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FRESHWATER SNAILS IN FIJI

FRESHWATER SNAILS IN FIJI. By Alison Haynes. Main Families. NERITIDAE Genera:Neritina, Clithon, Septaria 22 species Male and female individuals THIARIDAE Genera: Melanoides, Thiara 10 species Origins in South East Asia. Distribution of Neritids and Thiarids.

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FRESHWATER SNAILS IN FIJI

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  1. FRESHWATER SNAILS IN FIJI By Alison Haynes

  2. Main Families • NERITIDAE • Genera:Neritina, Clithon, Septaria • 22 species • Male and female individuals • THIARIDAE • Genera: Melanoides, • Thiara • 10 species • Origins in South East Asia

  3. Distribution of Neritids and Thiarids • Originated in South East Asia • Island hopped northwards (less) & southward • (most) and a few eastwards • Solomon Islands 28 species, 24 Fiji, 16 Samoa, 9 French Polynesia

  4. USP Concrete Drains • Diversity and abundance of neritids & thiarids • 40 m stretch 600m from sea both genera reach 800 individuals per m.

  5. Thiarids in drain

  6. Neritids in drain

  7. Neritina & Clithon • Difficult to tell apart • If spines present, must be Clithon • But not all Clithons have spines • All have operculum with longitudinal ridge/groove • Penis with penis sac

  8. Clithon • Male head with penis and penis pouch • Spermatophore • Operculum

  9. Neritina • E. Male head with penis • Spermatophore • operculum

  10. Septaria • 5 species in Fiji, 13 worldwide • Prefer fast flowing streams (Ovalau, Taveuni) • Distribution in stream depends on shape

  11. Septaria

  12. Thiarids • Found in ponds, drain, rivers and strteams • Melanoides tuberculata now worldwide • Reproduction by parthenogenesis – all female

  13. Other Species • Species with southern, • Australian or New Zealand relatives • Physastra nasuta • Fluviopupa pupoidea is endemic to Fiji • 4 mm high • Genus in Vanuatu, New Caledonia, Rapa Island • Lord Howe Island

  14. Endemic Thiarid, Fijidoma maculata • Found in inland Viti Levu in headwaters of Rewa & Ba rivers. • Shaped like a neritid for living in swift current. • Population in Wainibuka, Wailoa & • Ba rivers • Endangered

  15. Endemic Species, Acochlidium fijiense • Found only in Nasekawa R., Vanua Levu • Related to marine nudibranchs • One of the rare species found in freshwater. • Other species in Palau & Flores (Indonesia)

  16. Snails used as food

  17. Conservation of Freshwater Snails • Main threats • 1. Siltation caused by • logging of forests • road making • cultivation of steep hillsides • 2.Cause silt and grit to cover stream bottom • and the algal film on which the snails feed • E.g. cleaning tail race at Wailoa power station decimated F. maculata population downstreamin the Wailoa R.

  18. Conservation of Freshwater Snails • 2. Cyclones and storms • F. maculata population in Wainibuka R. reduced to 250 m-2 from 1475 per m-2 after 2 cyclones in 1985

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