Embryonic development of the histaminergic system in the ventral nerve cord of the Marbled Crayfish (Marmorkrebs).

The embryonic development of neurotransmitter systems in crustaceans so far is poorly understood. Therefore, in the current study we monitored the ontogeny of histamine-immunoreactive neurons in the ventral nerve cord of the Marbled Crayfish, an emerging crustacean model system for developmental studies. The first histaminergic neurons arise around 60% of embryonic development, well after the primordial axonal scaffold of the ventral nerve cord has been established. This suggests that histaminergic neurons do not serve as pioneer neurons but that their axons follow well established axonal tracts. The developmental sequence of the different types of histaminergic neurons is charted in this study. The analysis of the histaminergic structures is also extended into adult specimens, showing a persistence of embryonic histaminergic neurons into adulthood. Our data are compared to the pattern of histaminergic neurons in other crustaceans and discussed with regard to our knowledge on other aspects of neurogenesis in Crustacea. Furthermore, the possible role of histaminergic neurons as characters in evolutionary considerations is evaluated.

Effect of feeding quandong (Santalum acuminatum) oil to rats on tissue lipids, hepatic cytochrome P-450 and tissue histology.

Quandong kernels are a traditional Aboriginal food item; they are rich in oil and contain large amounts of an unusual fatty acid, trans-11-octadecen-9-ynoic acid (santalbic acid), but it is not known whether this acid is absorbed and/or metabolized. The oil was fed at 12.6% of total energy content in semi-synthetic diets to groups of male Sprague-Dawley rats for 10 and 20 days. Santalbic acid was found in the lipids of plasma, adipose tissue, skeletal muscle, kidney, heart and liver but not in brain. Hepatic microsomal cytochrome P-450 activity in animals fed for 20 days was significantly higher (P < 0.05) than in controls. Histopathological examination did not reveal any lesions in the tissues of any animal fed quandong oil. The fact that santalbic acid was readily absorbed, widely distributed in tissues and was associated with an elevated level of hepatic cytochrome P-450 indicates that further studies are required to investigate whether or not there is a hazard associated with the human practice of consuming quandong kernels.

Transition from marine to terrestrial ecologies: changes in olfactory and tritocerebral neuropils in land-living isopods.

In addition to the ancestors of insects, representatives of five lineages of crustaceans have colonized land. Whereas insects have evolved sensilla that are specialized to allow the detection of airborne odors and have evolved olfactory sensory neurons that recognize specific airborne ligands, there is so far little evidence for aerial olfaction in terrestrial crustaceans. Here we ask the question whether terrestrial Isopoda have evolved the neuronal substrate for the problem of detecting far-field airborne chemicals. We show that conquest of land of Isopoda has been accompanied by a radical diminution of their first antennae and a concomitant loss of their deutocerebral olfactory lobes and olfactory computational networks. In terrestrial isopods, but not their marine cousins, tritocerebral neuropils serving the second antenna have evolved radical modifications. These include a complete loss of the malacostracan pattern of somatotopic representation, the evolution in some species of amorphous lobes and in others lobes equipped with microglomeruli, and yet in others the evolution of partitioned neuropils that suggest modality-specific segregation of second antenna inputs. Evidence suggests that Isopoda have evolved, and are in the process of evolving, several novel solutions to chemical perception on land and in air.