Kuphus giant bivalve tube

Many years ago, while in a shell shop, I came across a large calcareous (calcium-carbonate) tube, about the size of a baseball bat. Although this tube resembled a giant "worm" tube, it is a tube made by an extant giant teredinid ("shipworm") bivalve that once lived in on the bottom of a muddy mangrove in tropical waters, most likely in the vicinity of the Philippine Islands.

The scientific name of this giant bivalve is Kuphus polythalamus (Linnaeus, 1767). It was originally by Linnaeus as Serpula polythalamia, but this name was later updated to Kuphus polythalmus. Yet, the incorrect spelling of the species name of Kuphus polythalamia is still used currently by many workers.



This first image shows the tube in question. This tube is 33 1/4 in. in length (the yardstick shown here is in inches).  The largest reported tube of K. polythalamus is 61 inches (155 cm) in length and 2.4 inches (6 cm) in diameter.

This image shows a closeup of the exterior of the tube near one of its ends, which is 2 in. in diameter.  


The life position of K. polythalamus is vertical  and with a tiny "Y" at its posterior end. Most of the calcareous tube is encased by the mud. At the anterior end of the tube (i.e., the widest part of the tube), there is a thin calcareous cap that covers the mouth of the bivalve. This cap must be resorbed periodically to allow the animal to grow. The cap had been removed by the time I got the specimen shown above. 

The maximum known size of Kuphus polythalamus is 155 cm (61 in. = about 5 feet) in length and 6 cm (2.4 in.)  in diameter. Thus, this bivalve is the largest known bivalve in the world. It lives in black, organic-rich muds (i.e., stinky) in mangroves/shallow bays in tropical and subtropical oceans in the Philippines, Indonesia, and Mozambique. This bivalve uses bacteria in its gills to convert hydrogen sulfide in the muds/water into nutrients. 

The top image above is a view somewhat downward into the tube and showing the incomplete posterior end of the shell I have. You can see the two holes for the siphons, side by side; one for intake of water, and the other for expelling water. Their fleshy ends would have extended into the water column above the calcareous tube. The branching part of the "Y" is at the narrowest part of the tube, where the two fleshy siphons stick out a short distance from the two holes, which as shown in the top image, are situated near the end of the tube, but within it. These siphons bring in water into the gills of the bivalve, and they can also expel water. 

The bottom image above is a view into down the anterior end of the tube, next to the mouth. A temporary cap at this wider end is missing. This end of the bivalve is stuck down into the mud during life. 

This giant bivalve is a member of the common wood-boring and wood-feeding bivalve family Teredinidae, which are among the least studied extant bivalves. Until recently, the biology of Kuphus polythalamus was very poorly known. You can now go online and watch a video all about this animal. Just type in the incorrect scientific name.

Kuphus has a fossil record of a few species, some of which are known from Oligocene/Miocene beds.

If you go online, you can watch a dissection of a K. polythalamus. It is taken from research by Distel et al. (2017). There is also a free pdf available for downloading.