THE BIOLOGY O F WOOU-UOltlNO TERlDlNlD MOLLUSCS
40 1
latu (Nagabhushanam, 1959) ; Nausitora dunlopei (Smith, 1963) ; N .
hedleyi (Saraswathy, 1967) ; Nototeredo norvagica (Lebour, 1938, 1946)
and Bankia gouldi (Sigerfoos, 1908). Fertilization of type (2) has
been recorded for Lyrodus pedicellatus (Roch, 1940 ; Becker, 1959) ;
L. diegensis (= L. pedicellatus) Kofoid et al., 1927) ; L. mediolobata
(Edmondson, 1942) ; Teredo navalis (Grave, 1928) ; T . poculifer (Smith,
1963) and Lyrodus pedicellatus (=Teredo bartschi) (Isham and Tierney,
1953). According to Turner (1966) the following species may also be
included since young larvae are present in the brood pouch of the
parent, Teredo furcifera, T . parksi, T. somersi, T . clappi, Lyrodus
afinis and L. massa. Turner feels that in Teredothyra matocotana and
T. dorninicensis also fertilization occurs in the mantle cavity. Owing to
the gregarious tendency in certain species (Nagabhushanam, 1959a)
with settlement confined to susceptible areas of the wood, there are
frequently localized concentrations of siphons on submerged timber.
This probably increases the likelihood of sperm shed into the slowly
moving water layer immediately adjacent to the surface of the wood,
being taken into the mantle cavity of a female (Lane, 1955). He further
suggests that insemination may be associated with interference with
the normal respiratory stream or that the sperm themselves or fluids
associated with them may cause retraction of the siphons and closure
of the burrow. The fertilized ovum is retained in the maternal mantle
cavity during early cleavage and later “ implants ” itself in the substance of the gill where early stages of development are completed.
The third type of fertilization has been recorded by Clapp (1951) in
Bankia gouldi.
At Rovigno d’Istria, Roch ( 1940) tried breeding Lyrodus pedicellutus using running sea water and at Berlin Dahlem Becker (1959)
reared this species in artificial sea water (temp. 20°C) for four generations and observed a noticeable lunar periodicity of spawning. Roch
(1940) noted a pronounced rhythm in the extrusion of the larvae from
the parent with a maximum at about 10 h before the astronomical full
moon. During a lunar eclipse the spawning ceased and was resumed
when the eclipse was over. Another maximum extrusion was observed
at the time of the last quarter of the moon. Roch feels that this rhythm
is neither dependent on the tides nor on the visibility of the moon.
Becker and Schulze (1950) have described culture methods used in the
rearing of Lyrodm.
IX. EMBRYOLOGY AND LARVAL DEVELOPMENT
A. The gametes
Several species incubate eggs in the mantle cavity or the gill until
they are developed as far as the free-swimming larval stage. Both this
40 1
latu (Nagabhushanam, 1959) ; Nausitora dunlopei (Smith, 1963) ; N .
hedleyi (Saraswathy, 1967) ; Nototeredo norvagica (Lebour, 1938, 1946)
and Bankia gouldi (Sigerfoos, 1908). Fertilization of type (2) has
been recorded for Lyrodus pedicellatus (Roch, 1940 ; Becker, 1959) ;
L. diegensis (= L. pedicellatus) Kofoid et al., 1927) ; L. mediolobata
(Edmondson, 1942) ; Teredo navalis (Grave, 1928) ; T . poculifer (Smith,
1963) and Lyrodus pedicellatus (=Teredo bartschi) (Isham and Tierney,
1953). According to Turner (1966) the following species may also be
included since young larvae are present in the brood pouch of the
parent, Teredo furcifera, T . parksi, T. somersi, T . clappi, Lyrodus
afinis and L. massa. Turner feels that in Teredothyra matocotana and
T. dorninicensis also fertilization occurs in the mantle cavity. Owing to
the gregarious tendency in certain species (Nagabhushanam, 1959a)
with settlement confined to susceptible areas of the wood, there are
frequently localized concentrations of siphons on submerged timber.
This probably increases the likelihood of sperm shed into the slowly
moving water layer immediately adjacent to the surface of the wood,
being taken into the mantle cavity of a female (Lane, 1955). He further
suggests that insemination may be associated with interference with
the normal respiratory stream or that the sperm themselves or fluids
associated with them may cause retraction of the siphons and closure
of the burrow. The fertilized ovum is retained in the maternal mantle
cavity during early cleavage and later “ implants ” itself in the substance of the gill where early stages of development are completed.
The third type of fertilization has been recorded by Clapp (1951) in
Bankia gouldi.
At Rovigno d’Istria, Roch ( 1940) tried breeding Lyrodus pedicellutus using running sea water and at Berlin Dahlem Becker (1959)
reared this species in artificial sea water (temp. 20°C) for four generations and observed a noticeable lunar periodicity of spawning. Roch
(1940) noted a pronounced rhythm in the extrusion of the larvae from
the parent with a maximum at about 10 h before the astronomical full
moon. During a lunar eclipse the spawning ceased and was resumed
when the eclipse was over. Another maximum extrusion was observed
at the time of the last quarter of the moon. Roch feels that this rhythm
is neither dependent on the tides nor on the visibility of the moon.
Becker and Schulze (1950) have described culture methods used in the
rearing of Lyrodm.
IX. EMBRYOLOGY AND LARVAL DEVELOPMENT
A. The gametes
Several species incubate eggs in the mantle cavity or the gill until
they are developed as far as the free-swimming larval stage. Both this