Surrounded by ocean on all sides, Taiwan is rich in ocean resources. Because of their striking colors and forms, sea slugs are known as “undersea jewels” and they often attract the attention of divers. Sea slug is the common name of the subclass Opisthobranchia in the Class Gastropoda of the Phylum Mollusca. This subclass includes nine orders in which nudibranchs (order Nudibranchia) are common in Taiwan. Nudibranchia is divided into four suborders: Doridina, Dendronotina, Aeolidina, and Arminina.
In Order to introduce the beauty of the marine life, Chunghwa Post is releasing a set of four stamps featuring Mexichromis multituberculata, Chromodoris willani, Gymnodoris ceylonica, and Glossodoris averni of the nudibranch suborder Doridina. The stamps were released on June 8, 2011. The designs were as follow:
1. Mexichromis multituberculata (NT$5): A species of sea slug in the family Chromodorididae, Mexichromis multituberculata has an ovate creamy white body, with purple-tipped tubercules on the back and purple, or sometimes orange-yellow, spots on the mantle edge. It has lamellate-shaped rhinophores. The upper halves of its secondary gills and rhinophores are purple. It can be found in the coral reefs off the northeast coast of Taiwan and Penghu.
2. Chromodoris willani (NT$5): A species of sea slug in the family Chromodorididae, Chromodoris willani has an elongate-ovate bluish-gray body with black spots or longitudinal stripes. Its soft bluish-gray to white mantle has no obvious tubercules and its width is larger than the body. A black spot is often presented between the lamellate-shaped rhinophores. Its secondary gills and rhinophores are translucent brown with small white spots. It can be found in the coral reefs off Kenting, Green Island and Orchid Island.
3. Gymnodoris ceylonica (NT$12): A species of sea slug in the family Gymnodorididae, Gymnodoris ceylonica has a cylindrical body, pointed at its posterior end; body is translucent white with small orange-red spots. It has a narrow mantle skirt. Its secondary gills are white with orange lines. Gills and rhinophores are non-retractile. Its gills are feathery and located around its anus in a circle or in an arc. The sea slugs shown in the stamp are mating. They exchange sperms with their genitalia and female ducts both located on the right side of their bodies. After mating, they separate to lay the fertilized eggs. They can be found in the coral reefs off Kenting and Green Island.
4. Glossodoris averni (NT$25): A species of sea slug in the family Chromodorididae, Glossodoris averni has an elongate-ovate white opaque body. Its mantle is smooth and wide, with orange frilly edge. Its foot also has orange edges. Its rhinophores are lamellate-shaped. Secondary gills and rhinophores are deep orange-red or crimson. It can be found in the coral reefs off Kenting.
The issued stamps were designed by Michael Hin-Kiu Mok, professor at the Institute of Marine Biology, National Sun Yat-sen University, and painted by the marine life artist Mr. Jheng Yi-lang.The stamps were printed by China Color Printing Co., Ltd. in color offset.
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