Saturday 9 December 2017

Acutogordius taiwanensis: A new species of Horsehair Worm from Taiwan.

Horsehair Worms, Nematomorpha, are parasitiod Worms related to Nematodes, but with a rather more complex life-cycle. The adult worms are extremely long, sometimes exceeding two meters in length, but seldom more than a millimetre in width, and are found in marine and freshwater ecosystems. The larval stages of these Worms are parasites, growing inside the bodies of other animals, and typically have a two-host life-cycle, with the young Worms infecting a secondary host shortly after hatching, then modifying the behaviour of this host so that it is more easily consumed by the primary host, inside which the Worm reaches maturity, emerging as an adult, typically with fatal consequences for the host. In freshwater Horsehair worms this primary host is typically a terrestrial invertebrate such as an Insect, enabling the Worms to reach new bodies of water and avoid seasonal drying of habitats.

In a paper published in the journal ZooKeys on 6 July 2017, Ming-Chung Chiu of the Department of Entomology at the National Taiwan University, Chin-Gi Huang of the Department of Earth and Life Science at the University of Taipei, and Wen-Jer Wu and Shiuh-Feng Shiao, also of the Department of Entomology at the National Taiwan University, describe a new species of Horsehair Worm from Taiwan.

The new species is placed in the genus Acutogordius, and given the specific name taiwanensis, meaning 'from Taiwan'. These Worms were found at a number of locations in Taiwan, with the primary hosts being a range of Crickets and Katydids and the secondary hosts being aquatic Snails. Adult male Worms reach 428 mm in length and 1.079 mm in width, though most are somewhat smaller, while females reach a maximum of 432 mm in length and 1.120 mm in width. Both are light brown in colour and covered in mucus.

Anterior end of Acutogordius taiwanensis. (A)–(C) Images of the anterior end showing the (A) white cap and dark-brown collar and (B)–(C) white spots scattered on the brown collar (D)–(F) SEM images of the anterior end surface that is (D) smooth (E) smooth but wrinkled on the tip with holes scattered on the dark-brown collar, and (F) wrinkled (A)–(F) are images from the same individual, respectively. Scale bars 500 μm (A)–(C), and 200 μm (D)–(F). Chiu et al. (2017).

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