The second species of the endemic Malagasy earthworm genus Howascolex Michaelsen, 1901; Howascolex farafangana sp. n. (Clitellata, Megadrili)

A recent survey of earthworms carried out in South East Madagascar resulted in collecting two species belonging to the endemic Malagasy earthworm genus Howascolex Michaelsen, 1901. One of the species proved to be identical to the generotype Howascolex madagascariensis Michaelsen, 1901. The other species Howascolex farafangana sp. n. represents the second species of the genus. The genus Howascolex was originally classified in the subfamily Octochaetinae Michaelsen, 1900. However, its close morphological similarity with the Malagasy acanthodriline species implies a homoplasious origin of the meroic excretory system of Howascolex and its inclusion in the family Acanthodrilidae Claus, 1880

New and little known earthworm species from Central Madagascar (Oligochaeta: Kynotidae)

The investigation of a small number of earthworms collected in Central Madagascar resulted in the discovery of two species new for science, Kynotus minutus and Kynotus parvus spp. nov. Apart from the descriptions and illustrations of the new species, the two little-known species Kynotus alaotranus Michaelsen, 1907 and Kynotus michaelseni Rosa, 1892 are recorded for the first time after the original description, and commented short diagnoses are provided. With the two new species described in this paper, the genus Kynotus now contains 20 species. The monogeneric earthworm family Kynotidae is endemic to Madagascar

Three new species of Kynotus from the Central Highlands of Madagascar (Clitellata, Megadrili)

The earthworm fauna of Madagascar is scarcely known. A recently launched exploration of the soil fauna (“Global Change and Soil Macrofauna Diversity in Madagascar”) resulted in the discovery of six new earthworm species belonging to the Malagasy endemic family Kynotidae. The success of the collecting campaign carried out between 2008 and 2011 inspired a new exploration of the earthworm fauna across the Central Highland Region of the island in the spring of 2015. During this expedition, two new species of Kynotus, K. ankisiranus sp. nov. and K. voimmanus sp. nov., were discovered. Barcoding of the recently collected species of Kynotus revealed that the unpigmented worms referred previously to K. alaotranus Michaelsen, 1897 also represented a new, still undescribed species, K. blancharti sp. nov

Plant-earthworm partnership to increase crop productivity in the tropics

International audienceTropical soils are often nutrient-depleted in their mineral form, which constrains crop growth. Therefore any process leading to the mineralization of N and P trapped into the soil organic matter need to be studied in order to developsustainable agricultural tools in a near future. Priming effect is defined as a stimulation of the soil organic matter mineralization (SOM) by the amendment of fresh organic matter (FOM). This microbially-mediated process is not completely understood. In theory, organic amendments could stimulate nutrient recycling from the SOM stock, provided that they will be managed under the right conditions. Endogeicearthworms are ecosystem engineers known to influence the dynamics of SOM as they ingest high amount of soil and assimilate one part of the organic carbonin relation with microbial activity stimulation. During the gut transit, microorganisms are awaked and their activities are stimulated by the small molecules contained in the mucus and by the meeting with fresh residues. During a first laboratory study we observed that earthworms could increase the Priming Effect intensity resulted from a fresh residue amendment*. Priming effect stimulation could be linked to specific bacterial phylogenetic groups* and its intensity was dependent on the type of soil and the earthworm species. Dichogaster saliensis a small size earthworm species living at the root vicinity of Bracharia sp. We observed that this species was able to generate an important priming effect in his gut, and therefore could mineralize nutrients liberated close to the roots. In a second experiment rice plants cultivated in outdoor pots were inoculated with increasing number of D.saliens specimens. At the rice maturity, a positive relationship between the number of earthworms and the number of grains per panicle was measured. As plant-fungi partnership, earthworm can also be a good partner, providing nutrients to the plant when most of nutrients are in the organic matter pool

New acanthodrilid species from Madagascar (Clitellata, Acanthodrilidae)

International audienceDuring collecting trips to Madagascar in the last decade several Acanthodrilidae sensu lato species were collected. The newly acquired material expresses high variability of the excretory system containing meroic, holoic vesiculate and holoic avesiculate species. The possible relationships of the Malagasy acanthodrilids is discussed and five species; Acanthodrilus hesperus, Eodriloides metandricus, Howascolex proprioporus, Howascolex vohimanus and Vazimbascolex alaotranus spp. n. are described. Vazimbascolex gen. n. represents also a new genus to science

New acanthodrilid species from Madagascar (Clitellata, Acanthodrilidae)

International audienceDuring collecting trips to Madagascar in the last decade several Acanthodrilidae sensu lato species were collected. The newly acquired material expresses high variability of the excretory system containing meroic, holoic vesiculate and holoic avesiculate species. The possible relationships of the Malagasy acanthodrilids is discussed and five species; Acanthodrilus hesperus, Eodriloides metandricus, Howascolex proprioporus, Howascolex vohimanus and Vazimbascolex alaotranus spp. n. are described. Vazimbascolex gen. n. represents also a new genus to science

Effects of the earthworm Pontoscolex corethrurus on rice P nutrition and plant-available soil P in a tropical Ferralsol

International audienceWe conducted a greenhouse experiment in mesocosms for 28 days to assess the effects of the endogeic earthworm Pontoscolex corethrurus on plant-available soil phosphorus (P) and rice (Oryza sativa) P nutrition in a Malagasy Ferralsol. To assess plant-available soil P, we determined the L-value by measuring the specific activity of P taken up from the soil by rice and by applying the isotopic dilution principle. Despite earthworm mortality, P. corethrurus significantly increased rice shoot biomass (+26%) and P nutrition (+65%), confirming that the soil used for the experiment was P-deficient. The L-value also markedly increased from 6.8 ± 0.9 to 14.2 ± 1.3 mg P mesocosm−1 in the presence of P. corethrurus. We estimated that the orthophosphate ions released due to earthworm mortality contributed to 30% of the L-value increase. We attributed the remaining 70% increase to the solubilization of native soil P during its transit through the digestive tract. Thereafter, we discussed the sources of uncertainty associated with the L-value calculation and their utilization to assess earthworm effects on P availability in further studies

Earthworm Inoculation Improves Upland Rice Crop Yield and Other Agrosystem Services in Madagascar

International audienceThe effects of earthworm inoculation and cropping systems on upland rice systems were examined over a four-year period in the Highlands of Madagascar. Each year, endogeic earthworms Pontoscolex corethrurus (Rhinodrilidae) were inoculated (EW+) at a density of 75 ind m−2 or were not inoculated (EW0). Inoculation was tested in three cropping systems: conservation agriculture (CA) and traditional tillage with or without residues restitution. Soil and plant properties were measured during the first three years while soil biological properties were assessed at the fourth year. At the end of the experiment, earthworm density was three-fold higher in EW+ than in EW0, demonstrating the success of the inoculation. Earthworm density was more important in CA than in tillage systems. Earthworm inoculation had higher significant effects on soil and plant properties than cropping systems. Earthworm inoculation had positive effects on soil macroaggregation (+43%), aboveground biomass (+27%), rice grain yield (+45%), and N grain amount (+43%). Intensifying earthworm activity in field conditions to meet the challenge of ecological transition is supported by our study