Digging with ‘hands’: observations of food capture in the flying gurnard Dactylopterus volitans (Linnaeus, 1758)

ABSTRACT

Videofilms of a foraging flying gurnard (Dactylopterus volitans) were collected at Itaipu, Niterói, RJ, Brazil. Analysis revealed details of the use of anterior parts of the pectoral fins which act as digging ‘hands’ to access infaunal prey items that are subsequently captured by oral suction feeding. Each pectoral fin has two distinct sections articulated separately on the pectoral girdle. The digging ‘anterior pectoral fin’ mainly consists of segmented and flexible fin rays but has an anterior robust unsegmented ray that provides an edge to the ‘hand’, allowing penetration of the substratum. The huge ‘posterior pectoral fins’ are supported by unsegmented rays. Most digging episodes involved one ‘hand’ and consisted of 1–7 cycles of movement with frequencies 1.15–3.74 cycles s^?1. During a cycle, the ‘hand’ is moved forwards and medially above the substratum, then is twisted medially and simultaneously depressed so that the anterior unsegmented ray impacts and enters the substratum. The hand is then drawn backwards and laterally to disturb the substratum. To prevent upward pitching of the head during digging, the ‘posterior pectoral fins’ are both moved anteriorly and laterally to shift the centre of gravity forwards while the caudal and ?second dorsal fins continue to provide propulsive force.     

Dynamics of individual flexible polymers in a shear flow.

Polymer dynamics are of central importance in materials science, mechanical engineering, biology and medicine. The dynamics of macromolecular solutions and melts in shear flow are typically studied using bulk experimental methods such as light and neutron scattering and birefringence. But the effect of shear on the conformation and dynamics of individual polymers is still not well understood. Here we describe observations of the real-time dynamics of individual, flexible polymers (fluorescently labelled DNA molecules) under a shear flow. The sheared polymers exhibit many types of extended conformation with an overall orientation ranging from parallel to perpendicular with respect to the flow direction. For shear rates much smaller than the inverse of the relaxation time of the molecule, the relative populations of these two main types of conformation are controlled by the rate of the shear flow. These results question the adequacy of assumptions made in standard models of polymer dynamics.     

Studies on the dye-binding fraction of soluble liver proteins from rats fed aminoazo dyes

Résumé Les auteurs ont étudié le profil électrophorétique du surnageant de foies de rats, nourris aux colorants azoïques cancérogènes. La fraction, dite protéine «h», a été isoléc et on a déterminé son poids moléculaire, sa teneur en colorant lié, en vitamines et en acides nucléiques et sa composition en acides aminés.

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This investigation was supported by the Institutional Grant 71 from the American Cancer Society and the Grant C-355 of the National Cancer Institute, Public Health Service to Drs.J. A. Miller andE. C. Miller, to whom we are greatly indebted.     

Properties and modes of action of specific and non-specific phospholipid transfer proteins

Summary We have described the mode of action of the phosphatidylcholine transfer protein (PC-TP), the phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) isolated from bovine and rat tissues. PC-TP and PI-TP specifically bind one phospholipid molecule to be carried between membranes. PC-TP, and most likely PI-TP as well, have independent binding sites for thesn-1- andsn-2-fatty acyl chains. These sites have different properties, which may explain the ability of PC-TP and PI-TP to discriminate between positional phospholipid isomers. nsL-TP, which is identical to sterol carrier protein 2, transfers all common phospholipids, cholesterol and oxysterol derivatives between membranes. This protein is very efficient in mediating a net mass transfer of lipids to lipid-deficient membranes. Models for its mode of action, which is clearly different from that of PC-TP and PI-TP, are presented.     

Diplecogaster tonstricula,a new species of cleaning clingfish (Teleostei: Gobiesocidae) from the Canary Islands and Senegal,eastern Atlantic Ocean,with a review of the Diplecogaster-ctenocrypta species-group

The Diplecogaster-ctenocrypta species-group is reviewed; it comprises two species. The clingfish Diplecogaster ctenocrypta from the Canary Islands is redescribed. The new species Diplecogaster tonstricula, a facultative cleaner of other teleosts, is described on the basis of eight specimens and colour photos from Senegal and the Canary Islands, eastern Atlantic Ocean. The species is small, apparently not exceeding 23 mm total length; it is characterised by having nine dorsal-fin rays, eight anal-fin rays, 24–25 pectoral-fin rays, 14–15 principal caudal-fin rays, 13–16 rakers on third gill arch, pelvic disc without lateral papillae in region A, disc region B with two rows of weak papillae, interorbital distance 4.1–4.6 in head length, distance between disc and anus 14–17% of SL, head and body with 10–13 narrow vertical brownish bars, cheek with a white ocellus surrounded by black, and with a small black spot in the middle. The new species is compared with other species of the genus; a key to the six known species of the eastern Atlantic, Mediterranean and Black Sea and South African genus Diplecogaster is presented. A checklist is provided for the species of Diplecogaster and their synonyms.     

Interaction of C-reactive protein with artificial phosphatidylcholine bilayers.

C-Reactive protein (CRP), the most characteristic of the 'acute phase proteins' (ref. 1) is thought to participate in the mediation and/or modulation of acute inflammatory processes, but its exact function is unknown. CRP has a Ca2+-dependent binding specificity for phosphorylcholine, the polar head group of two widely distributed lipids, lecithin (phosphatidylcholine, PC) and sphingomyelin (SM). A number of observations suggest that at least some of the biological activities of CRP depend on its interaction with phospholipids of cell membranes. In addition, interaction of CRP with PC- and SM-containing lipid dispersions and with PC-containing liposomes can activate the complement system. We report here that binding of CRP to model membranes of PC requires the incorporation into the bilayer of lysophosphatidylcholine (LPC). Thus, a disturbance of the molecular organisation of the bilayer appears to be necessary for binding of CRP. These findings provide a possible biochemical explanation for binding of CRP to damaged but not intact cell membranes and might be relevant to its biological function.     

Properties and modes of action of specific and non-specific phospholipid transfer proteins

We have described the mode of action of the phosphatidylcholine transfer protein (PC-TP), the phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) isolated from bovine and rat tissues. PC-TP and PI-TP specifically bind one phospholipid molecule to be carried between membranes. PC-TP, and most likely PI-TP as well, have independent binding sites for the sn-1- and sn-2-fatty acyl chains. These sites have different properties, which may explain the ability of PC-TP and PI-TP to discriminate between positional phospholipid isomers. nsL-TP, which is identical to sterol carrier protein 2, transfers all common phospholipids, cholesterol and oxysterol derivatives between membranes. This protein is very efficient in mediating a net mass transfer of lipids to lipid-deficient membranes. Models for its mode of action, which is clearly different from that of PC-TP and PI-TP, are presented.     

Modulation of brain polyphosphoinositide metabolism by ACTH-sensitive protein phosphorylation

Phosphorylation of membrane components is thought to be an important process in membrane function. Phosphorylated proteins and a special class of phospholipids, the (poly)phosphoinositides (poly PI), are implicated in the regulation of membrane permeability and synaptic transmission in neurones. For many years, protein phosphorylation and poly PI metabolism have been studied in parallel without knowledge of their possible interaction. We report here that the ACTH-sensitive protein kinase/B-50 protein complex which we recently isolated in soluble form from rat brain synaptosomal plasma membranes has lipid phosphorylating activity. Exogenously added phosphatidylinositol 4-phosphate (DPI) is phosphorylated to phosphatidylinositol 4,5-diphosphate (TPI), and this DPI-kinase activity is dependent on the state of phosphorylation of the protein kinase/B-50 protein complex. The results imply that phosphorylation of protein may affect the metabolism of (poly) PI in brain cell membranes.     

Vitamin A antibodies: Application to radioimmunoassay

Summary A radioimmunoassay for serum vitamin A is described which can detect as little as 1 ng of retinol. The statistical characteristics of this assay are presented and its use in a nutritional experiment is discussed.This work was supported by United States Public Health Service grant 2 RO1 AM19716.