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Towards a phylogenetic classification of dendrocoelid freshwater planarians (Platyhelminthes): a morphological and eclectic approach

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2006
R. Sluys
Abstract We explore and review the taxonomic distribution of morphological features that may be used as supporting apomorphies for the monophyletic status of various taxa in future, more comprehensive phylogenetic analyses of the dendrocoelid freshwater planarians and their close relatives. Characters examined are: (i) musculature of the pharynx; (ii) anatomy of the eye; (iii) distribution of testis follicles along the longitudinal axis of the body; (iv) epidermis of the body wall; (v) musculature of the ventral body wall; (vi) presence or absence of a penis papilla; (vii) position of the mouth opening; and (viii) anterior adhesive organ. A phylogenetic hypothesis, in the form of a character state tree, is developed. This hypothesis suggests that the Kenkiidae should be resurrected as a separate family, sharing a sistergroup relationship with the Dendrocoelidae. This sistergroup relationship is supported by the shared presence of an apomorphic anterior adhesive organ. Although the shape of the anterior adhesive organ, both within and between kenkiids and dendrocoelids, may differ considerably between species, they are all constructed according to the same principles. The monophyly of the Kenkiidae is supported by the presence of an apomorphic thickening of the marginal zone of the epidermis and presumably also by the presence of prepharyngeal testes. Within the Kenkiidae, the genus Macrocotyla should be considered as a junior synonym of Kenkia, which is characterized by the presence of an apomorphic ,planariid pharynx-type 2'. The monophyly of the Dendrocoelidae is suggested by the presence of a dendrocoelid type of pharynx. It is shown that multicellular eye cups with numerous photoreceptor cells are not restricted to the Dugesiidae and the Terricola but are also characteristic for the Dendrocoelidae; the phylogenetic implications of this character state distribution are discussed. It is pointed out that in planarians there may be a relationship between: (i) body size, the size of an eye cup and the number of its constituent pigment cells; and (ii) the size of an eye cup and the number of photoreceptor cells that it contains. Some tentative phylogenetic groups are suggested on the basis of the following presumed apomorphic characters: presence of transverse fibres in the ventral subepidermal musculature, presence of an extra longitudinal muscle layer in the outer pharynx musculature, a mouth opening that has shifted anteriad. It is suggested that the presumed monophyly of the genus Bdellocephala is supported by the apomorphic absence of a penis papilla, combined with a penial lumen provided with many plicae. Zusammenfassung Wir untersuchen und begutachten die taxonomische Verbreitung morphologischer Merkmale, die man als Apomorphien für die Monophylie verschiedener Taxa in einer zukünftigen umfangreicheren phylogenetischen Analyse der Dendrocoeliden und ihrer nächsten Verwandten heranziehen könnte. Zu diesen untersuchten Merkmalen gehören die Pharynxmuskulatur, die Augen-Anatomie, die Anordnung der Hodenfollikel entlang der Längsachse des Körpers, die Epidermis, die Muskulatur der ventralen Körperwand, das Vorhandensein oder Fehlen einer Penispapille, die Lage der Mundöffnung sowie des vorderen Hartorgans. Eine phylogenetische Hypothese wurde als character state-Stammbaum entwickelt. Hierin wird vorgeschlagen, die Kenkiidae wieder als eigenständige Familie und als Schwestergruppe der Dendrocoelidae zu betrachten. Dieses Schwestergruppen-Verhältnis wird durch den gemeinsamen Besitz eines apomorphen vorderen Haftorgans gestützt. Obwohl sich die Form dieses Organs sowohl innerhalb als auch zwischen Kenkiiden und Dendrocoeliden beträchtlich zwischen den Arten unterscheiden kann, ist es grundsätzlich gleich aufgebaut. Die Monophylie der Kenkiidae wird durch eine als apomorph betrachtete Verdickung des Epidermisrandes und durch das Auftreten praepharyngealer Hoden gestützt. Innerhalb der Kenkiidae sollte die Gattung Macrocotyla als Juniorsynonym von Kenkia angesehen werden, die durch den apomorphen Planarien-Pharynx-Typ 2 charakterisiert ist. Als Beleg für die Monophylie der Dendrocoelidae wird der Dendrocoeliden-Pharynx-Typ vorgeschlagen. Es wird gezeigt, dass vielzellige Augenbecher mit zahlreichen Photorezeptorzellen nicht auf die Dugesiidae und die Terricola beschränkt, sondern auch für die Dendrocoelidae charakteristisch sind; die phylogenetische Bedeutung dieser Merkmalsverteilung wird diskutiert. Es wird hervorgehoben, dass es in den Planarien wahrscheinlich eine Beziehung zwischen (i) Körpergröße, Größe der Augenbecher und Zahl der Photorezeptorzellen ebenso wie (ii) der Größe eines Augenbechers und der Zahl seiner Photorezeptorzellen gibt. Versuchsweise werden einige phylogenetische Gruppierungen auf der Basis der folgenden vermutlich apomorphen Merkmale vorgeschlagen: Vorhandensein transversaler Fasern in der ventralen subepidermalen Muskulatur, Auftreten einer zusätzlichen Längsmuskelschicht in der äußeren Pharynxmuskulatur und eine nach vorn verschobene Mundöffnung. Es wird weiterhin vorgeschlagen, die vermutete Monophylie der Gattung Bdellocephala durch das Fehlen einer Penispapille als Autapomorphie zu stützen, zusammen mit dem Merkmal eines durch viele Falten gekennzeichneten Penislumens. [source]

MOLECULAR SYSTEMATICS OF RIVER DOLPHINS INFERRED FROM COMPLETE MITOCHONDRIAL CYTOCHROME- B GENE SEQUENCES

MARINE MAMMAL SCIENCE, Issue 1 2002
Guang Yang
Abstract 1,140 bp of the complete mitochondrial cytochrome- b gene sequences of baiji (Lipotes vexillifer), franciscana (Pontoporia blainvillei), and Ganges river dolphin (Platanista gangetica gangetica) were determined to address the systematic position and phylogeny of extant river dolphins with combination of homologous sequences of other cetaceans. The neighbor-joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) phylogenetic analyses all identified the river dolphins into three lineages, i. e., Platanista, Lipotes, and Inia+Pontoporia. The Lipotes did not have sister relationship with either Platanista or Inia+Pontoporia, which strongly supported the referral of Lipotes to a separate family, i. e., Lipotidae. There were very high sequence divergences between all river dolphin genera, suggesting a relatively longer period of separation time than those among other odontocete families. [source]

The Jurassic Bivalve Genus Placunopsis: New Evidence On Anatomy and Affinities

PALAEONTOLOGY, Issue 3 2002
Jonathan A. Todd
The Jurassic bivalve genus Placunopsis Morris and Lycett, 1853 is shown to be an anomiid on account of the detailed anatomy of its hitherto unknown right valve and the corresponding musculature in the left valve. Herein the most appropriate choice for type species is considered to be P. inaequalis (Phillips, 1829), which accommodates a number of the larger Late Jurassic nominal species. A species from the English Bathonian previously confused with P. inaequalis is described as P. fuersichi sp. nov. Placunopsis inaequalis is shown to be closely related to Recent Pododesmus, which has previously been interpreted as the most ,primitive' of the extant anomiids on the basis of its anatomy. There is thus no need to retain a separate family for the genus, as has been proposed by some workers. The distinct small species P. socialis Morris and Lycett, 1853 can also be assigned to the anomiids on the basis of the differences between the structure of the outer layers in the two valves, and the presence of a byssal foramen. There is some suggestion of calcification of the byssus, but not enough detail is known of its musculature to justify transferring it to the genus Juranomia Fürsich and Werner, 1989 at this stage. The cemented bivalves traditionally referred to Placunopsis that are so common in the European Muschelkalk (Triassic) are not anomiids and thus require systematic revision. [source]

The Giant Zooxanthellae-Bearing Ciliate Maristentor dinoferus (Heterotrichea) is Closely Related to Folliculinidae

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2005
Wei Miao
Abstract. The small subunit rDNA sequence of Maristentor dinoferus (Lobban, Schefter, Simpson, Pochon, Pawlowski, and Foissner, 2002) was determined and compared with sequences from other Heterotrichea and Karyorelictea. Maristentor resembles Stentor in basic morphology and had been provisionally assigned to Stentoridae. However, our phylogenetic analyses show that Maristentor is more closely related to Folliculinidae. Our results support the creation of a separate family for Maristentor, Maristentoridae n. fam., and also confirm the phylogenetic grouping of Folliculindae, Stentoridae, Blepharismidae, and Maristentoridae, which we informally call ,stentorids'. Maristentor, rather than Stentor itself, appears to be most significant in understanding the origins of folliculinids from their aloricate ancestors. Our analyses suggest continued uncertainty in the exact placement of the root of heterotrichs with this phylogenetic marker. [source]