Limnadia Brongniart, 1820

Rogers, D. Christopher, 2020, Spinicaudata Catalogus (Crustacea: Branchiopoda)., Zoological Studies 59 (45), pp. 1-44 : 12-13

Limnadia Brongniart, 1820

= Monoculus Linnaeus, 1761

= Daphnia Herman, 1802

= Limnadella Girard, 1854

= Estheria Baird, 1860

Diagnosis: (modified from Rogers et al. 2012). Populations nearly always composed of hermaphrodites, with males exceedingly rare ( Sassaman 1995; Eder et al. 2000; Weeks et al. 2008). Amplexus is venter to venter. Rostrum variable; typically blunt in hermaphrodites and acute in males. Angle between rostrum and frons 100° to 80°. Occipital notch and condyle absent. Frontal organ pedunculate. Frontal organ length 2–2.5 times distance between base of frontal organ and ocular tubercle. Carapace dorsal margin smooth, lacking carinae, hinge line arcuate. Carapace surface between growth lines smooth or faintly malleate. Umbone absent. Carapace without pigmentation. Muscle scar angle 20 to 40° from normal. Thoracic segments smooth or with dorsoposterior ridge margined with spines or setae. Clasper endopods each bearing and apical suctorial organ. Endite IV with apical dense field of long spines. Eggs attaching to prolonged exopods of thoracopods X and XI. Telson without spiniform projection on ventroposterior angle, anteriad of cercopod base. Telson posterior spine rows confluent dorsally, confluence not projecting. Each row with 11–19 spines. Caudal filament originating at or above apex of dorsal spine row confluence. Caudal filament never borne on mound. Cercopods arcuate, with or without a medial longitudinal row of setae along proximal 30–40%. Setae simple, short, sometimes spiniform. Setal row terminates with 0–9 spines. Cercopod with subapical, dorsal cirrus, extending from 10–50% of cercopod length. Eggs 120–170 μm in diameter, double discoidal in shape. Eggs with narrow slit shaped depressions separated by low ridges.

Comments: Bellec et al. (2018) presents the most recent review of the genus, but it is still limited. Additional revisonary work is needed, and the eggs need to be compared and studied in detail. There is still one additional undescribed species in the USA (Rogers per. obs.). Sars (1903) reported and figured Limnadia sp. which he reared from soil collected in Sumatra, identifying the form as L. lenticularis . Whether this represents a new species or contamination from one of his European cultures of L. lenticularis remains to be seen.

Attributed Species