I had the distinct privilege of hearing Gerald Heslinga of Indo-Pacific Sea Farms discuss Tridacna clam aquaculture while at NextWave. Tridacnids are of particular interest to me, as I find them to be both gorgeous and individually unique, not to mention I’ve owned and gawked at a countless number of them throughout the years, so I found the presentation to be quite entertaining. Continuing on with the clam discussion from this past weekend, I’ve stumbled across a great video from Gerald and Indo-Pacific Sea Farms.
The video above focuses on four species of giant clam, T. crocea, T. maxima, T. derasa, and Hippopus hippopus since each can be found in the home aquarium and each represents a different type of morphology. The crocea and maxima clams are grouped together because they both have a wide byssal opening. This opening is located on the ventral side, or bottom, of the clam and is the area where the foot and byssal threads emerge to keep the clam attached to hard substrate. Because the area is so large, it is the clam’s most vulnerable spot. In the wild, these two species solve this problem by burrowing into the rocks, but in the aquarium their ability to achieve this protection depends entirely on where the hobbyist places them. A crocea or maxima clam in the sandbed is particularly exposed, especially since that’s where a majority of pests and predators occur.
The next two clams on the list are T. derasa and H. hippopus. They differ from the maxima and crocea clams in that they have a tiny, if almost non-existent bysall opening. As juveniles, these openings do exist to a greater extent, but as the clams age the opening closes. In the wild, derasa and hippopus clams live on sandy substrates and can grow quite large. For these reasons, neither of these two clams rely much on their byssus, and both are less prone to parasites and predators getting access to soft tissue via the bottom of the clam. In addition to a tiny byssal opening, H. hippopus has a thick shell and a shell hinge that comes together almost like a zipper. Because of this, hippopus clams are the “most predator- and parasite-resistant of the giant clams in mariculture operations and probably in aquariums as well”.
The take-home message to all of this is placing clams on the correct substrate is crucial to their long-term health and stability. Clams are very hardy and easy to care for, however predators and pests can find their way into your aquarium along with your clam.