Performance of shark teeth during puncture and draw: implications for the mechanics of cutting

The performance of an organism's feeding apparatus has obvious implications for its fitness and survival. However, the majority of studies that focus on chondrichthyan feeding have largely ignored the role of teeth. Studying the functional morphology of shark teeth not only elucidates the biological role that teeth play in feeding, but also provides insight specifically into the evolution of shark feeding because teeth are often the only structures available in the fossil record. In the present study, we investigate the puncture and draw performance of three general categories of extant teeth, tearing‐type, cutting‐type, and cutting–clutching type, as well as three fossil morphologies, utilizing a universal testing system. Differences in puncturing performance occurred among different prey items, indicating that not all ‘soft’ prey items are alike. The majority of teeth were able to puncture different prey items, and differences in puncture performance also occurred among tooth types; however, few patterns emerged. In some cases, broader triangular teeth were less effective at puncturing than narrow‐cusped teeth. There were no differences between the maximum draw forces and maximum puncture forces. Many of the shark teeth in the present study were not only able to perform draw and puncture equally well, but also many tooth morphologies were functionally equivalent to each other. The findings obtained in the present study lend little support to the belief that shark tooth morphology is a good predictor of biological role. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 271–286.     

Immunological and biochemical analysis of test matrix proteins in living and fossil foraminifers

The characterization of macromolecules from shell matrix proteins in living organisms is the fundamental first step in establishing molecular phylogenies. This is particularly important if ancient macromolecules will be used for the phylogenies. Approximately 500 individuals of Orbulina universa were picked from plankton tows taken in the Gulf of Mexico during spring 1990. Proteins were extracted from the tests of the individuals, and the molecular weights of the proteins were determined and compared to 2,000–4,000-year old samples. Gel electrophoresis of the soluble matrix (SM) from living O. universa showed at least ten protein bands, while electrophoresis of core-top O. universa showed two protein bands. Dot-immunobinding assays of proteins from living and fossil samples of O. universa , incubated against monoclonal antibodies raised against core-top O. universa SM, demonstrated a reactivity with the two proteins in common. Less reactivity was obtained with living samples of the benthic foraminifers Androsina lucasi and Archaias angulatus and core-top samples of the planktonic foraminifer Neogloboquadrina dutertrei. A partial protein sequence from one shell matrix protein approximately 65kD in size, from core-top Orbulina universa , showed a domain of polyaspartic acid at the NH₂ terminus. This is consistent with data obtained for other matrix proteins found in invertebrates and vertebrates. Sequence data provide insight into the role that the protein may play in the biomineralization of the test and will aid in modelling degradation. □ Foraminifera, test proteins, monoclonal antibodies , Orbulina, Androsina, Archaias, Neogloboquadrina, biomineralization, Dot-immunobinding assay, protein sequence.     

Mode of action studies of the acaricidal agent,epingaione

Summary

Activity directed isolation studies of the ethanol extract of Bontia daphnoides L (Myoporaceae) leaves and stems led to the isolation of epingaione, a sesquiterpene furan. This compound was previously described by Chinnock et al. (1987) from the same plant. The compound showed growth regulatory activities on gravid adult female Boophilus microplus Canestrini (the southern cattle tick). The dose required for inhibiting the hatching of B. microplus eggs by 50% (Fid₅₀)was 0.4±0.06 mg/g of the tick body weight. The Fid₅₀ dose inhibited the sequestration of protein into eggs oviposited by 80%. These eggs were non-agglutinated and wrinkled. Histological examination of ovarian sections from the treated ticks revealed significant degeneration of funicle cells and reduction in yolk content.     

Aminotransferase and the Production of Alanine During Hyperosmotic Stress in Paramecium calkinsi

When Paramecium calkinsi encounter hyperosmotic stress, intracellular free alanine increases. In vivo assays indicate that the reaction catalyzed by alanine aminotransferase contributes to the build up of alanine in response to hyperosmotic shock. ¹⁴C-pyruvate is converted to ¹⁴C-alanine in cells grown axenically at 200 mosm. When shifted to 600 mosm, the rate of conversion of pyruvate to alanine increases, and conversion at either 200 or 600 mosm is blocked by 1 mM aminooxyacetic acid (AOA), an inhibitor of aminotransferase. Intracellular free alanine increase is partially inhibited by AOA, and AOA prevents cells living in fresh water from acclimating to higher salinities, an indication that the increase in intracellular alanine is physiologically significant.     

Correlations Between Electrolyte Leakage and Degree of Saturation of Polar Lipids from Aged Potato (Solanum tuberosum L) Tuber Tissue

Age-dependent changes in the concn (nmol g d. wt^–1) andrelative proportion of polar lipid fatty acids in potato tubertissue were characterized over a 32-month storage period. Astubers advanced in age from 2 to 14 months, a decrease (approximately22%) in concn of both saturated (16:0, 18:0) and unsaturated(18:2, 18:3) fatty acids was evident. This decrease was followedby an exponential increase through 32 months. Electrolyte leakagestudies with excised tissue revealed age-dependent differencesin membrane permeability. The relationship between maximum electrolyteleakage (% total) and tissue age was described by a cubic polynomial.Leakage declined approximately 4% as tissues aged from 2 to7 months; however, from 7 to 24 months, leakage increased 21%.These trends were followed by partial restoration of membranefunction in 24 to 32-month-old tissues, as indicated by attenuatedleakage. Similarly, the trend in double bond index (DBI) withage was defined by a cubic polynomial; however, the minima andmaxima were the opposite of those for electrolyte leakage vs.age. The regression of DBI upon leakage was inverse and linear(r = –0·97, P < 0.01). Furthermore, the effectof decreasing temperature from 5 to –2 °C on tissuepermeability (after equilibration with the bathing medium) wasalso dependent upon DBI. The higher the DBI, the greater theresistance of the tissue to increased electrolyte leakage inducedby chilling temperatures (r = 0·99, P < 0·05).Although the evidence is largely correlative, it appears thatchanges in the degree of saturation of membrane lipids are relatedto age-dependent fluctuations in membrane integrity and maybe important in dictating chilling sensitivity in potato Potato (Solanum tuberosum L.), tuber age, electrolyte leakage, membrane fatty acids     

Changing Patterns of Gene Regulation in the Evolution of Arthropod Morphology

SYNOPSIS. What can the comparative study of gene expressionpatterns during development contribute to the study of phytogeny?I discuss the basic properties of gene networks that functionin development, using information gleaned from developmentalmodel systems. Using examples from the analysis of anteroposterior,dorsoventral and proximodistal axis formation, I outline howthe gene networks that pattern these three axes of developmentare linked in evolution. Finally, I discuss the types of analysesnecessary to further our understanding of how gene networksfunction in regulating the evolution of morphology     

Selection for enemy‐free space: eggs placed away from the host plant increase survival of a neotropical ithomiine butterfly

1. The selection of an oviposition site by a phytophagous insect can depend on many factors, including the risk of predation. Many species avoid predators by laying eggs where enemies searching host plants are unlikely to find them. 2. Females of the Peruvian butterfly, Oleria onega Hewitson (Lepidoptera: Nymphalidae: Danainae: Ithomiini) lay most of their eggs (76 ± 9%) off the host plant, Solanum mite Ruiz & Pav. These off‐host eggs may be laid up to 0.5 m from the nearest host‐plant individual, on twigs or leaf litter, as well as on living plants of species unsuitable for larval food. 3. Disappearance of eggs on and off the host plant was recorded by transferring eggs laid in captivity to known locations in the wild and recording rates of disappearance before the larvae emerged. After 2 days, eggs on the host were significantly more likely to have disappeared compared to eggs laid elsewhere. 4. We conclude that a high risk of predation is a likely trigger that caused O. onega to evolve a behaviour of laying eggs off its host plant.     

Developmental plasticity in a meristic character: the number of tentacles in the lophophore of a bryozoan species

There is increasing interest among evolutionary biologists in developmental plasticity. Previously ignored by many as being irrelevant to evolution because a plastic response to an environmental change is not inherited, the current, more positive, view of plasticity focuses on the fact that, although any individual plastic response is nonheritable, the overall pattern of developmental response to environmental variation (i.e. the developmental reaction norm) is heritable and may vary among genotypes within a population. Characters subject to plastic variation, like those that are entirely genetically determined, may vary in continuous, meristic or discrete ways. Of these, the least work has been carried out on meristic variation. In the present study, we contribute to the rectification of this imbalance by examining the plastic response of the number of tentacles in the lophophore of a species of bryozoan, Membranipora membranacea, to three environmental variables: temperature, salinity and food concentration. Because the approach taken was an experimental one, unlike the majority of studies of bryozoan tentacles to date, we are able to make statements about the causality of variation in tentacle number. The main conclusions of the present study are: (1) that plastic responses occur to all three environmental variables; (2) that these are part of a more generalized plastic response in the overall development of the zooids rather than being lophophore‐specific; and (3) that the issue of whether the relevant developmental reaction norms are adaptive or not is an open (and interesting) question. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 541–551.     

Comparison of the 24 kDa Flagellar Calcium-Binding Protein cDNA of Two Strains of Trypanosoma cruzi

ABSTRACT. DNA sequences encoding the 24 kDa flagellar calcium binding protein (FCaBP) of two strains of Trypanosoma cruzi were found to differ at fourteen positions, six of which result in amino acid differences. Four of the amino acid differences are located within the calcium-binding domains of FCaBP; however, none is predicted to affect the calcium-binding ability of the protein. Chromosomes harboring the FCaBP gene clusters differ in size among T. cruzi strains.