Some Aspects of Regeneration in the Scyphistoma of Cassiopea (Class Scyphozoa) as Revealed by the Use of Antimetabolites and Microspectrophotometry

As a continuation of studies of the regenerative capacitiesof the scyphistoma of Cassiopea, a series of experiments wasundertaken in which (i) regenerating fragments were culturedin the presence of various antimetabolites and (ii) Feulgenstainednuclei from control animals and regenerating fragments weremeasured by scanning, integrating microspectrophotometry. Theresults of the antimetabolite experiments were complex and variablebut nonetheless suggested that normal regeneration of functionalheads from fragments requires the synthesis of DNA, RNA, andprotein. Regardless of the type of antimetabolite, the mostfrequently observed morphological effect was prolonged or arresteddevelopment. None of the antimetabolites produced characteristicor unique abnormalities, although variation was observed inthe ability of the inhibited fragments to recover from the variousantimetabolites. Microspectrophotometric measurements of Feulgen-stainednuclei from control animals revealed that approximately 25%of the nuclei contained more than the diploid amount of DNAand thus were in either the S or G₂ phases of the cell cycle.In regenerating fragments, the frequency of nuclei in this categorydropped progressively to less than 6% by the end of 3 days butreturned nearly to control levels by the end of six days. Thenuclei also became somewhat enlarged and less dense during regeneration.     

Prevalence of Sarcocystis in Grackles in Maryland

SYNOPSIS. One hundred and fifty-nine grackles (Quiscalus quiscula) in Maryland were examined grossly and microscopically for Sarcocystis sp. Of 98 mature birds, 91 had Sarcocystis. None of 51 juvenile birds and none of 10 birds hatched in the laboratory had Sarcocystis. More mature females had Sarcocystis than did mature males. However, the number of intramuscular cysts (per bird) was greater in male grackles than in females. Both male and female grackles had more infections in the leg and thigh muscles than in breast muscles. No tongue or heart muscles contained Sarcocystis. No seasonal fluctuation in the number of infected birds was apparent.     

Enterocytozoon bieneusi Genotype Nomenclature Based on the Internal Transcribed Spacer Sequence: A Consensus

ABSTRACT. The standard method for determining the genotypes of Enterocytozoon bieneusi is based on the DNA sequence of the internal transcribed spacer (ITS) region of the rRNA gene. There are 81 genotypes with 111 genotype names: 26 genotypes have been identified exclusively in humans, eight have been identified in humans and in other hosts, 27 have been identified exclusively in cattle and pigs, six have been identified exclusively in cats and dogs, and 14 have been identified in miscellaneous hosts. Because none of these genotypes has taxonomic status and therefore do not adhere to the International Code of Zoological Nomenclature regarding naming, some genotypes have received multiple names, each different and in separate publications by different authors. Because of the proliferation of genotypes with overlapping names and multiple hosts the scientific literature has become confusing and difficult to efficiently utilize. To reduce confusion and provide guidance for future publications we tabulated all names, GenBank accession numbers, and author citations and propose that the first published name has precedence and should become the primary name used in all subsequent publications in which genotyping is based on ITS sequencing. In those publications the names and GenBank numbers that were submitted at later dates should also be provided by the authors as synonyms to aid readers and reviewers.     

Skeletal anatomy of the extinct shark Paraorthacodus jurensis (Chondrichthyes; Palaeospinacidae), with comments on synechodontiform and palaeospinacid monophyly

The skeletal morphology of Paraorthacodus jurensis, a Late Jurassic neoselachian from Nusplingen, is described based on the incomplete holotype and a newly discovered almost complete specimen. For the first time, the postcranial skeleton could be investigated. Paraorthacodus is characterized by a monognath dental heterodonty and tearing‐type dentition. The number of lateral cusplets in the lateral teeth differs between the holotype and the new specimen, possibly indicating sexual dimorphism. Clasper organs are not preserved in either of the two specimens. The notochord is sheathed by about 123 well‐calcified vertebral centra. The posterior‐most caudal vertebrae are lacking. The transition from monospondylous thoracic to diplospondylous abdominal vertebrae occurs at centra 48 and 49. The origin of the caudal fin is at the 80th centrum. Most conspicuous is the presence of a single spineless dorsal fin. In this respect, Paraorthacodus differs from most palaeospinacids, but resembles Macrourogaleus. Palidiplospinax possibly is sister to a group comprising Synechodus, Paraorthacodus, and Macrourogaleus (the Palaeospinacidae). A reinterpretation of dental and skeletal characters of synechodontiform taxa indicates that Synechodontiformes and Palaeospinacidae are monophyletic groupings of basal neoselachians. Synechodontiformes is probably sister to all living elasmobranchs.     

Different pathways are involved in the early development of the transient oral apparatus in anuran tadpoles (Anura: Leiuperidae)

The oral apparatus of anuran tadpoles is a unique structure composed of soft and keratinized parts surrounding the mouth. Among the many variations, a common oral apparatus involves a dorsal gap in the marginal papillae, keratinized jaw sheaths, and two upper and three lower rows of labial teeth. In Leiuperidae, besides this generalized morphology, four configurations are distinguished by the arrangement of the lower marginal papillae and the number of lower tooth rows. Study of the early oral ontogeny in 12 species representing these five configurations shows variations in the development of the lower marginal papillae and the third lower labial tooth row. Similar configurations may result from similar pathways (e.g. Physalaemus cuvieri group and Pseudopaludicola falcipes) or different pathways (e.g. generalized oral discs of Pleurodema and Physalaemus). Different oral configurations may result from overlapping trajectories ending at different stages (e.g. Physalaemus riograndensis and Ph. biligonigerus) or different trajectories (e.g. Ph. henselii and Ph. gracilis). Further studies are needed to interpret the role that heterochrony has played in evolutionary change within this family. The unsuspected variation occurring in this transient structure highlights its evolutionary potential and might be insightful in studies of anuran phylogenies that are largely based on adult characters. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 330–345.     

The genus Dugesia in Australia, with its phylogenetic analysis and historical biogeography (Platyhelminthes, Tricladida, Dugesiidae)

The new species Dugesia notogaea Sluys & Kawakatsu, sp. n. is described from Queensland, Australia, representing the first record of the genus Dugesia for that continent. A phylogenetic analysis of the 68 species of Dugesia resulted in the discovery of a new apomorphy for the genus, and a cladogram showing two major phyletic groups. The distributional range of one group has a western accent, whereas that of the other group has an eastern emphasis; the ranges of these two groups overlap in Africa and the Mediterranean region. We attempt to determine the ancestral area for both the Dugesiidae and Dugesia. A scenario for the historical biogeography of the genus Dugesia is discussed. In this scenario it is presumed that the geological history of the Australasian region enabled Dugesia's from southeast Asia to colonize northern Australia. © 1998 The Norwegian Academy of Science and Letters     

The effects of feeding regime on the growth and reproduction of the medicinal leech Hirudo medicinalis

1. The feeding frequency, the size of meals, the number of meals required to attain reproductive maturity and the number of meals taken between iteroparous reproductive bouts were determined in the laboratory under optimal conditions for the medicinal leech Hirudo medicinalis fed exclusively on mammalian (bovine) blood. In addition the number of bouts of reproduction and the numbers of cocoons and hatchlings per cocoon produced were determined.
2. The average time for H. medicinalis to reach reproductive maturity at 20°C was 289 days, at an average wet biomass of 8143 mg with two–nine separate bouts of cocoon production. The number of meals to first reproduction was 8.9 (mean meal size of 3066.7 mg), with a significant correlation between total mass of blood ingested and the numbers of reproductive bouts and number of cocoons produced. Mean lifetime cocoon production per individual was 12.43, with 3.9 hatchlings per cocoon.
3. The significant positive relationships between ingestion, fecundity and developmental rate observed support the hypothesis that declining abundances of field populations of H. medicinalis are the result of lower available energy for growth, reflecting leeches now feeding predominantly on amphibian blood of lower energetic value than mammalian blood.