Opisthobranch of the Week Data
I consider Madrella sanguinea to be uncommon on Okinawa, although I've collected a total of twenty individuals and have seen perhaps an additional half dozen since the first specimen was collected on the 19th of February, 1993. Both the collected twenty specimens as well as the observed animals were from beneath Tengan Pier. I've seen these animals at no other site on Okinawa. Quite remarkably, the majority of all animals were collected in the plankton, within a meter of the bottom during low visibility conditions brought about by moderately rough water conditions. It was difficult to assess the reason for their suspension in the plankton; possibly they were dislodged from the pier pilings above by wave action. They appeared to be neutral in the water and not actively precipitating out of the plankton to the underlying sediments.