StauroteuthisMartin Collins, Richard E. Young, and Michael Vecchione
A single genus and two species are currently recognized in the family. However similar octopods from outside the Atlantic Ocean have not been critically examined.
Stauroteuthids are peculiar, gelatinous cirrates with a mantle opening that forms a complete tube around the funnel. They also have peculiar gills and internal shells and a large web that is nearly equally developed between all arms. When observed from submersibles, this octopod commonly has its arms and web formed into a bell-shape (bell-shape posture). Sometimes when the octopod is disturbed, it will inflate the web and draw the arms together at their tips to form a "balloon" with the arms and web (balloon posture). These postures are thought to be involved in feeding and/or defense (Vecchione and Young, 1997).
A cirrate with ...
- long cirri and secondary webs.
- U-shaped shell.
- tubular anterior mantle.
- External morphology
- Anterior-posterior elongation of body pronounced; body extends well posterior to shell.
- Anterior mantle opening modified into a complete cyclinder formed by muscular mantle and encircling funnel base.(See "Comments" below.)
- Primary and secondary webs present.
- Web nodules absent.
- Cirri begin between suckers 2-6.
- Cirri length: Longest more than twice arm diameter.
- Cirri absent from arm tips. Cirri end before sucker 18-24.
- Suckers small, cylindrical.
- Suckers enlarged in male S. syrtensis.
- Beaks: See S. syrtensis.
- Mantle cavity
- Mantle septum
- Thick, open posteriorly.
- Olfactory organ
- Lies well inside of mantle cavity from free mantle margin. (See "Comments" below.)
- Gills have a diagnostic form. The secondary and tertiary lamellae are highly branching; the primary lamellae are difficult to recognize and don't form a symmetrical series along the gill; a large afferent vessel does not dominate the "top" of the gill.
- Internal anatomy
- Salivary glands
- "Anterior" salivary glands present.
- Digestive gland
- Digestive tract
- Simple U-shaped digestive tract.
- Large posterior lip glands present.
- Optic lobe
- Optic lobe spherical.
- Single optic nerve bundle passes through the white body.
- Salivary glands
- Mantle septum
- The shell is U-shaped.
One of the most unusual features of the family is the cyclindrical, muscular mantle opening. Stauroteuthis spp. are the only cirrates in which the free edges of the mantle fuse dorsally to form a tube. The two photos taken at the right in a aquarium show the tubular opening in one stage of contraction. The opening appears like an elevated ring around the base of the slender, protruding funnel. Judging from preserved octopods (see drawing below), this ring can be greatly extended. In other octopods, the mantle attaches anteriorly, on either side, to the cephalic cartilage; as a result the dorsal wall of the mantle cavity, in this region, consists of the head.
In a fresh, translucent Stauroteuthis (below), the pigmented mantle cavity has the shape of a bow tie due to the large, central unpigmented region occupied by the thick mantle septum and the pigmented extensions of the mantle cavity anterolaterally leading to the dorsal mantle cavity.
The two species are separated geographically (see below) but are very similar morphologically. Separation relies primarily on the differences in size and position of the suckers as seen in the following table:
|Max. sucker diam., mm||2.2-6||1.2-2.2||5.7-9.0||3.9-4.8|
|Position of largest suckers||12-16||1-3||9-14||9-14|
|Sucker index (rel. to head W.)||0.06-0.10||0.02-0.05||0.09-0.13||0.09-0.12|
Chunioteuthis Grimpe, 1916 is placed as a junior synonym of Stauroteuthis by Collins and Henriques (2000).
Submersible observations have been made on S. syrtensis and we assume that they apply to both species. S. syrtensis is commonly seen, when first approached, with the web inflated into a bell-shape (below left) with the arms separated from the primary web by the secondary web. A ballooning posture is occasionally seen (below right), usually following disturbance, in which the web is extremely inflated and closed at the arm tips.
Locomotion is via movement of the fins or the expulsion of water from the web. The latter method, however, is weak perhaps because of the loss of the strong connection of the web to the arms due to the presence of the secondary web. Small copepods have been found in the stomachs. This and the presence of large secretory lip glands suggest that mucous may be involved in the capture of prey. The above is summarized from Vecchione and Young, 1997.
Johnsen, et al. (1999) found that mechanical stimulation induced luminescence associated with the basal suckers of S. syrtensis (sex unknown). This is the only known case of bioluminescence in cirrate octopods and suggests that careful observations of living material may be useful. The function of the luminescence is unknown.
Presently stauroteuthids are known only from the Atlantic Ocean. They are thought to be benthopelagic in distribution (Collins and Henriques, 2000). That is, they are pelagic but reside in close proximity to the ocean floor.
Collins, M. A. and C. Henriques. 2000. A revision of the family Stauroteuthidae (Octopoda: Cirrata) with redescriptions of Stauroteuthis syrtensis and S. gilchristi. J. Mar. Biol. Ass. U.K., 80: 685-697.
Vecchione, M. and R. E. Young. 1997. Aspects of the functional morphology of cirrate octopods: locomotion and feeding. Vie Milieu 47(2):101-110.
Aberdeen University, Aberdeen, UK
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- Content changed 28 April 2008
Citing this page:
Collins, Martin, Richard E. Young, and Michael Vecchione. 2008. Stauroteuthidae http://tolweb.org/Stauroteuthis/20092/2008.04.28 in The Tree of Life Web Project, http://tolweb.org/. Stauroteuthis . Version 28 April 2008 (under construction).