Breeding of Fraser's Rainforest Snail

Introduction

In September 2009 four adult Fraser's Rainforest Snails, Sphaerospira fraseri, were acquired by the Australian Museum from the Melbourne Museum (wild founding stock were collected from Mount Glorious, Queensland) for display in the My Photo Studiosection of the 2009 Wildlife Photographer of the Year. The snails were initially housed in a plastic holding terrarium approximately 20cm long by 12cm wide and 15cm high. Moistened 10cm deep peatmoss was provided, sprayed daily and a short length of 6cm diameter PVC pipe was provided as a hide.

In December the Adults were put on display along with five Rhinoceros Beetles, Xylotrupes gideon and a Saint Andrew’s Cross Spider, Argiope keyserlingi, in an Exo Terra terrarium, 45cm long by 45cm wide by 60cm high, with 12cm deep peatmoss substrate. Lighting used included a 5.0 UVB compact fluorescent bulb and a 40w heat bulb. The top of the terrarium is mesh aluminium with a small computer fan which helps circulate the air through the enclosure. The exhibit also featured a 20cm X 10cm piece of driftwood and a 30cm diameter Birds-nest Fern, Asplenium australasicum.

Breeding Biology

Like all snails this species is hermaphroditic, meaning that individuals possess both sperm and eggs. Mating occurs over night whereby the two snails exchange sperm to fertilise each other’s eggs (Murphy 2002). Both animals can then lay eggs. Eggs of native Australian land snails have been recorded both under logs and roots as well as beneath leaf little slightly buried in open area.

Captive Breeding Records

On the 28th of February (14 weeks from being acquired) 44 creamy-white eggs of a approximately 4mm diameter were found in the enclosure. All were found beneath the piece of driftwood, with approximately half clumped together in a shallow burrow 2cm deep and the remainder loosely deposited across the surface below the driftwood. All eggs were found within or on the moister section of the peat moss.

The eggs were collected by hand and placed in a plastic take-away food container on top of 2cm of damp peatmoss. The clumped eggs were removed intact and placed directly into the container. No holes were made in the lid and ventilation was provided only once a day when the lid was lifted to gently mist spray the eggs with water. The eggs were kept at room temperature until hatching.

Eggs first began to hatch on the 18th of March and the container was moved to the live animal room which has an ambient average temperature of 21oC. The same container was used and spraying continued daily. On the 22nd of April the container was placed inside a plastic terrarium 15cm long by 10cm wide and 12cm high. The plastic top had 2mm wide gaps so a section of aluminium flywire was placed between the terrarium and the lid to prevent the young snails from crawling out.

Care of young

An enclosure was setup on the 18th of April, in the same terrarium, to resemble that of the adult snails. Four centimetres of damp peatmoss was placed on the bottom and a thin layer of leaf litter spread on the top. A 6cm diameter plastic lid with a 1cm gap cut in the side was added as a hide. At this time 32 surviving snails were recorded, all had approximately 4mm diameter shells and head to tail lengths of approximately 6mm.

Diet

The hatching snails were fed on the same diet as the adult snails; 'Mollusc Mix' a special blend originally produced by the Zoological Society of London to raise the endangered Partula Snails of French Polynesia (Henderson et al. 2008). Mollusc mix is specially formulated to provide protein, vitamins, calcium and other nutrients to snails and slugs which usually feed on fungi and algae in the wild. Additionally, Cuttlebone (the hard internal skeleton of another kind Mollusc; Cuttlefish) is provided as a source of calcium which snails need for healthy shell growth. A variation of mollusc mix has been developed for use at the Australian Museum.

Mollusc mix recipe used at the Australian Museum:

• 1 cup rolled oats
• 1 cup grass seeds
• ¼ cup koi pellets
• 1 tablespoon vitamin Powder
• 1 tablespoon calcium carbonate Powder
• 1 tablespoon tropical fish food with spirulina

The ingredients are blended into a fine powder then mixed with water and 5ml of liquid vitamin E to form a thick paste which can be frozen and then thawed, added with more water and mashed into a fine paste as needed.

Ten grams of Mollusc mix is presented to the hatchlings on a 4cm diameter plastic bottle top every three days. The food is placed under the plastic hide, where the snails spend most of their daylight hours.

Observational Notes

Like the adults, young snails are mostly active at night. Small trails of slime are present on all surfaces and the tiny snails can be found dormant in the upper corners of the terrarium. Around 90% of the snails congregate together beneath the plastic hide, although few are ever sighted on the feed dish and only one or two animals are emerged from their shells when the animals are inspected by lifting the hide.

To ensure all snails have equal oppertunity to feed, the snails would be collected on a weekly basis and placed on the food bowl. When left undisturbed the tiny snails emerge and feed, then move off from the feed dish.

So far the greatest challenge in raising the young of S. fraseri, is maintaining adequate high humidity without promoting mould growth which can cause health problems in molluscs. To counteract this, the flywire top is used to provide maximum ventilation, while at the same time being sprayed every day.

At the time of posting, the snails have once agian began to lay eggs in their display in My Photo Studio, this breeding behaviour could be stimulated by the exposing the animals to a slight drop in temperature caused by moving them into the exhibition space. 

References

Henderson, A, Henderson, D. and Sinclair J. 2008. Bugs Alive! A Guide to Keeping Australian Invertebrates. Museum Victoria. Melbourne.

Murphy, M. 2002. Observations on the behaviour of the Australian land snail Hedleyella falconeri (Gray 1834) (Pulmonata: Caryodidae) using the spool-and-line tracking technique. Molluscan Research. Vol 22: 149-164.