Rostanga pulchra MacFarland 1905

Rostanga pulchra lay their eggs in a spiral egg ribbon, which contains individual egg capsules that usually hold only one egg. The eggs will develop in the capsules for about 16 days, and can enlarge to about 160 microns. When the eggs hatch from the capsules, the pair of velar lobes have cilia that are used for movement, with the subvelar ridge containing shorter cilia. The larval foot is covered in cilia (possibly for sensory), with the pedal ciliary rejection tract running down the midline (used to reject food). The mantle begins as a fold near the shell edge, and as the shell grows, the mantle is moved both dorsally and laterally to create a mantle cavity. The veliger begins to develop eyes at about day 20, and pigmentation increases in the eyes as it ages. Rhinophores develop anteriorly to the eye spots very quickly. Once the veliger larvae have developed the propodium, eyespots, rhinophores, and dorsal papillae, they are considered competent larvae and are ready to metamorphose when exposed to their food group (Ophlitaspongia pennata)(Chia & Koss, 1978).

How to Distinguish from Similar Species: Aldisa sanguinea, which lives from Oregon to Baja California and also feeds and lives on red sponges, has perfoliate rhinophores.

On and around red sponges

Geographical Range: Point Craven, Alaska to the Gulf of California; Chile, Argentina

Depth Range: Intertidal to 102 m

Like all dorid nudibranchs, this species has a circle of gills around a mid-dorsal anus. Rostanga pulchra has no large dorsal outgrowths other than the rhinophores and gills but it does have tubercles scattered all over the dorsum. The gills can be completely retracted into sheaths. The color is red to orange-red, sometimes with a few tiny brown or black spots on the dorsum. The overall shape is oval, though it may taper toward the rear. The outermost papillae along the margins of the dorsum may have white pigment. The rhinophores have 10-12 vertically oriented leaves and end in slender papillae. The rhinophores and gills are the same orange color as the dorsum, although there may be white tips on the gills. Length to 1.6 cm.

Biology/Natural History: This species feeds on, and is often found on, red sponges such as Acarnus,Esperiopsis,Ophlitaspongia, and Plocamia. It lays its eggs in a tight orange circle on the sponges March to October. The larvae are planktonic for 30-45 days, then settle. An encounter with at least one prey sponge, Ophlitaspongia pennata, can induce larvae to settle. It is believed that its orange pigment comes from the sponge. Adults can locate and navigate to distant Ophlitaspongia sponges by smell. Some individuals seem to stay quite close to one area while others range for distant sponges. Predators may include the flatworm Notoplana acticola. The cephalaspidean predatory nudibranch Navanax inermis is repelled by secretions from Rostanga.

Rostanga pulchra is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Discodorididae.