Third contribution to the knowledge of water mites from the Comoros, with the description of two new species (Acari: Hydrachnidia).

New records of water mites (Acari: Hydrachnidia) from the Comoros are presented. Two species new to science, Torrenticola comorosensis (Torrenticolidae) and Sterkspruitia comorosensis (Hygrobatidae) are described; the latter species is the second known species of the genus Sterkspruitia Cook, 2003. First records are given for Limnochares crinita Koenike, 1898 and Mamersella thienemanni K. Viets, 1929. Additional measurements, figures and information on the morphology are given for specimens assigned to the Monatractides ventriosus-species complex.

Exploring the capacity of aquatic biofilms to act as environmental DNA samplers: Test on macroinvertebrate communities in rivers.

Aquatic biofilms are heterogeneous assemblages of microorganisms surrounded by a matrix of extracellular polymeric substances (EPS). Recent studies suggest that aquatic biofilms can physically act as sorptive sponges of DNA. We took the opportunity from already available samples of stone biofilms and macroinvertebrates specimens collected in parallel at the same sites to test the capacity of biofilms to act as DNA samplers of macroinvertebrate communities in streams. Macroinvertebrate communities are usually studied with metabarcoding using the DNA extracted from their bodies bulk samples, which remains a time-consuming approach and involves the destruction of all individual specimens from the samples. The ability of biofilms to capture DNA was explored on 19 rivers sites of a tropical island (Mayotte Island, France). First, macroinvertebrate specimens were identified based on their morphological characteristics. Second, DNA was extracted from biofilms, and macroinvertebrate communities were targeted using a standard COI barcode. The resulting morphological and molecular inventories were compared. They provided comparable structures and diversities for macroinvertebrate communities when one is working with the unassigned OTU data. After taxonomic assignment of the OTU data, diversity and richness were no longer correlated. The ecological assessment derived from morphological bulk samples was conserved by the biofilms samples. We also showed that the biofilm method allows to detect a higher diversity for some organisms (Cnidaria), that is hardly accessible with the morphological method. The results of this study exploring the DNA signal captured by natural biofilms are encouraging. However, a more detailed study integrating more replicates and comparing the biodiversity signal based on both morphological and molecular bulk macroinvertebrate samples to the one captured by biofilms will be necessary. Better understanding how the DNA signal captured by natural biofilms represents the biodiversity of a given sampling site is necessary before considering its use for bioassessment applications.

Eighteen new species of Oecetis McLachlan 1877 (Trichoptera, Leptoceridae) from New Caledonia.

Eighteen new species of Oecetis are described, diagnosed, and illustrated from New Caledonia: Oecetis amphora sp. nov., Oecetis ovula sp. nov., Oecetis ramosa sp. nov., Oecetis loyolaensi sp. nov., Oecetis millei sp. nov., Oecetis christinae sp. nov., Oecetis rostrata sp. nov., Oecetis alicae sp. nov., Oecetis oxybelis sp. nov., Oecetis dorsospina sp. nov., Oecetis multidentata sp. nov., Oecetis gracilis sp. nov., Oecetis rostra sp. nov., Oecetis triramosa sp. nov., Oecetis flucta sp. nov., Oecetis nouvellecaledoniensis sp. nov., Oecetis variabilis sp. nov., and Oecetis ovata sp. nov. A diagnostic key is provided for males of Oecetis species of New Caledonia. The species display similarities in genitalic characteristics but also a high diversity of apomorphic features. The new species were collected from lotic habitats across most of Grande Terre.

Fifth contribution to the knowledge of water mites (Acari: Hydrachnidia) from the Comoros: a checklist and description of one new genus and four new species.

New records of water mites (Acari: Hydrachnidia) from the Comoros are presented. One genus, i.e. Lagoenaxonopsalbia Pesic Smit, and four species, i.e. Platymamersopsis mayottensis (Anisitsiellidae), Torrenticola mayottensis (Torrenticolidae), Lagoenaxonopsalbia comorosensis (Aturidae) and Djeboa davecooki (Mideopsidae) are described as new to science. Arrenurus comorosensis Pesic Smit, 2015 is synonymized with Arrenurus flavus Smit, 2012. The first description of the female of Sterkspruitia comorosensis Pesic Smit, 2015 is given. The number of water mites known from Comoros now tallies 17 species in ten families.

Oribatid mites (Acari, Oribatida) from riverine environments of some islands in Oceania.

A checklist of identified oribatid mite taxa from riverine freshwater environments from six islands in Polynesia (New Caledonia, Tahiti, Moorea, Rurutu, Tubuai, Raiatea) is presented; 18 species, 16 genera and eight families were recorded. Trhypochthoniellus longisetus (Berlese, 1904) and Trimalaconothrus albulus Hammer, 1972 prevailed on distribution. Fortuynia smiti sp. n. (Fortuyniidae) is described from New Caledonia. The new speciesis morphologically most similar to Fortuynia marina Hammen, 1960 from New Guinea, but it differs from the latter by the longer notogastral setae dm, lm, c 2, p 1, epimeral setae 3b and adanal setae ad 1 and the presence of prodorsal lateral ridges.