Skate Raja Erinacea Research Articles

Effects of glycine and GABA on the ganglion cells of the retina of the skate Raja erinacea

Application of glycine and GABA caused inhibition of light-evoked activity from different populations of ‘ON’ center ganglion cells in the retina of the skate ( Raja erinacea). Cells affected by glycine were not affected by GABA and vice-versa. Addition of 100 μM strychnine to the glycine-containing perfusate caused a resumption in light-evoked responses of the cells. The action of GABA was antagonized by 100 μM bicuculline methochloride, but not by picrotoxin. Autoradiography revealed the presence of [ 3H]glycine accumulating amacrine cells.

Electrolyte transport by alkaline gland of little skate Raja erinacea.

Transepithelial flux studies and conventional intracellular microelectrode measurements were employed to examine the mechanisms of ion transport by the alkaline gland of the male skate, Raja erinacea. These studies reveal that the transepithelial potential is 6.9 +/- 0.6 mV, lumen reference, and that the transepithelial resistance is 140 omega . cm2. The short-circuit current across this epithelium is entirely accounted for by net secretion of Cl, whereas transepithelial active transport of Na does not appear to be present in this tissue. Cl secretion and/or short-circuit current are reduced by serosal furosemide and abolished when the bathing solution Na is replaced with choline or when ouabain is added to the serosal bathing solution. Intracellular microelectrode studies reveal that the apical membrane potential is -43 mV, cell interior negative to the mucosal bathing solution. The transepithelial resistance in these tissues was 103 +/- 12 omega . cm2 and the apparent fractional resistance, i.e., the ratio of the change in apical membrane potential to the change in transepithelial potential produced by passing current across the epithelium was 0.39 +/- 0.09. Ion substitution experiments demonstrated that the apical membrane is dominated by a large Cl conductance while the basolateral membrane contains a barium-sensitive potassium conductance. These results suggest that the mechanism of Cl secretion by the alkaline gland is similar to the mechanism described for a variety of Cl secretory epithelia.

Age, Growth, and Mortality of the Little Skate off the Northeast Coast of the United States

Abstract Age, growth, mortality, and yield per recruit of the little skate Raja erinacea in the Georges Bank-Delaware Bay region were investigated from trawl-survey data collected during 1968–1978. Eight age groups were observed in the population. The parameters of the von Bertalanffy growth equation are asymptotic length L∞ = 52.73 cm; growth coefficient K = 0.352; and hypothetical age at zero length t0 = -0.449 years. The length-weight relationship for both sexes combined over seasons is log10W = -2.641 + 3.229 log10L, where length L is in centimeters and weight W is in grams. Estimates of total instantaneous mortality rates Z for fully recruited ages (age 5 and older) ranged from 0.54 to 1.76 between 1968 and 1978. Natural-mortality values M ranged from 0.4 to 0.5; fishing-mortality values F ranged from 0.14 to 1.36, depending on the value of M assumed. Received May 13, 1983 Accepted March 21, 1984

Taurine uptake in atrial myocardium by a sodium-dependent β-amino acid system in the elasmobranch, Raja erinacea

1. Intracellular uptake in vitro of taurine (2-aminoethane sulfonic acid) was linear for more than 6 hr against a strong concentration gradient in intact beating atria of the skate Raja erinacea. The system is temperature dependent; it requires sodium, and is inhibited 45% by 10 −4 M ouabain. 2. Taurine uptake is strongly inhibited by the simultaneous presence of the carboxylic analogue, β-alanine. Neither α-aminoisobutyric acid nor γ-aminobutyric acid (GABA) competitively inhibit uptake. 3. No relationship was found between β-adrenergic stimulation and increased taurine uptake in this elasmobranch heart which, unlike the higher vertebrates, has no sympathetic innervation.

Scyllo-inositol and myo-inositol levels in tissues of the skate Raja erinacea

1. 1. Many organs of the skate Raja erinacea have been found to contain scyllo-inositol levels that are much higher than myo-inositol, the opposite to that found in mammals. 2. 2. Both inositols were found in all skate organs studied. 3. 3. myo-Inosose-2 was found to accompany the inositols in many of these organs.

Possible occurrence of character displacement in the sympatric skates Raja erinacea and R. ocellata (Pisces: Rajidae)

Raja erinacea and R. ocellata are sibling species which are positively correlated with each other by occurrence and numerical abundance. In sympatry the species undergo interactive segregation; R. erinacea feeds on a higher percentage of epifauna and R. ocellata feeds on a higher percentage of infauna.

Gills and kidneys in ureosmotic regulation in euryhaline skates.

Gills and kidneys in ureosmotic regulation in euryhaline skates.

Studies on the digestive lipase of the surf clam Spisula solidissima

Crude molluscan lipase was prepared by homogenizing in tris buffer either fresh or lyophilized crystalline styles of Spisula solidissima. Both preparations showed specific activities less than 2% of standard hog pancreatic lipase, and pH and temperature optima of 8.0 and 20°C, respectively. When compared with mammalian hog pancreatic lipase, the clam lipase was found to be the more versatile enzyme on primary wax esters as well as methyl esters. Neither lipase was capable of hydrolyzing the oleate or palmitate esters of the secondary alcohols of glycerol, cholesterol or isopropyl alcohol; however, both showed activity on the oleate ester of isobutyl alcohol, a primary alcohol. S. solidissima lipase, hog pancreatic lipase, and a lipase isolated from the pancreas of the skate Raja erinacea, all demonstrated an inability to hydrolyze the methyl esters of eicosatetraenoic, eicosapentaenoic and docosahexaenoic acids. The lipase-resistant polyunsaturated fatty acid esters are discussed in terms of their role in the lipid biochemistry of marine organisms.

Osmoregulation and urea metabolism in the little skate Raja erinacea.

Osmoregulation and urea metabolism in the little skate Raja erinacea.

Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris.

Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris.