396
N. BALAKRISHNAN NAIR AND M. SARASWATHY
previous breeding season left in the follicles are probably resorbed and
the epithelium undergoes a period of rest. By May or June gametogenic
activity is particularly evident in the male phase and it is probable that
these may provide the male gametes for the specimens bearing the type
" 3 " gonad of the female recorded above.
Thus in the Teredinidae three types of hermaphroditism may be
distinguished, simultaneous hermaphroditism, consecutive hermaphroditism and rhythmical consecutive hermaphroditism (Fretter and
Graham, 1964).
V. FECUNDITY
Shipworms are prolific especially those that have external fertilization. These produce comparatively smaller eggs (around 45 p
diameter). Teredo dilatata (= Psiloteredo megotara) produces over 100
million eggs in one spawning (Sigerfoos, 1908). The number of eggs and
larvae produced by one Teredo navalis has been reported to exceed
2 million (Kofoid, 1921a). Imai, Hatanaka and Sat0 (1950) collected
early veliger larvae of Teredo navalis from the gill chamber at the rate
of 20 000 to 50 000 per individual. The values for Teredo furcifera from
Bombay have been 7 000 for the first brood, the breeding potential
increasing with age, one brood of an adult may contain more than 30 000
veligers (Karande et al., 1968).
VI. AGE OR SIZE AT SEXUAL MATURITY
Shipworms are known to attain sexual maturity quickly after
settlement and metamorphosis. Bankia campanellata does so at a
length of about 12 mm at Visakhapatnam (Nagabhushanam, 1959),
Teredo (Lyrodus) mediolobata in Hawaii when only 10 mm long (Edmondson, 1942), and Teredo navalis at Sebastopol, Black Sea when
15-20 mm long (Bulatov, 1941). Teredo morsei (= T. navalis according
to Moll) removed from ropes in New Haven, Connecticut was sexually
mature when 10-12 mm long but those recovered from wood not until
40-50 mm (Coe, 1933a). T . navalis at Woods Hole is mature in 6 weeks
(Grave, 1937). For T . parksi the age at sexual maturity is about
2 months in Samoa (Miller, 1924a) and 24 days at Pago Pago Harbour
(Potts, 1923), for Lyrodw pedicellatus this period is nearly 8 weeks
(Becker, 1959) while for the tropical Teredo furcifera it is only about
20 days (Karande et al., 1968; Karande and Pendsey, 1969).
VII. BREEDING SEASON
Determination of the breeding period of the different species occurring in a locality is of particular significance. Of the several methods
N. BALAKRISHNAN NAIR AND M. SARASWATHY
previous breeding season left in the follicles are probably resorbed and
the epithelium undergoes a period of rest. By May or June gametogenic
activity is particularly evident in the male phase and it is probable that
these may provide the male gametes for the specimens bearing the type
" 3 " gonad of the female recorded above.
Thus in the Teredinidae three types of hermaphroditism may be
distinguished, simultaneous hermaphroditism, consecutive hermaphroditism and rhythmical consecutive hermaphroditism (Fretter and
Graham, 1964).
V. FECUNDITY
Shipworms are prolific especially those that have external fertilization. These produce comparatively smaller eggs (around 45 p
diameter). Teredo dilatata (= Psiloteredo megotara) produces over 100
million eggs in one spawning (Sigerfoos, 1908). The number of eggs and
larvae produced by one Teredo navalis has been reported to exceed
2 million (Kofoid, 1921a). Imai, Hatanaka and Sat0 (1950) collected
early veliger larvae of Teredo navalis from the gill chamber at the rate
of 20 000 to 50 000 per individual. The values for Teredo furcifera from
Bombay have been 7 000 for the first brood, the breeding potential
increasing with age, one brood of an adult may contain more than 30 000
veligers (Karande et al., 1968).
VI. AGE OR SIZE AT SEXUAL MATURITY
Shipworms are known to attain sexual maturity quickly after
settlement and metamorphosis. Bankia campanellata does so at a
length of about 12 mm at Visakhapatnam (Nagabhushanam, 1959),
Teredo (Lyrodus) mediolobata in Hawaii when only 10 mm long (Edmondson, 1942), and Teredo navalis at Sebastopol, Black Sea when
15-20 mm long (Bulatov, 1941). Teredo morsei (= T. navalis according
to Moll) removed from ropes in New Haven, Connecticut was sexually
mature when 10-12 mm long but those recovered from wood not until
40-50 mm (Coe, 1933a). T . navalis at Woods Hole is mature in 6 weeks
(Grave, 1937). For T . parksi the age at sexual maturity is about
2 months in Samoa (Miller, 1924a) and 24 days at Pago Pago Harbour
(Potts, 1923), for Lyrodw pedicellatus this period is nearly 8 weeks
(Becker, 1959) while for the tropical Teredo furcifera it is only about
20 days (Karande et al., 1968; Karande and Pendsey, 1969).
VII. BREEDING SEASON
Determination of the breeding period of the different species occurring in a locality is of particular significance. Of the several methods