313
distal opening of the intertentacular organ enter it head-fi rst
using a “random search process” (Temkin 1994 , p. 151). The
intertentacular organ actively regulates the passage of the
spermatozeugmata to the zooidal coelom, closing its opening. However, it does not discriminate between allosperm
and its own sperm (produced by the same colony).
Spermatozoids were been found on the ovary surface and
egg-sperm fusion was said to happen during or shortly after
ovulation. Nuclear-envelope breakdown appears to happen
about the same time. A polyspermic oocyte containing at
least 14 sperm nuclei was observed on one occasion (see discussion of Bonnevie’s ( 1907 ) paper above). Temkin described
egg release, activation, maturation and karyogamy in detail.
Delayed activation was considered a possible adaptation for
liberation/oviposition of the egg through the small supraneural pore.
Temkin ( 1996 ) studied fertilization in two ctenostome
and seven cheilostome species. Intraovarian monospermic
sperm-egg fusion was found in all nine species. In both eggbroadcasters studied, Alcyonidium sp. and Electra pilosa ,
sperm fuses with late-stage ovarian oocytes after germinalvesicle breakdown at or near ovulation. In the ctenostome
brooder Bowerbankia gracilis , sperm were found only inside
late-stage ovarian oocytes before germinal-vesicle breakdown. Temkin suggested that the rupture of the follicle-cell
layer may expose the oocyte to sperm, perhaps explaining
why only late-stage ovarian oocytes contain a sperm nucleus
in this species. However, Marcus ( 1938a , p. 81) wrote that in
the ctenostomes Alcyonidium sp. (as A. mamillatum ) and
Nolella stipata (as N . gigantea ), “we have verifi ed the presence of spermatozoids in ovocytes which are still growing”.
Chrétien’s ( 1958 ) results may indicate early intraovarian fertilization in A. diaphanum since polypide degeneration
begins before the onset of vitellogenesis (see above).
Sperm fuses with early ovarian oocytes in all the cheilostome brooders studied by Temkin ( 1996 ). He described
oocyte doublets and illustrated cytoplasmic bridges
between nurse cells and their siblings in some species.
Only one cell of each oocyte doublet is fertilized, and it
will become an egg. Sperm tails and midpieces were found
being resorbed in the oocyte cytoplasm (in Watersipora
arcuata ) or outside the oocyte (in Dendrobeania lichenoides ). There is only one vitellogenic doublet in each ovary,
but other previtellogeneic doublets may all possess sperm.
Ovaries were described with squamose, cuboidal or columnar cells. Spermatozoids were suggested to enter the maternal coelom through the intertentacular organ or supraneural
pore, accumulate on the ovary surface and later move
among the cells of the ovary. All these fi ndings show that
internal fertilization is the rule in Gymnolaemata, providing high levels of fertilization success. Additionally,
Temkin counted the number of the oocytes/oocyte doublets
in ovaries and measured them. He later published the
results of his experimental study on the movements of the
spermatozeugmata in Membranipora membranacea
(Temkin 2002 ; Temkin and Bortolami 2004 ).
The same species was used in experiments conducted by
Harvell and Helling ( 1993 ). They demonstrated large localized shifts (acceleration) in the timing and pattern of reproduction in response to simulated damage by predators
(trimming the colony periphery) and overgrowth by conspecifi c neighbouring colonies.
Santagata and Banta ( 1996 ) investigated brooding in the
cheilostome Scrupocellaria ferox . They discovered an
embryophore, consisting of hypertrophied epithelium and
funicular cells, and showed that the embryos more than double in volume while in the ovicell. The ovary is found in
association with a funicular cord in the basal perigastric coelom. They also investigated ovicell anatomy in this species
and proposed the hypothesis that vestibular brooding preceded ovicellar brooding (see Chap. 2 for critical analysis).
Ostrovsky ( 1998 ) studied ovicell anatomy and reproductive patterns in Cribrilina annulata and Celleporella hyalina .
Both species are protandrous colonial hermaphrodites with
sterile, male and hermaphrodite (dwarf and normal) autozooids in the fi rst case, and sterile, male and female (both
dwarf) autozooidal polymorphs in the second. It was discovered that dwarf zooids are hermaphrodite autozooids, not
females in C . annulata , and their “dwarfi sm” is not connected with sexuality as Powell ( 1967a ) thought. This species was stated to have reproductive pattern II. The
presumptive ovary contains two large female cells that might
be either oogonia or the fi rst oocyte doublet, surrounded by
peritoneum and associated with the proximal part of a differentiating polypide bud. The completely formed ovary is
located on the basal cystid wall associated with the funicular
cord. The complete female gonad contains up to six oocyte
doublets (one being vitellogenetic) and the mature oocyte is
macrolecithal- telolecithal. The ovary wall consists of columnar cells in its lower and squamous cells in its upper part.
Columnar epithelium surrounds the central area [intraovarian space] of the polygonal [basal] cells, with numerous
intercellular spaces. Celleporina hyalina was stated to have
reproductive pattern III (but see Chap. 1 of the main text). A
pair of oogonia develops in association with a polypide bud.
The mature ovary consists of polygonal cells and is suspended on the funicular cords. It contains up to three oocyte
doublets and the mature oocyte was described as microlecithal-homolecithal, contradicting the illustrations and description of Hughes ( 1987 ), who found macrolecithal eggs in this
species. Subsequent research has confi rmed the data of
Hughes (see Chap. 1 ). Sperm are frequently found among
ovarian cells in both species studied. Insemination is precocious, spermatozoids fusing with early previtellogenetic
oocytes. Syngamy and egg activation are delayed, based on
the fi nding of sperm heads in late oocyte. Muscles were
Appendices
distal opening of the intertentacular organ enter it head-fi rst
using a “random search process” (Temkin 1994 , p. 151). The
intertentacular organ actively regulates the passage of the
spermatozeugmata to the zooidal coelom, closing its opening. However, it does not discriminate between allosperm
and its own sperm (produced by the same colony).
Spermatozoids were been found on the ovary surface and
egg-sperm fusion was said to happen during or shortly after
ovulation. Nuclear-envelope breakdown appears to happen
about the same time. A polyspermic oocyte containing at
least 14 sperm nuclei was observed on one occasion (see discussion of Bonnevie’s ( 1907 ) paper above). Temkin described
egg release, activation, maturation and karyogamy in detail.
Delayed activation was considered a possible adaptation for
liberation/oviposition of the egg through the small supraneural pore.
Temkin ( 1996 ) studied fertilization in two ctenostome
and seven cheilostome species. Intraovarian monospermic
sperm-egg fusion was found in all nine species. In both eggbroadcasters studied, Alcyonidium sp. and Electra pilosa ,
sperm fuses with late-stage ovarian oocytes after germinalvesicle breakdown at or near ovulation. In the ctenostome
brooder Bowerbankia gracilis , sperm were found only inside
late-stage ovarian oocytes before germinal-vesicle breakdown. Temkin suggested that the rupture of the follicle-cell
layer may expose the oocyte to sperm, perhaps explaining
why only late-stage ovarian oocytes contain a sperm nucleus
in this species. However, Marcus ( 1938a , p. 81) wrote that in
the ctenostomes Alcyonidium sp. (as A. mamillatum ) and
Nolella stipata (as N . gigantea ), “we have verifi ed the presence of spermatozoids in ovocytes which are still growing”.
Chrétien’s ( 1958 ) results may indicate early intraovarian fertilization in A. diaphanum since polypide degeneration
begins before the onset of vitellogenesis (see above).
Sperm fuses with early ovarian oocytes in all the cheilostome brooders studied by Temkin ( 1996 ). He described
oocyte doublets and illustrated cytoplasmic bridges
between nurse cells and their siblings in some species.
Only one cell of each oocyte doublet is fertilized, and it
will become an egg. Sperm tails and midpieces were found
being resorbed in the oocyte cytoplasm (in Watersipora
arcuata ) or outside the oocyte (in Dendrobeania lichenoides ). There is only one vitellogenic doublet in each ovary,
but other previtellogeneic doublets may all possess sperm.
Ovaries were described with squamose, cuboidal or columnar cells. Spermatozoids were suggested to enter the maternal coelom through the intertentacular organ or supraneural
pore, accumulate on the ovary surface and later move
among the cells of the ovary. All these fi ndings show that
internal fertilization is the rule in Gymnolaemata, providing high levels of fertilization success. Additionally,
Temkin counted the number of the oocytes/oocyte doublets
in ovaries and measured them. He later published the
results of his experimental study on the movements of the
spermatozeugmata in Membranipora membranacea
(Temkin 2002 ; Temkin and Bortolami 2004 ).
The same species was used in experiments conducted by
Harvell and Helling ( 1993 ). They demonstrated large localized shifts (acceleration) in the timing and pattern of reproduction in response to simulated damage by predators
(trimming the colony periphery) and overgrowth by conspecifi c neighbouring colonies.
Santagata and Banta ( 1996 ) investigated brooding in the
cheilostome Scrupocellaria ferox . They discovered an
embryophore, consisting of hypertrophied epithelium and
funicular cells, and showed that the embryos more than double in volume while in the ovicell. The ovary is found in
association with a funicular cord in the basal perigastric coelom. They also investigated ovicell anatomy in this species
and proposed the hypothesis that vestibular brooding preceded ovicellar brooding (see Chap. 2 for critical analysis).
Ostrovsky ( 1998 ) studied ovicell anatomy and reproductive patterns in Cribrilina annulata and Celleporella hyalina .
Both species are protandrous colonial hermaphrodites with
sterile, male and hermaphrodite (dwarf and normal) autozooids in the fi rst case, and sterile, male and female (both
dwarf) autozooidal polymorphs in the second. It was discovered that dwarf zooids are hermaphrodite autozooids, not
females in C . annulata , and their “dwarfi sm” is not connected with sexuality as Powell ( 1967a ) thought. This species was stated to have reproductive pattern II. The
presumptive ovary contains two large female cells that might
be either oogonia or the fi rst oocyte doublet, surrounded by
peritoneum and associated with the proximal part of a differentiating polypide bud. The completely formed ovary is
located on the basal cystid wall associated with the funicular
cord. The complete female gonad contains up to six oocyte
doublets (one being vitellogenetic) and the mature oocyte is
macrolecithal- telolecithal. The ovary wall consists of columnar cells in its lower and squamous cells in its upper part.
Columnar epithelium surrounds the central area [intraovarian space] of the polygonal [basal] cells, with numerous
intercellular spaces. Celleporina hyalina was stated to have
reproductive pattern III (but see Chap. 1 of the main text). A
pair of oogonia develops in association with a polypide bud.
The mature ovary consists of polygonal cells and is suspended on the funicular cords. It contains up to three oocyte
doublets and the mature oocyte was described as microlecithal-homolecithal, contradicting the illustrations and description of Hughes ( 1987 ), who found macrolecithal eggs in this
species. Subsequent research has confi rmed the data of
Hughes (see Chap. 1 ). Sperm are frequently found among
ovarian cells in both species studied. Insemination is precocious, spermatozoids fusing with early previtellogenetic
oocytes. Syngamy and egg activation are delayed, based on
the fi nding of sperm heads in late oocyte. Muscles were
Appendices