Polypheretima Elongata Research Articles

A contribution to the earthworm (Annelida, Clitellata, Megadrili) fauna of the central Indian state Chhattisgarh, India

Drawida willsi was the first species of earthworm reported from Chhattisgarh state by Michaelsen in 1907. After that, only one survey of earthworm has been carried out there in 2021. Here we present a first-hand information on the survey of earthworms carried out in Chhattisgarh state in the year 2022. The study documents 12 species belonging to 4 families. Among these, Dichogaster affinis (Michaelsen, 1890) and Polypheretima elongata (Perrier, 1872) are exotic peregrine species. Species such as Drawida limella Gates, 1934, Lennogaster chittagongensis (Stephenson, 1917) and Octochaetona compta (Gates, 1945) expanded their distribution to central India. The study also noted the presence of microplastic for the first time in the ingesta of an earthworm (Lampito mauritii Kinberg, 1867) from India. Further detailed survey would add more species into the faunal list of Chhattisgarh, even species new to science.

Therapeutic Values of Earthworm Species Extract from Azad Kashmir as Anticoagulant, Antibacterial, and Antioxidant Agents.

Aims Current research aimed to explore the therapeutic values of different earthworms as antibacterial, anticoagulant, and antioxidant agents. Methods Ten different earthworms, i.e., Amynthas corticis, Amynthas gracilis, Pheretima posthuma, Eisenia fetida, Aporrectodea rosea, Allolobophora chlorotica, Aporrectodea trapezoides, Polypheretima elongata, Aporrectodea caliginosa, and Pheretima hawayana, were collected and screened for biological activities. Antibacterial effect analysis of earthworm species was done against fourteen bacterial pathogens, i.e., Escherichia coli, Serratia marcescens, Streptococcus pyogenes, Staphylococcus epidermidis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa (1), Salmonella typhimurium, Shigella flexneri, Enterobacter amnigenus, Serratia odorifera, Pseudomonas aeruginosa (2), Staphylococcus warneri, and Lactobacillus curvatus, via agar well diffusion, crystal violet, MTT, agar disc diffusion, and direct bioautography assays. Antioxidant potential was evaluated through ABTS and DPPH assays. Lipolytic, proteolytic, and amylolytic assays were done for lipase, protease, and amylase enzymes confirmation. In vitro anticoagulant effects were examined in the blood samples by measuring prothrombin time. Results Results revealed that all earthworm extracts showed the inhibition of all tested bacterial pathogens except P. aeruginosa (1), P. aeruginosa (2), S. warneri, and L. curvatus. The maximum zone of inhibition of E. coli was recorded as 14.66 ± 0.57 mm by A. corticis, 25.0 ± 0.0 mm by P. posthuma, 20.0 ± 0.0 mm by E. fetida, and 20.0 ± 0.0 mm by A. trapezoid. Cell proliferation, biofilm inhibition, the synergistic effect of extracts along with antibiotics, and direct bioautography supported the results of agar well diffusion assay. Similarly, P. hawayana, A. corticis, A. caliginosa, and A. trapezoids increase the prothrombin time more efficiently compared to other earthworms. A. corticis, A. gracilis, A. rosea, A. chlorotica, P. elongata, and A. trapezoides showed maximum DPPH scavenging potential effect. Conclusions The coelomic fluid of earthworms possessed several bioactive compounds/enzymes/antioxidants that play an important role in the bacterial inhibition and act as anticoagulant agents. Therefore, the development of new therapeutic drugs from invertebrates could be effective and potential for the prevention of the emergence of multidrug-resistant bacteria.

Metagenomic Exploration of Bacterial Community Structure of Earthworms’ Gut

Living organisms are naturally bestowed with unique and imitable qualities for maintaining ecological balance and earthworms are no exceptions. These so-called keystone species of terrestrial ecosystems are equipped with wonderful machinery, allowing them to nurture soil beautifully. Earthworm gut represents a potential microbial reservoir, having a complex interdependence with the host. The study aimed to profile bacterial community structure of three earthworm species belonging to two different life forms; Perionyx excavatus and Eudrilus eugeniae (epigeic), Polypheretima elongata (endogeic) respectively. Diversity analysis using 16S amplicon sequencing revealed that the dominant phyla were Proteobacteria (34.17-77.88) followed by Actinobacteria (13.43-35.54%), Firmicutes (1.69-15.45%) and Bacteroidetes (0.51-8.12%). The alpha diversity indices explicit similar gut microbiota of Perionyx excavatus and Eudrilus eugeniae and while higher alpha diversity was recorded in comparison to Polypheretima elongata gut. The taxonomic to the phenotypic annotation of 16S rRNA metagenomes revealed that dominance of Gram-negative bacterial community in all earthworm species while, Polypheretima elongata comprises higher percentage (78%) of Gram-negative bacterial community to Perionyx excavatus (32.3%) and Eudrilus eugeniae (38.3%). The oxygen requirement phenotypic analysis showed that all earthworm species were abundant with aerobic followed by anaerobic bacterial groups. Furthermore, functional metabolism phenotypic analysis revealed that a high abundance of ammonia oxidizers (29.3-80.2%), the gut microbiomes showed the relative abundance of sulphate reducer (22.6-78.7%), nitrite reducer (19.8-73.2%), dehalogenators (12.6-25.1%), illustrating in the role of these microbial communities in various degradation and bioremediation processes. The present study signifies the intrinsic gut microbiota of earthworm species for intensified biodegradation.

Assessment of Earthworm Community Structure in Industrial and Non-industrial Soils

The trend of industrialization in all over the world significantly altered the assemblages of species and their surrounding environments in the soil. In the present study, the earthworm community structures were assessed in the industrial and non-industrial soils. Total seven earthworm species i.e. Amynthas morrisi (Beddard), Lampito mauritii (Kinberg), Metaphire posthuma (Vaillant) and Polypheretima elongata (Perrier) belonging to family Megascolecidae while Eutyphoeus incommodus (Beddard), Eutyphoeus waltoni (Michaelsen) and Octochaetona beatrix (Beddard) belonging to family Octochaetidae were reported. It was also reported that the earthworm species, their abundance and biomass was significantly (p < 0.05) higher in non-industrial soils as compared to industrial soils. The Metaphire posthuma was reported as the most abundant earthworm species in both industrial and non-industrial soils. The diversity indices such as the Shannon-Wiener diversity index, Simpson index of diversity and species richness index were higher in non-industrial soils while the Simpson index and species evenness index were high in industrial soils. The soil properties such as pH, EC, TDS and heavy metals content were much higher in the industrial soils and significant negative correlation of above said soil properties with earthworm ecological characteristics. This study can be considered as indication that industrialization has much more negative effects on the earthworms and their community structures.

A Comparative Study on Earthworm Biodiversity &amp;amp; Species Habitat-Relationship of Hilly and Plain Areas of Sirohi District of Rajasthan, India

Extensive surveys of earthworm diversity were done in different habitats of plain and hilly areas of Sirohi district of Rajasthan, India. Earthworms differed in their ecomorphological characteristics and relative abundances in different habitats. A total twelve species of earthworms Pontoscolex corethrurus, Amynthas morrisi, Lampito mauritii, Metaphire posthuma, Megascolex konkanensis, Metaphire houlleti, Perionyx sansibaricus, Polypheretima elongata, Ocnerodrilus occidentalis, Dichogaster bolaui, Octochaetona beatrix and Gordiodrilus sp. were recorded from hilly and plain areas. Among these, ten species were found from plain area and nine from hilly area. Five earthworm species (M. konkanensis, M. houlleti, P. elongata, O. beatrix, Gordiodrilus sp.) were recorded for the first-time from Rajasthan. The plain area species P. elongata, O. beatrix and Gordiodrilus sp. were replaced by M. konkanensis and M. houlleti in hilly region. This showed the habitat preferences of earthworm species. Few species were present in a particular habitat of plain area, but they were absent in the same type of habitat in hilly area. The relative density, frequency and species diversity index of earthworm species differed in different habitats and areas. Earthworm diversity exhibited differing species-habitat relationship in hilly and plain areas. These findings may be utilized for eco-restoration of degraded land in similar habitats.

A checklist of earthworms (Annelida: Oligochaeta) in southeastern Vietnam

The earthworms of southeastern Vietnam are reported based on literature and samples collected during the period of 2012–2019. A total of 41 earthworm species of 12 genera in six families are recorded in the southeastern part of Vietnam. Of these, Polypheretima elongata and Dichogaster affinis are recorded for the first time in the region. The dominant family is Megascolecidae with 35 species of seven genera while each of the other families is represented by only one species, except for Octochaetidae which has one genus and two species. The comprehensive checklist also provides data of each species including examined specimens, distributions and remarks. An identification key to species is compiled for southeastern Vietnam.

Soil properties changes earthworm diversity indices in different agro-ecosystem

BackgroundEarthworm communities are generally very sensitive to physico-chemical properties of the soil in different agro-ecosystem i.e. cultivated or non-cultivated which directly or indirectly influence the earthworm survival. The difference in physico-chemical properties of soil at different sites contributed to the formation of population patches for earthworm species. Understanding the physico-chemical properties of soil at a particular site could facilitate the prediction of earthworm species at that site. The objective of the present study was to investigate the diversity, abundance, and distribution of earthworms in cultivated and non-cultivated agroecosystems and their physico-chemical properties affecting the earthworm diversity and abundance.ResultsTotal 10 species of earthworms i.e. Amynthas alexandri, Amynthas morrisi, Eutyphoeus incommodus, Eutyphoeus waltoni, Metaphire birmanica, Metaphire houlleti, Metaphire posthuma, Octochaetona beatrix, Perionyx excavatus, and Polypheretima elongata, were reported. Out of all the reported species, Metaphire posthuma was found to be the most abundant earthworm species in both cultivated and non-cultivated agroecosystems with the occurrence at 56.81% sites. The Shannon-Wiener index (H), Margalef species richness index (DMg) and Pielou species evenness (E) was ranged from 0 to 0.86, 0 to 0.64 and 0.78 to 1 respectively. The principal component analysis resulted in four principal components i.e. PC1, PC2, PC3 and PC4 which contributing variance (%) of 22.96, 19.37, 14.23 and 10.10 respectively. The principal component analysis also showed that physico-chemical parameters of soil such as EC, pH, TDS, texture, OC, moisture, etc. play a critical role in earthworm distribution.ConclusionThe conventional farming system has a negative effect on the earthworm diversity in the soil while the physico-chemical properties of soil also have a determinant effect on the same. Earthworms abundance in the present study have significant direct relation with soil properties at a particular site and vice versa. The diversity indices also change due to the conventional farming system which directly affects the earthworm abundance.

New species of Dichogaster Beddard, 1888 (Clitellata: Benhamiidae) with additional records of earthworms from Guadeloupe (French West Indies).

A survey of the earthworms of Guadeloupe was undertaken to improve knowledge of the diversity of native and introduced earthworms of the island and to evaluate native species for use in vermicomposting. Twenty-eight species were found, 8 introduced, 4 uncertain, and 16 presumed native. The introduced species are Pontoscolex corethrurus, Pontoscolex spiralis, Amynthas rodericensis, Perionyx excavatus, Polypheretima elongata, Dichogaster affinis, Eudrilus eugeniae, and Drawida sp. Juveniles of the genera Righiodrilus, Glossodrilus and Periscolex were found, but one cannot say if they are introduced or not without a confirmed identification. Omodeoscolex divergens was collected in several locations, with variation in color, size and male sexual function suggestive of long residence on the island, but we are counting this as of uncertain status and tentatively placing all in the same species. Late juveniles of a large endogeic species of a heretofore unknown genus of the Rhinodrilidae were found only in the most remote location sampled and are presumed to be native. Seven previously reported native Dichogaster were found. Eight non-recorded species of Dichogaster were found, five represented by single specimens or juveniles, for which we give only a brief precis. The three described here are Dichogaster spolstoni n. sp., Dichogaster caraibensis n. sp.,.and Dichogaster etaspiqui n. sp. These are compared to and differentiated from previously known Dichogaster species of the world and of Guadeloupe.

Extent of Heavy Metal Accumulation in Sewage Irrigated Soils and Their Impact on Distribution of Earthworm Communities: Linking Chromium and Zinc Toxicity on Growth and Reproduction in Selected Earthworm Species.

Soil ecosystem polluted by metals affect the structure of soil invertebrate population(s) and dynamics leading to altered distribution of species. This study focuses on earthworm distribution in sewage irrigated agricultural lands around Bangalore. The occurrence of reported species from the sampled areas is Eudrilus eugeniae, Lampito maurutii, Pontoscolex corethrurus, Polypheretima elongata, Perioynx excavates and Eisenia fetida. Laboratory studies conducted to evaluate feed ingestion rate and body mass changes in earthworms exposed to metal spiked soils revealed species specific pattern. Eudrilus eugeniae and Lampito maurutii showed a steep increase in body weight, while Pontoscolex corethrurus exhibited decreased trend upon Zn exposure. Contrarily a significant (p&lt;0.05) decline in body weight was evident in all the three species upon exposure to Cr spiked soils. The observed alterations in feeding and body mass index concomitantly influenced the reproductive parameters. Rate of hatchability and reproductive function found to be decreased in Cr spiked soils in all the three species studied. Contrarily, increased hatchability was observed in E.eugeniea and L.maurutii followed by a decrease rate in P.corethrurus upon exposure of Zn spiked soils. However, reproductive rate found to be increased in E.eugeniea and P.corethrurus with decreased trend in L.maurutii. Thus, use of sewage polluted water for irrigation purpose has led to increased soil metal concentration impacting earthworm physiology and distribution.

Darwin’s earthworms (Annelida, Oligochaeta, Megadrilacea) with review of cosmopolitan Metaphire peguana–species group from Philippines

A chance visit to Darwin allowed inspection of and addition to Northern Territory (NT) Museum's earthworm collection. Native Diplotrema zicsii sp. nov. from Alligator River, Kakadu NP is described. Town samples were dominated by cosmopolitan exotic Metaphire bahli (Gates, 1945) herein keyed and compared morpho-molecularly with M. peguana (Rosa, 1890) requiring revision of allied species including Filipino Pheretima philippina (Rosa, 1891), P. p. lipa and P. p. victorias sub-spp. nov. A new P. philippina-group now replaces the dubia-group of Sims & Easton, 1972 and Amynthas carinensis (Rosa, 1890) further replaces their sieboldi-group. Lumbricid Eisenia fetida (Savigny, 1826) and Glossoscolecid Pontoscolex corethrurus (Muller, 1857) are confirmed introductions to the NT. mtDNA barcodes newly include Metaphire houlleti (Perrier, 1872) and Polypheretima elongata (Perrier, 1872) spp.-complexes from the Philippines. Pithemera philippinensis James & Hong, 2004 and Pi. glandis Hong & James, 2011 are new synonyms of Pi. bicincta (Perrier, 1875) that is common in Luzon. Vietnamese homonym Pheretima thaii Nguyen, 2011 (non P. thaii Hong & James, 2011) is replaced with Pheretima baii nom. nov. Two new Filipino taxa are also described: Pleionogaster adya sp. nov. from southern Luzon and Pl. miagao sp. nov. from western Visayas.

Earthworms of the 'acaecate' Pheretima group in Vietnam (Oligochaeta: Megascolecidae), with description of a new species from the Mekong delta.

The 'acaecate' Pheretima group from Vietnam is revised, with description of a new species, Polypheretima mekongmontis sp. nov. A total of 18 species of three genera, Metapheretima Michaelsen, 1928, Planapheretima Michaelsen, 1934, and Polypheretima Michaelsen, 1934 has been recorded from Vietnam. Caecate species of Planapheretima are included here as well. Planapheretima arboricola (Rosa, 1890), Pl. lacertina (Chen, 1946), Pl. tenebrica (Chen, 1946), Polypheretima elongata (Perrier, 1872), and Po. taprobanae (Beddard, 1892) are originally recorded from other countries; all remaining species are native to Vietnam. The species Polypheretima tani (Thai, 1996) and Po. tiencanhensis (Pham, 1995) are transferred to the genus Metapheretima. A key to species and distribution maps are also presented.

Aerobic microbial activity in four tropical earthworm-soil systems. A mesocosm experiment

Soil organic matter (SOM) quality and carbon (C) availability may be major features influencing the effect of earthworms on the aerobic processes in clayey tropical soils. In this study, we assessed the effect of an anecic (Polypheretima elongata), an endogeic (Pontoscolex corethrurus) and an epigeic (Eudrilus eugeniae) earthworm on the aerobic microbial activity of two tropical soils, a calcic Vertisol and an acid Ferralsol, with clay content &gt;70% and very different organic C content and SOM stability. The soil–earthworm interaction was studied in a 6-month mesocosm experiment in a greenhouse using soils with and without (control soil) earthworm addition. Potential C mineralisation, actual net nitrogen (N) mineralisation and dehydrogenase activity (DHA), as indicators of the aerobic activity of the soils, and phosphorus (P) availability were determined during the trial. DHA was used as an indicator of the global aerobic activity. Earthworms had little effect on potential C mineralisation but significantly increased actual net N mineralisation. The increase in N mineralisation in the Vertisol was twice as great as, and longer (6 v. 3 months) than for the Ferralsol. Differences between soils for N mineralisation were associated with a less recalcitrant SOM in the Vertisol. Available P increased 10% in the earthworm treatments. Earthworm activity improved N and P availability. DHA was 15 times higher for the Vertisol than for the Ferralsol, but the positive effect of earthworms on DHA was greater for the Ferralsol. This effect was greater for E. eugeniae, probably because of surface burrows generated by this epigeic earthworm, which favoured oxygen entry into the soil. Differences between the two soils were greater for DHA than for C and N mineralisation, and this was observed for the control soils as well as for the earthworm treatments. This indicates that earthworm activity modified the rate of the aerobic processes but it did not affect the intrinsic biological properties of these tropical soils, which were controlled mainly by SOM quality and C availability.

Identifying earthworm's organic matter signatures by near infrared spectroscopy in different land-use systems in Tabasco, Mexico

In the state of Tabasco, South-eastern, Mexico, land-use changes such as the conversion of natural into agricultural systems, modify soil quality and the abundance of soil macrofauna, including earthworms. The aim of this study was to characterize by near-infrared spectroscopy (NIRS) the earthworms’ fingerprint in soil, in six sites including natural and agricultural ecosystems with low and high earthworm biomass and low and high earthworm diversity, in order to identify specific wavelengths that discriminate the presence/abundance of earthworm species and functional groups. The spectral region of 1860–1870nm was significantly correlated with total earthworm density, particularly at one of the sites (Cedar polyculture; r=0.8, p<0.05). Earthworm biomass had a specific NIRS wavelength according to the earthworm species and feeding category: 1820 and1860–1870nm wavelengths were significantly correlated with Polypheretima elongata (r2=0.7, p<0.05; mesohumic species) biomass and 2090nm for biomass of all Lavellodrilus species (polyhumics). Two species had a much wider spectral range: L. bonampakensis and Dichogaster saliens (an epigeic worm; 1690–2300nm, r2=0.7, p<0.05). Biomasses of Periscolex brachysistis and Diplotrema murchiei were not significantly correlated with any near infrared wavelength spectra analyzed. Combining a maximum of 4 species per wavelength, mesohumic earthworms had a wider wavelength spectrum than polyhumics. Therefore, earthworm species diversity, biomass and abundance are associated with soil quality (as measured by NIR spectra) and this relationship varies with species and ecological category. Sites with lower and higher earthworm diversity have lower and higher soil organic matter quality, respectively, as observed by the wider or narrower spectral range with which earthworm biomasses are correlated.

Cadmium-induced earthworm metallothionein-2 is associated with metal accumulation and counteracts oxidative stress

Abstract Metallothionein-2, a ubiquitous metal-inducible protein, is involved in direct metal sequestration and is associated with detoxification and metal accumulation in eukaryotic organisms. In this study, higher levels of cadmium (Cd) accumulation were detected in earthworms exposed to higher Cd concentrations or longer exposure times. However, the bio-concentration factor (BCF), derived from the ratio of the Cd levels in the earthworms to that in soil, indicated that earthworms could relatively efficiently remove Cd from soil with low Cd contamination levels. In addition, earthworm recombinant metallothionein-2 effectively eliminated oxidative DNA damage in vitro and was probably able to counteract DNA damage caused by Cd, as shown by the comet assay in earthworm coelomocytes. Because earthworm metallothionein-2 proteins were evaluated as possible biomarkers for heavy-metal pollution in soil, the metallothionein-2 genes of six Megascolecidae earthworms and one Glossoscolecidae earthworm were cloned and sequenced using mRNA differential display. Based on the resolved earthworm metallothionein-2 nucleotide sequences, quantitative PCR was used to investigate the metallothionein-2 transcription levels from three earthworm species (Metaphire posthuma, Polypheretima elongata and Pontoscolex corethrurus) in response to different Cd concentrations or exposure times. The result demonstrated that Cd treatments elevated metallothionein-2 transcription in a dose- and time-dependent manner. In conclusion, the induction of earthworm metallothionein-2 would not only provide cellular protection against Cd-induced oxidative stress but also increase Cd accumulation consistent with a potential role in bioremediation.

Modification of root density in pot experiments with two tropical earthworm species.

Three greenhouse experiments were performed to assess the role of two common tropical geophagous endogeic earthworm species, Pontoscolex corethrurus and Polypheretima elongata, on root density of several plant species in two soil types, a clayey Andosol and a sandy Alfisol, from Veracruz, Mexico. The equivalent of about 12 kg dry soil were placed into 20 l plastic pots and 3-14 individuals were inoculated to pots planted with common beans (Phaseolus vulgaris), Brachiaria decumbens pasture grass under four P fertilization regimes (0, 1.6, 8.4 and 10 kg P ha-1) and maize (Zea mays) with or without surface residues. Pots received only one species of earthworms (either P. corethrurus or P. elongata). At harvest, the pots were cut in half and a transparent plastic sheet (overheads) used to draw root and earthworm structures (burrows, casts) in vertical and horizontal (every 5 cm) planes. The drawings were scanned, binarized and submitted to image analysis techniques to determine the density of roots, casts and burrows. Root density was generally higher and there was a trend for more even distribution of roots in the soil, both horizontally and vertically, in the presence of earthworms. Nevertheless, few relationships were observed between root density and shoot biomass or the density of earthworm casts and burrows. A more diffuse (less aggregated) root distribution due to earthworms may aid plants in resistance to stress, although the induced changes in the root system may not necessarily lead to greater yields.

Cloning, expression, and characterization of cadmium-induced metallothionein-2 from the earthworms Metaphire posthuma and Polypheretima elongata

In this study we report the sequences of MT-2 cDNA from two species of Megascoleidae earthworms, Metaphire posthuma and Polypheretima elongata, by mRNA differential display after exposure of the organisms to cadmium. Complementary (c)DNA was verified as the MT-2 gene by the characteristics of its predicted translation product, namely a high cysteine content, conserved CXC motifs, and a molecular weight of around 8 kDa. Amino acid sequence alignment revealed a conserved TKCCG in the cloned MT-2 of both megascolecid earthworms instead of the corresponding conserved TQCCG found in lumbricid earthworms. The cDNAs corresponding to the two megascolecid MT-2 genes were expressed, and the MT-2 proteins were purified for biochemical characterization. The binding of Cu 2+ exhibited monophasic kinetics and those of Zn 2+ and Cd 2+ biphasic kinetics. The proteins bound more tightly to Cd 2+ than to Zn 2+ and more tightly still to Cu 2+. Zn-MT and apo-MT were the most effective at scavenging free radicals, followed by Cd-MT. In conclusion, MT-2s from M. posthuma and P. elongata showed unique sequence features compared to those of lumbricid earthworms. These earthworms could be used to evaluate heavy-metal pollution in soil due to the inducible MT-2 by cadmium exposure.

Using earthworms to test the efficiency of remediation of oil-polluted soil in tropical Mexico

This study focuses on the medium-term effects of soil bioremediation on mortality and reproduction rates of Eisenia fetida (laboratory experiment) and of the tropical earthworm Polypheretima elongata (field experiment). We compared soils restored with the two bioremediation technologies landfarming (LF) and compost-bioremediation (BI) with control soils and with soils contaminated with 1% and 2% of petroleum. Control and restored soils both were fertile and showed low hydrocarbon contents. The mortality of E. fetida was not influenced by soil restoration and by contamination with 1% petroleum; it only increased in soils contaminated with 2% petroleum. However, the reproduction rate of E. fetida was significantly lower in the soils restored with LF and in those contaminated with 1% crude oil and significantly higher in the soils restored with BI. P. elongata showed the same reaction as E. fetida. We conclude that it is important to include reproduction or other sub-lethal tests for earthworms when estimating the efficiency of restoration techniques.

Soil fauna abundance and diversity in a secondary semi-evergreen forest in Guadeloupe (Lesser Antilles): influence of soil type and dominant tree species

The importance of secondary tropical forests regarding the maintenance of soil fauna abundance and diversity is poorly known. The aims of this study were (1) to describe soil fauna abundance and diversity and (2) to assess the determinants of soil fauna abundance and diversity in two stands of a tropical semi-evergreen secondary forest. Soil macrofauna and microarthropod abundance and soil macrofauna diversity were described at two sites developed on different soils and with different site histories: (1) a natural secondary stand (natural forest) under two dominant tree species, Pisonia subcordata and Bursera simaruba, and (2) a planted secondary forest (planted forest) under three tree species, B. simaruba, Swietenia macrophylla, and Tabebuia heterophylla. The effects of both soil and main tree species’ litter quality were assessed to explain soil fauna abundance and diversity. The abundance of soil macrofauna was significantly higher in the soil under the planted forest, and soil fauna communities were contrasted between the two sites. In the planted forest, a soil-dwelling macrofauna community developed (mainly consisting of the anecic earthworm Polypheretima elongata). In the natural forest, soil macrofauna and microarthropod communities were located at the soil surface. The effect of plant litter quality varied according to each dominant tree species and was superimposed to soil effect. The lowest macrofauna abundance was associated with B. simaruba in the natural forest. T. heterophylla supported a much greater macrofauna community than the two other tree species studied at the same soil, and it appears likely that this is due to the palatability of its leaves compared with the other trees (low lignin, tannins, soluble phenols).

Enhancement of growth and reproduction of the tropical earthworm Polypheretima elongata (Megascolecidae) by addition of Zea mays and Mucuna pruriens var. utilis litter to the soil

The effect of light fractions of organic matter of different origin, on the growth and reproduction of the mesohumic endogeic earthworm Polypheretima elongata, has been tested in laboratory cultures. Earthworms were fed with savannah soil from “La Mancha” Veracruz (Mexico), added with different amounts of fresh or composted Mucuna pruriens var. utilis (Leguminosae), or Zea mays (Graminaceae) leaf material. Earthworm cultures were performed under controlled conditions of temperature (27 °C) and humidity (33% on a dry weight basis) during 63 days for the growth study and 98 days for the reproduction study. The highest individual fresh weight (5.8 ± 0.7 g after 63 days) and the highest cocoon production (33 ± 8.4 cocoons ind −1 in 98 days) were obtained when litter of M. pruriens var. utilis was added to the soil. Mucuna leaf material was more efficient when fresh, whereas maize litter gave higher growth and fecundity rates when composted for 6 weeks. The addition of organic matter from the light fraction of the soil did not improve earthworm growth.

Earthworm populations under tropical maize cultivation: the effect of mulching with velvetbean

Earthworm populations were studied in three tropical agroecosystems of southern Mexico: improved maize with a Mucuna pruriens cover crop (MM), continuous conventional maize (CM) and pastures (P). Three replicates and six monoliths were sampled in each agroecosystem. Three earthworm species were found, two native (Balanteodrilus pearsei, Larsonidrilus orbiculatus) and one exotic (Polypheretima elongata). In all systems, the dominant species was B. pearsei, with negligible presence of the exotic species in MM and P plots. Total abundance was significantly higher in MM than in CM; and earthworm biomass was also higher in MM than in CM and P. Juveniles of both native species dominated, mainly concentrated in the top 20 cm of soil. B. pearsei and L. orbiculatus displayed different preferences (within each agroecosystem) for soil organic matter, N and temperature. Further experiments are required to investigate whether mulching with M. pruriens results in an increased earthworm abundance and biomass through a N-improvement effect or as a result of microclimatic changes and to study the extent to which earthworms and M. pruriens are synergistic in enhancing maize growth.