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GALLERY



 
Tambja morosa
(Bergh, 1877)
 
Tambja morosa
Maximum size:  about 76 mm (Hoover, 2006).

Identification:  This distinctive animal has a dark greenish-black body decorated with bright turquoise spots and bands. In some animals the branchia have blue-green highlights. (Note 1)

Natural history:  Tambja morosa is a moderately common dorid in moderately exposed to highly exposed rocky habitats, particularly shaded cliffs. Rarely it may be found in Halimeda kanaloana beds. It occurs from about 3-36 m (10-120 ft). It lays an orange egg mass and feeds on a blue bryozoan. (Note 2)

Distribution:  Big Island, Maui, Lanai and Oahu: widely distributed in the Indo-Pacific.

Taxonomic notes:  It was first recorded in Hawaii at Puako, Big Island by Scott Johnson on May 19, 1978. It is referred to as the "gloomy nudibranch" in Hoover, 1998 & 2006.

Photo:  John Hoover:  Magic Island, Oahu; Oct., 1997.

Observations and comments:

Note 1:  Animals with blue-green highlights on their branchia are common in the western Pacific. However, the pattern was first reported in Hawaii in spring, 2013. Subsequently, it rapidly increased and, by the fall of 2014, the majority of animals found in Maui waters were that form. Perhaps, this is due to a recent introduction of larvae from the western Pacific (either natural or by humans)? Or, perhaps the change is the result of a "genetic switch" that's dependent on temperature or some other environmental factor?

Note 2:  At the sites we frequent, this species was fairly common in the late 1980s. Then, it became difficult to find for about 20 years. From 2011 to 2013, however, it became increasingly common and has remained so through 2017. That makes it a good example of long term population swings in nudibranchs. Our subjective impression is that the population increase is associated with a substantial increase in its food bryozoan.
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