62
Of special interest is the fi nding of sperm in the coelom
of the developing female zooid lacking a vestibulum as well
in the coelom of an ooecium in Celleporella hyalina
(Ostrovsky 1998 ). Sperm that succeed in penetrating into
a young sterile colony of this species may remain viable for
at least 2–3 weeks (up to 4–6), fertilizing oocytes as they
are formed (Manríquez et al. 2001 ; Hughes et al. 2002a ;
Hughes, personal communication, 2004). These fi ndings
indicate that sperm may freely move about within the colony,
from one zooid to another.
Marcus ( 1938a ) found sperm not only in male but also in
the female and sterile basal autozooids in a Celleporella colony. He suggested that sperm could move about in the colony
via the interzooidal communication pores. This idea has
been criticized (see Hughes 1987 ; Reed 1991 ; Ostrovsky
1998 , 2008b ) because these pores are plugged by pore-cell
complexes. In such cases it may be that sperm migrate into
growth zones (budding sites) prior to the completion of
transverse walls between zooids; i.e. from autozooids with
functioning polypides to those budding from them. In the
case of frontally budded female zooids in Celleporella ,
sperm must move from sterile autozooids into the buds of the
female polymorphs and even their developing ooecia
(see above). It is also possible that the rudimentary polypides
of female zooids may capture sperm. Hughes ( 1987 ) thought
that such polypides could not evert, but the discovery of parietal musculature and a compensation sac in the female zooid
(Ostrovsky 1998 ) indicates otherwise.
The fi nding of oocyte doublets in young zooids with nonfunctioning polypides in Callopora lineata shows that the
formation of early female cells proceeds at the expense of
colonial resources channelled to the developing zooid buds
via the funiculus. Although the fi rst previtellogenic oocyte
doublet is formed long before completion of the polypide,
the start of vitellogenesis is nevertheless delayed. It seems
natural that vitellogenesis cannot start in the absence of a
feeding polypide. However, the primary cause of this delay
appears to be not the lack of a nutrient supply (there being
intrazooidal nutrient transport in the colony) but the inability
to receive sperm (see also Bishop et al. 2000 ). My discovery
of a degenerating oocyte doublet long before polypide functioning begins confi rms the fi ndings of previous authors. As
soon as the polypide begins to function and sperm can enter
the zooid to achieve fertilization, the oldest oocyte doublet in
the ovary begins vitellogenesis. Apparently, sperm attractants are produced by very young gametes.
1.3.7 Oviposition
In Malacostegans, mature oocytes are released into the
environment via the intertentacular organ between the two
dorso- medial tentacles of the polypide. The same or a very
similar organ has been found in three species of brooding
cheilostomes (see Sect. 1.3.9 ). In other cheilostomes the mature
oocyte is transferred to the brood chamber via the supraneural pore, also located at the base of the dorso-medial tentacle
pair (summarized in Reed 1991 ; Ostrovsky and Porter 2011 ).
Until direct observations had been made, the mechanism
of oviposition, i.e. the transfer of the mature fertilized oocyte
into the brood chamber, had been debated by many of the
early naturalists (reviewed in Ostrovsky 2008a ; Ostrovsky
et al. 2008 ). Nitsche ( 1869 ) suggested that oviposition
occurred through a presumed pore between the bases of the
ooecium and the ooecial vesicle. According to Vigelius
( 1884b ), the egg was transferred to the brood cavity of the
ovicell through rupture/resorption of the ooecial vesicle. This
idea was supported by Delage and Hérouard ( 1897 ) and
Calvet ( 1900 ). Jullien ( 1888 ) proposed that oviposition might
occur with the help of the tentacle sheath in the female zooids
of Celleporella hyalina , since he failed to fi nd a polypide in
them. Levinsen ( 1909 , p. 66) agreed with this view for this
and some other species “where endooooecial ooecia are present with an operculum in common with the ooecium”, thus
suggesting the presence of an “inner connection” and “common cavity” between the zooid and the incubation chamber.
On the other hand, he stated that the egg should be released
from the cavity of the autozooid to enter the ovicell from outside (“eggs must pass directly from the zooecial aperture into
the ooecium”) in all other species with ovicells (p. 325).
Pergens ( 1889 ) was the fi rst to observe oviposition
(in Fenestrulina malusii ). Interestingly, he indicated that the
transfer of the oocyte to the ovicell occurred during polypide
degeneration, accompanied by considerable deformation of
the oocyte. However, Pergens’s paper was forgotten and the
fi rst description of oviposition was for a long time attributed
to Gerwerzhagen ( 1913 ), who managed to observe in detail
the transfer of the egg by the polypide from the cavity of the
maternal autozooid into the ovicell via the so-called supraneural
coelomopore in Bugula avicularia (summarized in Ostrovsky
2008a ; Ostrovsky et al. 2008 ). Observations showed that oviposition was accompanied by specifi c movements of the polypide, while the oocyte, being highly fl exible, was usually
(but not always) considerably deformed during its transfer to
the brood chamber (see Pergens 1889 ; Gerwerzhagen 1913 ;
Silén 1945 ; Corrêa 1948 ; Nielsen 1981 ; Dyrynda and Ryland
1982 ; Dyrynda and King 1983 ; Cook 1985 ; Zimmer, personal communication in Reed 1991 ; Maturo 1991b ). In
some species, the ovulated oocyte winds around the introvert
of the retracted polypide before oviposition. Dyrynda and
King ( 1983 ) described this phenomenon in Chartella papyracea . Such oocytes were also found in Cribrilina annulata ,
Menipea roborata and Sinuporaria sp. in the course of my
research (see also Ostrovsky 1998 ).
Prior to actual observations, the event sequence that constitutes oviposition was discussed by Jullien ( 1888 ). He did
1 Reproductive Patterns of Gymnolaemate Bryozoa: General Overview and Comparative Analysis
Of special interest is the fi nding of sperm in the coelom
of the developing female zooid lacking a vestibulum as well
in the coelom of an ooecium in Celleporella hyalina
(Ostrovsky 1998 ). Sperm that succeed in penetrating into
a young sterile colony of this species may remain viable for
at least 2–3 weeks (up to 4–6), fertilizing oocytes as they
are formed (Manríquez et al. 2001 ; Hughes et al. 2002a ;
Hughes, personal communication, 2004). These fi ndings
indicate that sperm may freely move about within the colony,
from one zooid to another.
Marcus ( 1938a ) found sperm not only in male but also in
the female and sterile basal autozooids in a Celleporella colony. He suggested that sperm could move about in the colony
via the interzooidal communication pores. This idea has
been criticized (see Hughes 1987 ; Reed 1991 ; Ostrovsky
1998 , 2008b ) because these pores are plugged by pore-cell
complexes. In such cases it may be that sperm migrate into
growth zones (budding sites) prior to the completion of
transverse walls between zooids; i.e. from autozooids with
functioning polypides to those budding from them. In the
case of frontally budded female zooids in Celleporella ,
sperm must move from sterile autozooids into the buds of the
female polymorphs and even their developing ooecia
(see above). It is also possible that the rudimentary polypides
of female zooids may capture sperm. Hughes ( 1987 ) thought
that such polypides could not evert, but the discovery of parietal musculature and a compensation sac in the female zooid
(Ostrovsky 1998 ) indicates otherwise.
The fi nding of oocyte doublets in young zooids with nonfunctioning polypides in Callopora lineata shows that the
formation of early female cells proceeds at the expense of
colonial resources channelled to the developing zooid buds
via the funiculus. Although the fi rst previtellogenic oocyte
doublet is formed long before completion of the polypide,
the start of vitellogenesis is nevertheless delayed. It seems
natural that vitellogenesis cannot start in the absence of a
feeding polypide. However, the primary cause of this delay
appears to be not the lack of a nutrient supply (there being
intrazooidal nutrient transport in the colony) but the inability
to receive sperm (see also Bishop et al. 2000 ). My discovery
of a degenerating oocyte doublet long before polypide functioning begins confi rms the fi ndings of previous authors. As
soon as the polypide begins to function and sperm can enter
the zooid to achieve fertilization, the oldest oocyte doublet in
the ovary begins vitellogenesis. Apparently, sperm attractants are produced by very young gametes.
1.3.7 Oviposition
In Malacostegans, mature oocytes are released into the
environment via the intertentacular organ between the two
dorso- medial tentacles of the polypide. The same or a very
similar organ has been found in three species of brooding
cheilostomes (see Sect. 1.3.9 ). In other cheilostomes the mature
oocyte is transferred to the brood chamber via the supraneural pore, also located at the base of the dorso-medial tentacle
pair (summarized in Reed 1991 ; Ostrovsky and Porter 2011 ).
Until direct observations had been made, the mechanism
of oviposition, i.e. the transfer of the mature fertilized oocyte
into the brood chamber, had been debated by many of the
early naturalists (reviewed in Ostrovsky 2008a ; Ostrovsky
et al. 2008 ). Nitsche ( 1869 ) suggested that oviposition
occurred through a presumed pore between the bases of the
ooecium and the ooecial vesicle. According to Vigelius
( 1884b ), the egg was transferred to the brood cavity of the
ovicell through rupture/resorption of the ooecial vesicle. This
idea was supported by Delage and Hérouard ( 1897 ) and
Calvet ( 1900 ). Jullien ( 1888 ) proposed that oviposition might
occur with the help of the tentacle sheath in the female zooids
of Celleporella hyalina , since he failed to fi nd a polypide in
them. Levinsen ( 1909 , p. 66) agreed with this view for this
and some other species “where endooooecial ooecia are present with an operculum in common with the ooecium”, thus
suggesting the presence of an “inner connection” and “common cavity” between the zooid and the incubation chamber.
On the other hand, he stated that the egg should be released
from the cavity of the autozooid to enter the ovicell from outside (“eggs must pass directly from the zooecial aperture into
the ooecium”) in all other species with ovicells (p. 325).
Pergens ( 1889 ) was the fi rst to observe oviposition
(in Fenestrulina malusii ). Interestingly, he indicated that the
transfer of the oocyte to the ovicell occurred during polypide
degeneration, accompanied by considerable deformation of
the oocyte. However, Pergens’s paper was forgotten and the
fi rst description of oviposition was for a long time attributed
to Gerwerzhagen ( 1913 ), who managed to observe in detail
the transfer of the egg by the polypide from the cavity of the
maternal autozooid into the ovicell via the so-called supraneural
coelomopore in Bugula avicularia (summarized in Ostrovsky
2008a ; Ostrovsky et al. 2008 ). Observations showed that oviposition was accompanied by specifi c movements of the polypide, while the oocyte, being highly fl exible, was usually
(but not always) considerably deformed during its transfer to
the brood chamber (see Pergens 1889 ; Gerwerzhagen 1913 ;
Silén 1945 ; Corrêa 1948 ; Nielsen 1981 ; Dyrynda and Ryland
1982 ; Dyrynda and King 1983 ; Cook 1985 ; Zimmer, personal communication in Reed 1991 ; Maturo 1991b ). In
some species, the ovulated oocyte winds around the introvert
of the retracted polypide before oviposition. Dyrynda and
King ( 1983 ) described this phenomenon in Chartella papyracea . Such oocytes were also found in Cribrilina annulata ,
Menipea roborata and Sinuporaria sp. in the course of my
research (see also Ostrovsky 1998 ).
Prior to actual observations, the event sequence that constitutes oviposition was discussed by Jullien ( 1888 ). He did
1 Reproductive Patterns of Gymnolaemate Bryozoa: General Overview and Comparative Analysis