Control of blood volume following hypovolemic challenge in vertebrates: Transcapillary versus lymphatic mechanisms.

Anurans have an exceptional capacity for maintaining vascular volume compared with other groups of vertebrates. They can mobilize interstitial fluids via lymphatic return at rates that are ten-fold higher than mammals. This extraordinary capacity is the result of coordination of specialized skeletal muscles and pulmonary ventilation that vary volume and pressure of subcutaneous lymph sacs, thus moving lymph to dorsally located lymph hearts that return lymph to the vascular space.

Land flatworms (Platyhelminthes, Geoplanidae) of São Tomé: a first account on their diversity, with the description of five new species.

The present contribution provides the first faunistic and taxonomic account of six species of land flatworm from the island of São Tomé, including five new species of the genus Othelosoma Gray, 1869 and the introduced Bipalium kewense Moseley, 1878. One of the new species represents the first African land flatworm that has specks on its dorsal body surface, instead of stripes or a more or less uniform colouration. At least two of the new species were observed to prey on snails.

Reed frog diversification in the Gulf of Guinea: overseas dispersal, the progression rule, and in situ speciation.

Oceanic islands accumulate endemic species when new colonists diverge from source populations or by in situ diversification of resident island endemics. The relative importance of dispersal versus in situ speciation in generating diversity on islands varies with a number of archipelago characteristics including island size, age, and remoteness. Here, we characterize interisland dispersal and in situ speciation in frogs endemic to the Gulf of Guinea islands.

Population genetics of the São Tomé caecilian (Gymnophiona: Dermophiidae: Schistometopum thomense) reveals strong geographic structuring.

Islands provide exciting opportunities for exploring ecological and evolutionary mechanisms. The oceanic island of São Tomé in the Gulf of Guinea exhibits high diversity of fauna including the endemic caecilian amphibian, Schistometopum thomense. Variation in pigmentation, morphology and size of this taxon over its c.

Physiological vagility and its relationship to dispersal and neutral genetic heterogeneity in vertebrates.

Vagility is the inherent power of movement by individuals. Vagility and the available duration of movement determine the dispersal distance individuals can move to interbreed, which affects the fine-scale genetic structure of vertebrate populations. Vagility and variation in population genetic structure are normally explained by geographic variation and not by the inherent power of movement by individuals.

Pulmonary compliance and lung volume are related to terrestriality in anuran amphibians.

Dehydration tolerance of anuran amphibians is directly related to their ability to mobilize lymphatic reserves, with more terrestrial species having more effective lymph mobilization dependent on specialized skeletal muscles acting directly on the lymph sacs and via pulmonary ventilation. Consequently, we tested the hypothesis that pulmonary compliance, lung volume, and femoral lymphatic sac volume were related to terrestriality-and, hence, lymph mobilization-for 18 species of aquatic, semiaquatic, or terrestrial anuran amphibians. Lung compliance and volume were significantly related to body mass, but there was no significant phylogenetic pattern.

Physiological vagility: correlations with dispersal and population genetic structure of amphibians.

Physiological vagility represents the capacity to move sustainably and is central to fully explaining the processes involved in creating fine-scale genetic structure of amphibian populations, because movement (vagility) and the duration of movement determine the dispersal distance individuals can move to interbreed. The tendency for amphibians to maintain genetic differentiation over relatively short distances (isolation by distance) has been attributed to their limited dispersal capacity (low vagility) compared with other vertebrates. Earlier studies analyzing genetic isolation and population differentiation with distance treat all amphibians as equally vagile and attempt to explain genetic differentiation only in terms of physical environmental characteristics.

Evolutionary implications of the distribution and variation of the skeletal muscles of the anuran lymphatic system.

Lymphatic return to the circulation in anurans is dependent upon the interaction of a number of skeletal muscles and lung deflation. We define character states and describe variation of these putative lymphatic skeletal muscles: the M. cutaneus pectoris (CP), M.

Lymphatic regulation in nonmammalian vertebrates.

All vertebrate animals share in common the production of lymph through net capillary filtration from their closed circulatory system into their tissues. The balance of forces responsible for net capillary filtration and lymph formation is described by the Starling equation, but additional factors such as vascular and interstitial compliance, which vary markedly among vertebrates, also have a significant impact on rates of lymph formation. Why vertebrates show extreme variability in rates of lymph formation and how nonmammalian vertebrates maintain plasma volume homeostasis is unclear.

Pulmonary compliance and lung volume varies with ecomorphology in anuran amphibians: implications for ventilatory-assisted lymph flux.

Vertical movement of lymph from ventral regions to the dorsally located lymph hearts in anurans is accomplished by specialized skeletal muscles working in concert with lung ventilation. We hypothesize that more terrestrial species with greater lymph mobilization capacities and higher lymph flux rates will have larger lung volumes and higher pulmonary compliance than more semi-aquatic or aquatic species. We measured in situ mean and maximal compliance (Δvolume/Δpressure), distensibility (%Δvolume/Δpressure) and lung volume over a range of physiological pressures (1.

Interspecific comparisons of lymph volume and lymphatic fluxes: do lymph reserves and lymph mobilization capacities vary in anurans from different environments?

The femoral lymph sac volumes and lymph mobilization capacity were compared in three anuran species that span a range of environments, dehydration tolerance, ability to maintain blood volume with dehydration, and degrees of development of skeletal muscles putatively involved in moving lymph vertically to the posterior lymph hearts. The femoral lymph sac volume determined by Evans blue injection and dilution in the femoral lymph sac varied interspecifically. The semiaquatic species, Lithobates catesbeianus, had the greatest apparent lymph volume expressed either as 18.

Lymph flux rates from various lymph sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of lymph.

A new method for quantitatively determining lymph flux from various lymphatic sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C(i)V(i)=C(f)V(f) following injection of Evans Blue into specific lymph sacs and measuring its appearance in the venous circulation. The apparent lymph volume was 57 ml kg(-1).

Lung ventilation contributes to vertical lymph movement in anurans.

Anurans (frogs and toads) generate lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very 'leaky' vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located lymph hearts. At present, it is unclear how lymphatic fluid that accumulates in central body subcutaneous lymph sacs is moved to the anterior and posterior lymph hearts in the axillary regions and how lymph is moved, against gravity, to the dorsally located lymph hearts.

Unique role of skeletal muscle contraction in vertical lymph movement in anurans.

Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous lymph sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana). Our hypothesis was that contraction of these muscles varies the volume, and hence pressure, within these lymph sacs, and that this pressure is responsible for moving lymph from ventral, gravitationally dependent reaches of the body to dorsally located lymph hearts. EMG activity of M.

Functional roles for the compartmentalization of the subcutaneous lymphatic sacs in anuran amphibians.

Compliance of the subcutaneous lymph sacs of the hindlimbs increases from distal to proximal, as does limb segment mass (and presumably rate of lymph formation), for the semiaquatic bullfrog Rana catesbeiana and the cane toad Bufo marinus but not the aquatic clawed toad Xenopus laevis. Subcutaneous lymph-sac compliances vary interspecifically. The distal-to-proximal increase in lymph-sac compliance and estimates of lymph formation rate in the various hindlimb segments indicate that partitioning of hindlimb subcutaneous lymphatic sacs establishes a differential decrease in the intra-lymph-sac pressure for R.

Lymph pools in the basement, sump pumps in the attic: the anuran dilemma for lymph movement.

Amphibians are a vertebrate group transitional between aquatic and terrestrial environments. Consequently, both increases and decreases in blood volume are a natural biological stress associated with aquatic and terrestrial environments. In comparison with other vertebrate classes, anuran amphibians have the most rapid compensation and greatest capacity to compensate for changes in blood volume and survive dehydration.

A molecular phylogenetic analysis of the family Rhacophoridae with an emphasis on the Asian and African genera.

Using characters from mitochondrial DNA to construct maximum parsimony and maximum likelihood trees, we performed a phylogenetic analysis on representative species of 14 genera: 12 that belong to the treefrog family Rhacophoridae and two, Amolops and Rana, that are not rhacophorids. Our results support a phylogenetic hypothesis that depicts a monophyletic family Rhacophoridae. In this family, the Malagasy genera Aglyptodactylus, Boophis, Mantella, and Mantidactylus form a well-supported sister clade to all other rhacophorid genera, and Mantella is the sister taxon to Mantidactylus.