EARTHWORM FAUNA OF THE ANDAMAN AND NICOBAR ISLANDS, INDIA

The first records of earthworms from the Andaman and Nicobar Islands were provided by Rosa (1891). He reported two species, viz., Lumbricus rubellus Hoffmeister and Eisenia foetida (Savigny) from the Nicobars. Both the species are now believed to have been transported to the Nicobars from Europe by man alongwith the soil around the roots of the introduced plants. Michaelsen (1907) discovered the first endemic earthworms, 'l,'iz., M etaphire (Pheretima s. 1.) andamanensis, Amynthas (Pheretima s. 1.) osmastoni and Amynthas (Pheretima s. I.) suctorius from the Andamans. Subsequently, more endemics belonging to Metaphire and ... 4mynthas were discovered by Stephenson (1925) and Gates (1932, 1936). The other reports on the earthworms of the Andaman and Nicobar Islands are limited to incidental records in the literature (Michaelsen, 1909 ; Stephenson, 1916; Gates, 1933, 1954, 1958, 1960, 1962a; Julka & Halder, 1975). Recently, Soota & Julka (1970) recorded fourteen species from these islands, all .of which probably have been introduced there. This article deals with a comprehensive account of twenty seven megadrUe species so far reported from the Andaman and Nicobar Islands. For a detailed account on the world distribution and synonomies of the. species Gates ~1972) may be consulted. The classification followed is that proposed by Gates (1959). For explanation of latest technical terms and conventions necessary for earthworm description, the articles by Ljungstrom (1970), Gates (1972) and Reynolds (1977) may be referred.

This article deals with a comprehensive account of twenty seven megadrUe species so far reported from the Andaman and Nicobar Islands. For a detailed account on the world distribution and synonomies of the. species Gates ~1972) may be consulted. The classification followed is that proposed by Gates (1959). For explanation of latest technical terms and conventions necessary for earthworm description, the articles by Ljungstrom (1970), Gates (1972) and Reynolds (1977) may be referred. ZOOGEOGRAPHY Of the twenty seven species (Table I) known from the Andaman and Nicobar Islands, twenty are exotic and are best excluded from zoogeographical discussions. The endemics belong to the former genus Pheretima s. 1. (Michaelsen, 1900) and now transferred to .Amynthas and Metaphire by Sims and Easton (1972). Relationships of the endemics are to be found with presently unknown Sumatran species (Gates, 1972). Geologically also, the Andaman and Nicobar Islands are believed to have once formed the part of the land mass of South East Asia. There was a continuous mountain range along the whole length of these islands connected to the Arakans of Burma at one end and to Sumatra at the other end. About 150 million years ago, due to geological activity, the land near about these islands was submerged and the summits of the mountain range standing out of the sea became the present day islands. According to Gates (1972), the separation of the islands from Burma must have been prior to that from Sumatra and before Eutyphoeu8 (endemic in Burma) could have reached so far south.
Among the twenty exotic species, 2 are of European, 7 of South or South East Asian, 2 of Soutp. American, 1 of Central American, 3 of African and 5 of Indian origin. All the exotics are suspected to have been introduced alongwith the soil around the roots of the plants brought by man to the islands. It is of course not definite that they have been introduced from their original homes directly to the Andaman and Nicobar group of islands but might have arrived via other continent. Gates (1976) records instances of interceptions of peregrine earthworms (transported by man) in soil around roots of ornamental plants arriving in U. S. A. by ships or aeroplanes. The European species, viz., Eisenia foetida and Lumbricus rubellus were not found in recent collections from the Andaman and Nicobar Islands (Gates, 1972).
Last pair of hearts in XI. Nephridia vesiculate; bladders ocarina-shaped. Testes probably metandric ; seminal vesicles present or absent, if present, only one pair in XII, rudimentary or small or large, extending back through 8-10 segments. Spermathecae adiverticulate, somewhat clubshaped. Tubercula pubertatis glands tripartite, in XVIII bigger in size., then diminishing posteriorly.
Range.-New Zealand, North America, Mexico, Europe, Iceland, some of the islands. in Atlantic Ocean, South Africa, Turkey, Iran, Afghanistan, U.S.S. R., Far East.

Amyntas alexandri
Pigmented, pigment reddish brown. Septa 8/9, 9/10 absent. Gizzard between septa 7/8 and 10/11 ; intestinal origin in XV or sometimes in XVI (1) ; intestinal caeca paired, simple, origin in XXVII, extending forward to XX. Last pair of hearts in XIII. Testes holandric, contained in paired and vertical or unpaired and horseshoe-shaped testis sacs, in X, XI, hearts and seminal vesicles of XI included; seminal vesicles in XI, XII. Prostates racemose, extending from XVI to XXII; duct variously looped. Spermathecae unidiverticulate ; duct markedly narrowed in parietes; diverticulum longer than combined lengths of duct and ampulla, arises from median face and ectal end of duct, with a slender stalk and a variously looped wider portion (seminal chamber) entally.
Pigmented, pigment red. Septa 8/9, 9/10 absent. Gizzard between septa 7/8 and 10/11 ; intestinal origin in XV; intestinal caeca paired, ~imf>le, origin in XXVII, extending forward to XXII. Hearts of X, XI lacking, last pair of hearts in XIII. Testes holandric, contained in paired and vertical or unpaired and lJ -shaped or annular testis sacs, in X, XI ; seminal vesicles in XI, XII, of XI included in testis sac.
Prostates racemose, small, confined to XVIII; duct straight or in a hairpin loop. Spermathecae unidiverticulate; duct shorter than ampulla; diverticulum shorter than combined lengths of duct and ampulla, middle portion looped, with an ovoidal seminal chamber at ental end, arises from anterior face and ectal end of duct.
Pigmented, pigment red (I). Septum 8/9 absent. Gizzard between. ~epta 7/8 and 9/10; intestinal origin in XV; intestinal caeca paired, simple, origin in XXVII, extending forward to XXIV. Last pair of hearts in XIII. Testes holandric, contained in unpaired and ventral testis sacs, in X, XI; seminal vesicles in XI, XII ; pseudovesicles in XIII, XIV. Prostates racemose, large, extending from XVII to XXII; ducts looped. Penial setae 1.13-1.25 mm long and 0.20-0.28 mm thick; ornamentation, circles of fine teeth towards ectal end. Spermathecae unidiverticulate ; duct shorter than ampulla; di verticulum longer than combined lengths of duct and ampulla, stalked, seminal chamber short and small, arises from anterior face and ectal end of duct. Gland to 1& male porophore in XV-XXV, bilobed, composed of numerous stalked glands, each passing to a common T-shaped duct with thick and straight horizontal limbs and a slender, vertical leg especially narrowed in parietes. Genital marking glands stalked.
Pigmented, pigment brown. Septa all present from 4/5. Gizzard in V ; oesophagus on its inner wall with longitudinal calCiferous lamellae in' X-XIII; intestinal origin in XV. Last pair of hearts in XIII. Prostat~s racemose; ducts straight. Testes holandric, free, in X, XI ; seminal vesicles in IX and XII. Penial setae with horseshoe-shaped or scoop-shaped tips, ornamentation of closely set circles of triangular teeth. Spermathecae bidiverticulate; ducts barrel-shaped; diverticula digitiform, from lateral and median faces of duct.
Pigmented, pigment red. Septa 8/9, 9/10 absent. Gizzard between septa 7/8 and 10/11 ; intestinal origin in XV (1) ; intestinal caeca paired, simple, origin in XXVII, extending forward to XXIII. Last pair of hearts in XIII. Testes holandric, contained in unpaired and ventral testis sacs, in X, XI ; seminal vesicles in XI, XII. Prostates racemose, extending from XIX to XXIII; ducts S-shaped. Spermatbecae unidiverticulate ; duct shorter than ampulla ; diverticulum longer than combined lengths of duct and ampulla, arises from median face and ectal end of duct, with a thread-like stalk and ovoidal seminal chamber; a lobed annular gland on parietes around base of each spermatheca. Genital marking glands stalked.
Re'marks.- Gates (1972) recognizes seven morphs within the houlleticomplex. The specimens of houlleti hitherto recorded from the Andatnan &. Nicobar Islands belong to H morph and smaller Hp morph.
Gizzard between septa 7/8 and 8/9 ; intestinal origin in XV; intestinal caeca simple, origin in XXVII, extending forward to XXIV. Last pair of hearts in XIII. Testes holandric, contained in unpaired testis sacs, of X ventral, of XI vertically U-shaped and including seminal vesicles of that segment; seminal vesicles in XI, XII; pseudovesicles small, in XIII. Prostates racemose, in XV-'XXI; ducts U-shaped. Spermathecae unidiverticulate; duct shorter than ampulla, diverticulum of variable length, with a short stalk and an ellipsoidal seminal chamber, arises from median face and nea~ ental end of duct. Genital marking glands sessile.