Platydoris inframaculata (Abraham, 1877)

Location: Pulau Bali, Indonesia
Date: 2006/10/17
Length: 150mm
Depth: 16.0m
Water temperature: 28.0℃

Description

A large dorid nudibranch reaching 63–180 mm in body length. The dorsum (notum) is mottled with white, pink, and brown, providing camouflage on sandy substrates. The ventral side, by contrast, is brightly coloured: a clean white ground bears scattered red splash-like markings of varying size on both the mantle and the foot, and along the mantle margin a row of small red dots is overlaid by an orange to yellow band. This vivid ventral pattern is the defining feature of the species. Some individuals show a variant pattern in which the ventral ground is whitish to greyish and bears large dark-brown spots arranged in a ring-like pattern, with red and orange tones reduced or absent.

Distribution

Type locality: Ambon Island, Indonesia. The original description (Abraham 1877) was based on a single preserved, decolorised specimen from Ambon. Subsequent records extend the species across the Indo-West Pacific, including the Philippines, Sri Lanka, Tanzania, New Caledonia, and the Red Sea. The species inhabits sandy and coral-rubble substrates.

Etymology

From Latin infra (below) + maculata (spotted), in reference to the conspicuous markings on the ventral side.

Remarks

The dorsal coloration is similar to that of the congener Platydoris ellioti, and the two species are frequently confused from dorsal images alone; the brightly coloured ventral pattern (white ground with red splashes and an orange-yellow marginal band) is the decisive distinguishing character. Because the species was described from a single decolourised preserved specimen, the interpretation of its living coloration was historically uncertain, but the ventral pattern is now widely accepted as the defining trait.