Pterygioteuthis Fischer, 1896

Introduction

Species of Pterygioteuthis are probably the smallest of all oceanic squids (Oegopsida). P. microlampas, for example, has a maximum size of 23 mm ML and short arms. One of the most distinctive features of the genus is the presence of a photophore on each eye that has a lid that can open and close over the organ. This photophore can produce a brilliant flash. The lid, presumably, allows a sudden beginning and end to the flash and, when closed, conceals the reflector that lies behind the photogenic tissue. Concealment is important as the reflector otherwise could reveal the squids presence in dark waters to predators that use luminescent search lights. A second pair of flashing photophores that lacks lids is located at the base of the gills. These latter organs are much larger than their counterparts in Pyroteuthis; the size difference is present in paralarvae and is helpful in distinguishing paralarvae of the two genera (Young, et al., 1992).

Members of the genus also have a distinctive hectocotylized arm that contains a peculiar toothed plate and large swollen regions containing folded, glandular tubes of unknown function (Chun, 1910).

Characteristics

1. Arms
   1. Arm hooks in one or two series depending on species.
   2. Less than 8 hooks/arm.
   3. Arms IV generally lack hooks (maximum two hooks present on right arm IV in male P. giardi).
   4. Left arm IV hectocotylized; toothed plate present.
      
      
2. Tentacles
   1. Tentacular club with four series of suckers; hooks absent.
      
      
3. Photophores
   1. Eyeball with a lidded photophore.
   2. Two or four separate photophores in tentacular stalk.
   3. Visceral photophores
      1. One anterior abdominal organ.
      2. Branchial organs larger than anal organs .
         
         
4. Oviducts
   1. Only right oviduct present.

Comments

Of the three species of Pterygioteuthis, P. giardi is the most distinctive. The major features  that separate it from the other species of Pterygioteuthis are:

1. the shape of the toothed plate on the hectocotylus.
2. the double, rather than single, series of arm hooks.
3. the lack of suckers on arms IV of females.
4. two rather than four tentacular photophores.
   

P. gemmata and P. microlampas are very similar but are separated by the larger size and greater number of arms hooks in the former.

Behavior

P. microlampas and P. giardi have been observed to produce a variety of different bioluminescent flashes with their lidded-ocular and branchial photophores. The latter photophores can be rotated to point the flash in different directions. These two pairs of photophores can flash for varying durations and in various combinations suggesting that flashing behavior which, presumably, deters predators is complex (Young, et al., 1982). P. giardi has also been shown to counterilluminate in the laboratory (Young, et al., 1980).

Distribution

Species of Pterygioteuthis are found throughout the tropical and temperate regions of the world's oceans but are virtually absent from the Mediterranean Sea. This map shows the general localities (white circles) where species belonging to this genus have been captured. Localities where pyroteuthids, other than Pterygioteuthis, have been captured are indicated by orange crosses. Only one record per locality is included (records listed here).

References

Chun, C. 1910. Die Cephalopoden. Oegopsida. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition, "Valdivia" 1898-1899, 18: 1-522 + Atlas.

Riddell, D. J. 1985. Enoploteuthidae of the New Zealand Region. Fisheries Research Bulletin. New Zealand Ministry of Agriculture and Fisheries, No.27: 1-52.

Young, R. E. 1972. The Systematics and Areal Distribution of Pelagic Cephalopods from the Seas off Southern California. Smithson. Contr. Zool., 97: 1-159.

Young, R. E., E. M. Kampa, S. D. Maynard, F. M. Mencher and C. F. E. Roper (1980) counterillumination and the upper depth limits of midwater animals. Deep-Sea Res., 27A: 671-691.

Young, R. E., K. M. Mangold and M. Vecchione. 1992. The enoploteuthid group of families. P. 55-66. In: Sweeney, M. J., C. F. E. Roper, K. M. Mangold, M. R. Clarke and S. V. Boletzky (eds.). "Larval" and juvenile cephalopods: a manual for their identification. Smithson. Contr. Zool., No. 513: 1-282.

Young, R. E., R. R. Seapy, K. M. Mangold and F. G. Hochberg. 1982. Luminescent Flashing in the Midwater Squids Pterygioteuthis microlampas and P. giardi. Mar. Biol., 69: 299-308.