Ribbed Macron Shell, Macron aethiops
Ribbed Macron Shell, Macron aethiops. Shell collected off the beach of San Juanico, Baja California Sur, February 2023. Size: 4.0 cm (1.6 inches) x 2.6 cm (1.0 inch). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato.
Ribbed Macron Shell, Macron aethiops. Shell collected off the beach of San Juanico, Baja California Sur, February 2023. Size: 7.4 cm (2.9 inches) x 4.9 cm (1.9 inches). Collection, photograph and Identification courtesy of Colin Campbell, DVM, Punta Chivato.
Ribbed Macron Shell, Macron aethiops. Shell collected off the beach of Guerrero Negro, Baja California Sur, October 2019. Size: 8.1 cm (3.2 inches) x 5.0 cm (2.0 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.
Phylogeny: The Ribbed Macron Shell, Macron aethiops (Reeve, 1847), is a gastropod mollusk that is a member of the Buccinidae Family of Whelk Shells. The genus Macron is one of eighteen genera in this family, and there are five species in this genus. They are also known as the Dusty Macron Shell and the Ethiopian Macron Shell. Early investigators believed the Smooth Version, Macron kellettii, was a separate species howevert E.A. Smith (1903) showed both forms constitute a single species. The World Registry of Marine Species (WoRMS) and MolluscaBase both place the genus Macron in the Buccinoidea Family incertae sedis, indicative that they are uncertain where to place this genus and have temporarily placed it in this family type.
Description: Ribbed Macron Shells are stout, and consist of five or six straight-sided whorls. They have a moderate spire. The siphonal canal is deep and curved. There is a second canal, located at the top of the large oval aperture. Each whorl is broadly shouldered giving the shell a turreted look. The whorls are encircled with broad flat ribs, which vary in number and width, separated by broad grooves. Sometimes the ribs are absent all together. The siphonal canal is deep and curved. There is a second canal, located at the top of the aperture. The ribs extend onto the outer lip of the aperture. The inner lip is wide and shiny. They have a thick greenish-brown to brown periostracum. Both the exterior and the interior of these shells are white in color. Ribbed Macron Shells reach a maximum of 8.7 cm (3.4 inches) in length and 5.4 cm (2.0 inches) in height. The similar looking Smooth Macron, Macron orcutti is smaller, smoother, and found only in Magdalena Bay, Baja California Sur.
Habitat and Distribution: Ribbed Macrons are found attached to rocks, and on muddy sand substrates between rocks. They live in the intertidal zone, and at depths up to 3 m (10 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters with the exception that they are absent from north of Punta Colonet, Baja California, along the central and northwest coasts of the Baja Peninsula. There are reports that they residence of the southern Sea of Cortez. There are also reports of them being found in Peru. It is unknown if this is based on misidentification or if this species is that discontinuous in its range.
Ecology and Behavior: Ribbed Macron are a poorly studied and understood species. There is very limited documentation of their diet, predation, reproduction or ecosystem interactions. They are thought to scavengers that feed on carrion. They are gonochoric and reproduce sexually, with internal fertilization. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented. From a conservation perspective the Ribbed Macron has not been formally evaluated. However, they are fairly common with a relatively wide distribution and should be considered to be of Least Concern.
Synonyms: Buccinum aethiops, Pseudoliva kellettii, and Purpura trochlea.