Rossia pacifica


Rossia pacifica (Berry, 1911) Stubby Squid, Short Squid
Synonyms: None
Phylum Mollusca Class Cephalopoda Subclass Coleoidea Superorder Decabrachia Order Sepiolida Family Sepiolidae
	Found in Friday Harbor, WA. Picture taken at Rosario Beach Marine Station, WA
	Photo by: Robbie Wheeling, July 22, 2002

Description: Sepiolids (along with squid) differ from octopus by having 2 tentacles along with the 8 arms (photo) and by having fins on their sides. The tentacles have suckers only on pads near their end. Their suckers are also on stalks instead of sessile. They differ from squid in having a body not much longer than wide, wide, rounded fins that attach along most of the body length (photo), their hectocotylus arms are dorsal, and their tentacles can be retracted into a pocket. The maximum dorsal mantle length of Rossia pacifica is about 5 cm in females and about 3-4 cm in males. The total length (including arms but not tentacles) of females is about 11 cm, of males is about 9 cm. The mantle is only about 1.5-2 times as long as it is wide, flattened above and below, rounded behind, and it is not fused to the head in the front. The fins are round with broad free lobes, almost as long as the mantle. The head is large and the arm lengths are variable. Usually the dorsal arms are the shortest and the third arms are the longest. The arm suckers are arranged in two rows in the proximal and distal portions of each arm (photo), and in two, three, and four rows in the middle portion. The suckers are alike in size on all arms except those of the dorsal arms of the male, which are hectocotylized with much smaller suckers. The tentacles may be extended longer than the body or retracted into a socket. The tentacles have slender terminal clubs (pads) bearing centrally up to eight partial rows of small suckers with chitinized teeth (photo). The animal color in life is a reddish brown above and pale below, or wholly opalescent greenish gray if disturbed.

How to Distinguish from Similar Species: No similar species.

Geographical Range: This species ranges along the north Pacific rim from Japan to southern California.

Depth Range: This species is benthic in coastal waters, subtidal (16-370 m) but on rare occasions at night found swimming at the shore in the intertidal zone.

Habitat: This species is fairly common on bottoms of sand or muddy sand.

Biology/Natural History: These small sepiolids crawl on their arms or swim, and dig shalow depressions in the sea floor in which they rest with their arms rolled under their heads. They inhabit shrimp beds. Over 80% of their diet consists of shrimp, although crabs, mysids, small fishes, and cephalopods are also eaten. Spawning occurs in the summer and fall in deep water. Each egg (4-5 mm in diameter) is contained in a large (8 mm by 15 mm) capsule. The capsules are attached singly or in small groups to seaweeds or other objects on the bottom.


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References:

Dichotomous Keys:
   Carlton, 2007
   Jorgensen, 2009
   Kozloff, 1987
   Scott and Blake, 1998

General References:
Morris et al., 1980
Norris, 2003

Scientific Articles:

Hochberg, F.G., 1998. Class Cephalopoda: Taxonomic Atlas of the Benthic Fauna of the Santa Maria Basin and the Western Santa Barbara Channel. Volume 8 part 1: The Aplacophora, Polyplacophora, Scaphopoda, Bivalvia and Cephalopoda, pp. 1-250. P.V. Scott and J.A. Blake, Editors. Santa Barbara Museum of Natural History, Santa Barbara, CA, USA

General Notes and Observations: Locations, abundances, unusual behaviors, etc.:
Nine species of dicyemid mesozoans have been recorded from the kidneys and branchial hearts of R. pacifica. Of these, only two are known to occur off the west coast: Dicyemennea brevicephaloides and D. parva.

Rossia This individual, with body length about 7 cm long not including tentacles, was also collected by otter trawl in the San Juan Channel. Photo August 2011 by Dave Cowles

This recently deceased individual, captured at 100 m depth by otter trawl in the San Juan Channel, has one tentacle extended past the arms. The petri dish the animal is in is 15 cm diameter. Although the animal is unresponsive its chromatophores are still changing colors. Photo by Dave Cowles, July 2022

This side view of the same individual shows the short body and rounded fins characteristic of this species. Photo by Dave Cowles, July 2022

This species typically remains on or near the bottom or buries in the sediment. This view of the animal's under (ventral) side shows its lighter pigmentation there and its excurrent siphon. Note also that the edges of the mantle cavity are free. Photo by Dave Cowles, July 2022

Here is a close-up view of one of the arms of the same individual. The scale is millimeters. Photo by Dave Cowles, July 2022

This closeup of the tentacle pad shows its different shape. The suckers are lined with yellowish flexible chitinous sheaths that no doubt help them fasten more tightly onto prey. The scale is millimeters. Photo by Dave Cowles, July 2022.

Authors and Editors of Page:
Anna Dyer (2002): Created original page
Edited by Hans Helmstetler 12-2002, Dave Cowles 2005

Rossia pacifica (Berry, 1911)

Stubby Squid, Short Squid