Two Aplacophoran Subclasses

Neomeniomorpha (Solenogastres): The creeping neomenioids retain a narrow foot in a ventral groove which begins anteriorly as a pedal pit. They have a papillate, a sensory supraoral vestibule, a single midgut organ combining stomach and digestive gland, serial sets of lateroventral muscle bands, they are simultaneous hermaphrodits and lack ctenidia in the mantle cavity. The photograph shows the pedal groove of Helicoradomenia sp. collected from a Pacific hydrothermal, deep-sea vent.

Helicoradomenia sp. Photo by A. H. Scheltema

Chaetodermomorpha (Caudofoveata): Chaetoderms lack a foot and pedal groove. They possess either a nearly or entirely cicumoral sensory cuticular shield, the midgut is separated into a stomach and glandular digestive diverticulum, serial sets of lateroventral muscle bands lacking, they are dioecious and chaetoderms possess one pair of ctenidia in the mantle cavity. This shows Chaetoderma canadense collected from St. Margaret's, Nova Scotia, Canada.

 Chaetoderma canadense   Photo by R. Robertson.

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