Carbohydrate dynamics and the crustacean hyperglycemic hormone (CHH): effects of parasitic infection in Norway lobsters (Nephrops norvegicus).

The effects of a dinoflagellate parasite (Hematodinium sp.) on carbohydrate metabolism were examined in the Norway lobster, Nephrops norvegicus. Five stages of infection were observed. These included uninfected (Stage 0), subpatently infected (SP), and patently infected (Stage 1-4) lobsters. During patent infection, the concentration of glucose in the hemolymph was reduced significantly from its value of 180 microg ml(-1) in uninfected (Stage 0) lobsters to 25.3 microg ml(-1) in Stage 3-4. These changes were accompanied by significantly lower levels of hepatopancreatic glycogen in lobsters at Stage 2 (2.01 mg g(-1)) and Stage 3-4 (0.84 mg g(-1)) of infection than in those at Stage 0 (16.19 mg g(-1)) and Stage 1 (14.71 mg g(-1)). Due to disruption of the normal feedback loops which control the release of crustacean hyperglycemic hormone (CHH), plasma concentrations increased with the severity of infection from 32.2 fmol ml(-1) in Stage 0 to 106.6 fmol ml(-1) in Stage 3-4. The increased CHH concentrations occurred concomitantly with reduced concentrations of plasma glucose and tissue glycogen. A significantly increased hemolymph CHH titer (107.7 fmol ml(-1)) was also observed during SP infection. It is concluded that the parasite places a heavy metabolic load on the host lobster.

Crustacean hyperglycemic hormone in the lobster nervous system: localization and release from cells in the subesophageal ganglion and thoracic second roots.

Crustacean hyperglycemic hormones (CHHs) are neuropeptides involved in the regulation of hemolymph glucose. The primary source of CHHs has been identified as the neurosecretory neurons of the eyestalk X-organ and its associated neurohemal organ, the sinus gland. We have identified another source of CHH-like peptides in the nervous system. With the use of immunocytochemistry, cells in the second roots of the thoracic ganglia have been observed to stain positively for CHH-reactive material. We also identified a pair of cells in the subesophageal ganglion that contain large amounts of CHH-reactive material. Depolarization of these cells with elevated potassium mediates a calcium-dependent release of CHH-like material from the ganglion as quantified with an enzyme-linked immunosorbent assay (ELISA).

Quantification of crustacean hyperglycemic hormone by ELISA in hemolymph of the lobster, Homarus americanus, following various stresses.

An ELISA was developed for the crustacean hyperglycemic hormone (CHH) from the lobster, Homarus americanus. It is sensitive to as little as 0.2 fmol of peptide. The assay was used to measure CHH in the hemolymph of intact lobsters after various environmental stresses. Increases in CHH were observed following emersion, exposure to high temperatures (23 degrees and 28 degreesC), and salinity stress (50 and 150% seawater). During emersion, concentrations of hemolymph glucose increased concomitantly with increases in CHH. Significant levels of hemolymph CHH were also measured in lobsters that had been eyestalk-ablated. These latter observations indicate that there may be a source of CHH other than the X-organ/sinus gland in the lobster.