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Intercapsular Embryonic Development of the Big Fin Squid Sepioteuthis Lessoniana (Loliginidae)

Intercapsular Embryonic Development of the Big Fin Squid Sepioteuthis Lessoniana (Loliginidae)

Indian Journal of Marine Sciences Vol. 31(2), June 2002, pp. 150-152

Short Communication

Intercapsular of the big fin lessoniana ()

V. Deepak Samuel & Jamila Patterson* Suganthi Devadason Marine Research Institute, 44, Beach Road, Tuticorin – 628 001, Tamil Nadu, India ( E.mail : [email protected] ) Received 18 June 2001, revised 22 January 2002

The masses of big fin squid, Sepioteuthis lessoniana were collected from the wild and their intercapsular embryonic development was studied. The average incubation period of the egg varied between 18-20 days. The started on the first day and the developed between third and fifth day. The started decreasing eighth day onwards. The with the primordia on the tip were prominent from tenth day. The yolk totally reduced between thirteenth and seventeenth day and the paralarvae hatched out on eighteenth day.The developmental stages of the embryo inside the capsules during the incubation period is understood.

[ Key words: Sepioteuthis lessoniana , intercapsular development ]

There are about 660 of in the the death of the embryo. Egg capsules were taken world , of which less than hundred species are everyday to study the developmental stages of the of commercial importance. In the Indian seas, about growing embryos. Size of the egg capsules, and 80 species of cephalopods exist but the main fishery is the embryos inside the eggs were recorded everyday contributed by only a dozen or so. Though they play till hatching. Various stages of development were ob- an important role in the economy of our country, their served and recorded as line drawings and photographs early cycle and reproductive are not yet with the help of a light microscope. understood clearly. In the global catch, The total incubation period of the big fin squid dominate by 77% followed by and Sepioteuthis lessoniana varied between 18-20 days. cuttlefish1. In India, the big fin squid is high valued From the first day the egg capsules gradually became next to the Pharaoh . enlarged by absorbing water. Unfertilized eggs had a pharaonis and is abundant in the coastal waters of the milky white colouration and were removed immedi- east coast of India. This study mainly focuses on the ately by visual examination. The average initial length embryonic development of big fin squid Sepioteuthis and width of the egg capsules were 58.2 and 12.6 mm lessoniana Lesson inside the capsules till hatching out respectively and the eggs measured 3 mm. Cleavage, of the fully developed from the eggs. Pre- cell division and segregation took place in the first sent study was carried out with the aim of culturing three days of incubation and the embryo measured 2 this commercially important cuttle under the mm in size. On the day before hatching, the capsules laboratory condition. measured 82.4 mm × 14.6 mm while the average size Wild spawned egg masses of big fin squid, Sepio- of the eggs and the developing embryos were 16 and teuthis lessoniana were collected from nylon net 11 mm respectively (Table 1). The incubation period pieces, which were set at a depth of 5 feet. The depos- of the eggs of squids and cuttle fish varied with the ited egg masses were transferred to the laboratory and species. In the case of Thai pygmy squid Idiosepius kept in glass aquaria measuring 12″ × 6″ × 12″ con- thailandicus, the incubation and embryonic develop- taining filtered seawater. Sixty percent of water in the ment has been studied in detail and the incubation3 tank was exchanged daily. The glass aquarium was period was reported as 12 days. In spineless cuttle fish covered with black chart paper to avoid the growth of inermis, it was 8-19 days with an average of algae, which may lead to the formation of a pale green 12.6 + 4.1 days and incubation period mostly colouration on the surface of the capsule leading to depended on temperature. Low temperature prolonged Short communication 151

Table 1 ⎯ The average size of the egg capsules, eggs and the the incubation period but normally the incubation last growing embryos during the developmental period for 3 weeks3. The incubation period of the eggs of S.lessoniana in Thailand4 varied between 20.2+2.6 No. of Average size of the Mean size of the Mean size of the 5 days egg capsules eggs (mm) embryos (mm) days while in Indonesia it was 15-16 days. In the (length × width) mm present study, the incubation time recorded was 18 days. 1 3 158.2 × 12.6 ⎯ The embryonic development is illustrated in the 2 3 263.3 × 14.0 ⎯ Figs 1 and 2. The developmental changes are ex- 3 3 55.6 × 12.5 ⎯ plained based on the morphological changes of the 4 61.3 13.2 5 2 × developing embryo. On the first day, the cleavage was 5 61.7 × 12.6 8 5 completed and the germ layers were found segregated 6 58.3 × 12.3 9 5 with the growth of blastoderm. The blastoderm could 7 63.2 × 12.4 10 7 be seen as a ring at the vegetal pole covering three 8 69.6 × 12.7 10 7 quarters of the egg on the second day. In the case of 9 69.0 × 12.8 12 8 Thai pygmy squid, only the enlargement of the blas- 10 74.1 × 14.6 15 8 toderm has been explained2. Sakai6 has schematically 11 74.7 × 15.5 15 10 explained the ring formation of the blastopore at 53 12 78.3 × 15.4 15 12 hours after fertilization in argentinus. Between 13 84.0 × 15.2 16 12 third and fifth day, organogenesis began from the in- 14 86.3 × 15.8 16 9 vagination and the mantle was visible in S. lesson- 15 82.7 × 15.5 16 9 iana. In the case of Thai pygmy squid, organogenesis 16 82.3 × 15.3 16 8 took place after 5 days of fertilization with the forma- 17 82.2 × 15.3 16 9 2 18 82.4 × 15.0 16 11 tion of , mantle and rotation of the embryo while in the Argentine squid, Illex argentinus6 it was 112

hours.

Fig 2 ⎯ Embryo development stages (BD – Blastodisc , CH – Chorion, EY – Eye , ML – Mantle, SG – Shell gland, AR – Arm, TE – , FL – Funnel, SP – Sucker Primordia, CH – , FN – Fin , GL – , IS – Ink Fig. 1 ⎯ Embryo stages of day 5 to 17 sac ,YO – Yolk, AR 1 – Arm 1, AR 2 – Arm 2 , AR 4 – Arm 4)

152 Indian J. Mar. Sci., Vol. 31, No. 2, June 2002

In S. lessoniana, the mantle started widening on the absorbed it. The egg size maintained at 16 mm from sixth day. Ocular cups and were evident on the day 13 onwards till the paralarva hatched out. On seventh day. The respiratory movements were clear eighteenth day, the paralarva hatched out and it was and the mantle length increased occupying one third 6 mm in size (Dorsal Mantle Length). The fins were of the total length on the eighth day. The yolk started functional and the was active if there was any to decrease gradually from the eighth day and the size mechanical disturbance. of the eggs and the embryos increased on the ninth The present study will be a base for knowing the day. In ten days old embryo, the tentacles were developmental stages, incubation and hatching out of prominent with the sucker primordia on the tip and on paralarvae for the big fin squid Sepioteuthis lesson- the eleventh day, the fins started to appear. Ink gland iana, to do further culture studies. was visible inside the thin transparent mantle. Chro- Authors are grateful to Dr. Jorgen Hylleberg, Pro- matophores on the body were clear on the twelfth day gram Director for the financial assistance to carry out but very pale in colouration. While in other squids this work through Tropical Marine Mollusc Pro- such as and Idiosepius thailandicus gramme (TMMP) project, DANIDA. the chromatopores were found visible after 150 hours th and 10 day respectively. The members of the class References cephalopoda are noted for their chromatophores, 1 Josupiet H, A change of direction for cephalopod consumption, which help them to camaflouge with their substrate Seafood Internatl, (2001) 25-27. and to escape from predators for defense or to hunt 2 Nabhitabhatta J, Life cycle of the cultured big fin squid Sepio- teuthis lessoniana Lesson, Phuket Mar Biol Cen Spe Pub for their prey. From thirteenth to seventeenth day, the No 16, (1996) 83-95. yolk totally reduced and the organs of the embryo 3 Danakusumah E, Studies on the biology and culture of the were fully developed. Decreasing of yolk is another neritic squid Sepioteuthis lessoniana Lesson : Effects of stock- character to confirm the development of embryo. The ing density on survival rate, Phuket Mar Biol Cen Spe Pub paralarvae having little yolk sometime hatched out No. 19, (1999) 223-226. 4 Nabhitabhatta J, Distinctive behaviour of the Thai pygmy with the yolk due to mechanical shock and after a few squid, Idiosepius thailandicus Chotiyaputta, Okutani and Chai- minutes of vigorous swimming, dropped the yolk and tiamvong,1991, Phuket Mar Biol Cen Spe Pub No.18, (1998) started swimming freely. Alagarswami7 noticed that 25-40. in Sepioteuthis arctipinnis (=Sepioteuthis lessoniana ) 5 Nabhitabhatta J, Life cycle of three cultured generations of spineless cuttle fish, (Ferussac & D’orbingy) the yolk sac was found to be carried along with the Phuket Mar Biol Cen Spel Pub No17, (1997) 289-298. embryo to outside for some hatchlings and discarded 6 Sakai M, Brunetti N E, Elana & Sakurai Y, Embryonic devel- after an hour. However in the present study the opment and hatchlings of Illex argentinus derived from artifi- paralrvae of this kind usually did not survive for long cial fertilization. Cephalopod Biodiversity, Ecology and Evolu- and were susceptible to bacterial infection. The size of tion, S. Afr J Mar Sci, 20 (1996) 255-265. th 7 Alagarswami K, On the embryonic development of the squid the embryo started decreasing from 14 day due to the (Sepioteuthis arctipinnis Gould) from the Gulf of Mannar, reduction of the yolk size as the developing embryo J Mar Bio Ass India, 8 (1966) 278-284.

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