click for previous page 788 Cephalopods Ommastrephidae OMMASTREPHIDAE Arrow squids, flying squids by M.C. Dunning iagnostic characters: Medium to large oegopsid squid (to D400 mm mantle length) with a strong, muscular torpedo- shaped mantle. Large muscular fins generally rhomboidal but may be attenuated posteriorly to varying degrees. Lateral arms (II, III) strongly keeled in many species. Funnel-mantle locking appa- ratus ⊥-shaped, sometimes fused with mantle and funnel elements. Suckers arranged biserially on arms and tetra-serially on ten- tacular clubs; chitinous sucker rings with sharp conical teeth.Buccal connectives attached to dorsal border of ventral arms (IV). Light organs present in some species on dorsal and ventral man- tle, viscera, and ventrally on eyes and head. Mouth surrounded by 10 append- ages (8 arms, 2 tentacles). mantle locking funnel locking One or both ventral arms cartilage cartilage hectocotylized in males, modifications vary from funnel- mantle elaborate development and locking sculpturing of sucker bases apparatus and trabeculae to simple ⊥-shaped head loss of suckers and stalks and development of protec- funnel tive membranes. Unlike most teuthoids which hatch as miniatures of the adults, ommastrephids have a dis- tinct larval form, the rhyn- choteuthion, in which the precursors to the tentacles mantle remain fused along their internal view of anterior length into a proboscis with mantle a terminal disc of suckers ventral view until the larva reaches (illustration: K. Hollis/ABRS) about 5 mm mantle length. Habitat, biology, and fisheries: In the Western Central Pacific, adult members of this family occur in deeper continental shelf, slope and throughout oceanic waters. Larvae and juveniles may also be found in shallow coastal waters. Ommastrephids are nektonic squid, associated with all depth strata from the surface to near the bottom.They are capable of extensive vertical and horizontal migrations.Ommastrephids feed on a broad range of crustaceans, fish, squid and other pelagic molluscs, and are at least partially cannibalistic. Known predators include seabirds, teleosts and sharks, whales, and dolphins. Ommastrephids form schools, which decrease in size as the animal grows. Evidence from commercial fishing operations suggests that neritic species congregate close to the bottom during the day, and move up through the water column at night. Oceanic species are often seen feeding at the surface at night. Juveniles of several species are able to glide like exocoetid flying fish to escape predators for distances in excess of 10 m. There is evidence for long-distance migration associated with spawning in some species. Ommastrephid squid are caught incidentally in demersal trawls in shelf and slope waters in the area. Also caught using baited or artificial lures or jigs, generally operated by hand. Exploratory use of jigging machines has been attempted for several species in the area with limited success. No target fisheries for these species currently exist in the area and regional catch statistics do not separate ommastrephids from other squids in most cases. The shelf and slope species in the area (Todarodes pacificus, Nototodarus hawaiiensis) are unlikely to represent large resources with the excep- tion of the broader slope areas off northwestern and northeastern Australia and in the South China Sea. The resource of the oceanic ommastrephids (especially Sthenoteuthis oualaniensis) may be large and is probably underexploited. Ommastrephidae 789 2 rows of Similar families occurring in the area hooks Onychoteuthidae: also relatively large muscular squids with an arrow-shaped terminal fin, but can be distinguished by the following 4 rows of characters: funnel-mantle locking cartilage simple, straight; ten- suckers, tacular clubs with biserially arranged hooks and marginal suckers; no hooks buccal connectives attached to ventral border (rather than to dorsal border) of ventral arms. Key to the species of Ommastrephidae occurring in the area Note: most ommastrephid species are easily identified in the field as adults. However, ontogenetic development or loss of light organs and variability in sucker dentition with growth may make identifica- tion of specimens smaller than 80 mm mantle length more difficult and specimens should be preserved and referred to regional tentacular club tentacular club teuthologists for confirmation. Onychoteuthidae Ommastrephidae 1a. Light organs apparent externally on head and/or mantle (skin may need to be removed to observe dorsal mantle light organs) ..............................→ 2 1b. No light organs visible externally ..................................→ 4 2a. A large oval light-organ patch present on dorsal mantle just posterior to head (Fig. 1a); funnel and mantle cartilages of locking apparatus fused (Fig. 1b) . Sthenoteuthis oualaniensis1/ (form with a dorsal light-organ patch) 2b. Light organs clearly visible on ventral mantle and head, no light organs evident on dorsal mantle; funnel and mantle cartilages of locking apparatus not generally fused ..........→ 3 3a. Nineteen spherical light organs arranged in a distinctive pattern on ventral mantle (Fig. 2) ......................................Hyaloteuthispelagica 3b. Light organs form 2 longitudinal stripes along the length of ventral mantle (Fig. 3) ... .........................................Eucleoteuthisluminosa light organ patch light funnel mantle cartilage organs in 2 cartilage spherical longitudinal light stripes organs b) funnel cartilage fused a) dorsal view with mantle cartilage ventral view ventral view Fig. 1 Stenoteuthis oualaniensis Fig. 2 Hyaloteuthis pelagica Fig. 3 Eucleoteuthis luminosa (after Wormuth, 1976) 1/ Two forms of Sthenoteuthis oualaniensis, the larger more abundant form with, and the smaller without, a dorsal light-organ patch, are known from the area. The former reaches in excess of 300 mm mantle length while females of the latter form reach maturity at less than 200 mm mantle length. It remains unresolved as to whether these represent separate species or whether onset of reproductive maturation at a small size triggered by unknown factors inhibits the formation of the light organ patch in the smaller form. 790 Cephalopods 4a. Mantle very slender, with elongated posterior tail (Fig. 4) ....................Ornithoteuthisvolatilis 4b. Mantle moderately stout, without an elongated tail (Fig. 5) ..............................→ 5 5a. Large medial tentacular sucker rings with a large tooth in each quadrant, separated by smaller subequal teeth (Fig. 5a) ..............................→ 6 5b. Large medial tentacular sucker rings with equal-sized or subequal teeth or with a single larger tooth present distally (Fig. 5b, c) ........................→ 7 6a. Two small round light organs on the intestine, one anteriorly near the anus and the other posteriorly (Fig. 6); ventral mantle uniformly coloured ....... .....................Sthenoteuthisoualaniensis2/ (form without a dorsal light-organ patch) 6b. No light organs on the intestine, but small spherical tail sub-cutaneous light organs distributed broadly in the enlongated, pointed ventral mantle in larger specimens (visible in the mantle ventral view wall when cut midventrally); mantle with a midventral bronze stripe (Fig. 7) ............Ommastrephesbartramii Fig. 4 Ornithoteuthis volatilis 7a. Medial tentacular sucker rings large tooth with approximately 30 subequal teeth (Figs 8a and 9) . Todaropsis eblanae 7b. Medial tentacular sucker rings with less than 25 teeth (Fig. 8a, c) ................→ 8 8a. Medial tentacular sucker rings with a single larger tooth distally → a) with large tooth b) with subequal c) with single large (Fig. 8c) ................. 9 in each quadrant teeth tooth distally 8b. Medial tentacular sucker rings Fig. 5 tentacular sucker rings with 16 to 20 subequal teeth (Figs 8b and 10) ........ about 30 ........Todarodespacificussubspecies teeth funnel a) Todaropsis eblanae 16-20 subequal teeth 2 light organs bronze stripe b) Todarodes pacificus large tooth distally intestine mantle internal view of anterior ventral mantle ventral view c) Nototodarus hawaiiensis Fig. 6 Sthenoteuthis oualaniensis Fig. 7 Ommastrephes bartramii Fig. 8 medial tentacular sucker rings 2/ See footnote on previous page. Ommastrephidae 791 9a. Arms with less than 30 transverse rows of biserial suckers; skin appears rough (Fig. 11) ........................................Nototodarushawaiiensis 9b. Arms with more than 35 transverse rows of biserial suckers; skin appears smooth (Fig. 12) ......................................Nototodarusgouldi dorsal view dorsal view dorsal view ventral view Fig. 9 Todaropsis Fig. 10 Todarodes Fig. 11 Nototodarus Fig. 12 Nototodarus eblanae pacificus hawaiiensis gouldi (illustration: K.Hollis/ABRS) List of species occurring in the area The symbol % is given when species accounts are included. Eucleoteuthis luminosa (Sasaki, 1915) Hyaloteuthis pelagica (Bosc, 1802) Nototodarus gouldi (McCoy, 1888) % Nototodarus hawaiiensis (Berry, 1912) % Ommastrephes bartramii (Lesueur, 1821) Ornithoteuthis volatilis (Sasaki, 1915) % Sthenoteuthis oualaniensis (Lesson, 1830) % Todarodes pacificus Steenstrup, 1880 % Todaropsis eblanae (Ball, 1841) References Dunning, M.C. 1988a. Todarodes pacificus pusillus new subspecies (Cephalopoda, Ommastrephidae) from northern Australian waters. Mem. Natl. Mus. Vict., 49:149-157. Dunning, M.C. 1988b. First record of Nototodarus hawaiiensis (Berry, 1912) from northern Australian waters with a reconsideration