Thuridilla bayeri (Marcus, 1965)

Thuridilla bayeri is common in the Marshalls; we have found more than 80 specimens at Enewetak, Kwajalein, and Utirik Atolls. The species was originally described based on specimens from Bikini Atoll, also in the Marshalls. Most specimens have been on lagoon reefs and pinnacles, where they are usually under or crawling on dead coral from the intertidal to depths of at least 15 meters. Some consider this species a form of Thuridilla gracilis. However, we have seen quite a number of both species and they seem consistently different. T. bayeri always has the row of blue or turquoise spots along the sides of the parapodia. Also, the eggs are a bit different. According to my notes, in T. bayeri egg masses, the individual eggs measured about 80Ám in capsules of about 110Ám diameter, and the eggs were piled two deep around an orange extra-capsular yolk string. In T. gracilis, eggs averaged around 115Ám in relatively large capsules of 230-245Ám, and spiralled singly around the orange extra-capsular yolk string.

The specimen below was found on a Kwajalein Atoll lagoon pinnacle on 27 September 2009.

The one below as found on 26 May 2013 on a Kwajalein lagoon reef.

Create 22 January 2007
Updated 6 August 2013

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