INVENTORY OF FLORA AND FAUNA OF MYANMAR:
A FRONTIER OF ASIAN BIODIVERSITY

Botanical and zoological surveys in Myanmar: Marine invertebrates

Surveys of marine invertebrate fauna were conducted four times between 2017 and 2020 in the Myeik (Mergui) Islands, which extends in the Andaman Sea off the peninsular region of the southern Myanmar. Hiroshi Saito and Toshihiko Fujita of the Department of Zoology surveyed marine benthic organisms focusing on mollusks and echinoderms.　

The sea of the Myeik Islands

The sea of the Myeik Islands is tropical and have well-developed coral reefs (left). Seagrass beds are widely found in shallow waters near the shore (right).

Survey sites and method

The surveys were conducted by scuba diving and snorkeling. There were a total of 62 survey sites, 30 of which were surveyed by scuba diving.

Survey by scuba diving

Marine invertebrates of the Myeik Islands

• 1. Magnificent sea anemone, Heteractis magnifica (Cnidaria, Anthozoa)
• 2. Penguin wing oyster, Pteria penguin (Mollusca, Bivalvia)
• 3. Coriocella nigra (Mollusca, Gastropoda)
• 4. Mole cowrie, Cypraea talpa (Mollusca, Gastropoda)
• 5. Hypselodoris pulchella (Mollusca, Gastropoda)
• 6. Common hairy crab, Pilumnus vespertilio (Arthropoda, Malacostraca)
• 7. Granulated sea star, Choriaster granulatus (Echinodermata, Asteroidea)
• 8. Banded sea urchin Echinothrix calamaris (Echinodermata, Echinoidea)

Results of surveys

Mollusks: Polyplacophoran (Chiton) fauna

Polyplacophora (Chitons) are mollusks with eight shells on their backs. During the surveys, 132 specimens in total were collected and they were classified into 20 species in 15 genera of 8 families. Eight of these species were recorded for the first time in the Andaman Sea, three of which were undescribed species. One of the undescribed species was described as a new species, Leptochiton myeikensis Saito & Aung, 2021.

A new species of the chitons, Leptochiton myeikensis Saito & Aung, 2021.

This species was described based on single specimen collected from a depth of 15 m at Maung Yin Island. Among 140 extant species of this genus known in the world, only five species have been known from tropical shallow waters. A, B. specimen in life, dorsal and ventral views; C, D. specimen in preserved condition, ventral and lateral views; E. underwater photograph. Scale bar: 1 mm.

Echinodermata

Echinoderms (Phylum Echinodermata) are spiny-skinned marine invertebrates with pentamerous body, and consist of beyond 7000 species. They include 5 classes: Crinoidea (sea lilies), Asteroidea (sea stars), Ophiuroidea (brittle stars), Echinoidea (sea urchins), and Holothuroidea (sea cucumbers).

Brittle stars were the most abundant in the surveys. In particular, the family Ophiotrichidae was found to be highly diverse, with some undescribed species. Many species are commonly found in Myanmar and in subtropical Japan. Genetic comparisons of Ophiothela danae, which have a unique life style of clinging to gorgonian corals (Cnidaria, Octocollaria), revealed that individuals from the Andaman Sea and from Japan are exactly the same species, and that geographical genetic differences are very small.

The complete mitochondrial genome sequence of 16,410 bp of Euapta godeffroyi (Sytaptidae), known as a very-long-bodied holothurian, was revealed. The result contributes to indicate that two sea cucumber families, Synaptidae and Chiridotidae are sister clades and that the Order Apodida composed of these two families is monophyletic.