Planctoteuthis oligobessa (Young 1972)

Valbyteuthis oligobessa

DESCRIPTION.—The thin, delicate mantle is saclike, except posteriorly where it tapers to a point. The anterior mantle margin is broad and only loosely surrounds the head and funnel.

The fins are small, about 23–33% of the M.L. in length. Each is roughly semicircular and has only slightly projecting anterior and posterior lobes. The broad, tubular conus of the pen projects posteriorly past the fins. It has been broken in all specimens so that its full extent is unknown. The fins join in the dorsal midline.

The funnel is very large; it reaches anteriorly to the level of the anterior margins of the eyes in mature specimens, but is smaller in immature forms. The funnel locking-cartilage is distinctive of the genus; the cartilage has an oval depression that deepens posteriorly where it is overhung by a small antitragus. The opposing mantle cartilage has the appearance of a human nose with a single nostril; the “nostril” locks with the antitragus. The dorsal member of the funnel organ is very small relative to the large size of the funnel. The organ is approximately shield-shape with a rough or papillate surface and an anterior papilla. This papilla, at its base, is slender, but distally it broadens in the transverse plane and is slightly cupped. The ventral pads are somewhat variable, but generally are elongate and oval and slant obliquely toward the midline. There is no funnel valve.

The head is elongate and cylindrical. The eyes are small; in all specimens, they have been damaged. The paired bridles and cephalic vein are prominent along the ventral surface of the head beneath the funnel. “Olfactory” papillae are present lateral to the funnel and considerably posterior to the eyes. Each consists of a very elongate stalk with a terminal swelling. The nuchal cartilage is straight, slender, and elongate. A central ridge with a median groove is barely detectable on its anterior half.

The arms are short, extremely delicate, and in the order IV>III>II>I. In young specimens, arms IV are greatly elongate (up to 130% of the M.L.), but in the mature animal they are less than the length of the mantle and only slightly longer than arms III. There is only a slight indication of protective membranes, and keels appear to be lacking from arms I–III, although lateral keels are present on arms IV. The suckers on the arms are biserially arranged along the entire length of each arm I–III. On arms IV, the suckers are broadly separated and arranged in apparent single file. These are preset only on the proximal end of the arms and number only 2-A on each arm.

The outer chitinous ring of each arm sucker consists of an outer row of parallel scales followed medially by 3–4 rows of scales with generally square bases. The latter bear large knobs which have enlarged, flattened ends in the most medial series of the distal half of the ring. On the proximal side of the ring, the knobs are replaced by hollow cylinders that have a portion of one side missing (Plate 24R). The inner chitinous ring has about 25–35 small, blunt teeth around the distal three-fourths of the margin. The proximal portion is nearly smooth.

The tentacles are relatively robust and long. Each tentacular club is short, only slightly expanded, and is not differentiated into a manus and a dactylus. Low, protective membranes are present on both borders. The suckers are arranged in 4 regular longitudinal rows over most of the club, but become slightly irregular at the tip and at the base of the club. The suckers of the ventral row are the largest. The suckers become progressively smaller in a transverse series, although the suckers of the dorsal row are still only slightly smaller than those of the ventral rows. Five or six suckers, arranged in 2 alternating rows, are present in the carpus. The larger of these is sligthly larger than the suckers of the club.

The buccal membrane connectives attach to the dorsal borders of arms I and II and to the ventral borders of arms III and IV.

No photophores could be found. This animal is covered with numerous reddish brown chromatophores.

The holotype is a gravid female. The mantle cavity is occupied almost entirely by a large mass of mature eggs and large nidamental glands. The ripe eggs are about 1.5 mm in diameter. Several large sperm reservoirs can be found in the enlarged ovary and, surprisingly, one can be seen protruding through each nephridiopore. Paired oviducts are present with enlarged oviducal glands. This is the first record of a mature specimen in the genus.

TYPE LOCALITY.—32°17′ N, 120°12′ W, eastern North Pacific Ocean.

LOCATION OF TYPE.—University of Southern California. U.S.C. Hancock collections, AHF Cephalopod Type No. 9.

bathypelagic