Implications of the mastoid anatomy of larger extant felids for the evolution and predatory behaviour of sabretoothed cats (Mammalia, Carnivora, Felidae)

Muscle attachments in the mastoid region of the skull of extant felids are studied through dissection of two adult tigers Panthera tigris (Linnaeus, 1758) Pocock, 1930, a lion Panthera leo (Linnaeus, 1758) Pocock, 1930 and a puma Puma concolor (Linnaeus, 1771) Jardine, 1834, providing for the first time an adequate reference for the study of the evolution of that region in sabretoothed felids. Our study supports the inference by W. Akersten that the main muscles inserting in the mastoid process in sabretooths were those originating in the atlas, rather than those from the posterior neck, sternum and forelimb. Those inferences were based on the anatomy of the giant panda, Ailuropoda melanoleuca (David, 1869) Milne-Edwards, 1870, raising uncertainties about homology, which were founded, as revealed by our results. The mastoid muscle insertions in extant felids differ in important details from those described for Ailuropoda , but agree with those described for domestic cats, hyenas and dogs. The large, antero-ventrally projected mastoid process of pantherines allows a moderate implication of the m. obliquus capitis anterior in head-flexion. This contradicts the widespread notion that the function of this muscle in carnivores is to extend the atlanto-cranial joint and to flex it laterally, but supports previous inferences about the head-flexing function of atlanto-mastoid muscles in machairodontines. Sabretooth mastoid morphology implies larger and longer-fibred atlanto-mastoid muscles than in pantherines, and that most of their fibres ran inferior to the axis of rotation of the atlanto-occipital joint, emphasizing head-flexing action.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 207–221.     

The influence of light environment on photosynthesis and basal methylbutenol emission from Pinus ponderosa

Methylbutenol is a 5-carbon alcohol that is produced and emitted by several species of pine in western North America, and may have important impacts on the tropospheric chemistry of this region. In the present study the response of methylbutenol basal emission rate (measured at a constant light intensity of 1500 µmol m⁻² s⁻¹ and temperature of 30 °C) to the light and temperature conditions of the growth environment was examined, using field-grown plants shielded with shade cloth of various densities. Methylbutenol basal emission rates increased linearly with the temperature of the growth environment but did not respond to the shading of foliage during growth and development. Both photosynthesis and basal methylbutenol emission rate declined in older needles; however, these declines appear to result from parallel but independent processes and not from basal MBO emission rate directly tracking photosynthetic rates. Older needles did not occupy cooler microenvironments within the canopy; and thus differing thermal microenvironment could not explain the reduced MBO emission in older needles.     

Chemotaxonomic study of seed glucosinolate composition in Coincya Rouy (Brassicaceae)

A total of 68 populations belonging to the genus Coincya Rouy (Brassicaceae) from the Iberian Peninsula was examined for seed glucosinolate composition. The presence of progoitrin, epiprogoitrin, glucosinalbin and gluconapin was recorded plus a fifth glucosinolate that could not be identified. A geographical clinal variation between progoitrin and epiprogoitrin was observed in the more widespread taxa, C. monensis subsp. orophila (Franco) Aedo, Leadiay & Murioz Garm. and C. moncnsis subsp. cheiranthos var. recurvata (All.) Leadiay. The fewest types of glucosinatc were observed in taxa with morphological characters considered more primitive, viz. subsp. hispida and var. recurvata. On the other hand, more complex and diverse composition was observed in the taxon with more advanced characters, viz. C. rupestris subsp. rupestris Porta & Rigo.     

N2 Fixation (C2H2-Reducing Activity) and Leghaemoglobin Content during Nitrate- and Water-Stress-Induced Senescence of Medicago sativa Root Nodules

Nitrate and water stress were used to induce senescence in rootnodules of alfalfa (Medicago sativa L. cv. Aragon). Nodule senescencewas assessed by determinations of the nitrogenase (C₂H₂-reducing)activity, and the leghaemoglobin (LHb) and total soluble proteincontents of the nodules. Nodules responded similarly to and water stress in many respects, but there was a significant difference.All parameters of nodule activity, expressed on the basis ofnodule dry weight (DW), consistently decreased following treatmentwith or during drought; there was a significant interaction (synergism) between the inhibitory effects of and water stress on nitrogenase activity, but sucheffects were merely additive in the case of LHb content or LHb/solubleprotein ratio. However, caused the selective decay of LHb with respect to other nodular soluble proteins,whereas the decrease of LHb during water stress was due to ageneral inhibition of protein synthesis and to an increasedproteolytic activity in the nodule cytosol rather than to aspecific proteolysis of LHb. Key words: Leghaemoglobin, Medicago saliva, nitrogen fixation, root nodule senescence, water stress     

Development and characterization of eight microsatellite markers in bullet tuna (Auxis rochei)

The bullet tuna (Auxis rochei) is a worldwide species of high commercial value in Spain. Nevertheless, little information is currently available about the genetic characteristics of wild A. rochei populations. In this survey, we have developed eight new microsatellites for the bullet tuna using an enriched genome library protocol. Primers were screened on a total of 78 individuals from three wild populations (Mediterranean, Atlantic, and Pacific), revealing seven to 27 alleles per locus with expected heterozygosities ranging from 0.63 to 0.97. These markers can be potentially useful tools for use in population genetic studies.     

Genetic,morphological, and dietary changes associated with novel habitat colonisation in the Canary Island endemic grasshopper Acrostira bellamyi

1. The large flightless grasshopper Acrostira bellamyi Uvarov, endemic to the island of La Gomera (Canary Islands), inhabits two different environments: the xeric euphorb shrubland, as is typical for congeneric Canarian species, and the humid laurel forest, a novel habitat for the genus. 2. We investigate genetic, morphological, and ecological variation among individuals of A. bellamyi from the two habitats. DNA sequence data were used to evaluate whether grasshoppers from the two environments represent distinct lineages. Morphological and trophic analyses were performed to assess phenotypic differentiation between the two different habitats. 3. Population genetic analyses support the hypothesis that the euphorb shrubland is the ancestral habitat for this species. Female laurel forest specimens are larger than those inhabiting the euphorb shrubland, and some external body parts exhibit significant morphometric differences between the two populations. Diet of shrubland individuals is completely different from that of laurel forest individuals. Although in each habitat they consume the most abundant plants, individuals are able to select food plants, which appear to be explained by their nutrient content. 4. Our results suggest that A. bellamyi has colonised laurel forest from shrubland, and that this habitat shift has resulted in genetic, morphological, and ecological changes, perhaps as an adaptation to this new habitat.     

UV radiation and phosphorus interact to influence the biochemical composition of phytoplankton

1. Numerous laboratory studies have shown that food quality is suboptimal for zooplankton growth. However, little is known about how food quality is affected by the interaction of potential global change factors in natural conditions. Using field enclosures in a high altitude Spanish lake, seston was exposed to increasing phosphorus (P) concentrations in the absence and presence of UV radiation (UVR) to test the hypothesis that interactions between these factors affected the biochemical and stoichiometric composition of seston in ways not easily predicted from studies of single factors. 2. Phosphorus enrichment increased the content of total fatty acids (TFA), ω3‐polyunsaturated fatty acids (ω3‐PUFA) and chlorophyll‐a : carbon (Chl‐a : C) and C : N ratios in seston. The pronounced increase in ω3‐PUFA was largely explained by the enhancement of 18:3n‐3 (α‐linolenic acid). In contrast, P‐enrichment lowered the content of highly unsaturated fatty acids (HUFA), the HUFA : PUFA ratio and, at high P loads, seston C : P ratio. Although phytoplankton assemblages dominated by Chlorophytes were not rich in HUFA, seston in the control had substantially higher 20:4n‐6 (arachidonic acid, ARA) content (79% of HUFA) than did P‐enriched enclosures. 3. The UVR increased the content of ω3‐PUFA and TFA in seston at the two ends of the trophic gradient generated at ambient and high concentrations of P, but decreased seston C : P and HUFA at all points on this gradient. ARA was not detected in the presence of UVR. 4. The interaction between P and UVR was significant for seston HUFA and C : P ratios, indicating that the effect of UVR in reducing HUFA (decreased food quality) and C : P ratios (enhanced food quality) was most pronounced at the low nutrient concentrations characteristic of oligotrophic conditions and disappeared as P increased. Therefore, any future increase in UVR fluxes will probably affect most strongly the food quality of algae inhabiting oligotrophic pristine waters although, at least in the Mediterranean region, these effects could be offset by greater deposition of P from the atmosphere.