Busyconid whelks first appeared within the waters of jap North America throughout the early Oligocene, about 32 million years in the past, in what was then the Mississippi Sea and is now the Mississippi River Basin. Because the oceans receded from the Mississippi, they unfold into the Gulf of Mexico and are actually discovered between Massachusetts within the north and the Yucatan Peninsula within the south. Aside from an launched inhabitants of the channeled whelk Busycotypus canaliculatus that has turn out to be established in San Francisco Bay in California because the Thirties, the household has by no means been discovered elsewhere. These are remarkably massive snails: smaller examples are nonetheless greater than 5 centimetres in size, and the most important of all get near a foot (Petuch et al. 2015). Mature shells have a big physique whorl, typically increased than the seen spire, with an extended siphonal canal. SCulpture of the shell, if current, is dominated by spiral components, and the shoulder of the whorls could also be marked by outstanding carinae and/or spines. As is customary for neogastropods, the classification of this group has shifted round a bit through the years, whether or not handled as their very own household or as a subfamily Busyconinae of the associated households Buccinidae or Melongenidae. In a current overview of the busyconids, Petuch et al. (2015) recognised fifteen dwelling species in six genera. The variety of fossil species that has been described is considerably bigger (over 100); not surprisingly, these massive strong shells have a wonderful fossil report. Nevertheless, it’s price noting that a number of the dwelling species could also be remarkably variable in shell morphology and I do not know whether or not fossil representatives have been topic to the identical systematic scrutiny.
All busyconids are predators on bivalves, notably on burrowing clams. Generally, the whelk envelops its sufferer in its muscular foot after which makes use of the sting of the shell lip to open the clam’s shell, permitting the whelk to insert its radula and rasp out the clam’s flesh. The popular technique of opening the shell is determined by the species of whelk and could also be classed as ‘wedging’ and ‘chipping’. ‘Wedging’ is essentially the most easy technique and believed to be the extra primitive; wedgers insert the shell lip into the hole between valves and instantly pressure them aside and/or forestall the clam shell from closing. ‘Chipping’ is extra concerned and carried out by members of the genera Busycon and Sinistrofulgur. On this technique, the sting of the whelk shell is rhythmically pounded in opposition to the commissure between the clam shell valves, progressively carrying on the valve margins till sufficient of a gap has been made to insert the radula. The method could take a number of hours of affected person hammering. Chipping requires extra energy and a heavier shell than wedging (chipping whelks could injury their very own shell in addition to the prey’s) but in addition permits the whelk to assault thicker-shelled clams.
Although every species of busyconid will typically use one or the opposite technique of opening prey, there are borderline examples. Bigger people of Busycotypus canaliculatus, normally a wedger, could undertake a course of like chipping although their assaults on the prey shell are normally much less systematic than true chippers. And whereas I have not discovered anyplace that claims as a lot, I believe that younger chippers could spend the sooner components of their life as wedgers untill they’ve developed the shell power for chipping. Dietl (2004) instructed that chipping behaviour could have originated twice amongst busyconids, based mostly on the fossil proof of its traces left on clam shells. The trendy chippers seem to derive from a single origin within the later Pliocene. Nevertheless, proof of an earlier and now seemingly extinct chipping lineage was additionally present in shells from the late Miocene. These earlier chippers seemingly didn’t belong to any of the fashionable chipping genera which aren’t recognized from the Miocene deposits through which chipped clams have been discovered. As an alternative, Dietl proposed that the perpetrator was a big Busycotypus.
Busyconid whelks have lengthy been of significance to folks dwelling in areas the place they’re discovered. Not solely are the shells eye-catching and decorative objects in themselves, the animals are additionally harvested for meals (although their meat is usually bought underneath deceptive names akin to ‘conch’ or ‘clam strips’). Archaeological examples have been discovered of busycon shells getting used for instruments; Petuch et al. (2015) illustrate an instance of a left-handed whelk Sinistrofulgur sinistrum shell with holes drilled into it that may have allowed it to be hooked up to a stick and used as a shovel. These animals are really an icon of North America’s jap seaboard.
Dietl, G. P. 2004. Origins and circumstances of adaptive divergence in whelk feeding habits. Palaeogeography, Palaeoclimatology, Palaeoecology 208: 279–291.
Petuch, E. J., R. F. Myers & D. P. Berschauer. 2015. The Residing and Fossil Busycon Whelks: Iconic Mollusks of Japanese North America. San Diego Shell Membership, Inc.