Recent Aedvances in Cephalopod Systematics

Kotaro TSUCHIYA Lab. Invertebrate Zoology

What’ the Cephalopoda

Squid landing in Japan�

Cephalopod evolution�Paleozoic Mesozoic Neozoic

Million yr

Cephalopods �Squid

Cuttlefish

Vampire squid

Bobtil squid Octopus

Molluscan Characters �

Current Classification of Mollusca �  Phylum Mollusca

Class Solenogastres Class Caudofoveata

  Eumollusca Class Polyplacophora

  Conchifera Class Monoplacophora

  Ganglioneura   Viscelloconcha

Class Gastropoda Class Cephalopoda

  Diasoma Class Scaphopoda Class Bivalvia

Sister Group of Cephalopoda �

Diasoma

Viscelloconcha

Gastropoda

Bivalvia

Scaphopoda Cephalopoda

Cephalopod Characteristic   A funnel derived from the molluscan foot or the

molluscan neck region (Shigeno et al., 2007).

  Circumoral arms that are derived from the molluscan head (J.Z. Young, 1965) or the molluscan foot (Shigeno et al., 2007).

  Chitinous beaks.

  Image-forming eyes.

Cephalopod Characteristic   A funnel derived from the molluscan foot or the

molluscan neck region (Shigeno et al., 2007).

Cephalopod Characteristic   Circumoral arms that are derived from the molluscan

head (J.Z. Young, 1965) or the molluscan foot (Shigeno et al., 2007).

Cephalopod Characteristic   Chitinous beaks.

Upper beak Buccal mass

Cephalopod Characteristic   Image-forming eyes.

Ontogeny & Phylogeny   Spiral cleavage - Discoidal cleavage   Larval development - Direct development

  → Lecithophora or Meloblastea Fischer, 1880 As Subphylum for CEPHALOPODA

trochophore

veliger

Gastropoda Cephalopoda

Squid and Octopus Decapodiformes and Octopodiformes �  What’s difference?

  Sucker morphology   Buccal rappet existence

Squid and Octopus

  What’s difference?   Modification of the fourth pair of arms as tentacles �

Current Classification of Cephalopoda Based on morphological character

Octopus share what?�Octopodiformes (over 200spp.)�  Octopoda Leach, 1818

  Cirrata Grimpe, 1916   Incirrata Grimpe, 1916

  Vampyromorpha Robson, 1929

Octopus share what?�Octopodiformes (over 200spp.)�  True arms II modified or absent   Horny rings in suckers absent�  Buccal crown absent �

Morecular Analysis�(Takumiya et al. 2006) �

16s rDNA 12s rDNA CO I

Morecular Analysis�(Yokobori et al. 2007) �

Mitochondria genome structure

Current Classification of Decapodiformes�  Clarke (1988) Morphological base

“Order Teuthoidea”   Divergent group in genus level   28 Families 71Genera   Most of the families are oceanic, mesopelagic

Oegopsida - Myopsida   Presence or absence of Cornea �  “closed eye” or “open eye”�  Coastal or Oceanic�

Family Chtenipterygidae - comb-fin squid   with suckers on the buccal membrane.   without carpal locking-apparatus on tentacles.   with branchial canals in gills.

Family Idiosepiidae

- pygmy squid �  Gladius (shell) rudimental but present   with an adhesive organ on the dorsal surface of the mantle

Idiosepius pygmaeus (6-8mm ML)

Family Australiteuthidae Lu, 2005   Myopsid eye   Spritted fins   Feather-shaped chitinous gladius

Australiteuthis aldrichi Lu, 2005 (<30mm ML)

Morphological comparisons of the major taxa within the Decapodiformes

Cornea Branchial Buccal Sucker Tentacle Interstellate canal suckers circular canal support circular pocket connective sucker muscle

Oegopsida No Yes No No No Yes Bathyteuthoidea No Yes Yes No Yes Yes Myopsida Yes Yes Yes/No Yes Yes Yes Idiosepiidae Yes No No No Yes ? Spirulidae No No No No Yes No Sepioidea Yes No Yes/No Yes Yes No

Recent Systematic Hypothesis ����������ー Molecular base

Morecular Analysis (Akasaki et al. 2006) �

mtDNA genome structure

Hypothesis from Morecular Analysis (Akasaki et al. 2006) �

mtDNA genome structure

Hypothesis from Morphological and Molecular complex Analysis result �

101 morphological characters mt cytochrom c oxydase subunit I ; nuclear

18S rDNA; D3 expansion fragment of 28S rDNA, Histon H3 �

Classification Updated

Young (2008)

�Species-level Taxonomy   Only 700 species are known from World

Ocean

Cryptic Speciation Coastal species (Loliginids, Sepiids)

Sepioteuthis lessoniana

Western Australia Triantafillos et al. (2005)

Japan Izuka et al. (1996)

Deep-sea Squids - still unexplored field   Nektonic species - net avoidance

  Difficult to catch adult specimens by sampling gear   Still unkown the mature, largest size in most of deep-sea

species   Life cycle, life history

Octopus - Labyrinth of Taxonomy   Scarce of hard tissue in octopus body

  Absence of stable key taxonomic character   Need to evaluate useful taxonomical information from living animals