16
structure of colonies, seasonal observations are required to
obtain a complete picture of changes in the distribution of
spermatogenic tissue in zooids of distant and related species.
1.2.2.2 Ovary
The female gonad of bryozoans is more compact than the
male one, though it may occupy a considerable volume. In
cheilostomes an ovary is represented by a group of oogonia
and oocytes of different age surrounded by accessory (follicle and “basal”) cells; strands of funicular tissue approach it
(see Sects. 1.2.3 , 1.2.4 , 1.2.5 and 1.2.6 ). The ovary is typically single, although the presence of two ovaries in some
zooids was mentioned by Calvet ( 1900 ) for Bugula simplex
and several ovaries by Schulz ( 1901 ) and Borg ( 1947 ) for
Einhornia crustulenta .
The location of the ovary varies. Information on its exact
(more or less) location is available for 72 species of Cheilostomata
(Reed 1991 ; Ostrovsky et al. 2008 , see also Appendix I). In 24
of them the female gonad is recorded only in the distal part of
the zooid, in 22 of them only in the middle part, and in six only
in the proximal part. The ovary was found to be located in the
proximal and middle parts of the zooid in seven species and
in the distal and the middle parts in ten species.
In the course of my studies I recorded over a dozen variations (with combinations) in the position of the female
gonad. Out of 133 examined species with ovaries, in 62 the
ovary was recorded only in the distal part of the zooid, in 19
only in the proximal part, and in 18 only in the middle part.
In 13 species the ovary was found both in the proximal and
middle parts, while in 15 it was found in the distal and middle parts. In three species ( Sinuporaria sp., Hippoporina
propinqua , Crepidacantha kirkpatricki ) ovaries were
recorded in the proximal, middle and distal parts of the
zooid. In Bicellariella ciliata the ovary was predominantly
located in the distal part of the zooid on its basal wall, and
only incidentally in the proximal half of the cystid where it is
associated with the gut (Moosbrugger et al. 2012 ; see also
Table 1.1 ). Thus, in cheilostome bryozoans the female sexual
gland is usually located distally; more rarely it is located in
the middle or proximally.
Spermatogenic tissue, on the other hand, develops in most
species in the proximal part of the zooid (see above). An
examination of species with hermaphrodite zooids showed
that in 14 out of 45 of them the location of male and female
gonads corresponded to the following scheme – the ovary
was located in the distal or middle parts of the zooid and the
spermatogenic tissue proximally. For instance, while in male
zooids of Arachnopusia unicornis male gametes occupied
the entire surface of the basal wall, in hermaphrodite zooids
they occupied only its proximal part (see Tables 1.1 and 1.2 ).
The above regularity was lacking in 31 species, demonstrating the most diverse expressions of relative gonad
positions. Male and female gonads are separate or they can
co-occur in proximal or distal parts of the zooid. For instance,
if spermatogenic tissue is located proximally and distally, the
ovary can be located, depending on species, (1) in distal,
middle and proximal parts, (2) the middle part only,
(3) middle and distal parts, or (4) the distal part only. If
spermatogenic tissue occupies the entire basal wall or most
of it, the ovary can be located (1) distally, (2) in the middle,
or (3) in the middle or proximal parts. In some species, male
and female gonads are located very close to each other,
with spermatogenic tissue being apposed to the ovary or
surrounding it ( Cribrilina annulata , Antarctothoa bougainvillei , Arctonula arctica , Reteporella sp.). In several cases,
male and female gonads can be situated in the same part of
the zooid but on different walls ( Mucropetraliella elleri ), or
spermatogenic tissue is located on the walls and the ovary is
located on funicular cords ( Porella smitti , Schizoporella
unicornis ) (Tables 1.1 and 1.2 ).
Similar fi ndings have been reported in the literature
(Reed 1991 ; Ostrovsky et al. 2008 ). In 17 out of 29 species
for which the position of both gonads in hermaphrodite
zooids is known, the ovary is located in the distal part of
the zooid and the spermatogenic tissue in its proximal part.
Other species are characterized by some of the combinations
described above.
According to the published literature, in most cases
(31 species) the ovary lies on the basal wall (usually apposed
to one of the lateral walls), being only sometimes suspended
in the zooidal cavity on funicular cords (six species). In eight
species the ovary either lies on the surface of the zooid wall
(basal or lateral) or is suspended on funicular cords (Reed
1991 ; Ostrovsky et al. 2008 , see also Appendix I).
I have found that the mature ovary lies on the basal cystid
wall in two thirds of the species studied (Figs. 1.2C, D , 1.3B, C ,
1.4 , 1.5 , 1.6A, C, D , 1.7A, C , 1.8C, D , 1.9 , 1.10B–E , 1.11 ,
1.12B, C , 1.14B–D , 1.15 , 1.16C, D , 1.18C, D , 1.19A , 1.21
inset, 1.23A , 1.24B , 1.27A, B , 1.30A and 1.35A, B, D ).
In many of them the ovary was found in either of two
locations – on the basal wall or suspended in the coelom on
funicular cords (Fig. 1.33F ). It often happens that the female
gonad with young oocytes is suspended on funicular cords
(Figs. 1.7B , 1.26B–F and 1.27D ) while the ovary containing
a mature oocyte doublet lies on the basal wall (Figs. 1.7A ,
1.27A, B ). Sometimes the ovary is suspended in the zooidal
cavity on funicular cords while attached by a narrow stalk to
the basal wall (Fig. 1.7D ). In a few species the ovary was only
found suspended in the coelom on funicular cords, sometimes touching the cystid wall (Fig. 1.12B, D ) (see Table 1.1 ).
In Myriapora truncata the ovary is located on the lateral wall,
not in contact with the basal wall (Fig. 1.33D ). In Celleporina
caminata the ovary lies against the lower surface of the frontal
shield of the maternal zooid, while in Smittina majuscula it
lies against the lower wall of the compensation sac. In four
species it is sometimes found on the proximal transverse
1 Reproductive Patterns of Gymnolaemate Bryozoa: General Overview and Comparative Analysis
structure of colonies, seasonal observations are required to
obtain a complete picture of changes in the distribution of
spermatogenic tissue in zooids of distant and related species.
1.2.2.2 Ovary
The female gonad of bryozoans is more compact than the
male one, though it may occupy a considerable volume. In
cheilostomes an ovary is represented by a group of oogonia
and oocytes of different age surrounded by accessory (follicle and “basal”) cells; strands of funicular tissue approach it
(see Sects. 1.2.3 , 1.2.4 , 1.2.5 and 1.2.6 ). The ovary is typically single, although the presence of two ovaries in some
zooids was mentioned by Calvet ( 1900 ) for Bugula simplex
and several ovaries by Schulz ( 1901 ) and Borg ( 1947 ) for
Einhornia crustulenta .
The location of the ovary varies. Information on its exact
(more or less) location is available for 72 species of Cheilostomata
(Reed 1991 ; Ostrovsky et al. 2008 , see also Appendix I). In 24
of them the female gonad is recorded only in the distal part of
the zooid, in 22 of them only in the middle part, and in six only
in the proximal part. The ovary was found to be located in the
proximal and middle parts of the zooid in seven species and
in the distal and the middle parts in ten species.
In the course of my studies I recorded over a dozen variations (with combinations) in the position of the female
gonad. Out of 133 examined species with ovaries, in 62 the
ovary was recorded only in the distal part of the zooid, in 19
only in the proximal part, and in 18 only in the middle part.
In 13 species the ovary was found both in the proximal and
middle parts, while in 15 it was found in the distal and middle parts. In three species ( Sinuporaria sp., Hippoporina
propinqua , Crepidacantha kirkpatricki ) ovaries were
recorded in the proximal, middle and distal parts of the
zooid. In Bicellariella ciliata the ovary was predominantly
located in the distal part of the zooid on its basal wall, and
only incidentally in the proximal half of the cystid where it is
associated with the gut (Moosbrugger et al. 2012 ; see also
Table 1.1 ). Thus, in cheilostome bryozoans the female sexual
gland is usually located distally; more rarely it is located in
the middle or proximally.
Spermatogenic tissue, on the other hand, develops in most
species in the proximal part of the zooid (see above). An
examination of species with hermaphrodite zooids showed
that in 14 out of 45 of them the location of male and female
gonads corresponded to the following scheme – the ovary
was located in the distal or middle parts of the zooid and the
spermatogenic tissue proximally. For instance, while in male
zooids of Arachnopusia unicornis male gametes occupied
the entire surface of the basal wall, in hermaphrodite zooids
they occupied only its proximal part (see Tables 1.1 and 1.2 ).
The above regularity was lacking in 31 species, demonstrating the most diverse expressions of relative gonad
positions. Male and female gonads are separate or they can
co-occur in proximal or distal parts of the zooid. For instance,
if spermatogenic tissue is located proximally and distally, the
ovary can be located, depending on species, (1) in distal,
middle and proximal parts, (2) the middle part only,
(3) middle and distal parts, or (4) the distal part only. If
spermatogenic tissue occupies the entire basal wall or most
of it, the ovary can be located (1) distally, (2) in the middle,
or (3) in the middle or proximal parts. In some species, male
and female gonads are located very close to each other,
with spermatogenic tissue being apposed to the ovary or
surrounding it ( Cribrilina annulata , Antarctothoa bougainvillei , Arctonula arctica , Reteporella sp.). In several cases,
male and female gonads can be situated in the same part of
the zooid but on different walls ( Mucropetraliella elleri ), or
spermatogenic tissue is located on the walls and the ovary is
located on funicular cords ( Porella smitti , Schizoporella
unicornis ) (Tables 1.1 and 1.2 ).
Similar fi ndings have been reported in the literature
(Reed 1991 ; Ostrovsky et al. 2008 ). In 17 out of 29 species
for which the position of both gonads in hermaphrodite
zooids is known, the ovary is located in the distal part of
the zooid and the spermatogenic tissue in its proximal part.
Other species are characterized by some of the combinations
described above.
According to the published literature, in most cases
(31 species) the ovary lies on the basal wall (usually apposed
to one of the lateral walls), being only sometimes suspended
in the zooidal cavity on funicular cords (six species). In eight
species the ovary either lies on the surface of the zooid wall
(basal or lateral) or is suspended on funicular cords (Reed
1991 ; Ostrovsky et al. 2008 , see also Appendix I).
I have found that the mature ovary lies on the basal cystid
wall in two thirds of the species studied (Figs. 1.2C, D , 1.3B, C ,
1.4 , 1.5 , 1.6A, C, D , 1.7A, C , 1.8C, D , 1.9 , 1.10B–E , 1.11 ,
1.12B, C , 1.14B–D , 1.15 , 1.16C, D , 1.18C, D , 1.19A , 1.21
inset, 1.23A , 1.24B , 1.27A, B , 1.30A and 1.35A, B, D ).
In many of them the ovary was found in either of two
locations – on the basal wall or suspended in the coelom on
funicular cords (Fig. 1.33F ). It often happens that the female
gonad with young oocytes is suspended on funicular cords
(Figs. 1.7B , 1.26B–F and 1.27D ) while the ovary containing
a mature oocyte doublet lies on the basal wall (Figs. 1.7A ,
1.27A, B ). Sometimes the ovary is suspended in the zooidal
cavity on funicular cords while attached by a narrow stalk to
the basal wall (Fig. 1.7D ). In a few species the ovary was only
found suspended in the coelom on funicular cords, sometimes touching the cystid wall (Fig. 1.12B, D ) (see Table 1.1 ).
In Myriapora truncata the ovary is located on the lateral wall,
not in contact with the basal wall (Fig. 1.33D ). In Celleporina
caminata the ovary lies against the lower surface of the frontal
shield of the maternal zooid, while in Smittina majuscula it
lies against the lower wall of the compensation sac. In four
species it is sometimes found on the proximal transverse
1 Reproductive Patterns of Gymnolaemate Bryozoa: General Overview and Comparative Analysis