FAO Species Identification Guide for Fishery Purposes Western

Ommastrephidae 789
Similar families occurring in the area
Onychoteuthidae: also relatively large muscular squids with an
arrow-shaped terminal fin, but can be distinguished by the following
characters: funnel-mantle locking cartilage simple, straight; tentacular
clubs with biserially arranged hooks and marginal suckers;
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 identification
of specimens smaller than 80 mm mantle length more difficult
and specimens should be preserved and referred to regional
teuthologists for confirmation.
tentacular club
Onychoteuthidae
2 rows of
hooks
4 rows of
suckers,
no hooks
tentacular club
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 oualaniensis 1/
(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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hyaloteuthis pelagica
3b. Light organs form 2 longitudinal stripes along the length of ventral mantle (Fig. 3) . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eucleoteuthis luminosa
a) dorsal view
light
organ
patch
funnel
cartilage
b) funnel cartilage fused
with mantle cartilage
Fig. 1 Stenoteuthis oualaniensis
mantle
cartilage
ventral view
spherical
light
organs
Fig. 2 Hyaloteuthis pelagica
(after Wormuth, 1976)
ventral view
light
organs in 2
longitudinal
stripes
Fig. 3 Eucleoteuthis luminosa
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.