No abstract

An identification key is provided for 21 larval types of Elmidae (riffle beetles) known to occur in French Guiana. Not all elmid genera known to occur in French Guiana are known in the larval stage. Nor are all the known larval types assigned to known elmid genera.

Neotropical, overseas regions of Europe are subjected to the same water policy objectives as the continental ones but were overlooked during recent developments of bioindicators that fulfil the Water Framework Directive guidelines. We designed a macroinvertebrate-based multimetric index [Indice Biotique Macroinvertébrés de Guyane (IBMG)] to assess ecological health in remote headwater-small streams of French Guiana, Europe's only overseas region of continental South America. Invertebrates were sampled at 95 sites including reference and impacted river reaches, following a standardized protocol. Among the 102 biological metrics calculated from site-specific data, we selected metrics exhibiting the best trade-off between high discrimination efficiency, low specificity, low redundancy and high stability under reference conditions. The IBMG is composed of two taxonomic richness-based metrics, two abundance-based metrics, one trait-related metric and a diversity index (Shannon's entropy). Each metric was weighted by its discrimination efficiency. Using a test data set, we found that the IBMG was sensitive to the range of disturbances in French Guiana. Finally, comparing the IBMG with other indices developed in other neotropical countries reveals that, for several reasons, multimetric indices developed in the neotropics may perform well in the context of the data sets used to generate them but would certainly fail to be robust when used elsewhere.

No abstract

The water mite taxon Scutobates Cook, 1966 was originally described from Liberia, and treated by Cook (1966) as a subgenus of Hygrobates Koch, 1837. One of the most striking characters of Scutobates is the absence of a dorsal furrow, a ring or partial ring of unsclerotised cuticle between the dorsal plate or closely fitting platelets and the ventral shield. In the Hygrobatidae, secondary sclerotization, where the integument of the idiosoma other than the coxae, gnathosoma, genital field and glandularia bases, hardens to form sometimes extensive and merging plates can be extensive. For example, in the genus Thoracohygrobates Lundblad, 1936 the secondary sclerotization extends from the venter laterally onto the dorsum leaving a strip of membranous integument, but there is no dorsal plate development and therefore no dorsal furrow (Cook 1974). In Scutobates, the dorsum is completely sclerotized and seamlessly merges with the venter. The absence of a dorsal furrow on a completely sclerotized watermite is very rare.