994; Maassen, 1995).
The reproductive biology of molluscs may be approached
through histological studies of the reproductive system or
through direct observations in the field or the lab anatomy (i.e.
Hodgson, Hanel & Loveridge, 1994; Heller et al., 1997). We did
not use histological studies, but, in addition to field observations, we studied the presence of spermatophores in the genital
tract. Spermatophores are exchanged during copulation in
Mastus (Maassen, 1995). According to Lind (1973), in a study
concerning Helix pomatia L., and Tompa (1984) in a review of
the Stylommatophora, the received spermatophore is dissolved
in the bursa of the recipient a few days after copulation. Thus,
the presence or absence of spermatophores within the genital
tract of land snails can define the reproductive period of the
species studied. Maassen (1995) used details of spermatophore
morphology as key characters in recognising Mastus species.
We therefore also examined the morphology of the spermatophores exchanged by copulating pairs.
MATERIALS AND METHODS
We conducted our research on Giouchtas Mountain (UTM:
LV30) in central Crete (Fig. 1). Giouchtas is a moderately high
limestone mountain separated from all other mountains of
Crete by lowland cultivations. The vegetation is maquis and
phrygana, and degraded maquis of Quercus coccifera, Quercus
ilex, and Calicotome villosa, while as the altitude rises, copses of
Pinus brutia and Cupressus sempervirens can be found. The study
area (approximately 500 m2) is a clearing with phryganic vegetation, located in the southeast side of Giouchtas Mountain, at
300 m altitude. The dominant plant species are Sarcopoterium
spinosum, Genista acanthoclada, and Coridothymus capitatus
(Thymus capitatus). The depth of the soil varies from a few
centimeters in some parts of the study area, up to half a metre
© The Malacological Society of London 2002
A. PARMAKELIS & M. MYLONAS
Figure 1. Crete, showing Giouchtas Mountain, where the study took place.
in others, as happens in many mountainous areas of Crete.
Stones offering shelter cover less than 5% of the total area. The
site has a Mediterranean climatic regime (Fig. 2) typical for
Crete; weather conditions during the study period are shown in
Fig. 3.
The Mastus species studied were Mastus olivaceus (Pfeiffer,
1846) and Mastus cretensis (Pfeiffer, 1846). Both are endemic to
Crete and the surrounding islets. Although Maassen (1995)
considers M. olivaceus of Giouchtas Mountain to be a distinct
species, and names it Mastus butoti Maassen, 1995, we will be
referring to it as M. olivaceus following Vardinoyannis (1994).
The two taxa studied are easy to distinguish on the basis of the
shell (Fig. 4) and the spermatophores (Fig. 5). The genitalia
of these two species are also profoundly different. M. olivaceus
has both a bursa copulatrix and a bursa diverticulum, while in
M. cretensis only a bursa-like diverticulum is present (Fig. 6).
The study lasted 6 months, from late September 1997 till late
March 1998 (Table 1). The period during which we collected
individuals from the study site falls within the rainy season
(Fig. 2) and coincides with the mating season of the Cretan
Mastus species, between the second half of October and the
end of February (Maassen, 1995). At the beginning of the study
we collected individuals every 20 days, but during the rainy
season we visited the study area every ten days (Table 1). In
each visit our goal was to collect at least 10 individuals (aestivating or active) of each species and as many copulating pairs as
possible. We searched under stones, under the shrubs, within
the soil close to the roots of the shrubs and in the grass. Notes
were taken of the resting sites and behaviour of the individuals
in the field. The study was terminated in late March as after that
time none of the individuals collected carried spermatophores
and only individuals with an epiphragm (indicative of aestivation) could be found.
As soon as a copulating pair was found it would be either
collected immediately or it would be allowed to complete copulation and collected afterwards. All individuals collected were
placed in 99% ethanol so that the spermatophore would be
fixed in the part of the terminal genitalia in which it was at the
time of collection. In total we studied 175 individuals and seven
pairs of M. olivaceus, and 113 individuals and one pair of M.
cretensis.
Although our field observations showed that aestivating individuals of Mastus species do not store spermatophores received
during the previous reproductive period, we collected and
dissected aestivating individuals from Giouchtas Mountain the
summer prior to our study in order to confirm this.
All spermatophores were photographed using a Scanning
Electron Microscope. The spermatophore of Mastus species is
divided into two main parts by the presence of a prominent
hook, which is formed within the caecum of the epiphallus.
The part of the spermatophore formed in the distal part of the
epiphallus corresponds to the distal part of the spermatophore,
whilst the part formed in the proximal part of the epiphallus is
the proximal part of the spermatophore (Maassen, 1995). Most
of the terminology used in this paper regarding the spermatophores follows Lind (1973) and Maassen (1995), while, where
necessary, some new descriptions are given by us. The spermatophore structures that contribute to the systematics of the
genus Mastus are situated in the distal part of the spermatophore and that was the part studied by us.
Figure 2. Mean monthly temperatures and total monthly precipitation in
Irakleio for a period of 67 years (data from Pennas, 1977).
Figure 3. Mean monthly temperatures and total monthly precipitation in
Foinikia (5 km northwest of Giouchtas Mt.) for the period 1997–1998
(Prefecture of Crete, 1998).
226
REPRODUCTION AND ACTIVITY OF MA S T US
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7
8
Figure 4. The shells of (A) M. cretensis. (B) M. olivaceus. Scale bar 5 mm.
phores (Table 1). In a total of 304 individuals of both species
studied during the period from September 1997 to March
1998, we observed 91 spermatophores of M. olivaceus and 37
of M. cretensis. In the distal part of the spermatophore of
M. olivaceus (Fig. 5) just after the prominent hook, five to seven
transverse ridges are present. These ridges gradually become
more acute and turn into spines that run on a longitudinal
ridge. The spines are not present in all the spermatophores,
but when present they become less prominent towards the tip
of the spermatophore, so that the only structure that reaches
the end of the distal part is the longitudinal ridge. The first
transverse ridge is not joined to the hook. The distal part is not
curved and its tip is dentate.
In spermatophores of M. cretensis (Fig. 5) just after the hook,
the distal part bears three main longitudinal ridges and two
less-prominent ones that run between the main ridges. These
ridges run along the distal part and reach the end of the
spermatophore. As a result, the transverse section of the distal
part is rectangular. The distal part of the spermatophore is
curved at the tip with one-and-a-half spiral and, in some cases,
more than three spirals. The tip of the distal part is not dentate.
In all the pairs collected, the spermatophores were located in
exactly the same part of the terminal genitalia in both partners.
In the pairs collected after copulation, the spermatophores
were found inside the bursa diverticulum in M. olivaceus and
inside the bursa in the case of M. cretensis. In M. olivaceus
collected during copulation the spermatophores were either
inside the penis or protruding out of it. The number of the
spermatophores found in each individual varied. In individuals
of M. olivaceus from one to three complete spermatophores
were found inside the bursa diverticulum. Partly dissolved
spermatophores were found inside the bursa copulatrix and/
or inside the top part of the bursa diverticulum.
In all the individuals of M. cretensis, only one spermatophore
was ever found in the bursa-like diverticulum at one time. That
part of the terminal genitalia also contained the remains of
dissolved spermatophores.
There are certain differences between the spermatophores
that M. olivaceus individuals exchange during copulation.
Similar differences are also found between the different
spermatophores received by a single individual. It is mainly the
ornamentation following the hook, on the distal part of the
spermatophore, which varies. For example, the exchanged
All samples are deposited in the collections of the Natural
History Museum of Crete (NHMC).
RESULTS
Activity
The results for each sampling occasion are presented in
Table 1. M. olivaceus emerged just after the first rains at the end
of September and ceased activity in the second half of January
(Fig. 7). During the active period, individuals of M. olivaceus
were mostly found under shrubs.
During aestivation (mid-January to late September) the
snails covered their shell aperture with a thin transparent
epiphragm and remained on the surface, hidden close to the
roots of the shrubs, mainly of Sarcopoterium spinosum and Genista
acanthoclada.
M. cretensis emerged in early November and remained active
till late March (Fig. 8). During the active period most snails
were usually found in the grass. A small number were also
found under stones and shrubs.
During aestivation all the individuals were found approximately 5–10 cm deep in the soil, whether under the stones,
under the shrubs, or within the weeds. The shell aperture was
covered with a thin, transparent epiphragm, usually with mud
attached to it.
Mating season
About 15 days after M. olivaceus emerged it started copulating,
as evidenced by pairs found in the field (Table 1) and the presence of spermatophores in the individuals (Fig. 9). The mating
season of M. olivaceus started in late September and ended in
early January. As indicated by the presence of spermatophores
within the bursa-like diverticulum of M. cretensis individuals,
this species started copulating in early November and continued till early March (Fig. 10).
Copulation and spermatophores
The duration of copulation in both species varies from 1 h up
to 4 h, as shown by the timing of the collected pairs.
None of the aestivating individuals of either species collected
during the summer prior to our study contained spermato227
A. PARMAKELIS & M. MYLONAS
Figure 5. Spermatophores of the studied species. (1) M. olivaceus. (1A) Transverse ridges. (1B) Spines running on a longitudinal ridge. (2) M. cretensis. (2A)
Longitudinal ridges.
both found in the bursa diverticulum of one of the partners,
were different: the fraction had very intense spines, while the
complete spermatophore lacked these spines. The spermatophores of the second partner were similar, in their distal part,
to the distal fraction of the first partner. Summarizing, in all
seven of the pairs of M. olivaceus there was not a single case in
which the number of transverse ridges or the number of spines
running on the longitudinal ridge, did not differ between the
two partners of the pair.
spermatophores in a pair of M. olivaceus each had a different
number of transverse ridges and spines in the distal part (Fig.
11). The spermatophores of two other copulating individuals
were also quite different: the spermatophore of the first individual had spines just after the transverse ridges of the distal
part, while the spermatophore of the second individual lacked
these spines entirely. In another pair of M. olivaceus, the
fraction of the distal part of the dissolved spermatophore and
the distal part of the complete spermatophore, which were
Table 1. Collection dates, total number of individuals, number of aestivating individuals, number of pairs, and number of spermatophores.
Mastus olivaceus
Mastus cretensis
Date of
Total no.
Aestivating
Spermatophores Spermatophores
Total no.
Aestivating
collection
individuals
individuals
Pairs
of individuals
of pairs
individuals
individuals
Pairs
of individuals
of pairs
Summer 1997
27/09/1997
20/10/1997
27/10/1997
05/11/1997
17/11/1997
25/11/1997
02/12/1997
11/12/1997
18/12/1997
24/12/1997
29/12/1997
08/01/1998
17/01/1998
24/01/1998
31/01/1998
07/02/1998
14/02/1998
21/02/1998
14/03/1998
29/03/1998
25
10
11
10
10
20
14
10
7
9
7
10
12
8
8
8
7
4
5
3
2
25
0
0
0
0
0
0
0
0
0
0
0
0
6
5
6
7
4
5
3
2
0
0
2
1
1
1
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
5
11
11
11
4
12
5
4
2
1
1
0
0
1
1
0
0
0
0
–
–
4
3
4
3
7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
14
1
3
2
3
10
7
10
9
9
7
3
3
8
5
6
7
5
6
6
4
14
1
3
2
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
5
2
5
4
4
3
0
1
3
1
3
0
1
0
1
0
–
–
–
–
–
–
–
–
2
–
–
–
–
–
–
–
–
–
–
–
–
228
Spermatophores Spermatophores
REPRODUCTION AND ACTIVITY OF MA S T US
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Figure 6. The terminal genitalia of (A) M. olivaceus. (B) M. cretensis. Abbreviations: BD, bursa diverticulum; BC, bursa copulatrix; DBC, duct of bursa
copulatrix; BLD, bursa-like diverticulum; VD, vas deferens; F, flagellum; DE, distal epiphallus; PE, proximal epiphallus; C, caecum; PR, penial retractor
muscle; P, penis; BW, body wall. Scale bar 5 mm.
DISCUSSION
(Pfeiffer, 1848) and Chondrula bergeri (Roth, 1839), which bury
themselves as deeply (Mylonas, 1982), or Trochoidea siphnica
(Kobelt, 1833), which hides even deeper (Mylonas, Botsaris,
Sourdis & Valakos, 1995).
The high rainfall that occurred during October 1997 (Fig. 3)
was not sufficient to activate M. cretensis individuals and this
allows us to speculate that, in order for M. cretensis to emerge,
besides high soil humidity, it could be that falling temperature
is also required. Falling temperature activating land snails has
been recorded before for the slug Arion ater (Dainton & Wright,
1985) and land snails of the genus Codringtonia (Hadjicharalambous, 1996). Additionally, this behaviour indicates
that there is an endogenous mechanism protecting M. cretensis
Activity
The emergence of Mastus individuals followed the first rains
(Figs 7 and 8), which usually occur in late September (Fig. 2),
as do the land snails of southern Greece, Israel and other
regions with a Mediterranean type of climate (Mylonas, 1982;
Heller et al., 1997).
Individuals of M. cretensis hid about 5–10 cm deep in the soil
and this partially agrees with the findings of Maassen (1995),
who mentions a depth of 30 cm. This burrowing behaviour is
not unusual for land snails of southern Greece, since there are
species smaller in size than M. cretensis, such as Orcullela scyphus
Figure 7. Numbers of active and aestivating individuals of M. olivaceus.
229
A. PARMAKELIS & M. MYLONAS
from emerging prior to its favoured period, since such high
rainfall does not usually occur during October (Fig. 2). On
the other hand, individuals of M. olivaceus, which aestivate at
the surface, near the roots of the shrubs, are activated just
after the first rains, indicating that their emergence relies
mostly on the humidity of their microhabitat.
Mating season
Most snail species in Greece reproduce during the autumn and
early winter, whilst some reproduce during spring (M. Mylonas,
personal communication; Hadjicharalambous, 1996). In northern Greece these two reproductive periods are not very
Figure 8. Numbers of active and aestivating individuals of M. cretensis.
Figure 9. Percentage of M. olivaceus individuals containing spermatophores.
230
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60
1
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4
5
6
7
8
Figure 10. Percentage of M. cretensis individuals containing spermatophores.
Figure 11. Morphology of the spermatophores exchanged by two copulating partners of M. olivaceus. (1) Spermatophore found in the first individual. (1A,
1B) Spines only reaching up to the mid-point of the distal part of the spermatophore. (2) Spermatophore found in the second individual. (2A, 2B) Spines
reaching near the end of the distal part of the spermatophore.
Heller et al., 1997). From the study of spermatophores of other
Cretan Mastus species, such as M. subaii Maassen, 1995, M.
ierapetrana Maassen, 1995, and other species belonging to the
M. cretensis complex (Maassen, 1995), the mating season was
also found to finish in late February, and thus we can conclude
that the duration of the reproductive period of Mastus species
well defined, while in southern Greece the two reproductive
periods are very discrete and have a limited duration. The
mating seasons of M. olivaceus (late September to early January)
and M. cretensis (late October to early March) fall within the
seasons mentioned for the land snails in southern Greece, the
Cyclades, and Israel (Mylonas, 1982; Hadjicharalambous, 1996;
231
A. PARMAKELIS & M. MYLONAS
often found in M. olivaceus where both a bursa copulatrix and
a bursa diverticulum are present, in M. cretensis only one
spermatophore was ever contained in the bursa-like diverticulum. The difference in this aspect of reproduction between the
two species studied enhances the significance of the bursa
diverticulum in the reproductive isolation of the species, and
so the presence or absence of a diverticulum should be considered an important taxonomic character of the genus, as
noted by Maassen (1995) as well.
In M. olivaceus both the bursa copulatrix and the bursa
diverticulum have a gametolytic function, as evidenced by the
presence of dissolved spermatophores inside both. In M. cretensis the destruction of spermatophores takes place at the top of
the bursa-like diverticulum.
Generally, snails form a single spermatophore at each mating (Tompa, 1984), but exceptions are known (Likharev &
Wiktor, 1980). In Mastus we did not find a single case of a
spermatophore being exchanged and another one being
formed subsequently within the epiphallus complex. Thus, the
multiple spermatophores found in the bursa diverticulum of
a single specimen are most likely to be the result of repeated
copulation, as has previously been recorded in other land
snails (Giusti & Andreini, 1988), probably with different partners.
Since in all pairs studied no spermatophore was found being
formed within the epiphallus complex, we conclude that the
formation of the spermatophore in Mastus is a very rapid procedure occurring just before copulation or a few seconds after
initiation of copulation, as is the case in most snails studied
(Lind, 1973; Tompa, 1984).
The spermatophore of M. cretensis was similar to that
described by Maassen (1995) from Giouchtas Mountain. On
the other hand, the spermatophores of M. olivaceus differed
from those of M. butoti described by Maassen (1995). The
differences concern the number of spines found in the distal
part of the spermatophore. Maassen (1995) examined two
spermatophores of M. butoti from two different localities and
described a row of about 18 conspicuous spines in the distal
part. Maassen (1995) did not, however, discriminate between
spines and transverse ridges (Fig. 5) and refers to both these
structures as spines. In the 91 spermatophores we examined,
the number of spines varied from 0 to 19, and the transverse
ridges from 5 to 7.
The study of the spermatophores of M. olivaceus reveals considerable variability in the ornamentation after the hook in the
distal part of the spermatophore. The number of transverse
ridges varies, as does the number of spines following the hook.
Such differences in spermatophore morphology should not
therefore be considered to be species-specific.
in Crete is approximately 4 months. This period is longer than
that period mentioned for other Greek species (Mylonas, 1982;
Staikou et al., 1988; Staikou, 1998). The difference in the initiation of the reproductive period between M. olivaceus and M.
cretensis may be the result of the different aestivation habits, and
the habitats that these two species occupy.
A schematic representation of the biological cycles of the
studied species is given in Fig. 12.
Copulation and spermatophores
Since in all the pairs studied the spermatophores of both partners were found in the same position in the terminal genitalia,
we conclude that simultaneous and reciprocal mating, which is
the most common situation in land snails (Tompa, 1984), is
supported by our studies on the genus Mastus.
In M. olivaceus, the presence of more than one spermatophore in the bursa diverticulum of an individual is not surprising, since in some land snails, from 10–20 spermatophores
have been found in the bursa of a single specimen (Tompa,
1984). However, whereas more than one spermatophore was
ACKNOWLEDGEMENTS
We are grateful to Professor R. A. D. Cameron (University of
Sheffield, UK), Professor J. Heller (Hebrew University of
Jerusalem, Israel), and an anonymous referee for their critical
suggestions that improved the manuscript. We would also like
to thank Dr K. Vardinoyannis (Natural History Museum of
Crete), for her valuable contribution in this study, S. Roberts,
for correcting the English text, and finally, Professor V.
Galanopoulos (University of Crete, Greece) and the laboratory
technician E. Papadogiorgaki, for the Scanning Electron
Microscope photographs of the spermatophores.
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Figure 12. The biological cycle of Mastus species on Giouchtas mountain
(A) M. olivaceus. (B) M. cretensis.
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8
9
40
1
2
3
4
5
6
7
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9
50
1
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3
4
5
6
7
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60
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7
8
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