Rhopalophthalmus anishi, Panampunnayil & Biju, 2006

Panampunnayil, S. U. & Biju, A., 2006, Four new species of the genus Rhopalophthalmus (Mysidacea: Crustacea) from the northwest coast of India, Journal of Natural History 40 (23 - 24), pp. 1389-1406 : 1396-1399

Rhopalophthalmus anishi sp. nov.

( Figures 28–40 )

Material

Holotype: adult male (IOBC-0504-10-50-1999). Allotype: adult female (IOBC-0504 A- 10-50-1999). Paratypes: two adult males and two adult females (IOBC-0504 B-10-50- 1999).

Kashelli: (19 ° 14.30 9 N, 73 ° 00.20 9 E), December 1996, 13 adult males, 13 adult females, eight immature males, seven immature females, and 33 juveniles.

Description

General form slender. Carapace broadly rounded in front, covering basal part of antennules, post-orbital spines small, continuing backward into faint keels; antero-lateral angles produced into strong spines; cheeks sinuous. Eyes stout, reaching beyond first antennular segment; cornea as broad as stalk and occupying distal third of eye ( Figure 28 ).

Basal segment of antennule in male as long as rest of peduncle, third segment short and stout, but short basal part of outer flagellum swollen and hirsute ( Figure 29 ). In female, basal segment much longer than rest of peduncle. Antennal scale long and narrow reaching clearly beyond antennular peduncle, five times as long as broad; antennal peduncle short, less than half length of scale; sympod with two long and two short spines ( Figure 30 ).

Mouthparts and first and second thoracic endopods as in R. mumbayensis sp. nov.

Thoracic endopods three to seven with three to five carpopropodal segments ( Figures 31–33 ). Vestigial endopod of male eighth thoracic limb straight, three-segmented, almost as long as basal segment of exopod, second segment with three to four plumose setae on outer distal corner, apex broadly rounded ( Figure 34 ). In female, eighth endopod longer than basal segment of exopod, slender, straight and unsegmented, distal end produced at apex into minute cusp with short seta ( Figure 35 ).

Pleopods in male biramous, first pleopod with unsegmented endopod and 10-segmented exopod ( Figure 36 ); second pleopod with 10-segmented endopod and 12-segmented exopod, distal segment of exopod with third long barbed setae ( Figure 37 ); third, fourth, and fifth pleopods similar with 10-segmented exopod and endopod ( Figure 38 ).

Telson moderately broad, longer than last abdominal segment, about twice as long as broad at base, distal half armed with 11 pairs of graduated spines, spines on distal border long and sharply pointed, outer pair distinctly longer than inner pair, subsidiary teeth sharp ( Figure 39 ).

Uropods longer than telson, two-segmented, endopod with single stout spine on middle inner margin; exopod longer than endopod ( Figure 40 ).

Length: adult male 9.7–11 mm; adult female 9.6–11.7 mm.

Etymology

This species is named after the first author’s son, Anish.

Remarks

This species can be readily distinguished by the combinations of the following characters: (1) thoracic endopods have three to five carpopropodal segments; (2) vestigial endopod of eighth thoracic limb is longer than the basal segment of the exopod in female and in male almost as long as the basal segment of exopod and (3) spines on the distal border of the telson are sharply pointed and the outer pair of spines are distinctly longer than the inner pair.

Rhopalophthalmus kempi O. Tattersall, 1957 is the only other species of the genus in which the endopod of the eighth thoracic limb in both sexes is longer than the basal segment of the exopod. But R. kempi differs from the new species in having a shorter antennal scale, only three carpopropodal segments and the inner pair of distal spines on the telson are longer than the outer pair.

Ecological note

The new species is a shallow-water form and the temperature and salinity recorded at the time of collection were 25.4 ° C and 16.4 psu, respectively.

Figures

Figures 28–35. Rhopalophthalmus anishi sp. nov. (male, unless indicated). (28) Anterior part of body. (29) Antennule. (30) Antenna. (31) Third thoracic endopod. (32) Fifth thoracic limb. (33) Seventh thoracic endopod. (34) Eighth thoracic limb. (35) Eighth thoracic limb of female.

Figures 36–40. Rhopalophthalmus anishi sp. nov. (male). (36) First pleopod. (37) Second pleopod. (38) Third pleopod. (39) Telson. (40) Posterior part of body.