Walvisteuthis rancureli (Okutani 1981)

Introduction

Walvisteuthis rancureli is a small squid of under 80 mm ML as an adult. This species is easily recognized by its short, broad shape and oval fins. Another diagnostic feature of Walvisteuthis species is the short, thin, blunt rostrum that is oriented perpendicular to the gladius.

The single recognized species has a very broad geographical distribution. The type locality is the tropical Indian Ocean. The junior synonym, Walvisteuthis virilis, was taken in the temperate South Atlantic. The specimens described here are from the tropical North Pacific, and we have seen specimens from the tropical Atlantic. Rancurel (1970) described specimens from the tropical South Pacific. For an onychoteuthid, this broad distribution suggests that "Walvisteuthis rancureli" probably represents a species complex. However, squid in present collections are insufficient to define possible species differences. This is partly due to the fact that nearly all squid have been recovered from the stomachs of fish. Acidity of the fish stomach will greatly damage the horny suckers and hooks. Because W. rancureli may represent a species complex, we include exerpts from the original descriptions of Onykia rancureli and Walvisteuthis virilis:

• Onykia rancureli: Description of the holotype
• Walvisteuthis virilis: Description of the holotype

Diagnosis

An onychoteuthid ...

• Fins oval, not drawn-out posteriorly (unique character).
• with gladius visible beneath skin in dorsal midline.
• with 3 occipital folds.

Characteristics

1. Arms
   1. Dorsal protective membranes of arms II and III greatly enlarged (ca. 2X) relative to their ventral protective membranes, and with long, well-defined trabeculae.
   2. Suckers lack distal fleshy knob (see Onychoteuthis).
      image info

      Figure. Oral view of proximal regions of arms II (upper) and III of W. rancureli, Hawaii, 65 mm ML, male. Photograph b R. Young.

2. Tentacular club
   1. A few marginal suckers present in subadults, presumably lost in adults.


3. Occipital region
   1. 3 occipital folds; large occipital membrane from fold 3 extends dorsally and curves to join occipital crest without forming a distict fourth fold. Olfactory organ lies at posterior end of fold no. 2.


4. Head
   1. The margins of the funnel groove are straight and define a sharply pointed V-shape. ol>
      image info

      Figure. Ventral view of head and funnel of W. rancureli, Hawaii, 65 mm ML, male. Photograph by R. Young.

5. Fins
   1. Oval with large anterior lobes; not drawn-out posteriorly (see Title illustration). The apical fin-angle is approximately 180°.


6. Photophores
   1. Absent. Note, in the photograph above, that the eye which has popped outside the eyelid, has no photophores on its ventral surface.


7. Gladius
   1. Short, blunt rostrum directed perpendicular to tip of gladius.
   2. Gladius visible in dorsal mid-line except at posterior tip of mantle.
      image info

      Figure. Lateral view of the posterior end of the gladius of W. rancureli showing rostrum, Hawaii, 37 mm ML. Photograph by R. Young.

Comments

The above description is based on specimens captured in Hawaiian waters.

Additional features of the description can be found here.

Nomenclature

Nesis and Nikitina (1986) described a new family of squids, "Walvisteuthidae", based on a mature male which they named Walvisteuthis virilis. The squid was somewhat similar to onychoteuthids but it had a number of very peculiar features that caused the authors to erect the new family. The status of this family has recently been reviewed by Tsuchiya (in preparation) and he concluded that Walvisteuthis virilis is a synonym of the onychoteuthid, Onykia rancureli. The peculiar features appear to be modifications that arise at sexual maturity. "Onykia" rancureli has been widely recognized as being very different from other members of this genus and several authors have suggested that a new generic name is needed (e.g., Toll, 1982; Tsuchiya and Okutani, 1991). This generic name is Walvisteuthis.

Life History

Paralarvae are known as small as 1.9 mm ML. The smallest paralarvae are extremely slender with a mantle width about 25% of the ML. Between this size and about 4-5 mm ML (Fig. A) they are easily recognized by their slender appearance and a distinctive elongate patch of large chromatophores along the dorsal midline. The eyes are dorsoventrally elongate and strongly buldge from the head. Club suckers are in two series, large (about the same size as the arm suckers) and prominent. At roughly 4-5 mm ML (Fig. B) the paralarvae begin a strong morphological change. They start to become relative broad, the eyes become hemispherical and the fins become much more prominent. At 7 mm (Fig. C) the squid is very broad for its length. Chromatophores are small and scattered but larger on the dorsal surfaces than ventral surfaces. On the ventral surface of the head the chromatophores are deep within the tissue and not readily visible in preserved specimens. By 12 mm ML the V-shaped funnel groove and the distinctive rostrum are present and hooks are beginning to form in the medial-ventral series on the club.

image info

Figure. Ventral and dorsal views of growth stages of paralarvae of W. rancureli, Hawaii. A - Small, slender-stage paralarva, 2.4 mm ML. B - Paralarva in transition between slender and squat-body forms, 4.5 mm ML. C - Squat-stage paralarva, 7.0 mm ML. The scale bar is 1 mm. Drawings by R. Young.

Distribution