scholarly journals Significance of the suture line in cephalopod taxonomy revealed by 3D morphometrics in the modern nautilids Nautilus and Allonautilus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amane Tajika ◽  
Naoki Morimoto ◽  
Neil H. Landman
Keyword(s):  
Computed Tomography ◽  
Geometric Morphometrics ◽  
Suture Line ◽  
Molecular Data ◽  
Isolated Populations ◽  
Earth History ◽  
Taxonomic Importance ◽  
Geographical Populations ◽  
3D Morphometrics ◽  
Geographically Isolated

AbstractAssessing the taxonomic importance of the suture line in shelled cephalopods is a key to better understanding the diversity of this group in Earth history. Because fossils are subject to taphonomic artifacts, an in-depth knowledge of well-preserved modern organisms is needed as an important reference. Here, we examine the suture line morphology of all known species of the modern cephalopods Nautilus and Allonautilus. We applied computed tomography and geometric morphometrics to quantify the suture line morphology as well as the conch geometry and septal spacing. Results reveal that the suture line and conch geometry are useful in distinguishing species, while septal spacing is less useful. We also constructed cluster trees to illustrate the similarity among species. The tree based on conch geometry in middle ontogeny is nearly congruent with those previously reconstructed based on molecular data. In addition, different geographical populations of the same species of Nautilus separate out in this tree. This suggests that genetically distinct (i.e., geographically isolated) populations of Nautilus can also be distinguished using conch geometry. Our results are applicable to closely related fossil cephalopods (nautilids), but may not apply to more distantly related forms (ammonoids).

An ultrastructural study of sertoli cells in two geographically isolated populations of Aphanius dispar

1992 ◽  
Vol 50 (1) ◽  
pp. 548-549
Author(s):  
Taber A. Ba-Omar ◽  
Philip F. Prentis
Keyword(s):  
Ultrastructural Level ◽  
Uranyl Acetate ◽  
Freshwater Teleost ◽  
Isolated Populations ◽  
En Bloc ◽  
The North ◽  
Group A ◽  
Ultrathin Sections ◽  
Group B ◽  
Geographically Isolated

We have recently carried out a study of spermiogenic differentiation in two geographically isolated populations of Aphanius dispar (freshwater teleost), with a view to ascertaining variation at the ultrastructural level. The sampling areas were the Jebel Al Akhdar in the north (Group A) and the Dhofar region (Group B) in the south. Specimens from each group were collected, the testes removed, fixed in Karnovsky solution, post fixed in OsO, en bloc stained with uranyl acetate and then routinely processed to Agar 100 resin, semi and ultrathin sections were prepared for study.

scholarly journals Morphological and Genetic Structure of Two Equivalent Astyanax Species (Characiformes: Characidae) in the Region of Paranaíba Arc

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Renan Rodrigues Rocha ◽  
Rosana de Mesquita Alves ◽  
Rubens Pasa ◽  
Karine Frehner Kavalco
Keyword(s):  
Geometric Morphometrics ◽  
River Basin ◽  
Dna Sequences ◽  
Haplotype Network ◽  
River Basins ◽  
Molecular Data ◽  
The Body ◽  
Present Species ◽  
Body Depth ◽  
Geometric Morphometric

The Astyanax scabripinnis complex is composed of a large number of almost morphological indistinguishable species, including Astyanax paranae and Astyanax rivularis, which exist in the Paraná and São Francisco Basins, respectively, and sometimes are considered subspecies of the A. scabripinnis group or even are cited just as A. scabripinnis. The two river basins are separated by the Upper Paranaíba Arc, likely the main cause of the isolation of these species. We used geometric morphometric tools and DNA analyses of populations of both species to identify the differences between them. Geometric morphometrics separated the two species into distinct groups, whose main difference was the body depth. This is generally related to the speed of the water flow in the river basins. The maximum likelihood phylogram based on mitochondrial DNA sequences formed two main clades: one composed of the population of A. rivularis and the other, of A. paranae. In the haplotype network, the species were similarly separated into two groups from the same ancestral haplotype, with A. rivularis dispersing into two lineages in the São Francisco River Basin. The distribution of A. paranae is a consequence of a secondary dispersion event in the Paraná River Basin. It forms two lineages from a haplotype derived from the ancestor. The vicariant effect of separate basins, through the elevation of the Upper Paranaíba Arc, led to the allopatric speciation of the populations originating the present species. The results of geometric morphometrics and molecular data of the fish show the importance of this geological event in the biogeography and evolutionary history of the ichthyofauna of the region and indicate that the isolation of these species seems to be effective.

scholarly journals Major features of protistan evolution: controversies, problems and a few answers

2006 ◽  
Vol 29 (1) ◽  
pp. 55-80
Author(s):  
Jere H Lipps
Keyword(s):  
Fossil Record ◽  
Molecular Data ◽  
Trophic Levels ◽  
Early Earth ◽  
Huge Number ◽  
Geologic Time ◽  
Earth History ◽  
Important Development ◽  
Fossil Evidence

The major features of protist evolution are fraught with controversies, problems and few answers, especially in early Earth history. In general they are based on molecular data and fossil evidence that respectively provide a scaffold and details of eukaryotic phylogenetic and ecologic histories. 1. Their origin, inferred from molecular sequences, occurred very early (>;3Ga). They are a chimera of different symbiont-derived organelles, including possibly the nucleus. 2. The initial diversification of eukaryotes may have occurred early in geologic time. Six supergroups exist today, each with fossils known from the Proterozoic and Phanerozoic. 3. Sex, considered an important development, may have been inherited from bacteria. 4. Precambrian protists were largely pelagic cyst-bearing taxa, but benthic forms were probably quite diverse and abundant. 5. Protists gave rise to animals long before 600 Ma through the choanoflagellates, for which no fossil record exists. 6. Acritarchs and skeletonized protists radiated in the Cambrian (544-530 my). From then on, they radiated and became extinct at all the major events recorded in the metazoan fossil record. 7. Protists dominated major environments (shelves and reefs) starting with a significant radiation in the Ordovician, followed by extinctions and other radiations until most died out at the end of the Permian. 8. In the Mesozoic, new planktic protozoa and algae appeared and radiated in pelagic environments. 9. Modern protists are important at all trophic levels in the oceans and a huge number terrestrial, parasitic and symbiotic protists must have existed for much of geologic time as well. 10. The future of protists is likely in jeopardy, just like most reefal, benthic, and planktic metazoans. An urgent need to understand the role of protists in modern threatened oceans should be addressed soon.

A new species of Pygopus (Pygopodidae; Gekkota; Squamata) from north-eastern Queensland

Zootaxa ◽  
2010 ◽  
Vol 2578 (1) ◽  
pp. 47 ◽  
Author(s):  
PAUL M. OLIVER ◽  
PATRICK COUPER ◽  
ANDREW AMEY
Keyword(s):  
New Species ◽  
Morphological Diversity ◽  
Genetic Data ◽  
Lower Number ◽  
Evolutionary Divergence ◽  
Isolated Populations ◽  
South Eastern ◽  
North Eastern ◽  
A New Species ◽  
Geographically Isolated

Based on a combination of morphological and genetic data, geographically isolated populations of Pygopus from northeastern Queensland, formerly referred to Pygopus lepidopodus (Lacépède), are herein described as a new species. Pygopus robertsi sp. nov. can be diagnosed from its congeners by a suite of scalation characters, including fewer keeled dorsal scales, presence of a single continuous row of supracilaries and a lower number of midbody scale rows. It is also deeply divergent genetically from samples of Pygopus lepidopodus from southern Australia. The known distribution of Pygopus robertsi sp. nov. is similar to that of a number of taxa centred upon relatively dry ecotonal habitats at the western edge of the rainforest blocks of north-eastern Queensland. Additional samples and systematic work will be required to examine the evolutionary divergence of apparently isolated populations of the new species, and the significance of considerable genetic and morphological diversity within remaining populations of Pygopus lepidopodus from south-eastern and southern Australia.

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