Prosopistoma indicum Peters 1967

Roopa, S. Ramya, Selvakumar, C., Subramanian, K. A. & Sivaramakrishnan, K. G., 2017, A new species of Prosopistoma Latreille, 1833 and redescription of P. indicum Peters, 1967 (Ephemeroptera: Prosopistomatidae) from the Western Ghats, India, Zootaxa 4242 (3), pp. 591-599 : 595-598

Prosopistoma indicum Peters 1967

Figs. 13–23

Material examined. 6 mature larvae, INDIA, Karnataka, Someshwara Wildlife Sanctuary, Tunga river, Minu Hole, 13°34’42.28’’ N, 075°06’12.58’’ E, 665 m, 19.V.2015, Coll. S. Ramya Roopa [ZSISRC-I/E 21]. 1 larva, INDIA, Tamil Nadu, Tirunelveli, Gadana river, Kallar, 0 8o 48'04.5’’ N, 77o18'05.3’’ E, 144 m, 20.VII.2013, Colls. C. Selvakumar & P. Kumar [ZSISRC-I/E 22].

Description. Mature larva. Body length 2.1 mm excluding caudal filaments. Head yellowish brown with median ocellus between antennae; width approximately 2.4 times length. Epicranial sutures feeble, passing through posterior margin of lateral ocellus and weakly passing through anterior margin of compound eye, continuing to lateral margin of head. Carapace general coloration yellowish brown with irregular (zig-zag) yellow pattern at approximately 0.6 times length of carapace from posterior margin of head. Distal end of carapace concave over exhalent notch ( Figs. 13 ).

Head. Antenna ( Fig. 15 ) 6-segmented including scape and pedicel, with segment III longest but shorter than combined length of segments IV–VI. Labrum ( Fig. 16 ) narrow, approximately 4.3 times wider than long. Left and right mandibles similar. Outer canine of mandibles longer and broader than inner canine, with three sub-equal apical teeth, inner tooth serrated near apex with 3 spines; inner canine with two apical teeth, inner one slightly larger, outer margin serrated near apex with 1 or 2 spines and inner margin serrated near apex with 2 spines. 3 long serrated bristles arising from base of inner canine. Single stout feathered seta present lateromedially on each mandible ( Fig. 17 ). Maxillae ( Fig. 18 ) crowned by rigid canine and three subequal moveable dentisetae; three long feathered stout bristles arising near base of apical canine and dentisetae on galea-lacinia. Single unserrated bristle arising about two-thirds of way down sclerotized section of galea-lacinia. Length ratio of maxillary palp segments from basal one to apical one: 2.4:3.6:1. Labial palpi 3-segmented, length ratio of labial palp segments from basal one to apical one: 2.1:2.25:1 ( Fig. 19 ).

Legs. Ventral margin of fore tibia with 6–8 pectinate setae ( Fig. 20 ). Tarsal claws of all three pairs of legs without denticles.

Abdomen. Abdominal gills I–VI. Gill I large and branched ( Fig. 21 ). Gill II broad, leaf-like and unbranched ( Fig. 22 ). Gills III–V with multiple branching filaments ( Fig. 23 ). Gill VI tiny, unbranched. Posterolateral projections of abdominal segments VII–IX broad, apex pointed. Three retractile, short and feathery caudal filaments present.

Sub-imago and Imago. Unknown.

Distribution. India (Western Ghats).

Diagnosis. Prosopistoma indicum Peters, 1967 is most similar to P. coorgum Balachandran & Anbalagan 2016 , a recently described species from South India. Common characters include (i) presence of 6-segmented antenna; (ii) carapace wider than long; (iii) distal end of carapace concave over exhalent notch; (iv) similar number of spines (3) on apex of inner margin of outer canine of mandibles; (v) similar number of spines (2) in P. indicum and 2-3 in P. coorgum on apex of inner margin of inner canine of mandibles; (vi) 3 long feathered stout bristles arising near base of apical canine and dentisetae on galea-lacinia; (vii) similar length ratio of labial palp segments from basal one to apical (2.1:2.25: 1 in P. indicum and 2:2.5: 1 in P. coorgum ); and (viii) presence of 6–8 pectinate setae in the ventral margin of fore tibia.

However, P. indicum may be distinguished from P. coorgum by the following combination of characters: (i) antennal segment III shorter than combined length of segments IV–VI ( Fig. 15 ); (ii) carapace general coloration yellowish brown with an irregular (zig-zag) yellow pattern at approximately 0.6 times the length of the carapace from the posterior margin of head ( Fig. 13 ); (iii) presence of 3 long serrated bristles at the base of inner canine ( Fig. 17 ); and (iv) gill II broad, leaf-like and unbranched ( Fig. 22 ).

Ecology. Prosopistoma indicum specimens were collected from riffle areas, and in some instances pool areas, of river Minu Hole and its tributaries, inside and outside Someshwara Wildlife Sanctuary, Karnataka, India and Kallar, Gadana River, Tirunelveli, Tamil Nadu . Unlike P. someshwarensis n. sp. which was collected only from forest streams, this species was collected from varied landscapes—forest streams, streams adjoining agricultural land and plantations, and streams adjoining villages. These streams had average widths ranging from 0.245 m to 12.28 m and average depths ranging from 1.31 cm to 30.85 cm through the three seasons of sampling. The pH ranged from 6.78 to 8.3, and water temperature ranged from 21.9°C to 34.3°C.

Figures

FIGURES 13 – 19. Larva of Prosopistoma indicum Peters, 1967, 13. Dorsal view; 14. Ventral view; 15. Antenna; 16. Labrum; 17. Mandible; 18. Maxilla; 19. Labium.

FIGURES 20 – 23. Larva of Prosopistoma indicum Peters, 1967, 20. Foretibia; 21. Gill I; 22. Gill II; 23. Gill III.