How Do You Know That an Eathworm Is Mature Enough to Breed
Earthworms are responsible for soil development, recycling organic matter and form a vital component inside many food webs. For these and other reasons earthworms are worthy of investigation. Many technologically-enhanced approaches have been used within earthworm-focused research. These take their place, may be a development of existing practices or bring techniques from other fields. Nevertheless, let us not overlook the fact that much can all the same exist learned through utilisation of more than basic approaches which accept been used for some time. New does not always equate to better. Information on community limerick within an area and specific population densities can be learned using simple collection techniques, and burrowing behaviour can be determined from pits, resin-insertion or simple mesocosms. Life history studies can be achieved through maintenance of relatively simple cultures. Behavioural observations tin be undertaken by direct ascertainment or with low cost webcam usage. Applied aspects of earthworm research can too be achieved through utilise of elementary techniques to enhance population evolution and even population dynamics can be direct addressed with utilise of relatively inexpensive, effective marking techniques. This paper seeks to demonstrate that expert quality research in this sphere tin can result from advisable application of relatively uncomplicated research tools.
1. Introduction
There is no need to make a case for studying earthworms, as their role within the soil has been recognized for more than a century [1]. Collectively, these organisms are able to pass vast quantities of soil through their guts and by doing so bring about the creation of an improved crumb structure which incorporates mineral and organic elements and can become a seedbed for found growth [2]. In addition, earthworms may aerate soils and increment water infiltration, hence reducing soil erosion, past burrow cosmos [three]. On top of all this some species are more than highly regarded equally they are attributed with ecosystem engineering capabilities; that is, they are able to directly influence the environment around themselves and the availability of resources to other organisms [4].
Many avenues of research are available and this article could very easily seek to review and critique some of the more advanced techniques currently in utilise within the sphere of earthworm ecology. These might include Dna-related work examining the genome of selected species [12]; ecotoxicology, post-obit the accumulation of, for example, heavy metals in the tissues of earthworms on contaminated land [13]; or, for case, isotopic work, looking at the transfer of radio-labelled elements through earthworm-linked nutrient chains [14]. However, such relatively high-tech methods volition not be the focus of this work, which seeks to by and large avoid reliance upon potentially plush and loftier-maintenance equipment. This article actually aims at doing one matter; it seeks to show that the employ of low-technology methods is still able to gain insights into cardinal questions relating to earthworms. Much is still to be fully understood about this group, and although many advances take recently been fabricated using sophisticated, expensive equipment/techniques, at that place is still room for the under-resourced professional or educated amateur to make a serious contribution. To demonstrate this, the commodity focuses on the post-obit: a description of simple collection techniques, which can assist in revealing a great deal of earthworm community structure, followed past investigation of a major earthworm activity—burrowing and then a close inspection of earthworm life history and behaviours. Each aspect will hopefully show that basic techniques exist within earthworm ecology that can reveal previously unknown information and assist in building a more comprehensive picture of this important animal group.
2. Drove Techniques (Kickoff Catch Your Earthworm)
It is oft desirable to quantify earthworm number or biomass in a given habitat and/or seek to collect them. A few species bear witness their presence by surface casting (e.g., Aporrectodea longa) or creation of middens (e.g., Lumbricus terrestris) simply most require some form of intervention to locate them, due to their totally subterranean existence. To this end, various techniques have been adult to enable earthworm collection. Digging is the simplest, equally information technology requires only a spade and perhaps a quadrat for density calculations but may detect only near surface (epigeic) earthworms and horizontal burrowing (endogeic) species. Adults of deeper burrowing (anecic) species may be missed unless the researcher is prepared to dig a hole to a depth of several metres!
An alternative to digging is the awarding of a vermifuge (expellent), which when poured on to the soil drives earthworms to the surface as it acts as a skin irritant when contacted in their burrows (direct application, e.g., via a syringe to L. terrestris burrows may be very effective). Various chemicals have been used, with a dilute solution of formaldehyde (formalin) currently recognized as a standard [15], but as this has been reported as carcinogenic, further options have been sought. It is as well suggested [16] that at that place are severe negative effects to other soil fauna, soil respiration, and vegetation encompass if formaldehyde is practical. A suspension of table mustard in water has been used [17], simply tests [10] take shown that a suspension of mustard pulverization (e.g., 50 thou in x litres water) is both cheaper and more effective. More recently apply of "hot" mustard has been used to give a more than consistent index of earthworm abundance beyond a range of soil types [eighteen]. As the type of mustard may also affect results, an excerpt derived from mustard seed Allyl isothiocyanate (AITC) has been used for earthworm collection [19]. AITC has recently been shown as a reliable and promising chemical expellant whether or not used in combination with hand-sorting [twenty]. Many researchers at present abet that the most effective collection technique is indeed a combination of digging and hand-sorting of soil (deposited e.g., on a plastic sail in the field) followed past application of a vermifuge to the hole created [10, twenty]. Different techniques have in the past given ascension to differential collection of species and provided results which are non directly comparable. By contrast, Table ane provides recent examples of data relating to earthworm density, biomass, and community structure from a diversity of British habitats using the same combination of digging and mustard application for collection.
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| Fundamental: Ach: Allolobophora clorotica; Ac: Aporrectodea caliginosa; Al: Aporrectodea longa; Ar: Aporrectodea rosea; Do: Dendrobaena octaedra; Dr: Dendrodrilus rubidus; Et: Eiseniella tetraedra; Lc: Lumbricus castaneus; Le: Lumbricus eiseni; Lr: Lumbricus rubellus; Lt: Lumbricus terrestris; Oc: Octolasion cyaneum; Ot: Octolasion tyrtaeum; Sm: Satchellius mammalis. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Another drove method is application of an electrical electric current to the soil. This method is attractive as niggling or no damage is done to the area sampled and only fallen leaves and overgrown vegetation need be removed prior to sampling to help earthworm detection. To date merely express work has been undertaken with this method, specifically in agronomical soils [21] maybe considering equipment is expensive as an extraction unit to sample 0.two at a time will price (at 2009 prices) in excess of $3000.
Having determined which earthworms are present in a given habitat, if desired, information technology is then possible to experimentally manipulate the earthworms themselves or resources, such every bit food, in the habitat. Several studies take used field enclosures to investigate the furnishings of earthworms on soil properties and plants [22, 23]. Such enclosures tin be formed with PVC walls, buried in slit trenches to a depth of up to 45 cm and a height of 15 cm above the soil surface. These have been shown to human activity equally effective barriers to lateral earthworm movements. Results take suggested that both earthworm removal and addition of field-collected earthworms inside enclosures can be an constructive and useful approach for assessing the influence of earthworms on ecosystem processes (run into Figure 1).
Associated with earthworm enclosures is a novel method ("tunnel" trapping) that tin can be used to notice and record emigration of earthworms. Trap units tin be combined with earthworm fencing in the field [24], or with mesocosms in laboratory experiments assuasive examination of emigration rates, while manipulating biotic and abiotic factors (e.1000., population density, community structure, predation, resource availability, temperature, precipitation).
Tunnel traps tin be prepared using 1 litre plastic pots with mounted needle-perforated lids. Holes ( mm) drilled in these smaller "capture pots" but below the lid permit insertion of PVC tubing (10 mm ID, 5 cm long) to connect to either earthworm fencing in field enclosures or larger soil-filled mesocosms. Surface migrating species can move from enclosures/mesocosms into traps via the tubing that is aligned at the soil surface (Figure 2). Movement of captured individuals back into containers is prevented by filling capture pots with soil or other suitable medium to half of their total book. Providing acceptable conditions (due east.g., soil and food) in capture pots can allow earthworms to survive for long periods therefore permitting relatively infrequent examination. Tunnel traps have been successfully used in both field and laboratory experiments which aimed to examine dispersal of the anecic L. terrestris every bit affected by population density and resource availability [24].
The types of uncomplicated investigation associated with earthworm sampling should permit some of the post-obit questions to be answered.
(i) Which species of earthworms are nowadays within the customs in the given habitat (ii) At what densities (number m-2) and biomasses (gm-2) are these animals present (iii) What proves to be the most efficient method for collection of given earthworm species (4) Can populations exist experimentally manipulated to examination density-related hypotheses (using addition/removal, fencing, and trapping)
3. Burrowing and Burrow Morphology
As with unearthing which species are present, equally previously described, working out which species are active and at what depths is not so elementary. Again, it unremarkably requires some form of intervention as many earthworms are relatively small and generally live below the surface of the soil. However, some species do proclaim their presence by depositing their casts (faeces) on the soil surface. This is specially truthful of larger species which may be excavation burrows and take relatively large amounts of globe to dispose of and others which are about constantly "head down" and "bottom up" producing surface casts. In temperate soils a good example of this is Aporrectodea longa (the black-headed or long worm). When present at loftier densities, this species is capable of almost totally covering the grass surface of a pasture with casts. It has been suggested that the corporeality of casting could even be used as a proxy for the density of (known casting) species nowadays in an surface area [25]. Where the spread of A. longa was beingness followed, after introduction to an unpopulated site, casting activity was used to follow dispersal of this species through the soil over many years [26, 27]. Another deep burrowing earthworm which provides signs of its presence on the soil surface is Fifty. terrestris. This species constructs "middens" and these structures are normally engineered higher up the opening of the about vertical couch used by this animate being. Scientists have been aware of such structures since Darwin's day, but the precise office is still uncertain. Middens consist of organic (e.g., leaf) and inorganic (e.g., pebble) materials gathered together by the resident earthworm and often cemented together with casts. Regulation of couch temperature and moisture content may be an obvious function, but protection from predators and provision of a food shop (a minicompost heap) may be others [28]. Whichever mode, the midden and associated burrow forms an integral part of the life of this relatively sedentary earthworm. Recent piece of work [29] has also revealed that many other earthworm species are associated with L. terrestris middens compared with adjacent nonmidden soil; so middens may play a major part in determining distribution of other earthworms at a microscale.
Nevertheless, most earthworms are mainly active beneath the soil surface; so most investigations need to proceed within the soil. Using burrows that open at the surface, such every bit those of Fifty. terrestris, is one way. Observations take shown that large burrows (often referred to as macropores; bore 8–x mm) may have the capacity to accept relatively large volumes of rainwater and help with prevention of surface soil erosion. Testing of this blazon of water entry into the soil is hands undertaken. The simplest method is to create a h2o-tight, isolated surface area at the soil surface (an infiltration "ring") covering a known surface area and and then add together a known volume of h2o to that area and record the time taken for all water to enter the soil. Comparing different areas within a given habitat/field can exist very revealing, especially when coupled with earthworm collection from the aforementioned areas. A slight elaboration on this technique is to use a vertical cavalcade of water (Marriot device) which can exist fed directly into a single burrow. Such work investigated the burrow systems of L. terrestris in agronomical systems [30]. Infiltration of water into burrows was examined with the resident earthworm present or after its removal (with a vermifuge)—the earthworm itself forming something of a plug. To further quantify and equate h2o ingress with burrow morphology, efforts were fabricated to assess the volume of individual burrows. This was finally accomplished by the utilise of a polyurethane resin, poured down the burrow and immune to set hard [30]. Subsequently the solid representation of the couch void was dug out by digging of a pit alongside. Utilise of coloured pigment within the resin makes visual inspection in situ and afterwards extraction much easier [31] (see Figure three). A simpler technique than use of resin is use of coloured dyes. Dyes such as methylene blueish in water can be poured into burrows or cracks in the soil [3] and then the area around excavated to come across the extent of couch systems present.
If admission to a large digging machine is possible, then excavation of a pit in whatsoever soil can exist very revealing. As mentioned "resin-cast" burrows tin exist revealed, just unadulterated burrows, if large plenty, may also exist seen. For case, during an investigation undertaken during a period of frost depth to 0.five m, [32] information technology was possible to follow burrows down to a depth of ane m by "picking abroad" at the exposed soil profile with knives. This investigation, more interestingly, revealed much on the behaviour of L. terrestris and the (usually) shallow working Aporrectodea caliginosa during relatively common cold periods. However, should it prove impossible to create a large soil pit, and so it is possible to consider the activities of earthworms nether more controlled conditions in a nonfield setting.
A soil pit exposes a cut surface through the soil profile, which is in essence a two-dimensional view. This can be recreated by production of what might be viewed as a "wormery"—a structure comprising 2 sheets of glass separated past a very pocket-size distance, for example, 5–viii mm. Such structures not merely have in the past been sold for domestic use (by children) to observe earthworms simply also have a more enquiry-focussed application. Early work [33] immune use of such structures to observe the couch germination of earthworms, and more recently these "Evans' boxes"—too referred to as 2D mesocosms—have been used [34] for similar aims but more specific objectives (see Figure four). These workers examined the burrowing of L. terrestris just were specifically interested in the interactions between the various life stages of this species and found, until then, previously unrecorded aspects of cocoon deposition in side chambers and encasement of these cocoons with castings (meet Figure 5). Such findings clearly demonstrate that observations of this type can reveal couch-related behaviours which may accept some significance in the life of these animals and not take been recognised before, even though this is a very well-studied species [28]. Table 2 shows some of the experimental data besides gathered from this investigation.
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| Handling | CTRL | CLtRm | LtRp | LtRm |
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| Total cocoons | 27.8 2.2 | 24.viii 9.0 | 26.2 7.iii | 12.6 2.seven |
| No spent cocoons | 2.0 2.ii | 3.3 2.6 | 5.iv three.0 | one.viii 2.5 |
| Hatchlings | i.8 two.9 | two.5 3.1 | 2.two 1.6 | ane.6 one.8 |
| Hatchling survival (%) | 67 29 | 71 34 | 47 33 | 67 24 |
| Hatchling mass (g) | 0.19 0.22 | 0.09 0.06 | 0.10 0.04 | 0.40 0.38 |
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Other means of tracking earthworm burrows and assessing burrowing behaviours under controlled atmospheric condition are available and might be thought more appropriate as they do not occur in 2 dimensions. Soil cores tin be extracted from the field (within suitable housing such every bit plastic cylinders), for example, past driving these into the soil from above and so maintaining them for the desired purpose. This may be to examine earthworm communities within and how they may assistance other ecosystem process, for case, by comparing intact cores with those frozen to remove earthworms. Relatively recently, use of X-ray tomography [35] has been used to determine burrow configurations in such cores. Whilst this may be a useful tool; information technology is one which required access to hospital-grade equipment and then it cannot be considered basic. All the same soil cores can be utilised to study relatively elementary "ecosystems" with earthworms as a component. These may let examination of different animal species present and besides plants growing at the soil surface, if kept in glasshouses. Inputs and out flows could also then be measured in elementary terms. Taken to extreme lengths, researchers have developed systems such as the "Ecotron" [36] which has incorporated earthworms into its experimental systems but this facility was produced at a cost of $i.5 million. Despite this toll and sophisticated equipment for measuring in and out flows of gases and liquids, the choice of earthworm species, as a part of a biodiversity and ecosystem behaviour experiment [37], may not have been appropriate to the given mesocosms. Over again, a situation, where most expensive and mod, does not necessarily mean well-nigh appropriate and insightful. Much more simple investigations in sealed mesocosms (pots) may not give ascent to the bigger ecosystem "film" but may provide practiced data on earthworm life histories (run across below).
Surface-related and burrow-associated investigations might enable some of the following questions to be addressed.
(i) Which species are nowadays at which horizons/depth in the soil profile (ii) What tin be learned from earthworm activities at the soil surface (iii) Practice burrows assist water infiltration (four) How can earthworm burrow extent and volume be measured (v) Can the field (cores) exist brought into and utilised in a controlled setting (6) Can mesocosms be used to detect earthworms burrowing behaviour more than closely
4. Life History Studies
Many species have been well documented and much is known of their life history, simply for case, ask whatsoever researcher to tell you what age an earthworm tin live to, or which life stage is responsible for dispersal and you may find that no uncomplicated answer is forthcoming (fifty-fifty for L. terrestris). Bang-up scope exists for gathering fundamental information on aspects of the life histories of most earthworm species. In United kingdom of great britain and northern ireland, where earthworms are reasonably well documented and a synopsis of species has been available in a number of revised forms for over 60 years [38, 39], data is still lacking in a number of quarters. For example, Dendrobaena attemsi is described from a single British record from Cumbria; even so we accept collected this species easily from wooded areas on the Island of Rum in Scotland. Every bit for the same species, and more importantly with respect to life history, entries such every bit "presumably biparental" and "capsules unrecorded" [39] show that much is withal to exist learned—and perhaps this can exist achieved relatively simply.
Wherever a researcher is based, there will be opportunities to collect local species of earthworm, every bit previously described. Providing that identification is not a trouble, at that place are then chances to answer bones questions on the life history of the species. Using the soil from where the animals were collected, it should be possible to maintain them in containers of a chosen size, appropriate for the given species and its ecological group. The state of affairs is to then ask relevant questions and seek to respond these through segregation of life stages and sampling at given fourth dimension intervals. An initial question might chronicle to the manner of reproduction shown past the given species; is it amphimictic (requiring sexual reproduction) or parthenogenetic? To solve this, in the least corporeality of time, immature individuals need to be isolated and kept thus until they mature. This will naturally crave consideration of their requirements in terms of, for case, soil, food, moisture, temperature, and space [twoscore]. Inspection at appropriate time periods, monthly, weekly, or more than oft for apace maturing animals volition determine when maturity (possession of a swollen clitellum) is reached. At this point the animals might usefully exist subdivided into ii groups 1 : 2. The smaller 3rd should be left in isolation and the larger two-thirds put into groups of 2 to give an equal number of singletons and pairs. These labelled containers tin and so be monitored for cocoon production over the following weeks.
Sampling for cocoons can be straightforward and require a h2o supply and a mesh of appropriate size—depending on cocoon size—which is a function of clitellum diameter. Contents of containers in which adults have been kept can be sieved to obtain cocoons. These can and then exist incubated in Petri dishes, or equivalent, on moistened filter paper or like at an appropriate temperature for the given species [xl] (Figure 6). If animals have been kept, for example, in soil columns, then the depth at which cocoons are deposited might be considered by sieving away different levels from the column (more than easily achieved if the cylinder in which they are housed is presplit (and taped together) along its length [41]). Incubation of cocoons can and then occur and time to develop and hatch can be monitored. To obtain cocoons more quickly for whatever species, mature animals which are field-collected tin can be employed direct in cocoon production studies and number produced per individual per time can exist recorded from the given conditions nether which they are maintained. Cocoons may be kept in groups or individually (depending on space available). The advantage of private incubation is that the number of hatchlings tin more easily be assessed, as many epigeic species produce more one hatchling per cocoon. To complete life cycle records, growth of hatchlings to maturity tin be assessed. This requires the type of conditions previously described only with periodic monitoring (and mass determination) until maturity is reached (see Effigy 7 for typical results). Manipulation of biotic and abiotic factors influencing the growth and reproduction of the earthworms, such equally population density [42], food quality [40], interspecific interactions [43], temperature [44], and a host of others and combinations thereof, can be considered. Finally to define the age to which earthworms tin alive, animals might need to be kept for some time.
Ane relatively elementary technique that might aid life history/population studies is the power to permanently marking (tag) private earthworms. Contempo work [45] has shown that it is possible, through injection of Visual Implant Elastomer (VIE), available from Northwest Marine Technology [46] to visually colour tag earthworms. In improver these tags take been shown to be retained in a number of earthworm species for more than than ii years and have no detrimental furnishings on growth to maturity, mating, and cocoon production in ane closely studied species, 50. terrestris [47]. This technique may well evidence to be valuable in earthworm age determination but may also reveal much from studies of population dynamics, in terms of capture, marker recapture exercises. Tagging captured animals and and so recapture data could help in learning much more of these organisms particularly in a diversity of habitats. Cohorts of the same species could be tagged with unlike colours in dissimilar years to let a better understanding, for case, of survival. Used in combination with density manipulation experiments, this type of exercise has already revealed aspects of L. terrestris dispersal and settlement under field conditions in managed woodland plots [24]. It should be noted that at current (2009) prices, this textile is relatively inexpensive, with a trial pack of VIE costing $42. Such an amount volition permit tagging of hundreds of earthworms (see Figures viii(a) and eight(b)).
(a)
(b)
Past collecting earthworms and maintaining them under controlled environmental conditions, it ought to exist possible to reply virtually of the following questions on life histories.
(i) What style of reproduction is exhibited by a given species (ii) Where in the soil are cocoons produced (iii) How long does cocoon incubation have before hatching occurs (iv) How many hatchlings are produced per cocoon (v) How long does information technology have for growth to maturity and at what mass is this reached (vi) Which factors (biotic or abiotic) may have a major influence on the above (vii) To what age does this species alive
5. Behavioural Studies
Many activities of earthworms, known for decades, withal present uncertainties in terms of interpretation. Equally, where glimpses of the subterranean world are provided, much tin can exist learned. Some behaviours relating to burrowing and casting have already been discussed; and so this section will concentrate on just a modest number of behaviours, such equally mating and dispersal and focus on techniques which may be of apply to further investigate them. Many authors accept reported mass emergence and dispersal of earthworms [2]. The timing of this may be seasonal or associated with particular atmospheric condition weather condition. The species concerned may vary but perhaps this behaviour has a mutual underlying cause? Often occurring at night, in urban settings it might normally get unnoticed, only for the fact that "stranded" earthworms may be institute the following morning on surfaces such as concrete or tarmac, into which they are unable to burrow.
En masse emergence of earthworms may oft follow periods of rain. Opinions vary, but some suggest that this is a function of earthworms exiting their burrows as a response to alluvion which might pb to potential death. We dispute this idea, as earthworms are able to survive lengthy periods of submergence in water, and support the hypothesis [28] that it is more closely related to dispersal. A question posed earlier related to the life phase at which earthworms disperse. Perhaps other related questions that need addressing are why would earthworms seek to disperse and what factors might encourage this? The "why" part may relate directly to evolutionary biological science. Fifty-fifty though they are hermaphrodite, many earthworm species prove sexual reproduction. Therefore mating may unremarkably occur with near neighbours. To bring about greater possible exchange of genetic fabric and avoid inbreeding, movement away from place of birth (dispersal) is required at some indicate in the life cycle. This then moves on to the "how" part. Movement through the soil is slow and may only boilerplate a few metres per twelvemonth [26, 48], but over surface movement by earthworms may be much more rapid [49]. To this stop, some earthworm species may utilise periods following rain to disperse every bit the wet atmospheric condition prevailing will raise movement beyond the soil surface and decrease the chances of desiccation and decease from exposure. It could be argued that such behaviour would non therefore exist institute in parthenogenetic species if this were the merely reason for emergence, and this is not the case as Octolasion cyaneum is such a species regularly located on the surface afterward some rains. Nevertheless, the latter may exist utilising wet weather condition to endeavor and disperse to increment its distribution. All of this may seem very bookish, but it does give reason for what is at present described.
To assess surface movement of earthworms, fencing of the type already described could be employed, along with traps if desired. In addition it is possible to "encourage" dispersal by simulating the stimuli that might be responsible. In the simplest terms, flood experiments could exist derived to sprinkle water on to enclosed plots, at known rates, and record qualitatively and quantitatively the (nocturnal) emergence of earthworm species (and life stages). Naturally other factors such as temperature, brightness of the moon, and more than may have an influence and demand to be considered. Nevertheless, such manipulations might reveal a great bargain on the dispersal behaviour of some of the species nowadays in known communities.
Another series of relatively simple experiment (with countless subtle developments) might exist employed to measure out direct deportment of earthworms on organic matter incorporation into soils. And then-chosen "litter pocketbook" experiments require known quantities of (air dried) organic matter from a site, to be enclosed in mesh constructions which permit, by the size of the mesh, access to certain groups of detritivorous soil organisms [9, 50]. This requires some knowledge of the groups nowadays and the type(s) of earthworm at the site simply comparisons beyond different habitats, for example, or below unlike stands of trees tin can exist revealing (see Figure 9). The litter bags need to be located at the soil surface (pinned downwards) or buried at chosen soil depths, to permit admission to different ecological groups. In improver or instead, selection bedchamber experiments can exist derived by offering laboratory-held earthworms dissimilar types of known food materials in specifically designed mesocosms [51]. Where an earthworm, such equally L. terrestris, feeds directly from the soil surface, experiments can also be fix to make up one's mind which nutrient is eaten/removed to the couch and if choices are fabricated [52]. This tin can be determined by observation of which cloth has been disturbed afterward the effect or more directly through recording of the actual behaviours in progress. Results from such laboratory experiments can show, for example, the preference for dissimilar agricultural/industrial waste product organic materials spread on fields where Fifty. terrestris is nowadays (see Effigy 10). Details on the type of applied science required for this are provided below.
Surface-related behaviours, as described with respect to dispersal, can exist recorded indirectly through trapping. Notwithstanding feeding and mating at the soil surface, where it occurs, may be improve recorded through direct ways. The full mating behaviour of 50. terrestris, including premating burrow visits by partners and the 3.5-hour mating itself, was first described after employ of video recording using a elementary security-type photographic camera setup, linked to a basic video recorder [53]. More recent work has examined details of the mating more than thoroughly [54]. This same engineering was also used to obtain results for food choice in this species [52]. Nevertheless, such work may at present be considered costly and has been overtaken by more contempo developments in the IT world, whereby a "webcam" can at present be obtained relatively inexpensively for similar use. This may seem to be a contradiction of the ethos of this article, merely as will exist seen, costs hither may be negligible. Recent work [55] has investigated, for example, the effects of pesticides and h2o inundation on earthworm behaviour. For further experiments in progress, examining calorie-free furnishings on surface-related behaviours of earthworms, equipment was obtained including web cams and the appropriate software (for use on a standard PC) for less than $100 (at 2009 prices). Figure eleven was obtained during this particular ready of experiments housing animals in plastic tubes (drainpipes).
Behavioural work with earthworms may still be regarded as in its infancy, although some major revelations have occurred, particularly with L. terrestris [53, 54]. From basic observations of mating behaviour, through mate option, to close scrutiny of copulatory interaction, has all been examined. Peachy telescopic nonetheless exists in the area of earthworm behaviour and some of the post-obit questions could be addressed.
(i) Which species showroom mass dispersal and which life stages are involved (2) How much leaf litter is removed or consumed by earthworms in given habitats (3) Can removal of organic affair into the soil be harnessed for soil improvement (iv) Is L. terrestris the only species that mates on the soil surface (five) Practice other earthworm species evidence mate choice
6. Field Manipulation of Populations (Profitable the Plough)
Where soils crave an input of earthworms, augmentation tin can exist brought about using the higher up information—collection, selection for activities, and even selection for mass culture before field-release. Earthworms, because of their activities in the soil, are, where appropriate, considered as vital components of a healthy, fully functional organisation. Reviews of research have shown that, across the globe and in numerous habitats, the provision of earthworms to sites where they were absent-minded, assistance with recolonisation, or improvements to the type of weather conducive to their survival can bring about marked positive changes in soil properties [56, 57].
Should areas be that are devoid of earthworms, for known or unknown reasons, then ane approach might be to (re)introduce them to site. Numerous methods are available to accomplish this but most can exist described simply every bit "collection and broadcast" using the type of collection techniques previously mentioned or "turf transfer", digging upward and translocating soil with grass attached. Both have been used and have positive attributes but equally have less attractive features (see Table three). To assist the reintroduction procedure, information gathered on earthworm life histories and requirements for civilisation take been coupled with further data relating to activities in the soil and interactions with other earthworm species [34, 40–43]. In this way a relatively unproblematic technique, the Earthworm Inoculation Unit of measurement (EIU), was devised [26] seeking to overcome the bug associated with the existing techniques. Irreverently known as "worms in bags" this technique seeks to cultivate a starter culture of adults under optimal atmospheric condition over a period of a few months. After this fourth dimension, population development inside the plastic-spring units means that all life stages, adults, cocoons, and hatchlings ought to be present. The EIUs can and so be transported to the desired inoculation site fix for introduction (come across Figure 12). Inoculation requires the contents of the EIUs to be inserted into an appropriately sized hole in the soil, later the plastic envelope has been carefully removed.
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| Technique | Advantages | Disadvantages |
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| Turf Cutting and relaying | Protective microenvironment | Densities ordinarily low |
| Cocoons transferred | Little command over species/numbers | |
| Mainly shallow working worms | ||
| Cutting machines/labour required | ||
| Damage to collection site | ||
| Chemic/physical extraction with broadcasting | High densities possible | Protective micro-environment absent |
| Species option possible | No cocoon transfer | |
| Mainly deep burrowing worms | ||
| Worms may be injured during extraction | ||
| Laborious and expensive | ||
| Damage to drove site | ||
| Earthworm Inoculation Unit of measurement (EIU) method | Protective microenvironment | Laborious and potentially expensive |
| Species option possible | (compared with above methods) | |
| Worms of known origin | ||
| Cocoons transferred | ||
| Loftier densities possible | ||
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The contents thereby retaining their original position in the soil contour and providing a protective microenvironment. Over the by two decades, results from both agricultural and mail-industrial settings have been positive [26, 48]. Spread of earthworms over one site at Calvert site was completed inside a decade and positive interactions were recorded with the presence of alder trees (Alnus glutinosa—which fix nitrogen) and earthworm density [27]. At one of the sites, farther investigations developed the EIU technique with improver of organic thing. This was a response to use of manure as "earthworm attractant traps" to augment assessment of the numbers and species nowadays on site [26].
Addition of earthworms to sites where they are absent-minded (for some reason) may be valuable and permit a number of questions to exist addressed.
(i) What factors brought about the removal of earthworms? (ii) What tin be done to remedy the situation? (iii) How can the success of the functioning exist measured (in terms of earthworms and soils)? (iv) Tin can more exist learned of earthworm populations from this type of work?
7. Conclusion
This article prepare out to demonstrate that low-technology methods are able to proceeds insights into fundamental questions relating to earthworms. Examples take been provided and management given towards investigations asking relatively unproblematic questions that can employ these techniques. In addition to the sections described on collection, burrowing, behaviour, life history, and manipulation of earthworms, others which have only been hinted at or possibly overlooked tin also be developed, and many of those included have an amount of overlap inside them. It is for the prospective researcher to place the preferred niche expanse of investigation and progress it to potentially create a new bending within the existing fields of knowledge. Science tends to require funding in order to advance, but one critical attribute is the development of ideas and the artistic utilize of available resource. Earthworm ecological research still has room for the utilize of basic tools.
Acknowledgments
The authors thank numerous site managers for admission to sites over the years and Colman'south of Norwich for provision of mustard pulverisation.
Copyright
Copyright © 2010 Kevin R. Butt and Niki Grigoropoulou. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in whatsoever medium, provided the original piece of work is properly cited.
Source: https://www.hindawi.com/journals/aess/2010/562816/
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