Antibody response to IR6, a conserved immunodominant region of the VlsE lipoprotein, wanes rapidly after antibiotic treatment of Borrelia burgdorferi infection in experimental animals and in humans.

Invariable region (IR)(6), an immunodominant conserved region of VlsE, the antigenic variation protein of Borrelia burgdorferi, is currently used for the serologic diagnosis of Lyme disease in humans and canines. A longitudinal assessment of anti-IR(6) antibody levels in B. burgdorferi-infected rhesus monkeys revealed that this level diminished sharply after antibiotic treatment (within 25 weeks). In contrast, antibody levels to P39 and to whole-cell antigen extracts of B. burgdorferi either remained unchanged or diminished less. A longitudinal analysis in dogs yielded similar results. In humans, the anti-IR(6) antibody titer diminished by a factor of > or =4 in successfully treated patients and by a factor of <4 in treatment-resistant patients. This result suggests that the quantification of anti-IR(6) antibody titer as a function of time should be investigated further as a test to assess response to Lyme disease therapy or to determine whether a B. burgdorferi infection has been eliminated.

Effect of Salinity on Ionic Shifts in Mesohaline Scyphomedusae, Chrysaora quinquecirrha.

Mesohaline populations of the scyphomedusae Chrysaora quinquecirrha are found in salinities ranging from 5{permill} to 25{permill}. Osmotic and ionic adjustments within this salinity range were investigated using C. quinquecirrha ephyrae budded from polyps in the laboratory and young medusae collected from the mid-salinity region of the Patuxent River, Maryland. When medusae were transferred from 20{permill} salinity to lower salinities (8{permill}, 12{permill}), concentrations of sodium and magnesium in tissue and mesogleal fluid fell rapidly and approached those of dilute seawater within 6 hours. There was some recovery of these levels relative to the 8{permill} medium, and they were significantly higher than the dilute seawater concentration after 1 week. Tissue concentrations of calcium showed no evidence of being regulated, whereas potassium was strongly regulated such that levels did not fall significantly following transfer of medusae to lower salinities. However, after 1 week, the concentration of potassium in mesogleal fluid approached that of the dilute medium. Extracellular space measured by direct blotting and weighing or using 35S was about 40%. As a result, estimates for intracellular potassium were revised to 17 mM1-1. The concentration of potassium in tissue remained stable following transfer to lower salinity, despite a substantial osmotic influx of water. This influx was measured as a >20% gain in body weight over 24 h following transfer of medusae from 16{permill} to 8{permill}. Mesogleal fluid was slightly hypo-osmolar to the medium at 15% and 20{permill} and slightly hyperosmolar to the medium at 5{permill} and 12{permill}. Sulfate concentrations in mesogleal fluid were 66%-70% those of the external medium. Medusae died or were unable to achieve positive buoyancy at 5%{permill}, which is probably very close to a lower salinity limit for C. quinquecirrha in the mesohaline Chesapeake Bay.

Differential Ingestion and Digestion of Bivalve Larvae by the Scyphozoan Chrysaora quinquecirrha and the Ctenophore Mnemiopsis leidyi.

We investigated predation on bivalve veligers by the scyphozoan Chrysaora quinquecirrha and the ctenophore Mnemiopsis leidyi. We found that the medusa stage of C. quinquecirrha captures, but does not digest, veliger larvae: 99% of oyster veligers (Crassostrea virginica) caught by medusae were egested alive within 7 h of capture, and 98% survived for 24 h after egestion; 98% of oyster, mussel (Mytilus edulis), and clam (Mulinia lateralis) veligers placed on the oral arms of medusae were rejected; all bivalve veligers in field-collected medusae were closed and full of tissue. Our laboratory evidence suggests that the shell of larval bivalves probably offers protection from medusae: 23% of dead, open veligers were ingested by medusae compared with 0.7% of live, closed veligers; open veligers were retained longer than closed veligers; and tissue excised from recently settled oyster larvae was ingested and digested. Freeswimming C. quinquecirrha ephyrae ingested but did not digest veligers. By contrast, the benthic scyphistoma stage ingested 69% of veligers that contacted their tentacles and digested 48% of those ingested. Each scyphistoma consumed an average of 1 veliger/day at densities of 0.3 veligers ml-1. However, larval settlement was not reduced on oyster shells bearing scyphistomae. By contrast to the results on C. quinquecirrha, ctenophores egested only 4% of veligers alive, and 25% of the veligers in their gut contents were digested. Predation on veligers by ctenophores was estimated to be 0.2 to 1.7%/day in Chesapeake Bay. We conclude that C. quinquecirrha medusae are not important predators of bivalve veligers, but rather may reduce their mortality by consuming ctenophores, which do eat veligers.

Influence of Siphonophore Behavior upon Their Natural Diets: Evidence for Aggressive Mimicry.

Collection by divers permitted determination of the natural diets of siphonophore species within II genera. Siphonophores that swim rapidly to spread their tentacles capture small prey, whereas those that swim very weakly capture much larger prey. Nematocyst batteries of two species of weak swimmers closely resemble copepods and fish larvae. Morphology, behavior, and diet suggest that these two species attract large prey by mimicking other zooplankton.