Table Of ContentPROC. BIOL. SOC. WASH.
106(3), 1993, pp. 602-605
AN UNUSUAL SQUID PARALARVA (CEPHALOPODA) WITH
TENTACULAR PHOTOPHORES
Deborah L. Loffler and Michael Vecchione
—We
Abstract. describe an unusual squid paralarva from the eastern North
Pacific. This paralarva has characters indicating it might be a gonatid, but if
so it is the first gonatid species known to have photophores on its tentacles.
Structures that might be photophores were also located on the interior of the
mantle. One other gonatid species, Gonatus pyros, is known to have photo-
phores but these are located only on the eyes. Gonatus pyros spawns in the
eastern North Pacific, and its early paralarva has not been described. We there-
fore tested the hypothesis that our squid may be an ontogenetic stage of G.
pyros. Tentacles ofyoung G. pyros were examined histologically to see ifpho-
tophore tissue might be embedded in the tentacles, but the results were incon-
clusive. We also examined early stages ofeight other gonatid species. None of
these had either tentacular or internal photophores. We therefore describe this
very unusual specimen, but its identity remains uncertain.
During examination of a collection of that our specimen may be an early stage of
cephalopods from the eastern North Pacific that species. If G. pyros were shown histo-
we found a paralarva with characters ofthe logically to have photophore tissue embed-
squid family Gonatidae, but also with what ded in its tentacles then we could argue that
appeared to be a single photophore on each G. pyros does develop tentacular photo-
tentacle and two more photophores on the phores early in life and that our specimen
interior wall of the mantle just anterior to could be that species.
the bases ofthe fins. Only one gonatid spe-
cies, Gonatus pyros Young, 1972, is known
Materials and Methods
to possess photophores, and in that species
a large photophore is located on the ventral The specimen (USNM 817795; ca. 5 mm
surface ofeach eye (Young 1972). The pres- ML) was collected in the eastern North Pa-
TW
ence ofphotophores in locations other than cific, offsouthern California at 34°N, 12
the eyes on this paralarva is therefore note- on 13 November 1969. Sampling time was
worthy. 1730-1800 and depth was approximately
mm
Few small gonatid paralarvae (< 10 215 m.
mantle length, ML) have been described, We examined the possibility that the
and little is known about them. Kubodera specimen was a Gonatuspyros because this
&
Jefferts (1984), in a study ofdistribution is the only photophore-bearing gonatid
and abundance of the early life stages of known, and it is found in abundance in the
&
North Pacific squids, found only three Go- sampled area (Kubodera Okutani 1981).
mm
natus pyros specimens < ML. Be- Examination of gross tentacular morphol-
1
cause G. pyros was omitted from descrip- ogy of the smallest G. pyros specimens in
mm
tions and keys to early paralarvae < 1 the collections ofthe National Museum of
ML &
by Kubodera Okutani (1981) and Natural History revealed no photophores
Okutani & Clarke (1992), we hypothesized but a damaged area was consistently found
VOLUME 106, NUMBER 3 603
at approximately the same location as the
photophores on our paralarva. The tenta-
(USNM ML
cles ofthree G. pyros, 727486,
32 mm, 17 mm, and 16 mm)were examined
histologically for embedded photophores.
These specimens had been fixed in formalin
and preserved in 45% isopropanol. Histo-
logical preparation included ethanol dehy-
dration, tissue embedding in paraffin, and
frontal sectioning at 6 jirw thickness. He-
matoxylin and eosin stains were used and
the sections were examined using light mi-
croscopy. Other gonatids from the National
Museum ofNatural History were examined
forthe presence ofphotophores. These were
the smallest specimens in the collection for
each species listed below and included: Ber-
(USNM ML
ryteuthis anonychus 575631,
68 mm), Gonatopsis borealis (USNM
ML mm
813458, 33 and 28 mm), Gonatus
onyx (USNM 730044, ML 30 mm and
USNM ML
730043, 17 mm), Gonatus ma-
dokai (USNM 884252, ML 15 mm and 15
mm), Gonatusfabricii (USNM 884254, ML
18 mm and 19 mm), Gonatus berryi(USNM
ML mm
729867, 12 and 12 mm), Berry-
(USNM ML
teuthis magister 814633, 17
mm
and 21 mm), Gonatus antarcticus
(USNM 884253, ML 42 mm).
Results
The specimen was identifiedto the family
Gonatidae using a paralarval key to the
cephalopod families (Sweeney et al. 1992).
Identification was based on the following
characters: arms with four rows of suckers,
robust tentacles with minute suckers along
most ofthe tentacular stalk and distinctive
tentacular clubs developing >4 rows of
minute suckers.
General morphology (Fig. 1).—Mantle:
Invertedbutbell-shaped, thin, muscular; fins
small, membranous; Mantle Width esti- shaFipge.e1s.timVaetnetdraflrvoimeiwnvoefrgtoendatmiadntplaer.alSacrva^lae.bMaarn=tle2
mated to be ca. 60% Mantle Length (ML). mm.
Funnel-lockingcartilage straight. Two small
spheres, possibly photophores, located on
interior wall ofmantlejust anterior to bases
604 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
ofthe fins, connected to a smaller centrally
located sphere.
Head: Squarish in shape, slightly narrow-
er than mantle opening; large anterolateral
eyes. No photophore anlagen on ventral
surface of eyes.
Arms: Stout, muscular. Arm formula
I=II=III»IV. Suckers tetraserial on arms
I, II and III. No suckers on arms IV.
Tentacles(Fig. 2): Stout, muscular, ca. four
times longer than longest arms, about 3.5
mm
long; smaller suckers covermost oforal
surface ofstalk, in two staggered rows prox-
imally, increasingto five rows ondistal stalk;
club developing on distal Vs with numerous
minute suckers in seven rows. Large pho-
%
tophore on aboral surface ca. oftentacle
length from base. Photophore diameter
about equal to tentacle diameter. Photo-
phore round and distinctly darker in shade
than tentacle. Photophore roughly spherical
mm and partially embedded in tentacular mus-
cle.
Digestive gland: Oblong with ink sac em-
bedded in ventral surface.
When the specimen was stained with
Methylene Blue, all tissues stained except
the structures we presume to be photo-
phores. Histological examination of G. py-
rostentacles failed to reveal photophore tis-
No
sue. photophores, either tentacular or
internal, were found on any of the other
gonatids examined. Photophores on the
paralarva were not sectioned because ofthe
uniqueness ofthe specimen.
Discussion
The specimen has familial characters to
classifyitasaprobablegonatidsquid. These
characters include: arms with four rows of
suckers, straight fiinnel-locking cartilage and
tentacular clubs with >4 rows of minute
suckers. Other squid families have species
with tentacular and/or internal photo-
phores. The Lycoteuthidae have both. But
Fig. 2. Ventral view of(left to right) arm IV, ten- no family other than Gonatidae is known
tacle, and arm III on right side. Scale bar = 1 mm. to havethe suckerpatterns ofthis specimen.
VOLUME 106, NUMBER 3 605
mm ML
Its size of 5 places it in the size species. However, the squid treated in this
range least known for gonatids. The pres- paper, although unidentified, remains note-
ence of tentacular (and perhaps internal) worthy in that it appears to be a gonatid
photophores, however, is without prece- squid with photophores on the tentacles.
dence in the family.
Gonatus pyros is the only species in the Acknowledgments
family Gonatidae that has been described We
thank Clyde F. E. Roper, Smithson-
to have photophores. The photophores of
ian Institution, for his comments and en-
G. pyrosare, however, in adifferent location
couragement. Support was provided by the
than the ones on our specimen. Gonatus
Registry ofTumors and Lower Animals in
pyros has a large oval photophore on the
the National Museum of Natural History
ventral surface of each eye (Young 1972)
for the histological work performed in this
whereas our gonatid paralarva lacks ocular
investigation. Keiko Hiratsuka Moore ofthe
photophores, but has one large round pho- NMFS
Systematics Laboratory inked the il-
tophore on the aboral surface of each ten- We
lustrations. appreciate reviews of the
tacular stalk and possibly a complex ofpho-
manuscript by Bruce B. Collette, Michael J.
tophores in the posterior mantle cavity. The
Sweeney, Clyde F. E. Roper, Tsunemi Ku-
location where the specimen was collected
bodera and Joseph B. Slowinski.
is in the general region where larger para-
larvae of G. pyros have been found (Ku-
& Literature Cited
bodera Jefferts 1984). Gonatus pyros
specimens > 1 mm ML were found to be Kubodera, T., & K. Jefferts. 1984. Distribution and
frequent and abundant off the Oregon and abundance ofthe early life stages ofsquid, pri-
Washington coasts between 40-50°N and marilyGonatidae(Cephalopoda, Oegopsida),in
140-120°W (Kubodera & Jefferts 1984). thenorthernPacific.—BulletinNationalScience
Museum, (Tokyo), Ser. A, 10(4):165-193.
Our histological examination was incon- & T. Okutani. 1981. The systematics and
,
clusive. Our inability to locate photophore identification of larval cephalopods from the
tissue does not mean that it was not there northern North Pacific—Research Institute of
at an earlier stage. Absorption ofparalarval North Pacific Fisheries, Hokkaido University,
Special volume, 131-159.
photophores has been suspected in the om- Okutani, T., & M. R. Clarke. 1992. Family Gona-
mastrephid squid Doscidicus gigas (C. F. C. tidae Hoyle, 1886. In M. J. Sweeney, C. F. E.
Roper, pers. comm.). The gonatid pho- Roper,K. Mangold, M. R. Clarke, &S. v. Bolet-
tophore tissue could have been completely zky, eds., "Larval" and juvenile cephalopods:
resorbed by 16 mm ML. If so, this could a manualfortheiridentification.—Smithsonian
explain the apparent weak spot in the ten- Contributions to Zoology 513:139-156.
Sweeney, M. J., C. F, E. Roper, K. Mangold, M. R.
tacles of the small G. pyros we examined. Clarke, & S. V. Boletzky, eds., 1992. "Larval"
In other words, we failed to support the hy- and juvenile cephalopods: a manual for their
—
pothesis that our paralarva is an early stage identification. Smithsonian Contributions to
of G. pyros but we do not feel that it has Zoology 513:1-282.
Young, R. E. 1972. The systematics and areal dis-
been refuted conclusively. Because the his-
tribution ofpelagic cephalopods from the seas
tological examination of G. pyros failed to off southern California.—Smithsonian Contri-
indicate embedded or resorbed photo- butions to Zoology 97:1-159.
phores, we have no evidence that our par-
NMFS
alarva is that species. Examination ofother Systematics Laboratory, National
gonatid species did not reveal any charac- Museum of Natural History, Washington,
ters to link our paralarva with any ofthose D.C. 20560, U.S.A.
