Streptocephalus spinier Gurney, 1906

Velu, Chinavenmeni S & Munuswamy, Natesan, 2005, Updated diagnoses for the Indian species of Streptocephalus (Crustacea: Branchiopoda: Anostraca), Zootaxa 1049, pp. 33-48 : 42-44

Streptocephalus spinier Gurney, 1906

Materials investigated. Akavedu (Andrapradesh) (16°20N, 80°27E). Accession numbers are DZ/NM/FS/151.

Measurements. 7 males (7.5–11.6); 5 females (6.3–10.5).

Description: male First antennae longer than eye and peduncle ( Fig. 5 A). Frontal appendage is sub­cylindrical, long, and divided into two segments. Each branch has a long, stout ventrally curved process ( Fig. 5 C) which has small papillae on the ventral side. Just beneath the frontal appendage, a sharp, conical spine­like structure is observed basally between the second antennae ( Fig. 5 B). Basal joint of second antennae has a slender, long antennomere at its distal end ( Fig. 5 B). Antennal appendage show three protuberances on its medial surface ( Fig. 5 C). Hand of second antennae is short and broad. Thumb is simple, long, slender, slightly curved, tapering towards the end and longer than the finger ( Fig. 5 D). A small bulge spur is present at the base of thumb ( Fig. 5 E). Angle between proximal and distal region of thumb is approximately 150°. Finger is broad, distally slender, approximately two­third of the length the of thumb and with large, acute triangular tooth at its base.

Mature adult has 11 pedigerous thoracic segments followed by genital segment. Seven apodous abdominal segments, with spines on the dorso­lateral side ( Fig. 5 F). Penes is long and coiled, the basal and non­retractile part has a posterior conical projection with spines on its surface ( Fig. 5 G, H, I). The retractile part of penes each has three rows of longitudinal spines ( Fig. 5 J). Cercopods are long and bear small stiff setae proximally and long fleshy spines distally ( Fig. 5 L). The number of setae and spines, however, differ considerably between individuals.

Female. Spiniform rostrum and frontal appendage are absent in females. The second antennae are reduced and blade­like. Abdominal segments are devoid of spines. The ovisac is narrow, cylindrical in shape and extends to fourth abdominal segment ( Fig. 5 K). Cercopods bear uniform, long thin setae and are devoid of fleshy spines.

Egg. Cyst surface is covered with a series of pentagonal structures, with raised ridges pointing upwards (looks like spines) ( Fig. 5 I), and covered with small pores on their surfaces ( Figs. 5 M, N).

Remarks. Streptocephalus spinifer Gurney, 1906 differs from other species in the following respects: the male has a frontal appendage; the second antennae of the male has a thumb and a finger; but no separate posterior or anterior ramus in hand; abdominal segments have spines; cercopods bears stiff setae and long fleshy spines. This species is smaller and slender than the other species. Cyst surface is pentagonal polygons with centered raised ridges.

Figures

FIGURE 5. Streptocephalus spinifer GURNEY. A. Male, lateral view of head. B. Ventral view of the frontal appendage showing spine. C. Frontal appendage. D. Medial view of antennae showing protuberances. E. Male antennae, lateral view. F. Male antennae, medial view. G. Abdominal segment showing spines. H. Lateral view of male genital region with spine on the distal end. I. Upper view of the same. J. Ventral view of the same showing protuberances at the basal end. K. Retracted penis showing the spines on the surface. L. Lateral view of female abdomen and broodpouch. M. Male, telson. N. Cyst. O. Details of cyst showing ridges, depression and pores.