Note on Lepidosiren annectens,Owen.

Refeering to Prof. Owen's paper on Lepidosiren in the 18th volume of the Society's “Transactions,” the author states that the conclusion at which that gentleman has arrived, that the animal in question is a Pish, although controverted by some of our best naturalists, appears to him to receive confirmation from one or two points in its structure on which no great stress has hitherto been laid. The first of these relates to the mode in which the gill is covered, having only a single small external opening, in which respect Lepidosiren makes a very near approach to Muræna. Secondly, the two peculiar anterior teeth in the upper jaw 80 closely resemble those of some Fishes, that the vignette representing these teeth in Echiodon Drummondii, given in Mr. Yarrell's “History of British Fishes,” might serve as well for the front teeth of Lepidosiren. Thirdly, the continuous dorsal, caudal and anal fin, and the absence of pectorals and ventrals, are common characters among Murænidæ. And fourthly, the true Fish-scales, together with the lateral line extending from the gill to the extremity of the tail, are characters peculiar to Fishes, and not to be found among Amphibian Beptiles. Assuming then that Lepidosiren is unquestionably a Fish, and not either a Reptile or an osculant between Fishes and Reptiles, Mr. Newman regards it as completely obliterating the boundary set up by Cuvier between the two great subclasses of Fishes, the Osseous and the Cartilaginous. In support of this opinion he quotes several passages from Prof. Owen's paper, and concludes by stating his conviction that it is “equally impossible to place it in either the Cartilaginous or Osseous series; and we are compelled either to establish an intermediate series, consisting of but three species or perhaps genera, or to break up those great divisions, which have received the almost universal approbation of naturalists. The first course seems most undesirable in an age in which we are exerting ourselves to find associates and allies for every abnormal form, however apparently isolated. The alternative, the mingling of cartilaginous and osseous fishes, seems inevitable.”     

Evaluation of quenching methods for metabolite recovery in photoautotrophic Synechococcus sp. PCC 7002

The first step of many metabolomics studies is quenching, a technique vital for rapidly halting metabolism and ensuring that the metabolite profile remains unchanging during sample processing. The most widely used approach is to plunge the sample into prechilled cold methanol; however, this led to significant metabolite loss in Synecheococcus sp. PCC 7002. Here we describe our analysis of the impacts of cold methanol quenching on the model marine cyanobacterium Synechococcus sp. PCC 7002, as well as our brief investigation of alternative quenching methods. We tested several methods including cold methanol, cold saline, and two filtration approaches. Targeted central metabolites were extracted and metabolomic profiles were generated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results indicate that cold methanol quenching induces dramatic metabolite leakage in Synechococcus, resulting in a majority of central metabolites being lost prior to extraction. Alternatively, usage of a chilled saline quenching solution mitigates metabolite leakage and improves sample recovery without sacrificing rapid quenching of cellular metabolism. Finally, we illustrate that metabolite leakage can be assessed, and subsequently accounted for, in order to determine absolute metabolite pool sizes; however, our results show that metabolite leakage is inconsistent across various metabolite pools and therefore must be determined for each individually measured metabolite.     

Earliest vertebrate embryos in the fossil record (Middle Devonian,Givetian)

Serial sectioning of a nodule encapsulating an adult specimen of the arthrodire placoderm Watsonosteus fletti from the Eday Flagstone Formation (Givetian) in the Orcadian Basin of northern Scotland has revealed the presence of a number of embryos within the adult. This specimen represents the oldest known record of fossilized vertebrate embryos. Thin sections of two of the slices have revealed the detailed histological structure of embryonic plates in placoderms, showing that as previously deduced from visual examination, the outer and inner layers were the first to form. Gut contents preserved near the embryos show that the species had a varied diet, with dermal bone fragments from sarcopterygians and placoderms.