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Some Additional New Zealand Cephalopods from Cook Strait

Family Sepiolidae — Genus Iridioteuthis Naef. 1912 — Iridioteuthis maoria n.sp. Figs. 3-6

Family Sepiolidae
Genus Iridioteuthis Naef. 1912

Iridioteuthis maoria n.sp. Figs. 3-6.

Animal small. Body short, bell-shaped in dorsal view, widest at anterior extremity, laterally compressed, terminating abruptly. Body approximately as deep as wide in adult specimens, much deeper comparatively in younger animals. Mantle smooth, continuous with integument of head dorsally. Ventral mantle margin extending forward well beyond the eyes and almost entirely covering the funnel, with a well-marked, anterior, median emargination and closely appressed to head which it almost completely covers ventrally but sweeping back laterally to expose the large, prominent eyes.

Fins very large, thin, outline rounded-oblong, base of attachment relatively short, plane of attachment of fins to body approximately median. In adults the anterior extremity of the fin does not reach the level of the eyes, and the posterior extremity does not extend as far as the postrior extremity of the body. In younger specimens the anterior extremity of the fins reaches the level of the eyes and the posterior extends beyond the posterior extremity of the body.

Head broad, short, flattened dorso-ventrally, dominated by the large eye-balls. Eye-balls extremely large, covered to a large extent by the integument, with a small, perfectly circular lid fold.

Funnel only visible after removal of the ventral mantle lobe, large and well developed, base wide, rapidly tapering to tip. In some specimens the tip is swollen, in all it is strongly muscular, aperture relatively small, especially in young examples. Funnel organ very large and swollen, consisting of a pair of divergently placed pads, one on each side of the median line. Locking apparatus consisting of an page 4elongate, narrow, cartilaginous groove at either side of the base of the funnel and long, thickened, corresponding grooves on the inner wall of the mantle.

Sessile arms short, bound together by a very well developed web, which reaches almost to the free extremity of the dorsal arms, but is entirely lacking between the ventral pair. Arms unequal in length, order 3, 4, 2, 1, the third pair conspicuously the longest and with a prominent membranous keel bordering the outer margin. A similar, much less conspicuous keel is developed on the fourth pair of arms. Suckers on all sessile arms in two rows, alternately placed in each row, closely spaced, the sixth, seventh and eighth suckers on the second pair of arms greatly enlarged. Individual suckers spherical, openings small, pedicels very short, armed with smooth, horny rings. Tentacles long and slender, club hardly differentiated from stalk. Stalk rounded near base, becoming flattened towards club, grooved medianly. Club bearing numerous, minute, crowded suckers.

Colour of preserved specimens a dull, brownish cream, suffused on the major part of the dorsal surface of the mantle, over the head and bases of the arms, tip of the funnel and the ventral shield with a dull, purplish black. Central portion of the dorsal surface of the mantle, head and proximal portion of web enveloping arms, set with rather elongate, closely set, irregular chromatophores. Outer surface of stalks of tentacles set with considerably smaller rather sparse chromatophores.

Holotype (M.11179) and three paratypes in Dominion Museum, Wellington.

Localities: Washed ashore on Paraparaumu Beach, Wellington, D. F. Watson, 9.8.54 (Holotype); trawled in Bay of Plenty, c. 130 fathoms, 1956. Presented K. Fraser; VUZ 17, 41° 31′ S, 174° 58′ E, Palliser Bay, Cook Strait, in 150–200 fathoms, 13.5.55.

This species is closely allied to the type species of the genus, Iridioteuthis iris Berry, described from off the Hawaiian Islands in 153–142 fathoms. There is little doubt that Berry's specimen was immature and the immature specimens of maoria n.sp. agree with Berry's descriptions of iris fairly closely. However, there are a number of differences, even between those immature specimens which appear to be valid differentiating characters, so that the two forms certainly represent different species. In Iridioteuthis iris it is the third pair of arms which develops greatly enlarged suckers, in I. maoria it is the second pair. This feature can be clearly seen in the two largest of the four New Zealand specimens available. Whether this feature represents hectocotylisation still remains to be determined. In addition the head and tentacles are longer in relation to mantle length in I. maoria than they are in I. iris. In the four examples seen, the head and tentacles are all bent ventrally in relation to the plane of the mantle and fins and if this feature is constant and real it will serve as an additional means of differentiation. During growth it would appear that the fins do not increase in size proportionately with growth of the mantle and the lateral compression of the mantle also becomes less marked.

This is only the second known species of the genus, but in view of the wide geographic distance between the two areas from which the genus is now known, it seems certain that additional representatives will come to light in the Pacific when the faunas of the intermediate depths are better known.

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Figs. 1, 2.—Mastigoteuthis flammea Chun. VUZ 86. 3, 4.—Iridioteuthis maoria n.sp., Holotype. 5.—Iridioteuthis maoria n.sp., mantle cavity. 6.—Iridioteuthis maoria n.sp., half grown specimen.

Figs. 1, 2.—Mastigoteuthis flammea Chun. VUZ 86. 3, 4.—Iridioteuthis maoria n.sp., Holotype. 5.—Iridioteuthis maoria n.sp., mantle cavity. 6.—Iridioteuthis maoria n.sp., half grown specimen.

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Measurements of Iridioteuthis maoria n.sp.
Holotype mm Bay of Plenty mm Bay of Plenty mm Cook Strait mm
Dorsal mantle length 17 11 12 13
Ventral mantle length 21 15 16 17
Length to base of dorsal arms 38 21 22 28
Extreme length of fin 16 12.5 13 13
Length of fin at base of attachment 8 8 7 9
Width of single fin 12 9 8 9
Width across fin 36 27 27 29
Diameter of body 19 9 10 14
Depth of body 18 14 14 14
Length of head 21 10 10 15
Width across eyes 16.5 11 11 11.5
Median length of dorsal shield 17 11 11.5 14
Length of funnel (median) 10
R.1 11 9
R.2 12.5 10
R.3 14 11
R.4 12 8
Length of right tentacle 44 22

The measurements for the lengths of the sessile arms has not been given for two of the specimens as they are too tightly bunched for measurements to be taken accurately.