Today, I’m bringing you an unassuming, juicy little sea snail that is very common on the rock shelves and pools of the Illawarra coastline. The mulberry whelk, Tenguella marginalba.
This little whelk is appropriately named for the shell’s black nodules and contrasting furrows that give it a berry-like appearance. They are roughly the size of a mulberry too, growing to a maximum of three and a half centimetres.
Although they are sweet looking, mulberry whelks are predators in the intertidal zone of north and eastern Australia. They use a hard, file-like modified tongue called a radula to bore a hole into other molluscs. As they bore into the shells of their prey with their radula, mulberry whelks release sulfuric acid-laced saliva to hasten the erosion of the calcium carbonate that composes the shell. Their favourite prey tend to be oysters and limpets, as well as barnacles, if the former two aren’t available on the menu.
The mulberry whelk shares its habitat and eating habits with another common snail, the cart-rut snail. But unlike the cart-rut snail, which ranges away from the rock shelves in search of prey, mulberry whelks stay and forage in the safety of their home in the rock crevices and cracks. The snails are able to stay in their cosy nooks even at low tide when the rock dries out, due to the presence of a leathery operculum, otherwise known as the snail’s front door. You’ll also see mulberry whelks in estuarine environments, where they tend to cause problems for oyster farmers by boring into the oysters and eating them before they can be harvested for our own plates.
I love a good taxonomy story and as I researched the mulberry whelk, two different genus names kept popping up: Morula and Tenguella. FYI, taxonomy is the practice of classifying and naming species and species groups. The genus is the first part of the scientific name describing a group of similar species, like Homo for humans, and the species name, sapiens, is the second part of the scientific name, describing a single species.
A little digging and I found out why there were two different names coming up for this one little snail. The snail was originally described in 1832 by a guy called Henri-Marie Ducrotay de Blainville who, besides having a long-winded name, was a failed painter-cum-comparative anatomist who was trained by taxonomy royalty: Cuvier and Lamarck. Then in 1965, the genus containing the mulberry whelk species was delineated and named Tenguella. Another taxonomist came along in 1985 and synonymised the genus Tenguella with the genus Morula (from the Latin morus, meaning mulberry).
Taxonomic names regularly go through changes and revisions as new information or new species come to light. Since the advent of ‘DNA barcoding’ (a method of classifying species based on their individual genetic signatures) in the 90s, genetic data has greatly impacted the field of taxonomy.
In 2013, researchers studied the genetic signatures of 52 similar species within a subfamily of whelks1. The researchers found that the whelks classified as Tenguella, then merged with Morula were, in fact, a genetically distinct group, despite a lack of morphological distinction. In the taxonomic equivalent of a dog chasing its tail, the group of seven species, including our mulberry whelk, had their genus name reinstated to Tenguella.
So there you have it, the little mulberry whelk you’ve probably walked over countless times is a 200-year-old taxonomic puzzle!
1. Martine Claremont, Roland Houart, Suzanne T. Williams, David G. Reid, A molecular phylogenetic framework for the Ergalataxinae (Neogastropoda: Muricidae), Journal of Molluscan Studies, Volume 79, Issue 1, February 2013, Pages 19–29, https://doi.org/10.1093/mollus/eys028