young, 6 mm
possible egg mass
Pleurobranchus varians Pease, 1860
|Maximum size: about 65 mm.|
pleurobranchid is covered with closely spaced conical
tubercles. A few scattered tubercles are noticeably larger than the
others and the background color ranges from light orange to dark
wine-red. The amount of white pigment is highly variable with many
lacking it entirely and some being almost completely white. (Note 1) In those
with only scattered white spots, the white pigment is concentrated on
the dorsal faces of the larger tubercles creating the illusion that
they are longer than they appear to be in dark individuals.
animals, the tubercles are poorly developed and the rhinophores have
white tips.The smaller tubercles and
lack of contrasting dark tubercles distinguish it from Pleurobranchus cf. peronii.
varians is a common nocturnal species found in moderately
protected to highly exposed rocky habitats and, occasionally, in Halimeda kanaloana beds. It occurs
in tide pools and subtidally to depths of 15 m (50 ft). Like many
pleurobranchs, it may autotomize portions of its mantle if disturbed.
it's rhinophores rhythmically while crawling and lays a cream egg mass
with a ruffled upper margin that hatches in about four days in the
Big Island, Maui, Oahu, Kauai and French Frigate Shoals: also reported from Vanuatu and the Philippines.
peronii in Kay, 1979 is of the dark form of this
species, instead (as is the photo in Kay & Schoenberg-Dole, 1991). Although Kay, (1979) suggests that it is
unidentifiable and Goodheart, et. al. (2015) suggests that it's an indeterminate Berthella sp., it seems possible that Pleurobranchus
marginatus Pease, 1860 is actually a small juvenile of P. varians. Goodheart, et. al. (2015) separates this species from Pleurobranchus albiguttatus (Bergh, 1905) and it was probably first reported in Hawaii by Pease in 1860.
light: Makena, Maui: July 6, 2008.
Observations and comments:
1: We've seen dark and
white-spotted animals paired under rocks on several occasions. (see photo) Also,
both color forms have identical flattened, wedge-shaped shells. Those
observations support placing them in the same species. The ratios between the color forms vary greatly from site to site
(and from year to year at a given site) suggesting that diet or some other environmental factor may play a role
in determining the pattern.