Conochilidae, Harring, 1913

Davies, Natalie, Lafleur, Alexandre, Hochberg, Rick, Walsh, Elizabeth J. & Wallace, Robert L., 2024, Key to sessile gnesiotrochan rotifers: Families, monospecific species in Flosculariidae, species of Atrochidae, Conochilidae, and Limnias, Zootaxa 5397 (4), pp. 497-520 : 507

Dichotomous key to species in family Conochilidae

1 Corona circular (not horseshoe-shaped) with prominent ventral gap absent; ventral (= lateral) antennae not within the corona; resting eggs with spiral furrow, but no hatching furrow evident; body length ~500 µm; monospecific genus................................................................ Conochilopsis causeyae (Vidrine, McLaughlin, & Willis, 1985) [ Segers and Wallace (2001) described its trophi and reallocated it to a new genus in Conochilidae .]

1’ Corona horseshoe-shaped with a prominent ventral gap....................................................... 2

2(1’) Ventral (= lateral) antennae within corona; colonies of several to many individuals; resting eggs not ornamented, but possess a hatching furrow; genus Conochilus ( Fig. 5 )................................................................. 3 [Trophi for the two species in genus Conochilus were (SEM) are found in Segers & Wallace (2001).]

2’ Ventral (= lateral) antennae not within corona; resting egg with spiral surface texture, but no hatching furrow evident; genus ( Conochiloides ) Conochilus ............................................................................. 4 [Trophi for the four species in the former genus Conochiloides were drawn by Ahlstrom (1938); SEMs of the trophi for C. dossuarius and C. natans are shown in Segers and Wallace (2001).]

3(2) Antennae not fused; colonies of 30–100 individuals; total body length 400–850 um (foot:body ratio, 2.2–2.4).......................................................................................... hippocrepis (Schrank, 1803)

3’ Antennae fused (except perhaps at distal end) into a single structure; small colonies (5–30 individuals) with total body length 200–450 um and foot:body ratio, 1.2–1.7 or larger colonies (50–400 or more individuals) with total body length <1300 µm (foot:body ratio 2.2–2.7)............................................................ unicornis Rousselet, 1892 [Includes a form previously known as Conochilus norvegicus Burckhardt, 1943 that produces colonies often with large numbers of individuals possessing elongate bodies that may be the result of allometric growth ( Edmondson 1959; Ruttner-Kolisko 1974). De Graaf (1953) provided information on the commensal protists that inhabit the gelatinous matrix and Yang et al. (2021) provided information on the ultrastructure of the secretions.]

4(2’) Antennae not fused; rami symmetrical, with 5–6 large clavate teeth on each uncus; total body length 280–510 µm............................................................................................ natans (Seligo, 1900)

4’ Antennae at least partially fused; rami symmetrical or not; variable number of large clavate teeth on each uncus.......... 5

5(4’) Rami strikingly asymmetrical, one side almost triangular in shape, the other sub-rectangular; 5 clavate teeth on each uncus; total body length 280–500 µm.......................................................... dossuarius (Hudson, 1885)

5’ Rami symmetrical or at least asymmetry scant.............................................................. 6

6(5’) Unci with 3/3 teeth; total body length 200–250 µm..................................... coenobasis (Skorikov, 1914) [Amphoteric females are known in this species ( Ruttner-Kolisko 1974).]

6’ Unci with 4/5 teeth; total body length 170–190 µm........................................ exiguus ( Ahlstrom, 1938) [An amphoteric female is shown in Fig. 5D .]

Figures

FIGURE 5. Species of Conochilidae. A. Conochilus hippocrepis (Schrank, 1803); B. Conochilus unicornis Rousselet, 1892; C. Conochilus coenobasis (Skorikov, 1914); D. Conochilus exiguus (Ahlstrom, 1938). This amphoteric female is evidenced by presence of a subitaneous embryo and a smaller male embryo. (The cone-lip is evident in C and D.) The foot in the variation of C. unicornis (C. norvegicus) is much longer (~4x) (see below). E. Examples of reported variation in the fusion of antennae in the Conochilus: consult Edmondson (1959) and Pejler (1956). Bars: 500 µm (A,B); 100 µm (C,D). (E. Redrawn from original art provided by W.T. Edmondson.)