Vocal morphology of the Physalaemus pustulosus species group (Leptodactylidae): morphological response to sexual selection for complex calls

Most male frogs in the genus Physalaemus produce a whine-like advertisement call. Male P. pustulosus , however, add chucks to the call. This enhances the attractiveness of the call to females, and has evolved under the influence of sexual selection despite the increased predation risk from the frog-eating bat ( Trachops cirrhosus ). This complex call is unusual, if not unique, among anurans because the two call components overlap in time. Here we investigate the morphological changes responsible for the production of complex calls.
The Physalaemus purtulosus species group consists of four species. Physalaemus pustulosus and P. petersi are sister species, and recently it has been shown that P. petersi produces chucks. Physalaemus coloradorum and P. purtulatus are sister species and neither is known to produce chucks. Two laryngeal characters vary within the species group. Physalaemus pustulosus has a large fibrous mass (FMI), whose vibration is responsible for production of the chuck. This mass is much smaller in the other three species. In P. pustulosus and P. petersi the FMI is anchored dorsally, deep within the bronchial process, the attachment is more extensive in P. pustulosus. Neither P. pustulatus nor P. coloradorum have such a dorsal attachment associated with their FMI. This character is responsible for allowing the FMI to vibrate independently of the vocal cords, that is, for the production of the complex call. Thus the morphological changes responsible for the evolution of this unusual behavioural innovation, the complex call, are gradual, and almost trival, in nature. This study also shows that the primitive condition of the larynx of the P. pustulosus and P. petersi ancestor, was predisposed to the production of complex calls.
We also document ontogenetic and sexually dimorphic patterns in larynx structure.     

Metabolism of N-(purin-6-yl)glycine by Soya Bean Callus

The growth of cytokinin-dependent soya bean callus has beenshown to be accelerated by adding N-(purin-6-yl)glycine to themedium. Two biologically active peaks were detected when thecallus was cultured with N-(purin-6-yl)glycine. These two peaksco-chromatographed with 6-(2, 3, 4-trihydroxy-3-methylbutylamino)purineand zeatin respectively. When ¹⁴C labelled N-(purin-6-yl)glycinewas applied to the callus, radioactivity was found with boththese compounds irrespective of whether or not the N-(purin-6-yl)glycinewas labelled in the side chain or in the 8-position of the purinering. Small amounts of zeatin appear to be produced from N-(purin-6-yl)glycinewhich could explain why this compound stimulates the divisionof soya bean callus. N-(purin-6-yl)glycine, soya bean callus, metabolism, radioactivity, cytokinins     

Identification of Zeatin and Zeatinriboside in Coconut Milk

Zeatin and zeatinriboside were identified from the milk of mature Cocos nucifera fruits. It would appear as if the two compounds are present in roughly equal proportions. Ethyl acetate extraction in a liquid-liquid extractor at an alkaline pH (8.0) proved to be a very efficient method of extracting zeatinriboside. Partitioning with water-saturated n-butanol proved to be the best way of extracting zeatin.     

Identification of Cell Division Inducing Compounds from Coconut Milk

The use of chromatographic techniques coupled with mass spectrometry, infra-red analysis and nuclear magnetic resonance revealed that the amino acid phenylalanine might be responsible for a large proportion of the cell division activity of coconut milk as determined by the soybean bioassay. The observation that zeatin can be removed very readily by partitioning against ethyl acetate at alkaline pH values, cautions against inclusion of this method as a purification step for extracting cytokinins from plant extracts. Mass spectrometry revealed the presence of an unidentified cell division substance with a molecular ion of 279 and which co-chromatographed with zeatinriboside on Sephadex LH-20.     

Enhanced assimilation rate and water use efficiency with latitude through increased photosynthetic capacity and internal conductance in balsam poplar (Populus balsamifera L.)

In outdoor common gardens, high latitude populations of deciduous tree species often display higher assimilation rates ( A ) than low latitude populations, but they accomplish less height. To test whether trends in A reflect adaptation to growing season length or, alternatively, are garden growth artefacts, we examined variation in height increment and ecophysiological traits in a range-wide collection of Populus balsamifera L. populations from 21 provenances, during unconstrained growth in a greenhouse. Rooted cuttings, maintained without resource limitation under 21 h photoperiod for 90 d, displayed increasing height growth, A , leaf mass per area and leaf N per area with latitude whereas stomatal conductance ( g _s) showed no pattern. Water-use efficiency as indicated by both gas exchange and δ ¹³C increased with latitude, whereas photosynthetic nitrogen-use efficiency decreased. Differences in δ ¹³C were less than expected based on A/g _s, suggesting coextensive variation in internal conductance ( g _m). Analysis of A – C _i curves on a subset of populations showed that high latitude genotypes had greater g _m than low-latitude genotypes. We conclude that higher peak rates of height growth in high latitude genotypes of balsam poplar are supported by higher A , achieved partly through higher g _m, to help compensate for a shorter growing season.     

Snail-eating frogs from the Ethiopian highlands: a new anuran specialization

Morphological studies and analysis of gut contents indicate that two species of montane Ethiopian frogs are specialized for selective feeding on terrestrial gastropod mollusks. Certain bony elements of the skull, such as the palatines and prevomers, are reduced and deflected dorsally, while lateral elements of the maxillary arch, such as die quadratojugals and maxillaries, are expanded. The nasal apparatus in both species is situated in an extreme anterior position. The two species are removed from the genus Kassina Girard and placed in die genus Tomierella Ahl. Morphology of the head suggests that these frogs grasp mollusks with their jaws, pull diem from die substrate, and swallow them whole. The sensory cues which trigger feeding are as yet unknown. Apparently, diese frogs are the first terrestrial vertebrates known to feed exclusively on whole mollusks, wimout crushing them or removing the soft parts from the shell.     

Sublethal Effects of Environmental Toxicants on Oligochaete Escape Reflexes

Soft-bodied oligochaetes that reside in soil and benthic environmentsare frequently exposed to pesticides and other environmentaltoxicants. Using noninvasive electrical recording techniques,some of the sublethal neurophysiological effects of these toxicantshave been assessed in selected terrestrial and freshwater oligochaetes:Lumbricus terrestris, Eisenia foetida, and Lumbriculus variegatus.Under laboratory conditions, short-term cutaneous exposure toa wide variety of toxicants produces sublethal and reversibledisruptions of giant nerve fiber spike activity and other bioelectricevents that mediate rapid escape reflexes. Generally, electrophysiologicaleffects include one or more of the following: (a) hypo- or hyper-excitability of giant fibers to mechanosensory stimulation,(b) reduction in giant fiber conduction velocity, (c) inductionof abnormal giant fiber activity (i.e., spontaneous, rebound,or ectopic spiking), (d) increased delay or block of centraltransmission between the medial giant interneuron (MGF) andits associated pool of motorneurons, and (e) attenuation ofMGF-mediated electrical potentials in longitudinal muscle. Theseefforts to describe the systemic impact and time course of neurotoxicanteffects in vivo are necessary steps in ultimately predictingthe ecological consequences of neurotoxicant exposure in situ.     

Reserve Mobilization During Germination of Tagetes minuta L.

Levels of albumins, globulins and starch were measured in dryTagetes minuta L. achenes (seeds) germinating at 25 °C andin those thermo-inhibited at 35 °C. In addition, the compositionof amino acids, fatty acids and free sugars was determined. In germinating seeds, albumins increased, while globulins decreased.At 35 °C, only a delayed decrease in globulins occurred.However, in both, the amino acids serine and glutamate increased.Lipid composition remained constant except for a slight declinein linoleic acid in the germinating seeds. At 25 °C, starchlevels increased with time while at 35 °C, there was onlya transient increase. Sucrose was the major free sugar foundin the seeds at all times, but its levels declined in the germinatingseeds. This was accompanied by an increase in the proportionsof glucose and fructose. No such changes in sugar compositionwere observed in the thermo-inhibited seeds. Tagetes minuta L., seed germination, reserve mobilization, thermo-inhibition     

Cytokinin Biosynthesis in Germinating Maize Embryos

Three-day-old germinating embryos of Zea mays were incubatedwith [8-¹⁴C]adenine for 8 and 24 h. Use of high performanceliquid and thin layer chromatography provided evidence for theincorporation of adenine by isolated germinating embryos intotrans-zeatin. These results are at variance with similar labellingstudies and possible reasons for this discrepancy are discussed. Key words: Adenine, germination, maize kernels, zeatin