Meredith L. Jones

On the Early Development of the Vestimentiferan Tube Worm Ridgeia sp. and Observations on the Nervous System and Trophosome of Ridgeia sp. and Riftia pachyptila

Stages in the development of the vestimentiferan Ridgeia sp., based on lengths of preserved specimens processed for scanning electron microscopy, were examined. Features of the nervous system and trophosome of Riftia pachyptila were studied by light, scanning-, and transmission-electron microscopy. Development proceeds from a trochophore-type larva with an anterior prototrochal ciliary ring and a posterior assemblage of transient larval setae, through intermediate stages, some of which lack endosymbiotic bacteria but all of which display additional transient features such as larval branchial filaments, a ventral medial process, and digestive tract, to a young juvenile stage that possesses endosymbiotic bacteria and exhibits the morphology characteristic of adult vestimentiferans. Larval branchial filaments are resorbed in later developmental stages and replaced by paired rows of ciliated branchial filaments with pinnules. The larval gut is divisible into foregut, midgut, and hindgut regions based on cytol...

Invertebrates of the upper chamber, Gatun Locks, Panamá Canal, with emphasis on Trochospongilla leidii (Porifera)

Observations were made on the horizontal distribution of certain invertebrates on the walls and floor of the upper chamber of the Gatún Lock system of the Panama Canal. The hydroid Cordylophora caspia (Pallas) and the gastrophod Neritina usnea Röding extended the full length of the chamber; the oligochaete Marionina sp. was confined to the upper half of the chamber (adjacent to Gatún Lake), and the amphipod Gitanopsis tortugae? Shoemaker, the isopod Munna sp. and the bivalve Mytilopsis sallei (Recluz) to the lower half; the sponge Trochospongilla leidii (Bowerbank) was distributed from the upper end to near the lower end of the chamber. A peculiar wedge-shaped distribution of T. leidii is thought to be a response to the influence of slight increases in salinity. Morphological observations on T. leidii are presented.

The presence of certain dehydrogenases among polychaetous annelids as shown by disc electrophoresis

Abstract 1. 1. Homogenates of nearly all polychaetous annelids examined from Massachusetts, Rhode Island, Delaware and Florida exhibited malate dehydrogenase activity, as determined by disc electrophoresis in polyacrylamide gels. 2. 2. About half showed activity for glucose-6-phosphate dehydrogenase, approximately a quarter for lactate dehydrogenase and fewer for α-glycerophosphate dehydrogenase and glutamate dehydrogenase. 3. 3. Measurements of relative mobilities of major bands indicate that there are many kinds of lactate dehydrogenase present among those polychaetes in which it occurs.

Oxygen binding by hemoglobin of the galapagos rift vent worm Riftia pachyptila Jones (Pogonophora; Vestimentifera)

Kinetics of the reactions of Riftia pachyptila hemoglobin with oxygen were followed spectrophotometrically by stopped-flow and laser flash photolysis techniques. The rate of oxygen dissociation increases 8-fold over the range 5–20°C (k = 2.2 s−1 at 10°C). Oxygen recombination following flash photolysis was biphasic. The rates of both slow and fast phases of the reaction were independent of temperature from 0 to 20°C (kfast′ = 7 · 106; kslow′ = 1 · 106 1 · mol−1 · s−1). As the oxygen affinity is relatively temperature independent, analysis in terms of the two-state model of Monod, Wyman and Changeaux (1965, J. Mol. Biol. 12 88–118) requires that the conformational equilibrium constant L decrease by approx. 50-fold between 3 and 15°C.