branchia
regeneration error
on food sponge
mating?
with egg mass
Goniobranchus sp. #1
Maximum size: 50 mm (Kay & Young, 1969).
Identification: This is a broad, flattened species with a white notum densely reticulated in red, a yellow marginal band, yellow rhinophores and orange-lined gills. The notum is decorated by a series of enlarged, dome-shaped pustules with violet-red tips. The latter feature distinguishes it from the similar appearing Goniobranchus petechialis and Goniobranchus sp. #5.
Natural history: Goniobranchus sp. #1 is commonly seen in moderately protected to exposed rocky habitats at depths of 6-60 m (20-197 ft). It is nocturnally active but may also be found under rocks, crawling on sand, or resting in the open on shaded cliffs during the day. Scott Johnson reports it apparently feeding on a white sponge but we've seen it associated with a yellow species showing feeding damage. It lays a light peach egg mass.
Distribution: Big Island, Maui, Molokai, Oahu, Kauai and Niihau: widely distributed in the Indo-Pacific.
Taxonomic notes: Although labeled in various sources on-line as a form of Goniobranchus tinctoria, this appears to be a distinct species based on the enlarged hemispherical pustules on the notum, its solid-yellow rhinophores and its nocturnal habits. It is listed as Chromodoris petachialis in Bertsch & Johnson, 1981 and Kay, 1979. Although Kay, 1979 suggests that it was first reported from Hawaii in Pease, 1860 as Doris reticulata, it seems more likely that that name refers to Sclerodoris sp. #1, instead. It may have been first found in Hawaii on Oahu in the 1960s as reported in Kay & Young, 1969 (as C. petachialis). However, the photograph illustrating the species in that paper appears to be of Chromodoris sp. #5 while the description may conflate the two. The photograph illustrating C. petachialis in Kay, 1979 is clearly this species. It's listed as Chromodoris sp. 1 (corrected in 2019 printing) and referred to as the "red-spotted nudibranch" in Hoover, 1998 & 2006.
Photo: PF: Makena, Maui; 2007.