Invertebrate neuropeptide hormones

The development of a long-term research program on the neurosecretory hormones of arthropods is described. The purification and full characterization of the first invertebrate neurohormones, the red pigment-concentrating hormone (RPCH) and the distal retinal pigment hormone (DRPH) demonstrated that they are peptides, an octapeptide and an octadecapeptide, respectively. Physiological function studies with the pure hormones and their synthetic preparations showed that the RPCH acts as a general pigment-concentrating hormone (PCH), and that the DRPH, in addition to its light-adaptive function, also constitutes a general pigment-dispersing hormone (PDH). In the regulation of the color-adaptation of the animals, the two hormones act as antagonists. The chromatophorotropic activities are widely distributed within the arthropod neuroendocrine systems. Purification of the pigment-concentrating activities from the locust corpora cardiaca lead to the isolation and characterization of the first insect neurohormones, the adipokinetic hormones (AKH I and AKH II). These two hormones, AKH I being a decapeptide and AKH II being an octapeptide, are close structural analogs to the crustacean PCH, demonstrating a common evolution of arthropod neurohormones. The hormones of this PCH-family all cross-react, but structure-function studies of the hormones show that quite different parts of their structure are involved in their binding to the various receptors.     

Invertebrate diversity on

Despite the global importance of New Zealands invertebrates, relatively little is known about them and their relationships with plants and plant communities in native habitats. Invertebrate diversity was examined by beating randomly chosen shrubs of the species Olearia bullata (Asteraceae) and Coprosma propinqua(Rubiaceae). Invertebrate taxon richness was assessed initially using morphospecies, which were identified subsequently by expert taxonomists. Though the taxon richness of invertebrates recorded from O. bullata was not significantly higher than that on C. propinqua (except for the orders Diptera and Hemiptera), there was a clear indication that O. bullata hosts a higher diversity of invertebrates. Mean number of taxa per shrub for O. bullata was higher in all cases (except Coleoptera), and so was the maximum number of taxa per shrub. Overall, O. bullata yielded 115 invertebrate taxa compared with 93 for C. propinqua. Moreover, 50 invertebrate taxa were restricted to O. bullata compared with 28 for C. propinqua. Since at least ten species of Oleariaare threatened or uncommon, this could be cause for concern with respect to the maintenance of invertebrate diversity. Therefore, sites where Oleariaspecies are still present are likely to be of significance for invertebrate conservation.     

Structures of Invertebrate Hemoglobins

Hemoglobin is widely distributed among the invertebrates. Intracellularhemoglobins consist of relatively small molecules with mol wtsof 15–17,000 or dimeric, tetrameric or octameric aggregatesof 15–17,000 mol wt subunits. Sequence homology is presentbut not extensive in those pigments which have been studiedand the characteristic myoglobin fold of vertebrate hemoglobinoccurs in at least two invertebrate hemoglobins. The wide arrayof aggregation states among invertebrate hemoglobins providessome simple models for understanding homotropic functional propertiesexhibited by many of these pigments. Polymeric extracellularhemoglobins are present in annelids molluscs crustacean arthropodsand nematodes. Annelid extracellular hemoglobins and chlorocruorinsconsist of 3 x 10⁶ mol wt two-tiered hexagonal arrays of submultipleswhich in turn are based on polypeptide chain subunits of molwt 14–16 000. Molluscan extracellular hemoglobins areconstructed from a different subunit arrangement. In the planorbidsnail and clam extracellular hemoglobins the subunits appearto be 175 000 and 300 000 mol wt linear series of 15–17000 dalton oxygen binding domains respectively. Planorbid snailnative hemoglobin presents circular structures 200 Å indiameter in the electron microscope with 10-fold symmetry inat least one view, and clam extracellular hemoglobins are huge345 by 1200 Å rodlike structures. Crustacean extracellularhemoglobins are also polymeric pigments and at least in a fewspecies appear to have subunits which are tandemly linked oxygenbinding domains. The polymeric hemoglobins of nematodes havemolecular weights of about 330 000. The subunit molecular weightand heme content suggest a value of 40,000 daltons which setthe nematode pigments apart from all other hemoglobins so farstudied. An overview of invertebrate hemoglobin structures andsome of the questions they pose are presented in this paper.     

Vertebrate/Invertebrate Trackways

The Ichnology Workshop held in 1998 in Bornholm, DK, evidenced significant differences between approaches used for studying vertebrate and invertebrate ichnites. In particular, trackways are used more in invertebrate ichno-studies than in vertebrate studies. This is due to the intrinsic characteristics of each category, primarily the multiple consequences of the order of magnitude gap in sizes, the opportunity to have more taxonomic information of the trackmaker with vertebrate ichnites, the usefulness of correlations with biotopes and facies with invertebrate ichnites, and practical parameters such as the probability of findings. That vertebrate and invertebrate ichnologists exchange ideas could certainly bring progress, however, significant differences between the two fields certainly remain. Using information on animal behavior to define ichnotaxobases would not be acceptable for most vertebrate tracks.