Cephalopod taxonomy

presentation will give idea on the taxonomic characters of cephalopods

1. Cephalopod Taxonomy Presented by; Suraj Kumar Pradhan FRM-MA5-01

2. Classification of mollusc.. Phylum Mollusca is classified into seven classes; GASTROPODA (single shelled  cowries, cones etc) BIVALVIA ( two shelled like clams, mussels etc) APLACOPHORA ( solenogasters ) MONOPLACOPHORA (segmented limpets) POLYPLACOPHORA ( or Amphineura as it was earlier called- Chitons ) SCAPHOPODA (tusk shells) CEPHALOPODA (nautilus, squids, Cuttelfish , octopus etc)

3. Cephalopods.. Greek ( kephalópoda ); "head-feet“ exclusively marine The study of cephalopods is a branch of malacology . Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids .

4. Characters of cephalopods Much advanced groups. 800 species of all over the world. Exclusively marine species. Bilaterally symmetrical. Shell spirally chambered,usually with or without shell embedded in mantle. Body may be globular or oval or arrow shaped and have fins on the sides. Body devided into head and trunk. Head bears a pair of large lateral eyes and mouth.mouth bears jaws and radula . Trunk consists of symmetrical and uncoiled visceral mass.

5. Con... Foot altered into a series of large prehensile suckers bearing arms of tentacles encircling mouth. Fin inserted laterally may surround the body( cuttle fish) or devided into two lateral fins placed more or less posteriorly (squids). Excreatory system consists of 2-4 pairs of nephridia . Nervous system highly developed and sexes separate. Last pair of tantacles has raproductive organ(like bulk of grape).

6. Con... an internal shell,dorsal in position either calcified or horny and transparent (pen or gladius in squid and cuttlebone in cutttle fish).In octapoda the shell is reduced to a plate of connective tissues. Cephalopods lacerete their pray with their parrot beak formed by a dorsal and a ventral mandible. Devided into three sub-classes; Sc-1 – coleoidea or dibranchiata Sc-2 – nautiloidea or tetrabranchiata sc-3 - ammonoidea

7. Sub-class 1 –coleoidea or dibranchiata Shell internal,embedded in tissue, calcareous,chitinous or cartilaginous. 8 or 10 circumoral appendeges with suckers. Only one pair of gills,funnel and tube like. Ink glands and chromatophore present. Devided into 4 orders; sepioidea teuthoidea (squids) octapoda vampyromorpha

8. Family identification....... 1. Cephalopods with eight circumoral arms, without tentacles; arm suckers arranged in two rows, without horny rings and stalks. Third arm tip of male spoon-shaped ( hectocotylized ) ......................................................................( Octopodidae ) Octopus. Cephalopods with ten arms eight being short and circumoral and two slender and tentacular . Suckers of the arms and tentacles stalked and equipped with armature ......................................................................... 2 2 . Shell (cuttlebone) internal calcareous in nature, body ovoid and dorsoventrally somewhat flattened. Fins narrow, marginal in position and extending on either side along the entire length of the mantle, not uniting at the end. Arms with mostly quadriserial suckers... ( Sepiidae ) .................................. 3 Shell ( gladius or pen) internal but chitinous in nature. Body cylindrically elongate. Fins either terminal or marginal in position uniting at the apex of the mantle .................................... 4

9. Con.......... 3. Cuttlebone broadly oval in shape and with a spine at the posterior end. The mantle without a glandular pore at the posterior extremity .................Sepia (S aculeata ) and S. Pharaonis ) Cuttlebone smaller in size, oval in shape and devoid of the spine. The mantle bears a small but distinct glandular pore at the posterior extremity......................................... Sepiella 4. Fins triangular or rhomboidal in shape, restricted to the posterior margin of the mantle ................... Loligo ( Loligo duvauceli ) Fins broad and extending almost to the entire length of the mantle ........................................ Sepioteuthis ( Sepioteuthis arctipinnis )

10. Order - sepiodea Internal shell ( sepion ) calcareous and either straight and laminated or coiled and chambered or absent. Eyes covered with skin and supplementary eyelid present. 8 sessile arms. 2 tentacular arms contractile and retractile into pockets. Suckers without stalks. Fin lobes free posteriorly .

11. Family - sepiidae Body either elongate or broad or very slender and dorsoventrally flattened. Fins marginal and narrow,extending all along mantle on either side. Internal shell( sepion ) present. Light organds absent. S. pharaonis , S. prashadi , S. aculeata , S. brevimana , S. elliptica , S. arasica , S. trygonina

12. Key to genera.. Cuttlebone calcified only in posterior half, anterior half chitinous …. Hemisepius . Cuttlebone entirely calcified; Cuttlebone with spine present on posterior end ; no glandular pore on ventral surface at posterior end of mantle…. Sepia . Cuttlebone without spine present on posterior end ; glandular pore on ventral surface at posterior end of mantle…. Sepiella .

13. SEPIA PHARAONIS (Ehrenberg) The body of the cuttlefish is stout and oval in outline and widest at the anterior end. In front, the mantle is produced middorsally into a triangular lobe and midventrally slightly emarginated Fins very wide and fleshy and originate a few millimetres behind the anterior margin of the mantle; fins broad, extend along the periphery of the mantle and reach the posterior extremity; funnel large and thick walled, reaching almost to the base of the ventral arms; a triangular valve present in the funnel.

14. SEPIA ACULEATA ( Fferussac and d'Orbigny ) The mantle is roughly oval, broadest near the anterior end; ventral margin of the mantle concave in the middle, middorsal projection has well-excavated sides. Fins narrow and originate a little behind the anterior margin of the mantle on the sides and extend to the end of the body where they are almost in contact with each other; head narrower than mantle opening ; funnel short and does not reach the base of the ventral arms; buccal lappets surrounding mouth are seven, with minute suckers at their extreme ends

15. Sepia brevimana Tentacular clubs short with 6-8 small subequal suckers. Cuttlebone flat and distinctly acuminate anteriorly , dorsal surface rugose , a shallow median groove in the striated area. The striae ' A ' shaped with a median shallow groove broadening anteriorly ; inner cone and its limbs pinkish in colour; spine small, sharp and slightly curved.

16. Sepia elliptica Tentacular clubs moderately long, with 10 rows of small suckers of uniform size. Cuttlebone thin, elliptical in shape, dorsal surface smooth ; two conspicuous lateral ridges more prominent anteriad resulting in three longitudinal furrows in striated area ; spine thick, sharp, long and well curved.

17. Sepia trygonina No fleshy projections on head', fins extend upto end of mantle ; tentacles with short clubs, suckers in eight rows, about five in third row enlarged. Cuttlebone lanceolate with acuminate anterior tip with edges of outer cone winged giving an arrow head appearance; spine small.

18. Order – teuthoidea (squids) Internal shell( gladius or pen) chitinous,feather or rod shaped. 8 sessile arms. 2 tentacular arms contractile but not retractile,pockets absent. Suckers stalked and with or without hooks. Finlobes fused posteriorly

19. Suborder – myopsida ( neretic squid) eyes completely covered with a corneal membrane. Family- Loliginidae Loligo duvauceli , L.uyii , Doryteuthis singhalensis , D. sibogae , Sepiotuthis lessoniana , Loliolus investigatoris

20. Suborder – oegopsida (oceanic squid) eyes not covered with a corneal membrane and open to the surrounding medium. Family- Onchoteuthidae ( Onchoteuthis banksi ) Family- Ommustrephidae ( Ommustrephes bartrami , Symplectiteuthis oualaniensis ) Family- Thysanoteuthidae ( Thysanoteuthis rhombus )

21. Key to genera.. Vane of gladius broad, with thin, curved edges ; posterior end of mantle moderately blunt; mantle not very narrow in males; fins usually less than 70% of mantle length…… subgenus Loligo Vane of gladius narrow, with thick, straight edges ; posterior end of mantle relatively pointed; mantle very narrow in males; fins usually more than 70% of mantle length……subgenus Doryteuthis vane

22. Loligo uyii Body short and stout; mid-rib of gladius clearly visible through dorsal mantle skin as a median dark line. Fins 55-65 per cent of mantle length ; Tentacular clubs large median manal suckers with smooth rings. In males left ventral arm hectocotylized almost the entke arm ; papillae on ventral margin fused with membrane.. • • •

23. Symplectoteuthis oualaniensis Funnel and mantle cartilages of the locking apparatus fused together. An oval photophoric pateh present middorsally near anterior margin of mantle. Muscle of mantle ventrally without embedded light organs; two intestinal photophores present

24. Doryteuthis singhalensis Mantle very long and stendo - with a ridge along midline in males; fins wide and long and more than 60 per cent of mantle length; half of left ventral arm heterocotylized used distally in males. gladius narrow with almost straight margins and tapering gradually to a narrow point.

25. Loligo duvauceli This is a common Indo-Malayan species occurring from South Africa to Formosa (Voss, 1963). In India it is commonly found on the east and west coasts The mantle is slender and tubular in outline and tapers gradually from about the middle to a blunt posterior end; the fins are smaller and rhomboidal in shape. The narrow head possesses ten arms including the two long slender tentacles. Sessile arms usually in the order 3.4.2.1. in length; suckers arranged in two rows in all arms; Chitinous rings of the arm suckers possess about 6 to 8 teeth and sometimes more as in the case of larger suckers of males; tentacular clubs bear four rows of suckers, the rings of which are equipped with 17 to 20 teeth; distal half of the left arm of the male is hectocotylized ; The gladius is narrow and slightly brownish in colour; the ink sac possesses two small light organs one on either side.

26. Order - octapoda Internal shell and nidamental gland absent. Body rounded or oval and with no lateral fins. 8 arms;suckers without stalks and without chitinous ring. Tentacles absent. Light organ absent.

27. Family - octopodidae Octopus have 8 arms. Without an external shell. Internal shell either vestigial or lacking. Great disparity seen in males and females in size and benthic in habitat. 2 suborder – cirrata and incirrata Sub order – Incirrata Family – Octopodidae Octopus dolfusi , O. aegina , Cistopus indicus Hapalochlaena maculso , Berrya keralensis Family – Argonautidae (fragile shell paper nautilus) Argonauta argo , A. hinas .

28. Octopus vulgaris Body distinctly warty, up to 1000 mm total length, with maximum arm spread of 3000 mm, but commonly much smaller . Arms are thick and stout, bearing two longitudinal rows of suckers. Arm length is 70-85 % of total length.

29. octopus mebranaceus 8 arms;suckers without stalks and without chitinous ring. Tentacles absent. Light organ absent

30. ORDER – VAMPYROMORPHA Physically, they somewhat resemble octopuses , but the eight main tentacles are united by a web of skin, and two smaller tentacles are also present. ( Vampyroteuthis infernalis )

31. Subclass 2- nautiloidea Shell external,coiled and chambered,more than 10(63 to 94) circumoral appendeges without suckers. 2 pairs of gills. Ink glands and chromatophores absent. eg ; nautilus pompilius endoceras

32. Sub-class 3 - ammonoidea Shell is external,coiled . Syphon is external. Extinct forms of mesozoic era. eg ; ammonites

33. Class: Cephalopoda Subclass: Nautiloidea Family: Nautilidae , e.g. Nautilus pompilius Subclass: Ammonoidea (Ammonite relatives, extinct) Subclass: Coleoidea Superorder : Octopodiformes Order: Vampyromorpha Family: Vampyroteuthidae Order: Octopoda Suborder: Cirrata Suborder: Incirrata Tribus : Argonautida Family: Alloposidae Family: Argonautidae , e.g. Argonauta argo , Family: Ocythoidae Family: Tremoctopodidae Tribus : ---- Family: Amphitretidae Family: Octopodidae , Family: Vitreledonellidae Family: Bolitaenidae Superorder : Decapodiformes Order: Teuthida Suborder: Oegopsida Family: Architeuthidae , Suborder: Myopsida Family: Loliginidae , Family: Chtenopterygidae Family: Bathyteuthidae Order: Sepiida Family: Sepiidae , Family: Spirulidae Family: Idiosepiidae Family: Sepiadariidae Family: Sepiolidae