Life Cycle of Vermicomposting Earthworms Eisenia fetida and Eudrilus eugeniae Under Laboratory Controlled Condition
Abstract
The study was initiated and reproductive efficiency of
vermicomposting worms to see the growth, reproductive biology and life
cycle of the vermicomposting earthworms (Eisenia fetida and Eudrilus eugeniae)
at the lab Department of Soil Science during 15 February to 10 June
2018. Determination of cocoon production rate, hatching success, number
of hatchling and growth of Eisenia fetida and Eudrilus eugeniae
in the cowdung media was conducted with plastic containers. The
experiment was designed under the single treatment cowdung with three
replications. Clitellum development started earlier in 3rd week of Eisenia fetida than Eudrilus eugeniae
(4th week). Number of cocoons produced per earthworm (21.8±3.0), mean
number of hatchlings from one cocoon (3.3±0.57), hatching success rate
(86.6%) was recorded higher of Eisenia fetida.
Cocoon production of E. fetida was started to release cocoon on the 6th week and Eudrilus eugeniae was started to release cocoon on the 7th week. Cocoon production ceased after 12 week for Eisenia fetida and 9 week Eudrilus eugeniae.
Maximum weights achieved per earthworm (1116±16.4 mg), net weight gain
per earthworm (819±12 mg), growth rate per worm per day (17.43±1.4 mg)
were higher in Eudrilus eugeniae comparison to Eisenia fetida.
The overall result of this study showed that better hatching success of
cocoons and number of hatchling per cocoon were recorded by Eisenia fetida earthworm species.
Keywords: Eisenia fetida; Eudrilus eugeniae; Earthworms; Life Cycle
Introduction
Earthworms are macroscopic clitellate oligochaete annelids that live
in soil. They are segmented worms, bilaterally symmetrical, with an
external gland (clitellum) for producing the egg case (cocoon), a
sensory lobe in front of the mouth (prostomium), and an anus at the end
of the animal body, with a small number of bristles (setae) on each
segment. They are hermaphrodite animals, and reproduction normally
occurs through copulation and cross-fertilization, following which each
of the mated individuals produces cocoons containing 1-20 fertilized
ova. The resistant cocoons, which are tiny and roughly lemon-shaped,
with shape differing between species, are usually deposited near the
soil surface, except in dry weather when they are laid at deeper layers.
Cocoons hatch after an incubation period that varies according to the
earthworm species and environmental conditions. Hatchling earthworms,
unpigmented and only a few millimeters in length on emerging from the
cocoons, gain their adult pigmentation within a few days. Assuming
favorable conditions, they reach sexual maturity within several weeks
after emergence.
Mature individuals of most vermicomposting species can be
distinguished easily by the presence of the clitellum, the pale or dark
colored swollen band located behind the genital pores. The clitellum
secretes the fibrous cocoon, and the clitellar gland cells produce a
nutritive albuminous fluid that fills the cocoon. Earthworms display
indeterminate growth and can continue to grow in size after completing
their sexual development although they do not add segments. According to
Reynolds and Wetzel [1], there are more than 8300 species in the
Oligochaeta, of which about half are terrestrial earthworms. On the
basis of their feeding and burrowing strategies, into three ecological
categories: epigeic, anecic, and endogeic [2]. Endogeic (soil feeders)
and anecic species (burrowers) live in the soil and consume a mixture of
soil and organic matter, and thus excrete organomineral feces. Epigeic
species of earthworms are litter dwellers and litter transformers; they
live in organic soil horizons, in or near the surface litter, and feed
primarily on coarse particulate organic matter.
They ingest large amounts of under composed litter and excrete
holorganic fecal pellets. These species are small in body size and
uniformly pigmented with high metabolic and reproductive rates,
which represent adaptations to the highly variable environmental
conditions at the soil surface. Different species of earthworms have
different life histories, occupy different ecological niches. Loh et al.
[3] reported higher cocoon production and weight gain by E. fetida
in cattle waste than in goat waste. Gunadi et al. [4] have studied
growth, reproduction, and mortality of E. foetida for over a year in
solid manure, pig manure, and supermarket waste solids. Worms
could not survive in fresh cattle solids, pig solids, fruit wastes, or
vegetable wastes. The growth of E. foetida in pig wastes was faster
than in cattle solids. Understanding the growth and reproductive
efficiency of vermicomposting worms in various substrates is highly
essential for effective utilization of earthworms in sustainable
waste management system [5-6].
As huge amount of wastes can be managed through more
population of earthworms [7] reproductive and growth
performance of various species of earthworms in a range of
substrates can act as useful biomarkers to measure the efficiency
of an earthworm species in vermicomposting or earthworm based
biotechnology [8]. Neuhauser et al. [9] have reported that the
weight gain by Eisenia fetida is positively correlated with food type.
Similarly, Nath et al. [10,11] have also described substrates that
provide earthworms with sufficient amount of easily metabolizable
organic matter, facilitate growth and reproduction. Hence, in the
present study, to see the growth, reproductive biology and life cycle
of the vermicomposting earthworms.
Material and Methods
Life cycle experiments were carried out in the lab Department
of Soil Science with average room temperature of 21-28°C and 60 to
80% moisture of the culture media during 15 February to 10 June
2018. For moisture determination, the sample substrates were
taken regularly (at 3 days interval) weighed, oven dried at 105°C
and cooled in desiccators for 1 hr and reweighed. The difference
between moist and dried samples were taken and then the moisture
content of beddings was adjusted to 60 to 80% and the temperature
was kept within the range of 21-28°C throughout the study period
[12]. In this experiment was designated as single treatment and
two earthworm species (Eisenia fetida and Eudrilus eugeniae) with
three replications. For experimentation 500g cowdung was filled
in the container. Twenty each earthworm species having individual
live weight (225 mg of Eisenia fetida and 284 mg of Eudrilus
eugeniae) were released into each experimental container.
Biomass, Maturation and Cocoon Production Date
Five hatchlings of earthworm species in good health condition
were taken from the above containers for reproductive potential
determination. The hatchlings were rinsed with distilled water to
remove any adhering material, dried briefly on paper towel, weighed
on electronic balance and finally introduced in each respective
experimental container. Three replicates were established.
To monitor the growth and maturation progress weekly, the
biomass was measured in batch of earthworm in each container
and three phases of the life cycle were observed, Pre-clitelleate
(incipient development of the clitellum, identified by appearance
of tuber culapubertasis), clitelleate (well-developed clitellum) and
regression (loss of the clitellum). At the same time, the first cocoon
production date for each worm was also determined. No additional
feed was added at any stage during the study period. On the basis
of the obtained data on the biomass of the worms other parameters
of earthworm such as growth rate or biomass increase rate (g/
earthworm/day), maximum weight achieved, and net weight gain
were calculated.
Reproductive Potential (Cocoon Production Rate) Determination
The experiments were conducted in cylindrical plastic
containers. Each container was filled with waste material based on
the feeding rate explanation of [13]. Three replicates were prepared
for each substrate and worm combination. Two freshly clitellated
species, in good health condition, were collected from the stock
culture and rinsed with distilled water to remove any adhering
material, dried briefly on paper towel, weighed with electronic
balance and finally introduced in each container containing. The
substrate in treatment container was examined daily in order
to determine the onset of cocoon production. Once the cocoons
appeared, they were separated by hand sorting, washed lightly
in distilled water and counted so as to determine total number of
cocoon and the fecundity or reproductive rate (cocoon/worm/day).
Cocoon Incubation Period, Number of Hatchlings and Hatching Success
To determine the incubation period (time lapse from cocoon
formation until the first hatchling emerged in days), hatching success
(total number of hatched cocoons), and number of hatchlings per
cocoons, fifteen freshly laid cocoons from treatment were taken
from the above containers and placed in containers which contained
the same material in which their parents were reared. Three
replicates were prepared. The beddings were observed daily for
the emergence of hatchlings in order to determine the incubation
period. As soon as the appearance of hatchling started, they were
removed daily using a fine painting brush and counted by hand
sorting in order to determine the total number of hatchlings that
emerged from a single cocoon. The number of unhatched cocoons
was also counted in order to determine the hatching success of
cocoons.
Results and Discussion
Growth Rate of Earthworm Species
The growth rate of two earthworm species in investigating
during the study period is given in Table 1. The biomass of
earthworm species showed progressive raise up to 6th week in E.
fetida and 7th week in E. eugeniae. In E. fetida where maximum
growth attained, E. fetida achieved their maximum weight achieved
889±90 mg/worm at a growth rate of 16.3±0.52 mg/worm/day in
the 6th week. In E. eugeniae where maximum growth attained, E.
eugeniae achieved their maximum weight achieved 1116±16.4 mg/
worm at a growth rate of 17.43±1.4 mg/worm/day in the 7th week.
Regarding the sexual maturity (clitellum development), E. fetida
was preclitelated on the second week and mature individual with
clitellum totally developed started to emerge on the 3rd week and E.
eugeniae was developed in 4th week of this experiment. Edwards et al. [14] and Monroy et al. [15] also reported that
rapid pre-reproductive phase of growth, followed by a phase of
progressive biomass and growth reduction once sexual maturity
was attained. These losses in worm biomass might be associated
with the exhaustion of food. As supported by [9] who reported
that when E. fetida received food below a maintenance level, it
lost weight. The weight reduction was also occurred because
the earthworms attained the matured stage. So, they utilized the
energy for reproduction purpose such as laying eggs, mating and
cocoon formation [6]. Reinecke et al. [16] reported a maximum
weight gain for E. eugeniae of 150 mg per week, at 25°C. Hait and
Tare [17] reported that temperature influences the biology of the
earthworm by modifying metabolic activity.
Rate of Cocoon Production by Earthworm Species
In this experiment, E. fetida was started to release cocoon on
the 4th week and Eudrilus eugeniae was started to release cocoon
on the 5th week (Table 2). The highest total number of cocoon was
attained in Eudrilus eugeniae (1016±31 cocoons at a reproduction
rate of 0.21 ± 0.07 cocoon/earthworm/day) at 9 weeks and E.
fetida (109 ± 14.9 cocoons at cocoon production rate of 0.39±0.05
cocoon/earthworm/day) was recorded in this study. Cocoon
production ceased after 12th week of Eisenia fetida and Eudrilus
eugeniae cocoon production was ceased in 9th week. Giraddi et al.
[18] who reported that better hatching success of cocoons that
indicate the cocoon viability. E. eugeniae reached sexual maturity in
as little as five weeks compared with E. fetida which took 6-8 weeks
to produce its first cocoon [19]. Reinecke et al. [16] who reported
that E. eugeniae started producing cocoons after 46 days. This is
a shorter time than the 6-8 weeks previously quoted for E. fetida
[20], and the 51 days reported for E. eugeniae [21].
Incubation Period and Hatching Performance of Cocoons by Earthworm Species
The incubation period range of two earthworm species were
completed in 18-26 days of Eisenia fetida and 12-21 days of
Eudrilus eugeniae. The mean number of hatchlings from one cocoon
was 3.3±0.57 in Eisenia fetida which comparison 2.23 ± 0.18 in
Eudrilus eugeniae. The cocoons produced generally demonstrated
good hatching performance in Eisenia fetida (86.6%) than Eudrilus
eugeniae (75.3%) (Table 3). Shalabi [22] who reported that the
average standard time taken to reach sexual maturity for E. fetida
was about 70 days. The result also varied from the result of Venter et
al. [23] who recorded 60 days for E. fetida to reach sexual maturity.
Conclusion
The reproductive ability of Eisenia fetida is higher than Eudrilus
eugeniaeit. However, to get accurate knowledge of the full potential
of the compost worm as waste processor, it is essential that the life
cycle of the worm on waste be studied thoroughly. Eisenia fetida is
very suitable as waste decomposer.
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