bivalves text index | photo index
Phylum Mollusca > Class Bivalvia > Family Mytilidae
Nest mussel
Arcuatula senhousia
Family Mytilidae
updated May 2020
Where seen? This tiny mussel appears to be seasonal on our Northern shores. Sometimes, it is very common, forming spongy carpets over vast areas of the shore near the low water mark, as well as on large boulders. At other times, it is not seen at all. It was previously called Muscuslita senhousia.

It is described as an opportunistic species characterised by fast growth and unique ability to colonise both hard and soft surfaces. On hard surfaces, it settles among other creatures that live there. On soft surfaces, the little mussels weave their byssal threads into an all-enclosing nest forming dense mats that can hold more than 2,000 individuals in one square metre. These mats rapidly change sandy bottoms into mud flats as they retain silt. Colonies fluctuate widely and unpredictably.

Mats coating boulders and the ground.
Pulau Sekudu, Dec 07

These tiny mussels can form vast mats.
Chek Jawa, Aug 07

Pulau Sekudu, Jul 07
Features: 1-2cm long. The two-part shell is thin, fragile and smooth. These tiny mussels build communal 'nests' out of byssal threads incorporating sediments, bits of broken shells and other debris. Large areas can be covered in such 'nests', pockmarked with little slits, each housing one mussel. These can carpet rocks or soft bottoms.

Sometimes confused with Little black mussels which are also small, but black and while they may also produce a kind of 'nest', this is not as thick and spongy as the mats created by the Nest mussels.

Pasir Ris, Feb 09

Photo shared by Loh Kok Sheng on his blog.
Friends and enemies: Sometimes, small Green mussels (Perna viridis) are seen growing among the tinier nest mussels. Animals seen on the mussels include Drills, Sand stars, flatworms: possibly eating them? Several times, Hairy spoon seagrass were seen growing on nest mussel beds.

Plain sand star seen on a nest mussel bed.
Pasir Ris, Feb 09

Silt flatworm seen on a nest mussel bed.
Changi, Jul 12
Hairy spoon seagrass growing on a nest mussel bed.
Changi, Jun 12

Human uses: These mussels are considered pests where they establish themselves outside their natural range, e.g., in New Zealand and California. They probably arrived as larvae carried in the ballast water of ocean-going ships. In China and Thailand, they are an inexpensive food and also used to feed poultry, shrimp and fish.

Nest mussels on Singapore shores
On wildsingapore flickr



  • Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore (pdf), Raffles Museum of Biodiversity Research, National University of Singapore.
links | references | about | email Ria
Spot errors? Have a question? Want to share your sightings? email Ria I'll be glad to hear from you!
wildfactsheets website©ria tan 2008