One species, two developmental modes: a case of geographic poecilogony in marine gastropods

Abstract

Background Poecilogony, the presence of two developmental modes in the same animal species, is a rare phenomenon. Few cases of poecilogony have been suggested for marine invertebrates including molluscs and even less stood extensive testing, mostly revealing a species pair with differing developmental modes. We studied a textbook example of poecilogony in the viviparous snail Planaxis sulcatus (Gastropoda: Planaxidae), for the first time throughout its entire distribution range. Results In the Western Indian Ocean and Red Sea this intertidal species is observed to have large, shelled juveniles, whereas in the Indo-West Pacific planktotrophic veliger larvae are released from a subhaemocoelic brood pouch. We uncovered a shift in developmental modes across its range: from west to east successively earlier developmental stages are released. Furthermore, genetic data based on mitochondrial DNA suggests to recognize P. sulcatus as a single species rather than a group of cryptic species. A reconstruction of the ancestral area of P. sulcatus based on molecular data outlines the Western Indian Ocean and the Indo-West Pacific as area of origin. Conclusion The findings supporting Planaxis sulcatus as a single widespread species and the geographical shift from one reproductive mode to another suggest for this species to truly represent a case of geographic poecilogony, i.e. differing developmental modes between populations of the same species. Furthermore, the results of our ancestral range estimation imply the release of planktotrophic larvae as the ancestral developmental mode.

Bioactive Compounds from Marine Heterobranchs

“…Other species of this genus also display antifeeding activities, such as T. costatus from Chile and T. peruvianus from South Africa [333,[335][336][337]. Contrastingly, species of the genus Siphonaria present two different classes of polypropionates, some of which are found in the mucus and mantle border, thus indicating some sort of deterrent role, and are considered to be de novo biosynthesized [338,339]. The first type of polypropionates is represented by acyclic compounds with a 2-pyrone and furanone rings, such as siphonarienolone (119), structurally related to the polypropionates of the cephalaspideans (see above).…”

“…This sea hare is able to modify dietary molecules from brown and red algae and also to de novo biosynthesize peptides and polypropionates, while it may also contain cyanobacterial metabolites [686]. We will summarize the cytotoxic activities of aurisides A and B (312,313), aurilol (314), doliculols A and B (315,316), dolabellin (317), auripyrones A and B (318,319), dolabelides A-D (320-323), aurilide (324), doliculide (325), auristatins (339)(340)(341)(342)(343)(344), and finally, dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)(335)(336)(337)(338)(346)(347)(348). In Japan, among the dietary compounds from red algae, the macrolide glycosides aurisides A and B (312,313) and aurilol (314), a polyether bromotriterpene, are cytotoxic to HeLa tumor cell line [687,688].…”

“…The most famous compounds of all heterobranchs are the diverse cytotoxic linear and cyclic peptides of D. auricularia, the dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)(335)(336)(337)(338)(346)(347)(348), which were probably used by the Romans [46,197]. Dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)(335)(336)(337)(338)(346)(347)(348) include many different active molecules, including linear and cyclic peptides, depsipeptides, peptides containing thiazole and oxazole heterocycles, and macrolides [479]. Dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)…”

“…Dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)(335)(336)(337)(338)(346)(347)(348) include many different active molecules, including linear and cyclic peptides, depsipeptides, peptides containing thiazole and oxazole heterocycles, and macrolides [479]. Dolastatins (192,(326)(327)(328)(329)(330)(331)(332)(333)(334)(335)(336)(337)(338)(346)(347)(348) are found in small amounts in sea hares and are suggested to originate from their diet, particularly from cyanobacteria of the genera Symploca, Caldora and Lyngbya [714][715][716]. Among the most known dolastatins, dolastatin 3 (192) and dolastatins 10-15 (326-331) display mild to strong biological activities and were further studied, such as the macrocyclic lactone dolastatin 19 (332); dolastatins C (333), D (334), H (335) and iso-dolastatin H (336); dolastatin G (337); and nor-dolastatin G (338) [694,[717][718]…”

Figure 2 from: Strong EE, Bouchet P (2020) Hidden in plain sight: two co-occurring cryptic species of Supplanaxis in the Caribbean (Cerithioidea, Planaxidae). ZooKeys 991: 85-109. https://doi.org/10.3897/zookeys.991.57521

“…Voucher registration numbers and GenBank accession numbers for sequenced specimens of Supplanaxis nucleus and S. nancyae. Sequences for Planaxis sulcatus, S. planicostatus, and S. niger were downloaded from GenBank (sourceWiggering et al 2020).…”