Transcript 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
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
USP Concrete Drains
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Diversity and abundance of neritids & thiarids
40 m stretch 600m from sea both genera
reach 800 individuals per m.
Thiarids in drain
Neritids in drain
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
Clithon
Male head with penis and penis pouch
Spermatophore
Operculum
Neritina
E. Male head with penis
Spermatophore
operculum
Septaria
 5 species in Fiji, 13
worldwide
 Prefer fast flowing
streams (Ovalau,
Taveuni)
 Distribution in stream
depends on shape
Septaria
Thiarids
 Found in ponds, drain,
rivers and strteams
 Melanoides
tuberculata now
worldwide
 Reproduction by
parthenogenesis – all
female
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
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
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)
Snails used as food
Conservation of Freshwater Snails
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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 downstream in
the Wailoa R.
Conservation of Freshwater Snails
 2. Cyclones and storms
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F. maculata population in Wainibuka R.
reduced to 250 m-2 from 1475 per m-2 after 2
cyclones in 1985