Stigmatoteuthis arcturi Robson, 1948

Introduction

Species of Stigmatoteuthis are distinctive in having very long arms relative to the ML and paired secondary reproductive organs (terminal organ (=penis), spermatophore gland complex, Needham's sac).

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Figure. Ventral view of the viscera of a fresh, mature male S. arcturi (head and arms missing) seen by cutting and spreading the mantle. Note the paired penes with both packed with spermatophores. Photograph by M. Vecchione.

Diagnosis

A Stigmatoteuthis ...

• with a tropical to subtropical Atlantic Ocean habitat.

Characteristics

1. Reproductive system
   1. Ejaculatory apparatus of spermatophore with numerous loops.
   2. Sperm mass of spermatophore 35-46% of spermatophore length.
   3. Hectocotylus with two sucker series throughout.
   4. Hectocotylus with papillated skin on ventral surface.

Comments

Species of Stigmatoteuthis are easily recognized by the Type 1a photophore pattern of the head which has 3 photophores in the Midline Series and no rogue photophore (see pattern of S. hoylei). S. arcturi can be most easily separated from S. dofleini by the complex looping found in the ejaculatory apparatus of the spermatophore and details of the hectocotylus. It is most easily separated from S. hoylei by the shorter sperm mass in the spermatophore. If mature males are not available, separation is based on capture location.

Species Stigmatoteuthis are characterized by the presence of:

1. Tentacular clubs
   1. Medial suckers of tentacular clubs greatly enlarged, more than 4X diameter of minute marginal suckers.
2. Photophores
   1. Type 1a pattern on head (e.g., 3 Midline Series photophores, 3 Basal Arm IV Row photophores and no rogue photophore).
   2. Basal Row on head with 8 photophores and 3 sawteeth.
   3. Right Basal Series on head present.
   4. Ends of arms IV without separate group of compound photophores.
   5. Compound photophores of large, uniform size and evenly spaced on anterior half of ventral mantle.
3. Tubercles
   1. Absent.
4. Mantle
   1. Skin of the mantle and elsewhere with dermal warts beneath outer epithelium in large squid.
5. Viscera
   1. Mail genitalia paired.

With the exception of the analysis of the head photophores, the above information is from Voss (1969) and Voss, et al. (1998).

Nomenclature

All world-wide specimens in Stigmatoteuthis were considered by Voss (1969) to belong to H. dofleini. Voss et al. (1992) after examining the type of Histiopsis hoylei Goodrich, 1896, placed all known specimens in the synonomy of this earlier named species, Histioteuthis hoylei (Goodrich, 1896). Voss et al., (1998) recognized that the Atlantic form was diffferent and should be called H. arcturi (Robson, 1948). They based the separation primarily on striking differences in the spermatophore and hectocotylus of the mature male. Unfortunately few mature specimens were known for comparisons. The males that represented H. hoylei came from north temperate waters off California and Japan. We have examined specimens from off Hawaii and found they have spermatophores with the distinctive ejaculatory apparatus of H. arcturi from the Atlantic but differ in some features of the hectocotylus. Therefore, the Pacific forms divide into a temperate North Pacific species which carries the name, H. dofleini, and a more southern species, H. hoylei. Instead of placing H. hoylei and H. arcturi in synonomy, we maintain the separation of these species as Voss et al., (1998) list other separating characters such as features of the gladius, beak, web and arm lengths that are not all related to maturity and are based on squids from a wider geographical range. We place all members of the hoylei-group into the genus Stigmatoteuthis.

In this clade of histioteuthids with bilaterally paired male secondary sexual organs, the first species described was Histiopsis hoylei Goodrich 1896. However, the type species of the nominal genus Histiopsis is H. atlantica, which has unpaired male organs and Histiopsis was subsequently placed in the synonomy of Histioteuthis (Voss,1969). Pfeffer  (1900) described the genus Stigmatoteuthis, with type species S. hoylei (Goodrich 1896) by monotypy. (This is not the same species as Meleagroteuthis hoylei Pfeffer, 1900 which, according to Nesis, 1987, is a synonym of Histioteuthis meleagroteuthis.) Therefore Stigmatoteuthis Pfeffer 1900 is the valid-genus name designated for a species in this clade.

Life History

Mature females are known from 176-204 mm ML; mature males from 72-125 mm ML (Voss, et al., 1998).

Distribution

Geographical distribution

Type locality: South Sargasso Sea, 26°54'N, 51°15'W.

The distribution of S. arcturi extends throughout the tropical and subtropical Atlantic between about 40°N and 30°S (Voss, et al, 1998).

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Figure. Distribution chart for S. arcturi. Chart modified from Voss, et al. (1998).

References

Voss, N. A. 1969. A monograph of the Cephalopoda of the North Atlantic: The family Histioteuthidae. Bull. Mar. Sci., 19: 713-867.

Voss, N. A., S. J. Stephen and Zh. Dong. 1992. Family Histioteuthidae. Smithson. Contr. Zool., No. 513: 73-91.

Voss, N.A., K. N. Nesis, P. G. Rodhouse. 1998. The cephalopod family Histioteuthidae (Oegopsida): Systematics, biology, and biogeography. Smithson. Contr. Zool., 586(2): 293-372.