Planctoteuthis oligobessaRichard E. Young and Clyde F. E. Roper
Planctoteuthis oligobessa is a small species (maximum size = 76 mm ML). It can be separated from subadults of other members of the genus by the small fins and few suckers on arms IV. Little is known of its biology.
DiagnosisA Planctoteuthis with ...
- 2-4 suckers on each arm IV.
- 2-4 suckers on each arm IV.
- Arm lengths: Arms I: 32-39% of ML (subadults); arms I: 24-25% of ML (adults); arms III: 47-61% of ML (subadults). arms IV: 121-135% of ML (subadults); arms II-IV 29-39% of ML (adults).
- Large arm suckers with 25-35 small, narrow, blunt teeth on distal 3/4 of ring.
- Clubs bilaterally symmetrical in shape.
- Club length 12-18% of ML.
- Suckers without teeth on inner ring.
- Clubs without keels.
- Locking apparatus with slender antitragus consisting of a single lobe.
- Length 23-33% of ML.
Paratype Paratype Holotype Sex -- -- Female Mantle length 34 34 76 Mantle width 11 11 28 Fin length 7 8 14 Fin width 12 -- -- Length, arm I 12 11 19 Length, arm II 15 15 27 Length, arm III 18 16 29 Length, arm IV 46 41 30 Club length* 6 4 -- Arm IV sucker count (left / right) 3 / -- 3 / 2 2 / 3
Individuals of Planctoteuthis taken in trawls invariably show a broken gladius at the posterior end of the fin. The existence of a long and decorative tail was not known until ROV photographs captured insitu images. These images were taken by the Monterey Bay Aquarium Research Institute. The ventrally bulging eyes identify it as Planctoteuthis and the locality off California strongly suggests that it is P. oligobessa. The function of the tail is unknown although Vecchione et al. (1992) noted that the tail of Chiroteuthis (see Chiroteuthidae page) causes the young squid to resemble certain siphonophores suggesting protective mimicry.
This species was originally described as Valbyteuthis oligobessa. Valbyteuthis is now placed in the synonomy of Planctoteuthis (Young, 1991).
The holotype is a gravid, mated female with mature ovarian eggs of 1.5 mm in diameter. Spermatangia were found within the ovary. Fertilization, apparently, is internal.
Figure. These two images of, presumably, P. oligobessa are apparently much older than those shown previously judging by the heavy pigmentation. Both images could be of adult squid, especially the bottom one with the damaged tail. Both images: © 2011 MBARI.
The vertical distribution of P. oligobessa off southern California extends from 700 - 1200m (the maximum depth of the trawling program). The highest capture rate occurred in the 1100-1200 m zone and this species was one of the deepest living cephalopods taken in this program (Roper and Young, 1975). There is no difference between daytime and nighttime distributions.
P. oligobessa has been described only from the waters off southern California and northern Baja California; Nesis (1982/87) indicates that the distribution extends to Indonesian waters.
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- Content changed 22 November 2011
Citing this page:
Young, Richard E. and Clyde F. E. Roper. 2011. Planctoteuthis oligobessa http://tolweb.org/Planctoteuthis_oligobessa/19496/2011.11.22 in The Tree of Life Web Project, http://tolweb.org/. Version 22 November 2011 (under construction).