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Tuatara: Volume 32, April 1993

Some Observations on Egg Development and Captive Rearing of New Zealand Minute Landsnails (Mollusca: Hydrocenidae, Endodontidae)

page 28

Some Observations on Egg Development and Captive Rearing of New Zealand Minute Landsnails (Mollusca: Hydrocenidae, Endodontidae)


Minute Landsnail eggs were collected in the field and incubated indoors. Successful batching of eggs was recorded for Serpho kivi (Gray), Phenacohelix giveni (Cumber), Therasia traversi (E A Smith). Omphalorissa purchasi (Pfeiffer), Flamulina perdita (Hutton), and Paralaoma species. Apart from Serpho kivi which was observed ovipositing, the actual date of laying was not known. Some notes on the life span of sub-adult snails collected in the litter are included.


There is an almost total lack of basic life history data on New Zealand landsnails. “For the numerically dominant Punctidae and Charopidae we do not know feeding specialisations, length of life, breeding seasons, annual or seasonal fluctuations in numbers.” to quote Solem et al. (1981) This paper records some opportunistic observations on the hatching times, growth rates, and life span of 22 species of minute landsnails from four North Island localities.

Methods and Locations

Hakirimata Range, Tainui Biological Region, Raglan District. Infomap 260-S14 973896 150 m.

Eggs were collected on 28 March 1982. The initial group of eggs was taken because it was possible to date the laying. A mature Serpho kivi was seen just completing laying a cluster of pellucid eggs in deep wet litter on the ground. The eggs were transferred carefully with Tawa (Beilschmiedia tawa) leaves from adjacent litter. Extra litter was taken to prevent desiccation. The litter was housed in a 1.2 litre glass jar with lid, and daily examination and records were kept. The jar was kept in a room with good overhead light but no direct sunshine. Successful hatching occurred, so further collections of eggs were studied in the same fashion. A light mist spray was used spasmodically to maintain suitable moisture levels. If no snails were visible on inspection of the jar it was put briefly into sunlight.

This proved to be a good method of making the snails more active. Occasionally a check was made at night but active snails were seen infrequently. After eight months when there was no longer any sign of activity, the litter was checked again and then dried out. (Test ended 16 November 1982.)

Okareka. Northern Volcanic Plateau, Rotorua lakes. Infomap 260-U16 026304 400 m.

Small transparent eggs were collected on 10 April 1984 in a mamaku fern stem (Cyathea medullaris) 30 cm off the ground. Extra litter was collected but care was taken to leave reasonable visibility in the jar. Many slime trails formed on the glass. The upper trails were removed with damp tissue on two occasions.

Minginui, East Volcanic Plateau, Whirinaki District. Infomap 260-V18 321725 400 m. A raft of flattened bluish eggs were collected 20 April 1984 - on bark. Small oval eggs were collected from the ground at the same time. Loose litter was also added to maintain moisture levels and provide food.

Kaimai, Roberts Farm, Northern Volcanic Plateau, Otanewainuku District. Infomap 260-U15 731679 220m. A collection of gelatinous, transparent eggs was page 29 made on 18.5.89 and smaller eggs were subsequently discovered in the extra litter. This egg batch was only monitored until 25 July 1989, and on 23 September 1989 all landsnails present were dead.


Serpho kivi. Eggs of this species from Hakirimata provided the most complete data on development, since their time of laying was known. These eggs darkened after 21 days and hatched after 58 days. When the litter was dried out only three shells were found. The maximum number of animals seen moving around the jar was 3, although a minimum number of 12 eggs had been collected.

Five weeks after hatching the snails gathered on the lid of the jar. They continued to move to a lesser extent but returned to the lid to rest. One snail died after 106 days. Two lived 132 days. The small shell was broken, the others measured 1.5 mm, 1.4 mm. Adult diameter 8.5–10.0 mm. (Powell)

Seven S. kivi from Kaimai hatched after only 30 days after collection. They moved around in the litter and one was recorded dead on the lid after 31 days. The remaining 6 were alive and on or near the lid at 38 days, but were not checked again.

Omphalorissa purchasi. Four hatchlings of this species from Okareka were seen after 61 days. The eggs had not been seen in the litter, and the snails lived in the litter for 280 days. Omphalorissa purchasi were not measured, the shells were missing when the litter was dried out.

Phenacohlix giveni. Twenty three hatchlings appeared after 25 days on 4 May 1984. Three died after 114 days, and one lived 171 days. The maximum measurement was 3.9 mm — one complete body whorl plus 2 riblets. Powell gives width as 5.00–6.00 mm. This indicates a growth-rate from hatchling to half-grown in less than six months in captivity. The colour pattern appeared after 39 days, before the first riblet formed. It was fortuitous that a succession of the fungus Mycena miniata, a toadstool, grew in the jar and was eaten by two species of snail. The Phenacohelix juveniles were frequently seen resting close by the fungus. The stipe of the fungus was eaten more than the cap. One Therasiella neozelanica was also seen adjacent to the Mycena. This food was not available for the second batch of Phenacohelix juveniles which hatched on 1 August 1984. This was 107 days since collection (time of laying unknown). These snails lived a minimum of 35 days and were not seen after this. Measurements were 0.9 mm, no riblets.

Therasiella neozelanica (Cumber). Two snails inadvertently collected in the litter were seen moving for 244 days.

At no time did the membranous plaits on the periostracum collect litter or dirt. For illustration see Cumber (1967). Growth was almost imperceptible during the period of captivity. Some plaits were damaged or missing when measured: 2.5 mm–3.0 mm. Maximum diameter of adults is 4.0 mm including plaits, (Cumber 1967).

Paralaoma sp. three snails were collected in the litter and seen for 143 days, but no trace of shells was found in the litter when dried.

Also present in the litter when it was collected were — Laoma marina (Hutton) lived 212 days, diameter 3.1 mm. Adult diameter 3.5 mm.

“Mocella” maculata lived 294 days, diameter 2.6 mm. Adult diameter 3.2 mm.

The following observations are all from the Minginui sample.

Therasia traversi. Thirty five eggs hatched after 38 days. They were all dead 63 days later, and lack of food was the most likely cause. The bark took up much space in the jar and therefore less litter was available to hatchlings. Colour pattern was showing after 27 days. Measurements were diameter 1.5–2.0 mm. Adult diameter 12.0 mm.

page 30
Paralaoma sericata. Three eggs hatched after 113 days in the jar. These were seen up to 28 days later but not again. On checking dried litter they appeared to have grown on for a further 42 days. Collected in the litter by chance were the following species, all were dead 36 weeks later.
Huonodon pseudoleiodon (Suter)11.4 mm
Paralaoma lateumbilicata (Suter)11.1 mm
Cavellia buccinella (Reeve)22.3 mm, 2.7 mm
Paralaoma new species 2910.8 mm
Live snails seen during the observation period, but shells not found at the count included:
Therasia traversi6
Huonodon hectori (Suter)1
“Mocella” maculata2
Paralaoma n.sp.11
Paralaoma sp2
Charopa montivaga (Suter)1
Phenacohelix sp2

This would indicate that shell breakdown occurs in moist litter in a terrarium.

The final group of snails appeared in the Kaimai sample:

Flamulina perdita. 105 hatchlings emerged from the smaller eggs in the litter after 39 days (17 June 1989). Two weeks later 38 had migrated to the lid of the jar, but 30 were dead within two days. Five remained alive 39 days after hatching and were still growing. The smallest measured were 0.7 mm and the largest were 1.2 mm in diameter. Maximum diameter of adults 5.75 mm.

The following group were alive after 71 days:
Allodiscus urquharti (Suter)21.2 mm, 1.3 mm
Therasiella neozelanica (Cumber)21.0 mm, 1.4 mm
Paralaoma n.sp. 293 (1 broken)0.8 mm, 0.9 mm
Paracharopa goulstonei (Climo)11.1 mm
Laoma serratocostata (Webster)20.9 mm, 1.0 mm
Cavellia buccinella10.9 mm


It is possible to incubate minute landsnail eggs indoors without elaborate equipment and ultimately build up data on behaviour and feeding habits of particular snails. As no carnivorous snails were kept in captivity, the snails surviving longer periods found sufficient food on the leaf litter enclosed.

The small red-coloured fungus Mycena minata was a good food source for Phenacohelix giveni.

Eggs which showed blue colouration when collected hatched more quickly and it was observed that further colour changes occurred near hatching. For this reason only transparent eggs should be collected in order to gather more accurate data on hatching times. In this study the egg stage varied from a minimum of 25 days to a maximum of 113 days. Eggs of two arboreal species were included in these observations. Although laid at ground level, the newly hatched snails migrate upwards at 14 days in F. perdita, and 35 days in S. kivi.

Juveniles of Flamulina perdita may be more food specific than S. kivi with the result that they migrate earlier. Very small F. perdita have been observed at about 1 m and higher on the bark of Podocarpus totara and Dacrycrpus dacrydioides. Small snails included in the litter by chance are able to live for several months in captivity. Since they do not aestivate they can be assumed to be getting sufficient food and moisture. Seven to nine months was recorded for several species.

The growth-rate of Therasiella neozelanica in captivity was imperceptible page 31 (measurement was not possible without damage to incubating eggs) for seven months suggesting a life span of three or more years.


I would like to thank Dr. F. Climo for assistance, identification and encouragement over a number of years and Dr. G. Gibbs for editorial advice and comments.


Cumber, R. A. 1967: The Genus Therasiella (Mollusca - Flanmulinidae) in the North Island Mainland with descriptions of three new species. Transactions of the Royal Society of New Zealand. Zoology. 10: 61–70.

Powell, A. W. B. 1979. New Zealand Mollusca. (Collins).

Solem, A., Climo, F. M. & Roscoe, D. J. 1981. Sympatric Species diversity of New Zealand land snails. New Zealand Journal of Zoology 8: 453–485.