Phylogenetic relationships and molecular evolution in uropeltid snakes (Serpentes: Uropeltidae): allozymes and albumin immunology

Multilocus electrophoretic methods and microcomplement fixation comparisons of serum albumin are used to assess phylogenetic relationships among species of uropeltid snakes, to infer aspects of their population biology and biogeography, and to evaluate their relationships to other primitive snakes (Henophidia). There is very good agreement between phylogenetic inferences derived from the electrophoretic data and those derived from the albumin immunological data. Protein variation detected by electrophoresis is relatively high among 17 operational taxonomic units (OTUs) examined. The mean number of alleles per locus (5.1 across all OTUs), levels of polymorphism (25% of loci), and heterozygosity (4–6%), are typical of, or greater than, values reported for other snakes. Species of uropeltids are genetically highly differentiated, as measured by genetic distances (lowest interspecific Nei's unbiased genetic distances, 0.22-0.27 among several Sri Lankan species; 2.3 between Teretrurus of India and other uropeltines). The phylogenetic tree most consistent with both the immunological and electrophoretic data shows uropeltines from Sri Lanka to be monophyletic, but the Indian species are paraphyletic with respect to those from Sri Lanka. Rhinophis travancoricus of India is inferred to be the sister taxon to the Sri Lankan radiation. As the genera are presently understood, neither Rhinophis nor Uropeltis appears to be monophyletic. A biogeographic scenario derived from the phylogenetic hypothesis suggests an early diversification of uropeltids in India, followed by a single invasion into the lowlands of Sri Lanka. Subsequent evolution on Sri Lanka resulted in occupation of montane biotopes. Cylindrophis is the sister group to uropeltines and is considered a member of the Uropeltidae. The immunological data indicate no phylogenetic association between uropeltids and other ‘anilioid’ taxa, specifically Anilius, Loxocemus or Xenopeltis, although we cannot rule out a very remote relationship. We specifically reject the hypothesis that uropeltines and scolecophidians form a clade relative to henophidians. High levels of genetic variation and a trend toward negative F_IS values for polymorphic loci in three populations suggest generally large effective population sizes and outbreeding in these species. The niche-width variation hypothesis for allozyme loci is not supported by the uropeltid data. In comparison to other vertebrates, the relationship between Nei's genetic distance and albumin immunological distance in uropeltids suggests either conservative albumin evolution or strong differentiation at electrophoretic loci.     

Sound Production in the Salientia: Mechanism and Evolution of the Emitter

Frog sounds involve expulsion of air through the larynx. Inmating, release, rain, and territorial calls, the air vibratesvocal cords and/or arytenoid cartilages. Sound is amplifiedand radiated by the distended buccal cavity and vocal sacs.Distress calls are emitted with open mouth, with minimum laryngealmodulation. The trunk is filled by inflation cycles, but airis driven out by synchronized contractions of the body wallmusculature. The pressure levels are more than five times thoseduring ventilation. In the release call of Bufo valliceps the dilatators and constrictorsof the larynx fire simultaneously keeping the larynx closed.As the pulmonary pressure reaches a peak they cease firing.The arytenoids then separate and vibrate, as do the vocal cords.The dilatators terminate the sound pulse by pulling vibratorsout of the air stream, hence the very sharp termination. Prolongedrelease call sequences include interpulse Teinflations thatreturn air from buccal cavity to lung. Frogs apparently evolved from amphibians too small to use aspirationbreathing. Vocalization represented a critical factor in theirsocial organization and its importance locked these animalsinto reliance upon pulse-pumping rather than the more efficientaspiration breathing.     

Crocodilians in Perspective!

The prediction of the 1960s that crocodilians would soon beextinct has happily proven to be unduly pessimistic. The survivaland recovery of substantial stocks provides us with the unexpectedopportunity to learn about their adaptations, important notonly because of their place as relicts of a major reptilianradiation, but also as giant animals, reptiles substantiallylarger than all but marine turtles.     

Differences and Similarities: Comparative Methods in Mastication

Comparison is the key to biological study and both similaritiesand differences aid in sharpening our understanding of structuresand processes. The initial comparison represents an observationallevel; followed by decisions aboutpossible homology, analogyand homoplasy which represent levels that have less certainty.Analogous homoplasies are presumably the most useful conditionsfor characterizing functional constraints. Operational criteriaare discussed, as are minimal technical standards for procedurespermitting characterization of functions and roles in the masticatorysystem.     

Vertebrate Morphology: Tale of a Phoenix

The last 25 years have seen a renaissance in the use of structuralprinciples in biological study. Analytical methods have beenrefined and new concepts introduced. Systematic applicationshave imposed new demands because cladistic methods have emphasizedthe need for correct interpretations of individual characters.Developmental approaches now permit association of characters;however, newly described genetic mechanisms may pose questionsabout structural criteria forhomology. Structural charactersprove significant, both in evaluation of the possible rolesof morphological characteristics and in establishing the realityand level of adaptation. Morphology, ever more, is an area ofactive researches promising significant results.     

zpl, a new gene in drosophila required for neurogenesis

zpl(zip-like) gene mutant embryos showed the cuticular defect with alternative denticle rows and a hole from head to abdomen.zpl mutants also caused the overgrowth of neural cells and axons both in CNS and PNS as well as the wrong pathway of neural fasciculation and the disappearance of hypophysis,as shown by whole mount embryos stained with antibody against HRP and MAb-22C10.Genetic analysis has provided evidence that zpl,located in the right arm of the second chromosome(between 75 and 102 genetic map units),is a new gene closely related to the zip gene.