Arrhoges occidentalis

Arrhoges occidentalis, common name the American pelicanfoot, is a species of medium-sized sea snail, a marine gastropod mollusk in the family Aporrhaidae, the pelican's foot snails or pelican's foot shells.[1]

Arrhoges occidentalis
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Caenogastropoda
clade Hypsogastropoda
clade Littorinimorpha
Superfamily:
Stromboidea
Family:
Aporrhaidae
Genus:
Arrhoges
Species:
A. occidentalis
Binomial name
Arrhoges occidentalis
(Beck, 1836)
Synonyms[1][2]
  • Aporrhais occidentalis (Beck, 1836)
  • Rostellaria occidentalis Beck, 1836
  • Aporrhais mainensis C. W. Johnson, 1926
  • Aporrhais occidentalis var. mainensis Johnson, 1926
  • Aporrhais labradorensis C. W. Johnson, 1930
  • Aporrhais occidentalis var. labradorensis Johnson, 1930

Morton (1956) considers Arrhoges occidentalis as the most primitive member of the family Aporrhaidae.[3]

Distribution

This species is distributed infralittoral, circalittoral and bathyal in the North West Atlantic Ocean and along the North American coast from Labrador and Massachusetts to off North Carolina. It lives on sand or mud at depths between 10 and 550 m. Off North Carolina it is usually found in deep water.

Description

The gray to yellowish-white shell is strong and has a high, pointed spire. Its length is between 4.1 and 6.4 cm (1⅝I -2½ inch) The shell has 8–10 well-rounded whorls, each of which shows many strong, curved axial ribs crossed by crowded, fine spiral threads (that may be worn away) on the outer layer. The body whorl contains 20–25 folds. The aperture is long and narrow. It has a thick, shiny white outer lip that suggests a triangular, winglike expansion. The parietal wall and the outer lip are thickened internally. The small operculum is horny and claw-shaped. It is narrow and has smooth edges.

The maximum recorded shell length is 70 mm.[4]

Habitat

The minimum recorded depth for this species is 3.5 m.; maximum recorded depth is 1829 m.[4]

Feeding patterns

The animal uses its proboscis to probe in muddy gravel or in sand, searching for food. It feeds on macro algae particles, benthic diatoms Pleurosignia sp., on detritus and also remains of animal matter, such as sponge spicules.

Life cycle

Sexes are separate or simultaneous hermaphrodites (but self-ferilization is usually prevented due to various mechanisms). Copulation occurs at night from March to April. The small eggs are deposited in the sand or on debris singly or in small groups by the female. The larvae hatch as free-swimming plankton-feeding individuals.

Predators

The American pelicanfoot has as potential predators the gastropod Colus stimpsoni Dall, 1902, the crab Cancer irrotatus Say, 1817 and the Atlantic wolffish Anarhichas lupus Linnaeus, 1758 . The well-developed outer shell lips of the adults give them an adequate protection against the claws of Cancer irrotatus.

gollark: As an upper bound for how good it is, maybe.
gollark: H.265 is *definitely* not... four times the "compression efficiency".
gollark: Although maybe not because of diminishing returns.
gollark: But I guess 2x the quality at 2x the bitrate seems completely plausible.
gollark: I've heard it can do up to maybe 50% *bitrate* savings.

References
  1. Arrhoges occidentalis (Beck, 1836). Rosenberg, G. (2010). Arrhoges occidentalis (Beck, 1836). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=531617 on 28 October 2010 .
  2. Marine biodiversity : Aporrhais occidentalis Beck, 1836. accessed 28 October 2010.
  3. Morton J. E. (1956). "The evolution of Perissodonta and Tylospira (Struthiolariidae)". Trans. R. Soc. N.Z. 83: 515–524.
  4. Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". PLoS ONE 5(1): e8776. doi:10.1371/journal.pone.0008776.

Further reading
  • Harald E. Rehder, Field Guide to North American Seashells, National Audubon Society, Ninth printing, 1996, ISBN 0-394-51913-2
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