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food hydroid


sp. #19
Tenellia sp. #19
Maximum size:  1.7 mm.

Identification:  This is a tiny, cream species with mottled rust-red pigment on the bases of the cerata.

Natural history:  The single known Tenellia sp. #19 was found on a hydroid-covered Nassarius splendidulus collected in a sand sample taken from a depth of 12-16 m (39-52 ft) in a Halimeda kanaloana bed. It was observed feeding on the hydroid (probably a Cytaeis sp.) while held. (Note 1) It was never observed to leave the host shell but moved to the apex of the shell when the snail burrowed. (see photos) When resting, it flattened itself out in the channel formed by the suture. When prodded, it "flared" its cerata and/or attempted to retreat beneath the sand surrounding the shell without leaving the shell's surface.

Distribution:  Maui.

Taxonomic notes:  It was first recorded in Hawaii from Black Rock, Maui by CP on April 15, 2005 and was formerly placed in the genus Cuthona.

Photo:  CP: 1.7 mm; on Nassarius splendidulus: Black Rock, Maui; April 15, 2005.

Observations and comments:

Note 1:  Two Nassarius splendidulus were collected in a sand sample on April 15, 2005. At the time of collection, it was noted that one of the shells had much better developed hydroids than the other. The latter animal was photographed and both were held in a dish with sand. On the 18th, additional photos were taken that showed little difference in the hydroid. The Tenellia was first noticed on April 23 and additional photos were taken on the 24th showing the greatly reduced hydroids. Subsequently, feeding on the hydroids was observed under the microscope. Perhaps, the Tenellia came in on the snail that already had reduced hydroids, then transferred to the snail with intact hydroids in the close proximity of the holding dish?
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