The association between the fruit of the modern-day, low-coastal (tidal estuarine), jungle-dwelling, nipa palm (Nypa fruticans Wurmb) and ocean-dwelling mussels (clams) is not one that you would expect to find hundreds of kilometers from the nearest palm trees (at 11°S in Australian oceanic waters). Yet, they do co-occur!
Example of a typical low-tidal estuarine environment habitat of the modern nipa palm (image derived from Wikipedia).
Nipa is one of the oldest angiosperm plants and probably the oldest palm species. It first appeared during the late Cretaceous (Maastrichtian Stage) 56 mya (million years ago) and had a pan-tropical distribution until middle Miocene time (13 mya). Fossilized nuts of confirmed Nypa dating to the early Eocene occur in deposits of the London Clay.
Nipa palms originated in Indonesia, Malaysia, Philippines, Thailand, and Papua Guinea. It is native to the Indian and Pacific Oceans. The genus is montypic because N. fruticans is its only member.
Unlike most palms, the nipa palm’s trunk grows beneath the ground. Only the leaves and stalk grow above ground. The leaves of the plant extend up to 9 m in height, and its flowers, are red or yellow in color. The fruit is made up of many seeds arranged in tough, spiky fibrous clusters, up to 25 cm (10 inches) in diameter. Each cluster (ball) has its own stalk. Eventually, each ball detaches from its stalk and can float away on the tide.
The clusters have to be ripped apart, and each cluster yields many large nuts. It takes skill, much effort, and a strong cutting tool (machete) to expose the nuts (see videos on YouTube and Wikipedia).
Two attached bivalves (mussels) of Aphrodita longissima in situ on a nipa-nut cluster (figure from Loch, 1990).
Other bivalves found today that can attach to nipa nuts include Adipicola longissima (Theile and Jaekel) and Idasola coppingeri (E.A. Smith).
Due to limited production, widespread other-crop cultivation, and a lack of harvesing practices, as well as deforestation and habitat destruction have put the Nipa palm at risk.
Several mollusks [e.g., 2 bivalves—Crassostrea and Brachiodontes; nine gastropods (including Nerita, Littoraria, and Tegula); 2 barnacles (including Lepas); and 1 chiton] have also been reported as associated with nipa rafts floating in the ocean (Raven, 2019)
It is suspected that these nuts and other wood trawled by these oceanographic ships were derived from Papua rather than the Australian mainland. Nipa palm nuts can float for considerable distance and duration.
Oceanographic research vessels cruising in tropical waters occasionally find shallow-marine bivalves living on the ends of nipa nuts. These cruises typically occur in the open-ocean areas overlying 1600 m of water!
REFERENCES CONSULTED
https://www.youtube.com/watch?v=BEQZ-kpo905g
en.wikipedia.org 2024.
Ian Loch. 1990 (February). Mussels on nuts. Australian Shell News, no. 69, a newsletter of the Malacological Society of Australia, pp. 1-2.
Raven, J.G.M. 2019. Notes on molluscs from NW Borneo-dispersal of molluscs through nipa rafts. The Festivus 5, issue 1, pp. 1-10.
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