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Pleurobranchus grandis
Pease, 1868
 
Pleurobranchus grandis
Maximum size:  about 300 mm. (Hoover, 2006); perhaps as large as 800 mm (Kay, 1979).

Identification:  The notum of this species is covered with a tile-like pattern of flattened tubercles composed of rings of smaller tubercles surrounding larger central ones. Hawaiian animals appear to range from dark red brown to deep violet although cream and cream spotted animals are common elsewhere in the Indo-Pacific. Very young animals are cream with violet-brown tipped tubercles that are less developed than in mature animals. Clusters of tubercles are separated by a network of white lines that disappear as the animal matures.

Natural history: On Maui, Pleurobranchus grandis is a moderately rare species that we've found at moderately exposed to exposed rocky sites at depths of 5-10 m (15-33 ft) as well as in moderately protected sand habitats at 18 m (60 ft). However, it's listed as "fairly common at depths of about 30 m (98 ft)" in Kay, 1979 and has also been photographed to depths of 74 m (243 ft) by HURL submersibles. Rarely, it can be found in tide pools. Like Pleurobranchus forskalii, it usually caries the posterior portion of its mantle in a siphon-like fold (see photo).

Distribution:  Maui and Oahu: Widely distributed in the Indo-Pacific.

Taxonomic notes:  The description of Pleurobranchus violaceus Pease, 1864 in Kay, 1979 appears to refer to this species. Goodheart, et. al. (2015) tentatively lists Pleurobranchus violaceus Pease, 1863 as a synonym of P. grandis. However, it also seems possible that Pease's animals were Pleurobranchus peronii (due to ambiguity in the description and the likely depth of collection). It's listed as Pleurobranchus sp. 2 in Hoover, 1998 and is referred to as the "tiled pleurobranch" in Hoover, 1998 & 2006.

Photo:  Scott Johnson: about 150 mm: found by Stan Jazwinski; Kihei, Maui; Aug., 1977.

Observations and comments:

Note 1:  ( )
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