FRESHWATER SNAILS IN FRESHWATER SNAILS IN FIJIFIJI

By Alison HaynesBy Alison Haynes

Main FamiliesMain Families

NERITIDAENERITIDAE Genera:Neritina, Clithon, Genera:Neritina, Clithon,

SeptariaSeptaria 22 species22 species Male and female Male and female

individualsindividuals THIARIDAETHIARIDAE Genera: Melanoides,Genera: Melanoides, ThiaraThiara 10 species10 species Origins in South East AsiaOrigins 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 Diversity and abundance of neritids &

thiarids 40 m stretch 600m from sea both

genera reach 800 individuals per m.

Thiarids in drainThiarids in drain

Neritids in drainNeritids in drain

Neritina Neritina & & ClithonClithon

Difficult to tell apartDifficult to tell apart If spines present, must If spines present, must

be be ClithonClithon But not all But not all Clithons Clithons

have spineshave spines All have operculum All have operculum

with longitudinal with longitudinal ridge/grooveridge/groove

Penis with penis sacPenis with penis sac

Clithon

Male head with penis and penis pouch

Spermatophore

Operculum

Neritina

E. Male head with penis

Spermatophore

operculum

SeptariaSeptaria

5 species in Fiji, 13 5 species in Fiji, 13 worldwideworldwide

Prefer fast flowing Prefer fast flowing streams (Ovalau, streams (Ovalau, Taveuni)Taveuni)

Distribution in stream Distribution in stream depends on shapedepends on shape

Septaria

ThiaridsThiarids

Found in ponds, drain, Found in ponds, drain, rivers and strteamsrivers and strteams

Melanoides Melanoides tuberculatatuberculata now now worldwideworldwide

Reproduction by Reproduction by parthenogenesis – all parthenogenesis – all femalefemale

Other SpeciesOther Species

Species with southern,Species with southern, Australian or New Zealand Australian or New Zealand

relativesrelatives Physastra nasutaPhysastra nasuta Fluviopupa pupoidea is Fluviopupa pupoidea is

endemic to Fijiendemic to Fiji 4 mm high4 mm high Genus in Vanuatu, New Genus in Vanuatu, New

Caledonia, Rapa IslandCaledonia, Rapa Island Lord Howe IslandLord Howe Island

Endemic Thiarid, Endemic Thiarid, Fijidoma maculataFijidoma maculata

Found in inland Viti Found in inland Viti Levu in headwaters of Levu in headwaters of Rewa & Ba rivers.Rewa & Ba rivers.

Shaped like a neritid Shaped like a neritid for living in swift for living in swift current.current.

Population in Population in Wainibuka, Wailoa &Wainibuka, Wailoa &

Ba riversBa rivers EndangeredEndangered

Endemic Species, Endemic Species, Acochlidium Acochlidium fijiensefijiense

Found only in Found only in Nasekawa R., Vanua Nasekawa R., Vanua LevuLevu

Related to marine Related to marine nudibranchsnudibranchs

One of the rare One of the rare species found in species found in freshwater.freshwater.

Other species in Palau Other species in Palau & Flores (Indonesia)& Flores (Indonesia)

Snails used as foodSnails used as food

Conservation of Freshwater SnailsConservation of Freshwater Snails

Main threatsMain threats 1. Siltation caused by1. Siltation caused by logging of forestslogging of forests road makingroad making cultivation of steep hillsidescultivation of steep hillsides 2.Cause silt and grit to cover stream bottom2.Cause silt and grit to cover stream bottom and the algal film on which the snails feedand the algal film on which the snails feed E.g. cleaning tail race at Wailoa power station E.g. cleaning tail race at Wailoa power station

decimated decimated F. maculata population F. maculata population downstreamdownstream in in the Wailoa R.the Wailoa R.

Conservation of Freshwater SnailsConservation of Freshwater Snails

2. Cyclones and storms2. Cyclones and storms F. maculata F. maculata population in Wainibuka R. population in Wainibuka R.

reduced to 250 mreduced to 250 m-2-2 from 1475 per m from 1475 per m-2-2 after 2 after 2 cyclones in 1985cyclones in 1985