Leydigiopsis curvirostris Sars, 1901

Sharma, B. K. & Sharma, Sumita, 2012, Notes on some rare and interesting Cladocera (Crustacea: Branchiopoda: Anomopoda: Chydoridae) from Deepor Beel, Assam, India, Journal of Threatened Taxa 4 (1), pp. 2304-2309 : 2307-2308

Leydigiopsis curvirostris Sars, 1901 ( Images 9-10 )

Characters: Body with maximum height in the middle. Postero-dorsal and postero-ventral corner of valves rounded. Ventral margin of valves protruded before the middle; entire ventral margin with concentric rows of dots and with setae which continue along posterior margin in a row of fine hairs. Rostrum very long and curved posteriorly. Distance from apex of rostrum to apex of antennule nearly twice the length of antennule. Head-shield with two broadly connected main head pores and two small pores close to them. Plate of labrum triangular and with slightly pointed apex. Ocellus about as large as the eye. Postabdomen large; its dorsal margin distinctly convex and distal to the anus; distal end of postabdomen rounded. Preanal corner distinct with double row of 16–20 anal denticles, decreasing in size proximally and a row of lateral spinules on each side. Claw large, with setae on the concave margin and with a small basal denticle.

Remarks

Six species of rare and interesting chydorid Cladocera are reported from Deepor Beel. These include four globally interesting elements viz., the Australasian Disperalona caudata, the Asian Kurzia (Rostrokurzia) brevilabris and the Indo-Malayan Alona macronyx , while Leydigiopsis curvirostris is known elsewhere only from Brazil and Nicaragua.

Kurzia (Rostrokurzia) brevilabris is an interesting addition to the Indian Cladocera . Originally described from Thailand (Rajapaksa & Fernando 1986), this species is also known from Sri Lanka and Philippines. Our present report from northeastern India, therefore, merits biogeographic importance for extension of its range within the South Asian region. Hudec (2000) dealt with five known Kurzia spp. and proposed their subgeneric differentiation into Kurzia sensu strictu and Rostrokurzia. K. (Rostrokurzia) brevilabris is a member of the latter. This sub (tropical) Asian species can be distinctly differentiated from other members of this genus by its diagnostic reduced labrum.

Disperalona caudata, another globally important species, was described from Mudginberri Lagoon, Kakadu National Park, Australia ( Smirnov 1996). Sanoamuang (1998) reported it from northeastern Thailand as its first record fromAsia. Sharma&Sharma (2007) reported D. caudata from two floodplain lakes (Deepor and Raidong beels) of the Brahmaputra River basin, Assam extending its distributional range to the Indian subcontinent. This Australasian species depicts an interesting link between the cladoceran fauna of northeastern India, Southeast Asia and Australia. Further, it is known from India, to date, from the state of Assam only.

Leydigiopsis , a very rare genus, was described from Brazil by Sars (1901) and until the end of 20 th century, it was presumed to be distributed in South and Central America only ( Sinev 2004). In addition, Sanoamuang (1998) examined its single specimen from Kalasin province of northeastern Thailand but could not ascertain species status. Sinev (2004) categorized this genus to be insufficiently studied and remarked on the unclear status of Asian Leydigiopsis . Sharma & Sharma (2007) extended its distributional range to the Indian subcontinent based on an earlier report of L. curvirostris in Deepor Beel. The present study re-affirms its occurrence, restricted to the Assam State only. We believe that disjunct occurrence of this chydorid of North American origin in India may represent an example of its introduction by man and thus deserves further analysis.

The Indo-Malayan Alona macronyx is a new record from Assam. The first Indian report of this species referred to Indialona jabalpurensis , a new species described from Madhya Pradesh by Rane (1983), which was considered as a synonym of A. macronyx (refer Rajapaksa & Fernando 1987; Sharma & Sharma 1990). This species was recorded for the first time from northeastern India from Meghalaya (Sharma 2008), and our report further extends its distribution to the adjoining state of Assam. Alona guttata tuberculata and Coronatella anodonta are new records from Assam; the latter is recently observed from the Nokrek Biosphere Reserve of Meghalaya ( Sharma & Sharma 2011) while Sharma (2008) reported the former again from Meghalaya. These two taxa are, hence, known to date only from the northeastern region of India

Figures

Image 9. Leydigiopsis curvirostris Sars, parthenogenetic female