Divariscintilla yoyo
ORDER
Veneroida
FAMILY
Galeommatidae
TAXONOMY
Divariscintilla yoyo Mikkelsen and Bieler, 1989, Indian River Lagoon, Fort Pierce Inlet, Florida, United States.
OTHER COMMON NAMES
None known.
PHYSICAL CHARACTERISTICS
Animal is globular, about 0.5 in (10–15 mm) in length, translucent white, with a small wedge-shaped, fragile, permanently gaping internal shell covered nearly entirely by external mantle folds. Anterior cowl is wide and flaring; there are two long retractable anterodorsal "cephalic" tentacles and a single short pallial tentacle next to the excurrent siphon on the posterodorsal midline. The foot is large and muscular with an elongated narrow posterior portion used in byssal attachment and "hanging" behavior. There are three to seven sensory flower-like organs on the visceral mass near the mouth.
DISTRIBUTION
Restricted to type locality, Indian River Lagoon in eastern Florida, United States.
HABITAT
Epibenthic; bysally attached to smooth walls of shallow-water sand burrows constructed by mantis shrimp Lysiosquilla scabricauda (Lamarck, 1818), in a commensal relationship.
BEHAVIOR
Yo-yo clams crawl in a snail-like fashion on a muscular foot, seeking a suitable vertical surface for attaching a short byssus thread secreted by a gland in the anterior portion of the foot. Once attached, the thread is picked up by a gland at the posterior tip of the foot, from which the animal then "hangs." Periodic contractions of mantle muscles for clearing the mantle cavity of waste products jerk the entire animal in the manner of a yo-yo.
FEEDING ECOLOGY AND DIET
Filter feeder; presumably benefits from currents generated by host mantis shrimp in its burrow as well as feeding on particles from the shrimp's predatory activities.
REPRODUCTIVE BIOLOGY
Simultaneous hermaphrodite; broods larvae in outer demi-branch and suprabranchial chamber; releases shelled, swimming veligers. Life span unknown.
CONSERVATION STATUS
Not listed by the IUCN, although restricted range near commercial harbor makes it particularly vulnerable to habitat alteration.
SIGNIFICANCE TO HUMANS
None known.
