Dhimurru Rangers made a wonderful discovery last month when they stumbled upon a rather strange looking thing (see image below) on the beach at Banambarrnga (Rainbow Cliffs).
After much speculation as to what the thing could be (invertebrate?, jelly fish?, shark egg?),one of the staff emailed their daughter, a student in Marine Biology at James Cook University (JCU) who correctly identified it as an egg case of the World’s largest living snail; Syrinx aruanus, commonly known as the Giant Whelk, Australian trumpet or the False trumpet.
These giant snails live on sandy bottoms in the intertidal zone down to 50 metres water depth and have a range across the northern half of the Australian coastline extending into southern New Guinea and Indonesia. Where it has not been overfished, it is locally common. (Abbott & Dance, 1982).
This enormous marine gastropod can grow to a shell length of around 70cm, and can weigh in excess of 15kg. They are a carnivorous predatory snail, that feed on large tube-dwelling polychaete worms (some as much as one metre long); using their 250 mm proboscis, to get to the worms.
Mature females produce large (15cm) egg cases which they attach to rocks, shells or coral. Within the egg case, the young snails develop in individual egg capsules, then eventually hatch and crawl away as juveniles.
This type of life history is known as direct development (that is, the larvae are not released into the sea water). Direct developing molluscs such as these are subject to local extinction because there are no means of planktonic-stage re-seeding from other areas. This, and their popularity as ornaments or specimens make them a target species for protection.
Although rarely seen, juvenile specimens are sometimes washed ashore after storms and cyclones in our area.
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Information and Images Courtesy of the Queensland Government www.qm.qld.gov.au
"Ngilimurru bukmak djaka wangawu - All of us together, looking after country"