The unglamourous millipede is a strong soil nutrition builder

When talking about biodiversity, it is that of the forests, oceans and large biomes that often get the most attention. Correspondingly, charismatic species such as tigers, elephants, apes, birds, snakes, turtles, even frogs are the attention-grabbers of the animal world. Butterflies and dragonflies too sometimes make the cut.

But it is in the ecosystem of the soil wherein lies a small, private invertebrate that toils to provide ecosystem services far greater than those provided by charismatic animals. The millipede, the veteran of soil ecosystem, is in dire need of attention as it is hurtling towards extinction.

Millipedes are soil specialists living on the ground, in shallow sub-terranean habitats, among the leaf-litters or in the soil. They are adapted to live in humid conditions under moderate temperatures, so are predominantly abundant in the tropics and sub-tropical regions of the globe. Forest floors with abundance of leaf litter is fairly well-buffered against temperature and moisture fluctuations thus providing the pedes with a favourable environment.

From an evolutionary point, millipedes  were among the first to inhabit land during the Ordovician period (approximately 450 million years ago). Mainly herbivores and mostly detritus feeders (organisms that feeds on dead plant or animal matter), it is believed that millipedes may have played a major role in soil formation and nutrient cycling during the Paleozoic era. Now, destruction and pollution of the soil  are sounding the death knell for these creatures.

The myth of the thousand legs

Called Maravaṭṭai’ in Tamil, Tēraṭṭa in Malayalam, Saavirakaalu in Kannada, Bahupādi in Telugu and Gojar in Hindi, millipedes are arthropods in the class diplopoda. The word diplopoda (diplo-two; poda-legs) describes their predominant feature – most segments of their body have two pairs of legs. Although the word millipede is derived from Latin words mille-thousand and ped-foot, no single species discovered so far has that many legs. On an average, legs present may be from 11 to 375 pairs, with the North American Illacme plenipes found to have the maximum number of legs at 750. In size, millipedes range from a body length of 1.4 mm to 30 cm long. When hatching from eggs, millipedes do not have many segments and legs. They show what is known as an anamorphic development, that is, new segments and legs are added after every moult. It may take many years for millipedes to attain maturity, environmental factors playing a major role in this process.

Based on their morphology and ecology millipedes have been classified into five groups: bulldozers or rammers, borers, wedgers, rollers or pill-millipedes and bark dwellers or bristly millipedes.

The neglected arthropod gets renewed attention

It is estimated that there could be at least 80,000 species of millipedes worldwide of which about 10,000 species have been described, classified into 15 orders, 144 families and 2,950 genera. About 270 species from 11 orders and 23 families have been described from India. Of these, at least 93 are from south India, where they have been comparatively studied better. Fifty four species of giant pill-millipedes recorded could well be endemics according to C. Attems, considered as the “Father of Indian Myriapodology.”

However, the numbers do not reflect the real diversity of these creatures in India owing to the lack of research in the field of millipede taxonomy. This is reflective of a worldwide trend as diplopodolagists or myriapodalogists are few. Given this situation, the chances of many millipede species fading into darkness is quite real.

 

Known to adapt and exist in several microhabitats and niches, millipedes do not tend to move from place to place; hence a forest may play host to several species of millipedes. This lack of mobility is also a reason for their populations being easily decimated as habitats get destroyed.

R. I. Pocock a renowned myriapodologist, while presenting a paper on new millipede species at Bombay Natural History Society in 1892, had remarked about the neglect that this group as a whole: “They are difficult to preserve, obscure in characters…with no marketable value worth mentioning and little or nothing of interest in their habitats to attract the attention of naturalists…”

However, in recent times there has been a revival of interest in the ecology of millipedes and their conservation.

The deteriorating quality of soils, increasing need for alternatives to fertilisers, a greater awareness towards the relationship between food consumed and human health has tempted a few scientists, farmers and others to look for natural alternatives. Millipedes are natural decomposers. With their ability to recycle nutrients and aerate soils they are gaining attention for their role in improving the ability of soil. A body of work from researchers across the globe, including India, has showing that millicompost (compost created by decomposition of vegetable and plant waste by millipedes) is not only an alternative but may be better than even vermicompost.

Composting with millipedes

Mechanical breakdown of decaying organic matter during feeding, coupled with faecal matter providing a surface for microbial action, makes the millipede a  valuable composting agent. Scientists from the Mangalore University, Alagappa University and the Madurai Kamaraj University have found that the millipede can also perform the same function as the earthworm, also a soil invertebrate, which has gained popularity for use in producing organic fertiliser. In their research they discovered that the quality of millicompost was superior to that of vermicompost. One of the species experimented with were the pill millipedes found commonly distributed in most ecosystems.

Pill millipedes or ball millipedes are small stout creatures of the genus Arthrosphaera. Nearly 40 species of Arthrosphaera are confined to southern India (Attems, 1936), abundant in diversity and distribution in Western Ghats.

A study on the impact of pill millipede compost on plant growth and dry matter yield compared the effect of millicompost (produced using Arthosphaera magna) with traditional farm yard manure (decomposed mixture of cattle dung and urine with straw and litter) on black gram crop. It was  found that millicompost had a positive effect on the growth and yield of the gram. The study also found  that millicompost produced from plantation residues compensated for the nutrients that were unavailable to plants through farm yard manure. This finding suggests then that millicompost is a good alternative to chemical fertilisers that are generally added to compensate for nutrient deficiency.

In another experiment to compare the efficiency of the Arthrosphaera magna millipede and earthworm in composting floral wastes and the quality of compost thus generated, it was found that there is a significant difference in the biochemical quality of the two composts. The nitrogen and phosophorus content was higher in millicompost than vermicompost. Additionally, millicompost also brought down the pH of the soil from 8.2 on day 1 to 6.6 by day 60. A similar value calculated for conventional compost and vermicompost was 7.1 and 6.8 respectively. The effect of millicompost on the growth of capsicum — from height of the plant to the number and weight of the fruits — was also better than what was obtained with vermicompost. Factors such as the millipedes’ ability to consume wastes five times their body weight, the ability to lock away nutrients in their faecal matter and then release them periodically and the microorganism diversity in their gut all contribute to the superior quality of millicompost.

Arthosphaera magna is not the only millipede species that can be used to produce compost. Anoplodesmus sp., Orthomorpha coarctata and Xenobolus carnifex, are all commonly seen millipedes in India that are capable of composting waste.

Millipedes do not move very far from their habitats unless humans transport them. This coupled with the fact that the litter chemistry determines their presence or absence, suggests that they can be considered as reliable indicators of soil health.

CITATION:

• Hopkins S. P., and Read H. J. 1992. The biology of millipedes. Oxford University Press, Oxford, New York,Tokyo in The Myriapoda-Vol 2- Treatise on Zoology Anatomy,Taxonomy, Biology. Edited by Alessandro Minelli. Brill Leiden-Boston 2015
• Sierwald P., and Reft A. J. 2004. The millipede collections of the world. Field Museum of Natural History. University of Illinois.
• Golovatch S. I., and Wesener T.  2016. A species checklist of the millipedes (Myriapoda, Diplopoda) of India. Zootaxa 4129 (1): 001–075.
• Attems, C. 1936. Diplopoda of India. Em. Ind. Mus. Vol. XI. Pp. 133-23.
• Ambarish C. N., and Sridhar K. R. 2013. Observations on pill-millipedes of the Western Ghats (India). Journal of Agricultural Technology. Vol. 9(1): 61-79.
• Sridhar et al. 2006. Evaluation of pill millipede (Arthrospaera Magna) compost on plant growth and dry matter yield. Electron. J. Environ. Agric. Food Chem.5 (2), [1323-1329]
• Ramanathan B., and Alagesan P. 2012. Evaluation of millicompost versus vermicompost. Current Science, Vol. 103, No. 2.
• Warren M.W.,  and Zou  X. 2002. Soil  macrofauna  and  litter  nutrients in three tropical tree plantations on a disturbed site in Puerto Rico. Forest Ecology and Management, 170: 161–171.
• Report upon collections of Myriapoda sent from Ceylon by … of the Government Central Museum, Madras, by R. I. Pocock, of the British (Nat Hist.) Museum. Read before the Bombay Natural History Society, 5 April 1892.