Mastigotragus pyrodes (Young 1972)

Mastigoteuthis pyrodes

DESCRIPTION.—The mantle is cylindrical for most of its length, but posteriorly it tapers rapidly, and the muscular portion terminates in a blunt point just posterior to the anterior end of the fins. The mantle continues past this point as a narrow cylindrical cord of tissue which merges into the tail. The tail extends for a short distance posterior to the fins, but its exact extent is uncertain since it is invariably damaged. The pen appears to extend to the tip of the tail. Anteriorly, the mantle projects strongly in the nuchal region, but less so in the areas of the mantle locking-cartilages.

The fins are large, about 60% (excluding the tail) of the M.L., and nearly circular in outline. The anterior lobes are attached for the most part, but project anteriorly very slightly.

The funnel reaches approximately to the level of the posterior edges of the lenses. It contains a large valve and a well-developed funnel organ with an inverted V-shaped dorsal pad bearing a small anterior papilla, and 2 oval ventral pads. The funnel locking-cartilage has an oval depresion with a strong tragus on the medial margin. Occasionally, a low antitragus can be detected; however, it is usually not apparent.

The head is slightly broader than long. Its width is nearly equal to the M.W., and its length is approximately 20% of the M.L. The eyes are very large, occupying almost the full length and depth of the head. An eye sinus is not apparent on the eyelid. A crescentshape patch of tissue borders the posterior margin of the eyelid, and a small “olfactory” papilla is located posterior to each eye.

The arms are large, the ventral pair extremely so, being comparable to the mantle in length. The arm formula is IV>II>III>I. Although the arms are generally damaged, they appear to contain rather feeble protective membranes supported by flabby, triangular trabeculae. Arms IV have large lateral keels. It is not possible to determine the presence or absence of swimming keels on the other arms due to damage. The suckers are arranged biserially and have slender stalks arising from large conelike bases which are fused with the lateral trabeculae. The oral face of each arm IV is very narrow and the suckers are forced nearly into a single row, particularly in the distal half of the arm. The number of suckers in the proximal half of each arm in the largest female (165 mm M.L.) is 36, 36, 39, and 38 for arms I through IV, respectively. Each sucker ring bears sharply pointed teeth on the distal margin and truncate teeth on the lateral margins. The total number of teeth varies roughly between 10 and 15. The proximal edge of the chitinous ring is smooth. There is no evidence of hectocotylization in males.

The tentacles are very long, over twice the mantle length, and very slender. The club is unexpanded and approximately 50% of the tentacle length. The club possesses a microscopic protective membrane with tiny trabeculae which defines the borders of the sucker-bearing portion of the club. The proximal end of the club is damaged in all specimens, so its exact structure cannot be determined with certainty; however, it appears that the sucker-bearing area tapers rapidly to an abrupt end. Distally, the suckers progressively cover increasingly more of the club surface until they completely surround the tentacle a short distance from its tip. The smallest suckers occur at the tip of the club. The largest suckers occur in a broad area about one-third of the club length from its distal end and are arranged in approximately 18–22 rows. The suckers have long, slender stalks which result in a disorderly arrangement in preservation and makes an exact determination of the number of rows difficult. The club suckers are elongate in the proximal-distal plane. The outer chitinous ring is broad and each lateral margin of its inner edge has 2–3 greatly enlarged, blunt teeth that project into the aperature of the sucker. The inner ring has 3 distinct blunt teeth on the distal margin; the proximal and lateral margins are smooth. The largest suckers on the club measure 0.28–0.32 mm in the long diameter of the holotype (110 mm M.L.). The club in its middle portion has a diameter about 7 times the width of the largest suckers of this portion.

The numerous photophores present are almost exclusively in the outer integument and, therefore, are easily lost with only a small amount of abrasion. As a result of such injury to the present specimens, it is impossible to determine the exact distribution of light organs. The ventral surface of the mantle is covered with small photophores which appear to diminish in number laterally. On the ventral surface of each fin, adjacent to the mantle, photophores are lacking, while lateral to this area scattered light organs appear, but gradually diminish toward the lateral margins of the fins. Thus, there appears to be a somewhat narrow patch of photophores down the ventral surface of each fin. Photophores are abundant on the dorsal surface of the fins, particularly on the lateral halves. Both the dorsal and ventral surfaces of the funnel are sprinkled with photophores as are the ventral and lateral surfaces of the head. A large light organ is present deep in the tissue near the anteroventral margin of each eyelid. It is oval in shape and may be completely hidden by an aggregation of dark chromatophores. Numerous light organs are present on the ventral surface of arms IV.

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

The color in preservation consists of a reddish purple background pigmentation upon which dark reddish purple chromatophores occur in the outer integument.

TYPE LOCALITY.—33°32′ N, 118°23′ W, eastern North Pacific Ocean.

LOCATION OF TYPE.—University of Southern California, U.S.C Hancock collections, AHF Cephalopod Type No. 7.

Mastigoteuthis pyrodes is a species of whip-lash squid.