New Type of SIOP Structure in Serpulidae: Formation and Evolutionary Implications (original) (raw)
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Zoologica Scripta, 2006
Phylogenetic relationships within Serpulidae (Sabellida, Annelida) inferred from molecular and morphological data. -Zoologica Scripta , 35 , 421-439. We assessed phylogenetic relationships within Serpulidae (including Spirorbinae) using parsimony and Bayesian analyses of 18S rDNA, the D1 and D9 − D10 regions of 28S rDNA, and 38 morphological characters. In total, 857 parsimony informative characters were used for 31 terminals, 29 serpulids and sabellid and sabellariid outgroups. Following ILD assessment the two sequence partitions and morphology were analysed separately and in combination. The morphological parsimony analysis was congruent with the results of the 2003 preliminary analysis by Kupriyanova in suggesting that a monophyletic Serpulinae and Spirorbinae form a clade, while the remaining serpulids form a basal grade comprising what are normally regarded as Filograninae. Bremer support values were, however, quite low throughout. In contrast, the combined analyses of molecular and morphological data sets provided highly resolved and well-supported trees, though with some conflict when compared to the morphologyonly analysis. Spirorbinae was recovered as a sister group to a monophyletic group comprising both 'filogranin' taxa ( Salmacina , Filograna , Protis , and Protula ) and 'serpulin' taxa such as Chitinopoma , Metavermilia , and Vermiliopsis . Thus the traditionally formulated subfamilies Serpulinae and Filograninae are not monophyletic. This indicates that a major revision of serpulid taxonomy is needed at the more inclusive taxonomic levels. We refrain from doing so based on the present analyses since we feel that further taxon sampling and molecular sequencing are required. The evolution of features such as the operculum and larval development are discussed.
American Museum Novitates, 2004
A well-developed second ural half-centrum is a peculiar characteristic of the caudal skeleton of certain siluriforms, not seen in other Recent ostariophysans. Although the character has been previously recorded in the literature, its exact taxonomic distribution, structure, ontogeny, and phylogenetic meaning within siluriforms are not yet determined. In this paper, the degree of development of the second ural half-centrum is surveyed across the order. The ontogeny of the relevant axial structures in the posterior region of the vertebral column is reported in representative siluriform taxa. The condition where the second ural centrum is well formed and forms a complete intervertebral joint anteriorly with the compound caudal centrum is considered derived within siluriforms, a character state homoplastic with the primitive state in more distant teleostean outgroups. Various catfishes display that derived condition, which is informative about relationships at different levels within the group. The most inclusive of those clades is the superfamily Sisoroidea, including the families Amblycipitidae, Akysidae, Sisoridae, Erethistidae, and Aspredinidae. The placement of the neotropical Aspredinidae into an otherwise exclusively Asian clade has important biogeographical implications and the structure of the second ural centrum provides additional support to that hypothesis. Based on the currently available knowledge on the relationships among catfishes, a well-developed second ural centrum is hypothesized to be a result of six different events in siluriforms.
The type genus of Serpulidae, Serpula Linnaeus, 1758, along with closely related genera Crucigera Benedict, 1887 and Hydroides Gunnerus, 1768, accounts for approximately one-third of all described species in the family. Although previous morphological and molecular studies unequivocally indicate that these three genera constitute a monophyletic group, the status of each genus remains unknown. In this study, the relationships among and within the genera Serpula, Crucigera, and Hydroides were investigated using maximum parsimony and Bayesian analyses of nuclear (18S and 28S rDNA) and mitochondrial (cytochrome b) genomic molecular markers plus morphology. The phylogeny supports the monophyly of Hydroides, but Serpula forms a paraphyletic basal grade and Crucigera is polyphyletic. The lack of close relationship between Hydroides and Crucigera indicates that their similar opercular features are not homologous.
Invertebrate Systematics, 2008
The type genus of Serpulidae, Serpula Linnaeus, 1758, along with closely related genera Crucigera Benedict, 1887 and Hydroides Gunnerus, 1768, accounts for approximately one-third of all described species in the family. Although previous morphological and molecular studies unequivocally indicate that these three genera constitute a monophyletic group, the status of each genus remains unknown. In this study, the relationships among and within the genera Serpula, Crucigera, and Hydroides were investigated using maximum parsimony and Bayesian analyses of nuclear (18S and 28S rDNA) and mitochondrial (cytochrome b) genomic molecular markers plus morphology. The phylogeny supports the monophyly of Hydroides, but Serpula forms a paraphyletic basal grade and Crucigera is polyphyletic. The lack of close relationship between Hydroides and Crucigera indicates that their similar opercular features are not homologous.
Acta Zoologica, 2006
Abstract Spadella, M. A., . Spermiogenesis and introsperm ultrastructure of Scoloplax distolothrix (Ostariophysi: Siluriformes: Scoloplacidae). -Acta Zoologica (Stockholm) 87 : 341-348 Spermiogenesis in scoloplacids is characterized by initial lateral development of the flagellum, nuclear rotation, medial nuclear fossa formation, complex centriolar migration, and cytoplasmic channel formation. The scoloplacid spermiogenesis is similar to those found in Diplomystidae, the most primitive siluriform family. The scoloplacid spermatozoa have all the main characteristics of introsperm. They exhibit a conic head, a symmetric midpiece, a medial flagellum, and no acrosome. The conic forward-elongated nuclei contain homogeneous chromatin. The thin extremity of the nuclei is strongly curved and along its internal face there is a well-developed membranous compartment. The centrioles are completely inside the medial nuclear fossa, perpendicular to each other and with an electron-dense material between them. In a cross view of the midpiece, the mitochondria form a ring surrounding internally the cytoplasmic channel, and in a longitudinal view they are organized in a row along it. Several elongated vesicles are distributed peripherally, mainly concentrated in the mid-piece basal region. The flagellum contains the classical axoneme (9 + 2) and has two lateral projections or fins. The spermatozoa of scoloplacids share several characteristics with those of Auchenipteridae. Since these two families are not phylogenetically related this similarity seems to be due to convergence once both families are, until now, the only known siluriform families with introsperm.
2016 Winkler et al. - Forelimb anatomy of Serengetilagus Laetoli
The forelimb elements of the leporid Serengetilagus praecapensis, from the famous Laetoli sites in Tanzania, occur in three stratigraphic levels. Most come from the Upper Laetolil Beds, the middle unit. Size frequency distributions of limb dimensions demonstrate one highly variable population with no clear trends through time. Statistical analyses cannot be used to support the presence of more than one species. Sexual dimorphism also is not apparent in the samples, but may have contributed to the variability in sizes. Anatomical traits of the forelimb ally Serengetilagus praecapensis with smaller, less cursorial leporids like the modern European rabbit Oryctolagus. Serengetilagus praecapensis has a predicted body mass in the range of 1.2-1.6 kg. Like some smaller modern rabbits, its forelimb suggests the capability for burrowing.
Journal of Morphology, 2008
The morphology and histology of male and female reproductive systems were examined in Scoloplax distolothrix. Internal insemination was documented in this species by the presence of sperm within the ovaries. Mature males and females have elongated genital papillae, exhibiting a tubular shape in males and a plain heart-shape with two median protuberances in females. The testes are two elongated structures that converge ventrally, under the intestine, towards the genital papilla. They are joined at the caudal end, forming an ovoid single chamber for sperm storage. Secretory regions were not observed. In the lumen of the testicular tubules, spermatozoa can be tightly packed along their lengths, but do not constitute a spermatozeugmata. The lumen of the sperm storage chamber and spermatic duct are filled with free spermatozoa without the accompanying secretions. The ovaries are bird-wing shaped, saccular structures that converge ventrally under the intestine, towards the genital papilla. They are joined at the caudal end, forming a tubular chamber possibly destined for oocyte storage. An oviduct with an irregular outline connects the chamber to the tubular region of the genital papilla. No distinct sperm storage structure was found in the ovaries. The unique male and female genital papillae suggest that these structures are associated with the reproductive mode in scoloplacids, representing evidence for insemination. The occurrence of free spermatozoa, without the accompanying secretions and not arranged in a spermatozeugmata can be associated with the presence of a tubular male genital papilla for sperm transfer to the female genital tract. This reinforces the idea that sperm packets are not necessary for all inseminating species. The male reproductive system in scoloplacids is very different from that in auchenipterids, a second catfish family with insemination, which indicates that the occurrence of insemination is not connected to the internal morphology of reproductive organs.
Organisms Diversity & Evolution, 2007
Phylogenetic relationships of (19) serpulid taxa (including Spirorbinae) were reconstructed based on 18S rRNA gene sequence data. Maximum likelihood, Bayesian inference, and maximum parsimony methods were used in phylogenetic reconstruction. Regardless of the method used, monophyly of Serpulidae is confirmed and four monophyletic, wellsupported major clades are recovered: the Spirorbinae and three groups hitherto referred to as the Protula-, Serpula-, and Pomatoceros-group. Contrary to the taxonomic literature and the hypothesis of opercular evolution, the Protulaclade contains non-operculate (Protula, Salmacina) and operculate taxa both with pinnulate and non-pinnulate peduncle (Filograna vs. Vermiliopsis), and most likely is the sister group to Spirorbinae. Operculate Serpulinae and poorly or non-operculate Filograninae are paraphyletic. It is likely that lack of opercula in some serpulid genera is not a plesiomorphic character state, but reflects a special adaptation.