Link: https://www.scielo.br/j/zool/a/39cb6vDrSBw437MNdx4CPPS/
- MACHADO F.M & PASSOS F.D (2022). Revisiting the morphological aspects of the Anomalodesmata (Mollusca: Bivalvia): a phylogenetic approach. Invertebrate Systematics 36: 1063-1098
Link: https://www.publish.csiro.au/IS/justaccepted/IS22028
Abstract: The Anomalodesmata Dall, 1899 includes some of the rarest and most specialized species of marine bivalves. This rarity has consequently constituted the greatest obstacle for understanding their internal relationships due to the low representativeness of species present in any phylogenetic reconstructions. Therefore, with the primary purpose of creating a more comprehensive morphological analysis, data including all the anomalodesmatan families were gathered into a cladistic analysis. Our data set includes, for the first-time, information about members of the families Clistoconchidae, Cetoconchidae, Protocuspidariidae, Spheniopsidae and the recently described Bentholyonsiidae. Information on shell morphology, anatomy, and behavior of anomalodesmatans were compiled through a review of the literature (from 1895 to 2022) plus a re-analysis of shells and internal anatomy of some fresh collected and archived specimens in museum collections around the world. Our analysis suggests a deep division of the Anomalodesmata into two distinct clades: the first generally composed of shallow water species from 12 families, and a second clade of a carnivorous lineage mainly comprising deep water species from 10 families. Consequently, a new topology for Anomalodesmata is suggested bringing new insights into the interfamilial relationships of this, sometimes bizarre, clade of bivalves.
- MORTON B & MACHADO F.M (2021). The origins, relationships, evolution and conservation of the weirdest marine bivalves: the watering pot shells. A review. Advances in Marine Biology 88: 137-220.
Link: https://www.sciencedirect.com/science/article/pii/S0065288121000018
Abstract: The fossil record shows that the two clavagelloid or watering pot families evolved at different times, the Clavagellidae first in the late Mesozoic (100–66 mya), the Penicillidae later in the Cenozoic (33–23 mya)—the former originally with, thus, a near-global Tethyan distribution, the latter restricted to the Indo-West Pacific. Representatives of the two clavagelloid families, moreover, have wholly different adventitious tube/crypt structures and, thus, methods of formation suggesting that evolutionary experiments have been undertaken to achieve such radical architectural novelties. This has resulted in one of the most surprising examples of convergent evolution in the Bivalvia. But, what were the ancestors of the Clavagelloidea? The shell and internal morphology of representatives of the three recognized genera of the Lyonsiidae, that is, Lyonsia, Entodesma and Mytilimeria, are described. Species of the latter two genera are highly specialized epibenthic, byssate, nestlers and embedded symbionts of ascidian colonies and sponges, respectively. Species of Lyonsia, however, are mostly shallow endobenthic burrowers. On the basis of these studies, it is concluded that species of Lyonsia can be regarded as representative of the ancestral watering pot (Clavagelloidea) condition. Evidence for this conclusion include the mineralogy, characteristics and ligament structure of the shell and features of the anatomy, importantly the modification of the vestigial pedal retractor muscles to form simple (Clavagellidae) and more complex (Penicillidae) proprioreceptors. Such an anatomy-based conclusion is supported to some extent by DNA analyses of representatives of the Lyonsiidae and the two constituent families of the Clavagelloidea. To some extent because all clavagelloids are exceedingly rare hindering such analyses. Such rarity, however, also argues for the strict conservation of all the species of the Clavagelloidea.
- MORTON B & MACHADO F. M (2019). Predatory marine bivalves: A review. Advances in Marine Biology 84: 1-98.
Link: https://www.sciencedirect.com/science/article/pii/S006528811930032X
Abstract: Most bivalves are suspension feeders. On the deep sea floor, however, some are predators, typically of meiobenthic crustaceans: copepods, cumaceans and ostracods. Propeamusiid scallops are one such group of predators. The largest numbers of predators, however, belong to the bivalve subclass Anomalodesmata and constitute, as currently recognised, some 500 species belonging principally to the Verticordioidea (120), Poromyoidea (75) and Cuspidarioidea (304) with four, two and four constituent families, respectively. A further family, the Parilimyidae, is considered to be derived from the Pholadomyoidea—the anomalodesmatan ancestor. These, generally small (< 60 mm shell length), nacreous and thin-shelled predators share many anatomical features that formerly allowed them to be collectively classified as the Septibranchia. Although this name is now rarely used, it refers to their possession of a ctenidially-derived septum in the mantle cavity and functioning in prey capture. Generally, there is a trend, possibly evolutionary, from a typical bivalve ctenidium (Parilimyidae and some Verticordioidea) to a complete septum (other Verticordioidea, Poromyoidea and Cuspidarioidea). In addition, the inhalant siphon, foot, labial palps, mouth and its lips play a role in prey capture, and ingestion. Similarly, the stomach is modified to digest such, typically chitinous, ingested prey. Most septibranchs are either consecutive or simultaneous hermaphrodites with self-fertilisation possibly usual and with some evidence in a few of larval brooding. Notwithstanding, the deep sea septibranch species are poorly studied with virtually nothing being known about their wider distributions, ecology, detailed reproductive strategies and life history traits.
- MORTON B, MACHADO F. M & PASSOS F. D (2019). The anatomy of the miniature predator Trigonulina ornata (Bivalvia: Anomalodesmata: Verticordiidae) from continental shelf waters off Brazil. Marine Biodiversity 49 (6): 1-16.
Link: https://link.springer.com/article/10.1007/s12526-019-01017-y
Abstract: The anatomy of one of the smallest non-septate carnivorous bivalves is described herein and is the first anatomical study of a member of the genus Trigonulina. This paper shows that similar to other verticordiids, Trigonulina ornata d’Orbigny, 1853 possesses a suite of anatomical features that include a prey-capturing inhalant siphon, a septum, an absence of labial palps and capacious mouth, which characterize it as a carnivorous marine bivalve. A discussion about the origin of the septibranch septum is provided showing that the condition seen in T. ornata could be representative of the transition within the Anomalodesmata between suspension-feeding type E ctenidia and the non-filamentar septibranch condition. Finally, fertilized and encapsulated eggs within the visceral mass, the presence of hypobranchial glands plus larval prodissoconch size collectively suggest self-fertilization and the possible early brooding behaviour by T. ornata.
- MACHADO F. M, PASSOS F. D & GIRIBET, G (2019). The use of micro-computed tomography as a minimally-invasive tool for anatomical study of bivalves (Mollusca: Bivalvia). Zoological Journal of the Linnean Society, 186: 46-75.
Link: https://doi.org/10.1093/zoolinnean/zly054
Abstract: Micro-computed tomography or micro-CT is a minimally invasive technique capable of generating 2D images and 3D tomographic reconstructions of small-sized animals without destroying the physical specimens. The technique has been previously applied to the study of bivalves, and here we extend it to study the anatomy of eight anomalodesmatan species through the exclusive use of a tomographic approach. Freshly fixed and museum specimens of Anomalodesmata, one of the least understood clades of bivalves, were selected and scanned. Tomographic anatomical descriptions were generated for Pandora pinna (Pandoridae), Lyonsia alvarezii (Lyonsiidae), Allogramma formosa (Lyonsiellidae), Trigonulina ornata (Verticordiidae), Poromya rostrata (Poromyidae), Cetoconcha spinosula, Cetoconcha aff. smithii (Cetoconchidae) and Cuspidaria glacialis (Cuspidariidae). The main internal anatomical features often evaluated for anomalodesmatans were documented. The tomographic images allowed for a detailed description of anatomical structures, including the mantle, ctenidia, labial palps and siphons, as well as the digestive, reproductive and nervous systems. This non-destructive technique thus proved to be an efficient tool for describing the anatomy of bivalves. The potential of micro-CT in concert with the constant development of new scanners, bring fresh perspectives to the anatomical study of bivalves. Poromya spinosula is transferred to Cetoconcha and Cetoconchidae, as Cetoconcha spinosula (Thiele, 1912) comb. nov.
- CAMPOS A, INTROINI G.O, TALLARICO L.F, MACHADO F.M, PASSOS F.D & RECCO-PIMENTEL S.M. (2018). Ultrastructure of the spermatozoa of three species of Anomalodesmata (Mollusca, Bivalvia) and phylogenetic implications. Acta Zoologica, 101 (2): 156-166.
Link: https://doi.org/10.1111/azo.12282
Abstract: Anomalodesmata is the rarest and most specialized group of the class Bivalvia. In general, scarce data on sperm ultrastructure of anomalodesmatan are available in the literature. Aiming to contribute to an understanding of spermatozoon morphology in this group, the present study describes the ultrastructure of male gametes of three species—Cardiomya cleryana (Orbigny 1842) (Cuspidariidae), Pandora brevirostris Güller and Zelaya 2016 (Pandoridae) and Thracia similis Couthouy 1839 (Thraciidae). C. cleryana has an acrosome located at the anterior region, and the mitochondria are symmetrically arranged, while the spermatozoa of P. brevirostris and T. similis have unique characteristics, in particular the association of the acrosome with the midpiece and asymmetric mitochondria. This position of the acrosome appears to be peculiar among Anomalodesmata and is unknown for non‐anomalodesmatan bivalves. The present ultrastructural description of spermatozoa contributes to differentiate the studied species, bringing new insights about the sperm features of anomalodesmatan species and shares several characteristics with that of other species of the two lineages proposed by molecular phylogeny
- PASSOS F. D, MACHADO F. M & FANTINATI, A (2017). Shell morphology of a new Brazilian species of Kelliellidae and a brief review of the genus Kelliella (Mollusca: Bivalvia). Marine Biodiversity, 49 (1): 207-219.
Link: https://link.springer.com/article/10.1007/s12526-017-0782-4
Abstract: The bivalves of the families Vesicomyidae and Kelliellidae are common bottom inhabitants of the deep-sea, with some taxonomic controversy concerning the smaller forms of the former, which are frequently confused as species of the latter. Based on specimens collected from shallow waters of the southeastern Brazilian coast, a new species of Kelliella is described, through a detailed description of its shell, which is compared with those from other species already referred for this genus. Its minute valves with rounded contour and a marked lunule are very similar to those of K. miliaris, the type-species of kelliellids, differing in only some details of the hinge dentition. Most species of the genus Kelliella are currently assigned to the genus Vesicomya, causing great difficulties as far as knowledge of the real diversity of the family Kelliellidae. This study represents part of a continuing work on new discoveries regarding t he marine molluscs of the southwestern Atlantic. Here, a review of the genus Kelliella is provided, highlighting some shell features that will be important in future comparative studies between these bivalve families.
- MACHADO F. M, MORTON B & PASSOS, F. D. (2017) Functional morphology of Cardiomya cleryana (d'Orbigny, 1842) (Bivalvia: Anomalodesmata: Cuspidariidae) from Brazilian waters: new insights into the lifestyle of carnivorous bivalves. Journal of the Marine Biological Association of the UK, 97 (2): 447-462.
Link: http://dx.doi.org/10.1017/S0025315416000564 (Watch the video - Cardiomya cleryana behaviour - in Supplementary material)
Abstract: Of the more than 800 Recent species of Anomalodesmata only 16 have been studied alive. The Septibranchia, comprising a number of carnivorous bivalve superfamilies, are no exception to this generalization and, until recently, no living member of this group has been studied since the 1980s. Collected from the shallow, shelf seabed off Brazil, Cardiomya cleryana is one of only a few species to have its morphology described in recent years and the first ever anomalodesmatan to be filmed alive. Important anatomical features such as a greatly extensible foot to secure itself in the sediment with a single byssal thread, exhalant siphon inter-tentacular projections and micro-papillae on the surface of the siphonal tentacles are described. Observations on the species’ behaviour have revealed a lifestyle hitherto not recorded for any septibranch, indeed any anomalodesmatan. The anchoring mechanism of C. cleryana using an extraordinarily long byssal thread is described for the first time. The life position of C. cleryana is at 45° to the sediment-water interface whereas other cuspidariids have been considered to orient themselves vertically. An anatomical comparison between Cardiomya and Bathyneaera has revealed close affinities. This study thus provides new insights into the morphology and behaviour of the Cuspidariidae.
- BONINI A, INTROINI G. O, TALLARICO L. F, MACHADO F. M & RECCO-PIMENTEL S. M. (2016) Shell morphology and sperm ultrastructure of Solen tehuelchus Hanley, 1842 (Bivalvia: Solenidae): New taxonomic characters. American Malacological Bulletin, 34 (2): 73-78.
Link: https://doi.org/10.4003/006.034.0202
Abstract: Solen tehuelchus Hanley, 1842 is currently the only razor-clam reported from Brazilian waters. Although its shell is well known and similar to the other Solenoidea, their anatomical aspects are poorly studied. Recently some living specimens of S. tehuelchus were obtained from a Brazilian beach, allowing the removal of their testes for an ultrastructural analysis. In order to add a new anatomical feature for this species and provide a brief comparison between some related taxa, the shell and sperm ultrastructure were described in detail. The present study showed that characteristics of the spermatozoa of S. tehuelchus are similar to those of other solenids, although certain sperm ultrastructural characteristics such as a short acrosome with an electron-dense base and rounded nucleus are also similar to the species Tagelus plebeius (Lightfoot, 1786) (Solecurtidae). Herein, we have added new anatomic and taxonomic data hitherto unknown to science. The sperm morphology of S. tehuelchus, might in the near future bring new insights into the systematic of Solenidae.
- MORTON B, MACHADO F. M & PASSOS F. D. (2016) The organs of prey capture and digestion in the miniature predatory bivalve Spheniopsis brasiliensis (Anomalodesmata: Cuspidarioidea: Spheniopsidae) expose a novel life-history trait. Journal of Natural History, 50 (27-28): 1725-1748.
Link: https://www.tandfonline.com/doi/abs/10.1080/00222933.2016.1155780
Abstract: Spheniopsis brasiliensis, from depths of 17–148 m off the southern Atlantic coast of Brazil, is a predator of epipsammic micro-crustaceans which it sucks into the infra-septal chamber using a raptorial inhalant siphon and internally generated hydrostatic suction forces. Prey items, which include ostracods, are thought to be pushed into the funnel-shaped mouth using the foot. The stomach is capacious with a short style sac conjoined briefly with the mid gut and possessing a stubby crystalline style. Internal stomach architecture is simplified, with no identifiable sorting areas (unlike other cuspidarioids) and lined virtually completely by a gastric shield. The exoskeletal remains of digested prey are held in the posterior end of the stomach and not in a specialised waste storage pouch as in the con-familial Grippina coronata. The mid gut, hind gut and rectum are all extremely narrow and, thus, only the smallest of faeces can be accommodated and transmitted for anal discharge. Spheniopsis brasiliensis, like G. coronata is a self-fertilising simultaneous hermaphrodite with encapsulated lecithotrophic eggs brooded internally. Both taxa are thus ovovivaporous. It is also believed that both taxa are univoltine so that larvae and the exoskeletal prey remains are all released post mortem. Cuspidariids are generally regarded as dioecious but, recently, Cardiomya costellata has been shown to be a non-brooding simultaneous hermaphrodite. The distinguishing characters between cuspidariids and spheniopsids thus appear to be their differing reproductive strategies and life history trait.
- MORTON B, MACHADO F. M & PASSOS F. D. (2015) The smallest carnivorous bivalve? Biology, morphology and behaviour of Grippina coronata (Anomalodesmata: Cuspidarioidea: Spheniopsidae) preying on epipsammic microcrustaceans in the southwestern Atlantic off Brazil. Journal of Molluscan Studies, 82 (2): 244-258.
Link: https://academic.oup.com/mollus/article/82/2/244/2607357
Abstract: The Spheniopsidae are today represented by five living species of Spheniopsis and nine of Grippina, distributed in the Pacific and Atlantic Oceans. Little is known of their anatomy and the phylogenetic position of the family within the Bivalvia is debated. In order to investigate these questions, the functional morphology of Grippina coronata obtained from the continental shelf off Rio de Janeiro and Espírito Santo States, Brazil, has been examined. Less than 2 mm in shell length, the siphonal apparatus of G. coronata is complex, with seven sensory papillae, and the ctenidia are reduced to transverse septa pierced by four pairs of ciliated pores. There are no labial palps and the stomach is of Type II with epibenthic harpacticoid and ostracod prey identified inside it. Although there is an intestine producing faeces, the stomach also possesses a unique waste storage pouch for exoskeletal remains of digested prey. Collectively, these features suggest that the Spheniopsidae comprise carnivorous taxa belonging to the Cuspidarioidea within the Anomalodesmata. Grippina coronatais a self-fertilizing simultaneous hermaphrodite that, uniquely, broods fertilized oocytes within the ovarian follicles and, thereby, provides the first example of intrafollicular fertilization and brooding in the Bivalvia. Release of the encapsulated oocytes must be by parental death, which coincidentally releases the exoskeletal remains from the storage pouch. Such post mortemsemelparity creates a life-history trait hitherto unrecognized in the Bivalvia.
- MACHADO F. M & PASSOS, F. D. (2015) Spheniopsidae Gardner, 1928 (Bivalvia): Conchological Characters of Two New Species from off Brazil, Southwestern Atlantic. American Malacological Bulletin, (33): 1-9.
Link: https://doi.org/10.4003/006.033.0207
Abstract: The Spheniopsidae Gardner, 1928 comprises four living species of Spheniopsis Sandberger, 1861 and eight of Grippina Dall, 1912, the latter restricted to the Pacific Ocean, the former also occurring in the Atlantic. Spheniopsis brasiliensis new species and Grippina coronata new species are described from the Brazilian southeastern coast, based on a detailed study of their shells. They are distinguished from already described species mainly by differences in the outline of the valves, external sculpture and right hinge dentition. Shallow micro-pits present all over the outer surface of the dissoconch are viewed as similar to those already described for cuspidariids. They may, thus, represent further evidence for the relatedness of spheniopsids and cuspidarioideans. The new species from Brazil represent the first finding of these rare minute bivalves of this family from the southwestern Atlantic.
- TALLARICO L, INTROÍNI G. O, BONINI A, PASSOS F. D, MACHADO F. M, ARRUDA E. P & RECCO-PIMENTEL S. M. (2015) Spermatozoan ultrastructure and mitochondrial gene sequence of Caryocorbula caribaea (d'Orbigny, 1853) (Corbulidae: Bivalvia), a species with plasticity in shell morphology. Molluscan Research, (36): 1-6.
Link: https://www.tandfonline.com/doi/abs/10.1080/13235818.2015.1052127
Abstract: Systematics of Corbulidae supported by anatomical and conchological studies remains confused and controversial because of the considerable phenotypic plasticity of their shells. Ultrastructural spermatozoan study and molecular analyses have been performed to contribute valuable information, which could be used in taxonomy. Electron microscopy was used to analyse sperm cells from specimens of Caryocorbula (Gardner, 1926) exhibiting shell differences. The spermatozoon was of the aquasperm type, showing short acrosome, barrel-shaped nucleus, midpiece composed of four spherical mitochondria and simple flagellum. In addition, about 860 base pairs of mitochondrial large ribosomal subunit (16S rRNA) were sequenced from each individual. The consistent similarity shared by spermatozoa and DNA sequences from all studied specimens indicated that they belonged to one coherent unit, Caryocorbula caribaea (d'Orbigny, 1853), despite the extraordinary plasticity exhibited by their shells.
- PASSOS F. D & MACHADO F. M. (2014) A new species of Cyamiocardium Soot-Ryen, 1951 from shallow waters off Brazil, with a discussion on the anatomical characters of the Cyamiidae (Bivalvia: Cyamioidea). American Malacological Bulletin, (32): 122-131.
Link: https://doi.org/10.4003/006.032.0110
Abstract: Cyamiocardium domaneschii n. sp. is described from shallow waters off the Southeastern coast of Brazil. An anatomical study provides comparisons with other Cyamioidea. It has a small shell (up to 3.1 mm in length), valves with a rounded contour, external radial sculpture, a distinct large prodissoconch, and hinge structure characteristics of the genus Cyamiocardium Soot-Ryen, 1951. Three well-defined pallial openings are present; tentacles border the anteriormost part of the pedal opening and the inhalant and exhalant apertures. The inner demibranchs are larger than the outers, do not have interlamellar junctions, and form a spacious brooding chamber. It is dioecious and developing oocytes are covered by a thin follicular tissue, which persists as a covering of each brooded young. Offspring are retained up to the juvenile stage, and are attached to the gill filaments by a long stalk. The foot has a narrow, grooved ventral sole; no byssus threads were observed. An active burrowing or crawling behavior is suggested for C. domaneschii n. sp., as there are well developed statocysts. This finding of a cyamiid from Brazil represents the extension of the geographical distribution of this family further north in the southwestern Atlantic Ocean. This study also reveals that some anatomical characters are variable in the genus Cyamiocardium: in C. denticulatum (Smith, 1907), there are only two pallial openings and its foot does not have a ventral sole. The attachment of young to the gills are not related to nourishment, and here for C. domaneschiin. sp. it is suggested that the stalk is only used as a “safety belt”, preventing embryos and juveniles to be released before the end of their development. More studies remain to be done on the anatomy of cyamioideans, particularly on living specimens; we paid attention to common characters used for discussions on the taxonomy and biology of these bivalves.
- TALLARICO L. F, PASSOS F. D, MACHADO F. M, CAMPOS A, RECCO-PIMENTEL S. M & INTROINI G. O. (2014) Bivalves of the São Sebastião Channel, north coast of the São Paulo State, Brazil. Check List, (10): 97- 105.
Link: https://www.biotaxa.org/cl/article/view/10.1.97/10364
Abstract: The north coast of the São Paulo State, Brazil, presents great bivalve diversity, but knowledge about these organisms, especially species living subtidally, remains scarce. Based on collections made between 2010 and 2012, the present work provides a species list of bivalves inhabiting the intertidal and subtidal zones of the São Sebastião Channel. Altogether, 388 living specimens were collected, belonging to 52 species of 34 genera, grouped in 18 families. Tellinidae, Veneridae, Semelidae, Ungulinidae, Mactridae, Solecurtidae, Corbulidae, Cardiidae, Lucinidae, Cooperellidae, Nuculidae, Psammobiidae, Donacidae, Solenidae, Periplomatidae, Thraciidae and Arcidae were the most representative families in this collection. Among the identified species, Caryocorbula caribaea, Codakia pectinella and Diplodonta punctata were intertidally abundant, while Macoma uruguayensis and Pitar fulminata were subtidally abundant.
- VITONIS J. E. E. V, ZANIRATTO C. P, PASSOS F. D & MACHADO F. M. (2012). Comparative studies on the histology and ultrastructure of the siphons of two species of Tellinidae (Mollusca: Bivalvia) from Brazil. Zoologia (Curitiba), (29): 219-226.
Link: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1984-46702012000300005
Abstract: Despite the great importance of the siphons for infaunal bivalves, only a few studies have examined their tissues using histology techniques or scanning electron microscopy. In the present study, the siphons of Tellina lineataTurton, 1819 and Macoma biota Arruda & Domaneschi, 2005 were investigated. The siphon walls are composed by a series of muscle sheets of longitudinal ("L"), circular ("C") and radial ("R") fibers, with a clear pattern common to both species: there is a main median longitudinal layer (Lm), and two peripheral circular layers, one inner (Ci) and one outer (Co), near the epithelia. A median circular layer (Cm) separates an internal (Lmi) from an outer (Lmo) median longitudinal layer. Further, the Co is split by a thin outer longitudinal layer (Lo), forming Coi and Coo layers, the former being obliquely oriented. Thin radial fibers (R) delimit clear packages of Lmi and Lmo fibers. In each siphon, there are six longitudinal nerve cords, running within the Lmi layer, adjacent to the Cm. The inhalant and exhalant siphons of M. biota are very similar in structure, but the Lmo of the exhalant siphon is almost twice as thick as its Lmi, while in the inhalant siphon these layers have similar thicknesses; the Coi is very thick, especially in the exhalant siphon. The inhalant siphon of T. lineata is very similar to that of M. biota, differing only with respect to the thickness of the Coi, which in the former species is not as well developed as in the latter. The Lmo of the exhalant siphon of T. lineata is by far the most developed layer, with the Lmi represented only by uniseriate small cells; in the vicinities of the nerve cords, the Cm is split in two layers. The epithelia of both siphons of M. biota and T. lineata bear ciliated receptors, which were difficult to observe as they were frequently covered with mucus. It was possible to observe that cilia are present in both species, differing in length and in the number per receptor between the inhalant and exhalant siphons, and between the species. Detailed comparisons among the siphons of M. biota and T. lineata and other bivalve species are very difficult, because of at least two reasons. First, each investigator has used different methods to prepare and observe the siphons through histological sections; and second, different nomenclatural schemes are used to describe the musculature of the siphons, causing confusion when the same layers are compared among different species. In order to unify the nomenclature of tissue layers of the bivalve siphons, we now propose a scheme to name these layers based on topological homology.
