Defining a Clade by Morphological, Molecular and Toxinological Criteria: Distinctive Forms related to Conus praecellens A. Adams, 1854

Abstract

We carried out a definition of the species group to which Conus praecellens A. Adams 1854 belongs using a combination of comparative morphological data, molecular phylogeny based on standard genetic markers and toxinological markers. Prior to this work, Conus praecellens was generally postulated to belong to a clade of similarly high-spired, smaller Conusspecies such as Conus pagodus Kiener, 1845, Conus memiae (Habe & Kosuge, 1970) and Conus arcuatus Broderip & Sowerby, 1829. The molecular phylogeny and toxinological data demonstrate that these prior hypotheses are incorrect, and that instead, Conus praecellens is in a branch of Conus that includes Conus stupa (Kuroda, 1956), Conus stupella (Kuroda, 1956), Conus acutangulus Lamark, 1810 and surprisingly, some species that are morphologically strikingly different, Conus mitratus Sowerby, 1870 and Conus cylindraceus Broderip & Sowerby, 1830. A more careful analysis of the morphologically diverse forms assigned to Conus praecellens suggests that from the Philippine material alone, there are at least three additional undescribed species, Conus andremenezi, Conus miniexcelsus and Conus rizali. A reevaluation of protoconch/early teleoconch morphology also strongly suggests that Conus excelsus Sowerby III, 1908 is related to these species. Together, the different data suggest a clade including the 10 species above that we designate, the Turriconus (Shikama and Habe, 1968) (clade; there are additional distinctive forms within the clade that may be separable at the species level. The phylogenetic definition using the multidisciplinary approach described herein provides a framework for comprehensively investigating biodiverse lineages of animals, such as the cone snails.

Figure 1

High-spired Conusspecies previously postulated to be related to Conus praecellens : Top from left: Conus acutangulus , “typical form”, Conus acutangulus , “deep-water form”, Conus nereisMiddle from left: Conus praecellens , “Aliguay form”, Conus praecellens , “sowerbii form”, Conus andremenezi , new species, Conus pagodus , Bottom from left: Conus miniexcelsus , new species, Conus rizali , new species, Conus arcuatus. All of the specimens shown are from the Philippines, except for Conus arcuatus.

Figure 2

Two morphospecies with non-“ praecellens-like” protoconchs from Aliguay. All of the specimens shown are from Aliguay Island, Philippines, except the lower left specimen which was collected from southern Japan. Top row: Conus andremenezi ; Bottom row: Conus miniexcelsus. Note the generally finer pattern and narrower shell shape of Conus miniexcelsuscompared to Conus andremenezi. In addition the spiral ribbons of the body whorl of Conus miniexcelsusare smooth, but are distinctly crenulated in Conus andremenezi.

Figure 3

Three distinctive forms with “ praecellens-like” protoconchs. Top row is a series of Conus praecellens , “sowerbii forms”. Bottom is Conus praecellens , “Aliguay form”. In the middle row are two specimens of Conus rizali , new species. The diagnostic morphological differences between the three forms are discussed in the text.

Figure 4

An illustration of the “miniexcelsus -like complex”. Shown are five specimens (left five) and close ups of their respective protoconchs (right five). Left, top and bottom: Conus miniexcelsus , middle: Conus excelsus , and right top and bottom: Conus acutangulus. Although the shells are different in pattern and size at maturity, note the similar purplish brown translucent protoconchs, followed by the ivory white early teleoconch whorls before the regular shell pattern is initiated. Typical Conus acutangulus(top right) and the “deep-water form” (bottom right) are both distinctly more nodulose while there is a striking similarity between Conus excelsusand Conus miniexcelsusin their protoconchs and early teleoconch whorls.

Figure 5

Phylogenetic tree of some Conus species based on 12SrRNA sequences. Species shown in Figure 1 are indicated with arrows. Branches are labeled with Bayesian confidence values (posterior probabilities expressed as percentages). These data clearly separate Conus acutangulusand Conus praecellensfrom the Conasprellaspecies with 100% confidence and join them with C. stupaand C. mitratuswith 97% confidence.

Figure 6

Distinctive forms proposed to belong to the Turriconusclade. Top row (showing the shell and in the inset, a close-up of the corresponding protoconch), from left to right: Conus excelsus; miniexcelsus; acutangulus , “typical form”; acutangulus , “deep-water form”; andremenezi; praecellens , “sowerbii form”; rizali; praecellens , “Aliguay form”. Lower row, from left to right: Conus stupa; stupella; mitratus; cylindraceus. The protoconch of Conus stupais not shown; it is extremely eroded in the figured specimen.

Figure 7

Toxinological analysis. Predicted mature toxin sequences from two distinct branches of the O-superfamily of conopeptides for four members of Turriconus: Conus acutangulus, Conus mitratus, Conus praecellensand Conus stupa. An independent comparison of the toxin sequences from the two branches, the hydrophilic ω and the hydrophobic δ, each demonstrate the close relationship between the different species of the Turriconus clade analyzed.

Figure 8

Comparison of two morphospecies collected in Aliguay Island, Philippines. The specimen at the left is Conus miniexcelsus , and on the right is Conus praecellens , “Aliguay form”. Top: The whole shell; Bottom: A close-up of the protoconch and first few teleoconch whorls. Note the different shape and color of the protoconchs and the characteristic switch in Conus miniexcelsusfrom a triangular translucent purplish brown protoconch, to the ivory white first teleoconch whorls, and finally to the normal maculated pattern. There are characteristic sculptural differences in the early teleoconch whorls between the two specimens as well.