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Ecology and Conservation

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Our colleagues at the Marine National Park Headquarters (MNPH) discovered a group of miniscule-sized, shrimp-like, bottom-dwelling crustacean creatures on a sea grass bed at the depth of 1m from the water surface during their conservation patrol trips around the Dongsha Lagoon. After the creatures were sampled, recorded, and submitted for further identification, it has been confirmed that the found species falls within the Malacostraca class, the Tanaidacea order (translated as 「原足目」or 「異足目」in Mainland China), and the Leptocheliidae family(likely the Leptochelia genus). It was not just the first time this species was discovered at the Dongsha Atoll National Park, but also there was yet to be any creature of that family recorded before in the Catalogue of Life in Taiwan。

Tanaidaceans make up a minor group within the crustaceans. More than 1200 species are recorded in this order. They can be found both in fresh water and in the deep sea. Yet the majority of them inhabit the marine environment and a particularly large number of species are found and recorded in the deeper layer of the ocean (at a depth of more than 200m.) Most of them are miniscule in size (2-5 mm in length) and are bottom dwellers. In terms of the appearance, their carapace covers the first two segments of the thorax, with the first pair of limbs in a claw shape. They have 6 ambulatory thorax segments, 5 abdominal segments, and 5 pairs of abdominal limbs, with a pair of uropods at the end of the final segment, while the shape varies by sex. The sample collected in Dongsha as illustrated in the picture is a terminal-age male insect with considerably long clawed gnathopods。

Figure 1. The Tanaidacean creature (Leptocheliidae) on the Dongsha sea grass bed resembles a shrimp at the first sight, but its flatter body shape and the unique uropods reveal its real identity.
Figure 1. The Tanaidacean creature (Leptocheliidae) on the Dongsha sea grass bed resembles a shrimp at the first sight, but its flatter body shape and the unique uropods reveal its real identity.


Research shows that tanaidaceans that inhabit the deep sea are diverse in species but are relatively small in their individual populations. In contrast, those that inhabit shallow water environments are less diverse in their species but are larger and more densely distributed in terms of their populations. It was observed this time at the Dongsha Lagoon area that there is a considerable number of populations in smaller areas, which is consistent with the observation presented in foreign studies。

In addition, the tanaidaceans do not undergo a true planktonic stage during their life cycle. The larva grows within the marsupium of the mother until it becomes a bottom dweller. Perhaps such ecological characteristic has limited the ability of its population to expand and migrate, so that the species found in different regions are often remarkably different from one another. The sea grass bed in the Dongsha Lagoon not only creates a unique grass landscape in the ocean, but also provides a supreme shelter and feeding environment for marine creatures with its lively green foliage. How many more tanaidaceans habitants are there on the Dongsha sea grass bed? What are their ecological characteristics? These little secrets and wonders in the sea all await our further discoveries。

Figure 2. The Dongsha sea grass bed is like a green magic carpet, attracting various kinds of creatures to inhabit it, while stimulating human beings’ curiosity and desire to explore the unknown
Figure 2. The Dongsha sea grass bed is like a green magic carpet, attracting various kinds of creatures to inhabit it, while stimulating human beings’ curiosity and desire to explore the unknown。

(Photos and texts by Chiang Chun Ting at the Planning and Management Section.)

 

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