A review of the Eviota zebrina complex, with descriptions of four new species (Teleostei, Gobiidae)

The Eviota zebrina complex includes eight species of closely-related dwarfgobies, four of which are herein described as new. The complex is named for Eviota zebrina Lachner & Karnella, 1978, an Indian Ocean species with the holotype from the Seychelles Islands and also known from the Maldives, which was once thought to range into the Gulf of Aqaba and the Red Sea eastward to the Great Barrier Reef of Australia. Our analysis supports the recognition of four genetically distinct, geographically non-overlapping, species within what was previously called E. zebrina, with E. zebrina being restricted to the Indian Ocean, E. marerubrumsp. nov. described from the Red Sea, E. longirostrissp. nov. described from western New Guinea, and E. pseudozebrinasp. nov. described from Fiji. The caudal fin of all four of these species is crossed by oblique black bars in preservative, but these black bars are absent from the four other species included in the complex. Two of the other species within the complex, E. tetha and E. gunawanae are morphologically similar to each other in having the AITO cephalic-sensory pore positioned far forward and opening anteriorly. Eviota tetha is known from lagoonal environments in Cenderawasih Bay and Raja Ampat, West Papua, and E. gunawanae is known only from deeper reefs (35–60 m) from Fakfak Regency, West Papua. The final two species are E. cometa which is known from Fiji and Tonga and possesses red bars crossing the caudal fin (but lost in preservative) and a 9/8 dorsal/anal-fin formula, and E. oculineatasp. nov., which is described as new from New Guinea and the Solomon Islands, and possesses an 8/7 dorsal/anal-fin formula and lacks red caudal bars. Eviota oculineata has been confused with E. cometa in the past.

Microbial Shift in the Enteric Bacteriome of Coral Reef Fish Following Climate-Driven Regime Shifts

Replacement of coral by macroalgae in post-disturbance reefs, also called a “coral-macroalgal regime shift”, is increasing in response to climate-driven ocean warming. Such ecosystem change is known to impact planktonic and benthic reef microbial communities but few studies have examined the effect on animal microbiota. In order to understand the consequence of coral-macroalgal shifts on the coral reef fish enteric bacteriome, we used a metabarcoding approach to examine the gut bacteriomes of 99 individual fish representing 36 species collected on reefs of the Inner Seychelles islands that, following bleaching, had either recovered to coral domination, or shifted to macroalgae. While the coral-macroalgal shift did not influence the diversity, richness or variability of fish gut bacteriomes, we observed a significant effect on the composition (R2 = 0.02; p = 0.001), especially in herbivorous fishes (R2 = 0.07; p = 0.001). This change is accompanied by a significant increase in the proportion of fermentative bacteria (Rikenella, Akkermensia, Desulfovibrio, Brachyspira) and associated metabolisms (carbohydrates metabolism, DNA replication, and nitrogen metabolism) in relation to the strong turnover of Scarinae and Siganidae fishes. Predominance of fermentative metabolisms in fish found on macroalgal dominated reefs indicates that regime shifts not only affect the taxonomic composition of fish bacteriomes, but also have the potential to affect ecosystem functioning through microbial functions.

Genomics analysis of hexanoic acid exposure in Drosophila species

Drosophila sechellia is a dietary specialist endemic to the Seychelles islands that has evolved to consume the fruit of Morinda citrifolia. When ripe, the fruit of M. citrifolia contains octanoic acid and hexanoic acid, two medium chain fatty acid volatiles that deter and are toxic to generalist insects D. sechellia has evolved resistance to these volatiles allowing it to feed almost exclusively on this host plant. The genetic basis of octanoic acid resistance has been the focus of multiple recent studies, but the mechanisms that govern hexanoic acid resistance in <D. sechellia remain unknown. To understand how D. sechellia has evolved to specialize on M. citrifolia fruit and avoid the toxic effects of hexanoic acid, we exposed adult D. sechellia, D. melanogaster and D. simulans to hexanoic acid and performed RNA sequencing comparing their transcriptional responses to identify D. sechellia specific responses. Our analysis identified many more genes responding transcriptionally to hexanoic acid in the susceptible generalist species than in the specialist D. sechellia. Interrogation of the sets of differentially expressed genes showed that generalists regulated the expression of many genes involved in metabolism and detoxification whereas the specialist primarily downregulated genes involved in the innate immunity. Using these data we have identified interesting candidate genes that may be critically important in aspects of adaptation to their food source that contains high concentrations of HA. Understanding how gene expression evolves during dietary specialization is crucial for our understanding of how ecological communities are built and how evolution shapes trophic interactions.

Strateole-2: High-resolution observations of the tropical tropopause layer with long-duration balloons

&lt;p&gt;Strateole-2 is a project aimed at studying the coupling between the troposphere and the stratosphere in the deep tropics. The project originality pertains to the use of long-duration ballons, which can fly for several months at 18 or 20 km altitude. The first Strateole-2 campaign took place from November 2019 to February 2020: 8 balloons with various instrumental configurations were released in the lower stratosphere from Seychelles Islands, in the Indian Ocean.&lt;br&gt;This first campaign was primarily devoted to testing all systems (balloons, gondolas, and instruments) developed for the project, and was very successful: the balloons flew for 85 days onaverage over the whole tropical band, and most instruments performed nominally. In-situ meteorological measurements performed every 30-s on each flight provide a unique description of gravity-wave activity in the tropics and its relation to deep convection. The first observations of aerosols and water vapor onboard long-duration balloons were also achieved, which e.g. highlighted the tape recorder signal in the tropical lower stratosphere. Very innovative instruments also premiered during the campaign: RACHuTS, a light reeled payload, for instance performed 50 high-resolution vertical profiles of temperature, aerosols and water vapor down to 2km below the balloon, crossing several times the cold-point tropopause. ROC collected hundreds of temperature profiles down to the middle troposphere through GPS radio-occultations. Last, one balloon also carried a nadir-pointing backscatter lidar, which has described the underlying convection at unprecedented temporal resolution. An overview of the flights and first results will be presented.&lt;br&gt;Two forthcoming balloon campaigns are planned within Strateole-2, in 2021-22 and 2024-25. Each will release 20 balloons.&amp;#160;&lt;/p&gt;

Does Drosophila sechellia escape parasitoid attack by feeding on a toxic resource?

Host shifts can drastically change the selective pressures that animals experience from their environment. Drosophila sechellia is a species restricted to the Seychelles islands, where it specializes on the fruit Morinda citrifolia (noni). This fruit is known to be toxic to closely related Drosophila species, including D. melanogaster and D. simulans, releasing D. sechellia from interspecific competition when breeding on this substrate. Previously, we showed that larvae of D. sechellia are unable to mount an effective immunological response against wasp attack, while larvae of closely-related species can defend themselves from parasitoid attack by melanotic encapsulation. We hypothesized that this inability constitutes a trait loss due to a reduced risk of parasitoid attack in noni. Here we present a lab experiment and field survey aimed to test the hypothesis that specialization on noni has released D. sechellia from the antagonistic interaction with its larval parasitoids. Our results from the lab experiment suggest that noni may be harmful to parasitoid wasps. Our results from the field survey indicate that D. sechellia was found in ripe noni, whereas another Drosophila species, D. malerkotliana, was present in unripe and overripe stages. Parasitic wasps of the species Leptopilina boulardi emerged from overripe noni, where D. malerkotliana was the most abundant host, but not from ripe noni. These results indicate that the specialization of D. sechellia on noni has indeed drastically altered its ecological interactions, leading to a relaxation in the selection pressure to maintain parasitoid resistance.

Genomics of a killifish from the Seychelles islands supports transoceanic island colonization and reveals relaxed selection of developmental genes

How freshwater fish colonize remote islands remains an evolutionary puzzle. Tectonic drift and trans-oceanic dispersal models have been proposed as possible alternative mechanisms. Integrating dating of known tectonic events with population genetics and experimental test of salinity tolerance in the Seychelles islands golden panchax (Pachypanchax playfairii), we found support for trans-oceanic dispersal being the most likely scenario. At the macroevolutionary scale, the non-annual killifish golden panchax shows stronger genome-wide purifying selection compared to annual killifishes from continental Africa. Reconstructing past demographies in isolated golden panchax populations provides support for decline in effective population size, which could have allowed slightly deleterious mutations to segregate in the population. Unlike annual killifishes, where relaxed selection preferentially targets aging-related genes, relaxation of purifying selection in golden panchax affects genes involved in developmental processes, including fgf10.

Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae)

Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 are two genera of hesionid errant annelids (Hesionidae, Hesioninae) whose species have 16 chaetigers (21 segments). Leocrates species are free living in rocky or mixed bottoms, whereas Leocratides species are usually symbiotic with hexactinellid sponges. Marian Pettibone revised both genera as part of the R/V Siboga Expedition monographs 50 years ago, and most of her ideas have remained unchallenged regarding synonymy for genera and species. For example, she included three genera as junior synonyms of Leocrates: Lamprophaes Grube, 1867, Tyrrhena Claparède, 1868, and Dalhousia McIntosh, 1885, and from 21 nominal species, she regarded only eight as valid. In this revision, all material available was studied, and different morphological patterns were noted in nuchal organs lobes, pharynx armature, and chaetal features. Leocratides species belong to a single pattern; however, in Leocrates several patterns were detected. Three patterns are present for nuchal organs lobes: barely projected posteriorly (horizontal C-shaped), markedly projected posteriorly (U-shaped), and with lateral transverse projections (L-shaped). In the pharynx, upper jaws were noted as single, fang-shaped, or as double, T-shaped structures, whereas the lower jaw can be single, fang-shaped, or a transverse plate. Neurochaetal blades can be bidentate with guards approaching subdistal tooth, unidentate without guards, or with guards hypertrophied projected beyond distal tooth. The combinations of these features are regarded as different genera and consequently, Leocrates is restricted (including Tyrrhena), but Dalhousia, and Lamprophaea (name corrected) are reinstated, and three new genus-group names are proposed: Paradalhousia n. gen., Paralamprophaea n. gen., and Paraleocrates n. gen. Further, the standardization of morphological features allowed several modifications and the recognition of novelties. Thus, four type species were redescribed, four others were reinstated, 10 were newly combined, and 18 from different World localities are described as new. The new species are Lamprophaea cornuta n. sp. from the French Polynesia, L. ockeri n. sp. from the Hawaiian Islands, L. paulayi n. sp. from the Red Sea, L. pettiboneae n. sp. from the Marshall Islands, L. pleijeli n. sp. from La Réunion, L. poupini n. sp. from the French Polynesia, Leocrates ahlfeldae n. sp. from India, L. harrisae n. sp. from the Revillagigedo Islands, L. mooreae n. sp. from New Caledonia, L. reishi n. sp. from the Marshall Islands, L. rizzoae n. sp. from the Seychelles Islands, L. rousei n. sp. from Papua New Guinea, L. seidae n. sp. from the French Polynesia, Leocratides jimii n. sp. from Madagascar, Paralamprophaea bemisae n. sp. from the Maldives, P. crosnieri n. sp. from Madagascar, P. leslieae n. sp. from Kiribati, and P. meyeri n. sp. from the French Polynesia. However, Leocrates japonicus Gustafson, 1930 is a nomen nudum. Keys are included for identifying all hesioninae genera, and for all species in all the included genera.

Does Drosophila sechellia escape parasitoid attack by feeding on a toxic resource?

ABSTRACTHost shifts can drastically change the selective pressures that animals experience from their environment. Drosophila sechellia is a species restricted to the Seychelles islands, where it specialized on the fruit Morinda citrifolia (noni). This fruit is known to be toxic to closely related Drosophila species, including D. melanogaster and D. simulans, releasing D. sechellia from interspecific competition when breeding on this substrate. Previously, we showed that D. sechellia is unable to mount an effective immunological response against wasp attack, while the closely-related species can defend themselves from parasitoid attack by melanotic encapsulation. We hypothesized that this inability constitutes a trait loss due to a reduced risk of parasitoid attack in noni. Here we present a field study aimed to test the hypothesis that specialization on noni has released D. sechellia from the antagonistic interaction with its larval parasitoids. Our results from the field survey indicate that D. sechellia was found in ripe noni, whereas another Drosophila species, D. malerkotliana, was present in unripe and rotting stages. Parasitic wasps of the species Leptopilina boulardi emerged from rotten noni, where D. malerkotliana was the most abundant host. These results indicate that the specialization of D. sechellia on noni has indeed drastically altered its ecological interactions, leading to a relaxation in the selection pressure to maintain parasitoid resistance.

An annotated checklist of myxomycetes from the Seychelles Islands, Indian Ocean

The checklist provided herein contains 143 species and infra-specific taxa of myxomycetes representing six orders, 12 families and 29 genera known from the Seychelles Islands. These records are the result of 878 field collections and 468 samples processed with the use of the moist chamber techinque. The overall study involved expeditions to the granitic group of islands Mahé, Praslin, La Digue, Curieuse, Félicité, and data from the literature for the coral Aldabra atoll. The taxonomic structure of the myxomycete biota for the islands studied indicates a predominance of members of the order Physarales (74 taxa). Th e main genera are <em>Physarum</em> (38 species and two varieties), <em>Didymium</em> (17 species), <em>Cribraria</em> (11 species), <em>Arcyria</em> (eight species) and <em>Stemonitis</em> (six species and two varieties). For all six islands only a single species of myxomycete (<em>Physarum crateriforme</em>) was shared in common. For the total assemblage of species recorded from all of the islands, 4% species were abundant, 12% species were common, 29% were found occasionally, 42% were rare, and 13% species had only a single record. The most abundant species were <em>Arcyria cinerea</em>, <em>A. denudata</em>, <em>Diderma effusum</em>, <em>Hemitrichia calyculata</em>, <em>Physarum compressum</em>, and <em>P. melleum</em>. Based on data from 50 different localities with 90 collecting plots, 32% of all specimens were associated with coastal vegetation, 30% with lowland localities, 19% with intermediate forests, 9% with riverine forests, 8% with mountain forests, and only 2% with mangrove swamps. In general, this annotated checklist clearly shows that isolated tropical islands can support a diverse assemblage of myxomycetes.

The Australian Paratrichapus Scott (Coleoptera: Ciidae)

The genus Paratrichapus Scott, 1926 currently comprises four species, one described from the Seychelles Islands in the Indian Ocean, one from Indonesia and two from New Zealand. Here, the first Australian species of Paratrichapus are described, as follows: P. australis sp. n., P. burwelli sp. n., P. christmasensis sp. n., P. metallonotum sp. n. and P. peckorum sp. n. Data on their geographic distribution and host fungi are provided, as well as an identification key.