Disparalona Fryer, 1968

Neretina, Anna N., Garibian, Petr G., Sinev, Artem Y. & Kotov, Alexey A., 2018, Diversity of the subgenus Disparalona (Mixopleuroxus) Hudec, 2010 (Crustacea: Cladocera) in the New and Old World, Journal of Natural History 52 (3 - 4), pp. 155-205 : 159-160

Subgenus Disparalona Fryer, 1968 s. str.

Type species

Lunceus rostratus Koch, 1841 = Disparalona rostrata ( Koch, 1841) now. Explicitly designated by the taxon author ( Fryer 1968) (case 67.5 of the ICZN 2000).

Emended diagnosis

Parthenogenetic female. Middle-sized Chydorinae , length of adult parthenogenetic female up to 0.5 mm. In lateral view, body oval, low (especially in the posterior part), with maximum height almost at the middle. Height/length ratio about 0.60. In dorsal and ventral view body moderately compressed laterally, in some species lateral processes on valves present. Head small, with relatively long rostrum (distance between centre of eye and ocellus is two times shorter than distance between centre of ocellus and tip of rostrum). Dorsal and posterior margins of valves convex, posterodorsal angle expressed, posteroventral and anteroventral angles broadly rounded. Posteroventral angle of valve with or without denticle. Inner side of valve posterior margin covered by a row of numerous fine setules located quite close or far from the edge of margin, setules decreasing in size distally. Sculpture of valves and head strongly developed. Sculpture of posterior and anterior portion of valves is represented by parallel sometimes anastomosing lines and polygons. Surface between them may be covered by additional fine striation, represented by more short lines. Surface of head in some species also with parallel long lines. Structure of head pores are typical for the subfamily Chydorinae : two major bordered pores and two minute pores between them located slightly asymmetrically to midline, closer to anterior major pore than to posterior one. Surface between pores without ornamentation. Labral keel relatively long with drawn tip or short with rounded tip. Postabdomen relatively short (postanal margin almost subequal in size to anal margin or slightly longer). Postanal margin slightly convex. Distal angle of postabdomen is broadly rounded. Postanal margin is armed by composite denticles, decreasing in size proximally. Anal margin and lateral surface of postanal margin are covered by bunches of fine setules. Postabdominal claw is long, subequal in length to anal margin, with two basal spines of different size. Antenna I typical for chydorids, antennular sensory seta slender, arising subdistally, subequal in length to antennular body. Antennal formula: setae 0 – 0-3/1 – 1-3, spines 1 – 0-1/0 – 0-1. Antenna II with massive, long spine on proximal exopod segment (this spine longer than the middle exopod segment). Five thoracic limbs. The number of setae on thoracic limbs is typical for subfamily Chydorinae . Inner distal lobe of thoracic limb I with three thin setae of different length, the largest seta hook-like or not. Two lateralmost setae covered by short setules on exopodite of limb IV are relatively long, subequal in size. Ephippial female is similar with parthenogenetic female in lateral view. Ephippium is not specially bordered from the rest of valves, brownish, contains single egg.

Male. In lateral view, body oval, elongated, up to 0.36 mm in length. Armature of valves and ornamentation similar to parthenogenetic female. Postanal margin of postabdomen of different shape (almost straight, convex or concave). Postabdominal claw with one or two basal spines. Gonopores open laterally or ventrally near claw bases. Antenna I with male seta located almost at the middle of antennular body near sensory seta. Limb I with massive copulatory hook.