Floscularia (Koste, 1978)

Lafleur, Alexandre, Davies, Natalie, Hochberg, Rick, Walsh, Elizabeth J. & Wallace, Robert L., 2024, Key to sessile gnesiotrochan rotifers: Floscularia (Monogononta; Flosculariidae), Zootaxa 5471 (4), pp. 401-421 : 409-410

Dichotomous key to species of genus Floscularia

1 Animals possessing mucrons; ventrolateral antenna elongate; ventral lobes larger than dorsal lobes; tube with small pellets or with large, ovoid fecal pellets embedded in gelatinous material or with only gelatinous material without pellets ( Fig. 2C )... ................................................................................................... 2 [Mucrons, if present, are best seen at apex of the anterior end in contracted animals.]

1’ Animals lacking mucrons ( Fig. 2C ); ventrolateral antenna short; ventral lobes much larger than dorsal lobes, dorsal lobes very small and almost confluent along their dorsal margin; tube comprising gelatinous material embedded with large, egg-shaped masses; total body length ≤1600 µm; solitary ( Fig. 3 )........................................ janus ( Hudson, 1881) [The trophi have been documented by Koste (1978) and Kutikova (2007). Kutikova (2007) reports the masses to be “fecal lumps,” but also discusses their production in a modulus structure as follows. “Under the crown, below the oral funnel, an angular lower lip (length 30 µm) protrudes with a pit where fecal lumps (size 83–98 x 45–56 µm) are created for building a house. The pit is lined with cilia.” Koste (1978) also refers to the mass as large pellets loosely associated with detritus and feces.] Regardless, if little particulate matter is available, F. janus may produce “fairly transparent, irregular tubes” ( Edmondson 1940). The larvae of F. janus may settle on filamentous algae in a series: i.e., the individuals are assembled in order of size (age) even when adequate space is available for arbitrary settling ( Edmondson 1940).Apparently very rare in the plankton, W.T. Edmondson, pers. commun. Cosmopolitan.]

2(1) Mucrons smoothly curved (arched) without accessory projections.............................................. 5

2’ Mucrons other....................................................................................... 3

3(2’) Mucrons bifid (tips with one tooth point forward and one inwardly) or mucrons complex and variable; pellet tube comprising densely or loosely packed, round pellets................................................................... 4

3’ Mucrons not bifid (tips flexed ventrally at near right angles pointed) ( Fig. 2C ); pellet tube comprising densely packed, bullet-shaped pellets; labium elongate, pointed; unci teeth weakly differentiated ( Fig. 2E ) total body length 500–2000 µm; solitary or colonies 2–c.35 individuals. ( Fig. 4 )................................................... conifera ( Hudson, 1886) [The trophi have been documented by Segers (1997). The ultrastructure and tube of this species has been studied by Yang and Hochberg (2018a). Edmondson (1945) studied the dynamics of population growth and the social structure of solitary and colonial animals. The propensity to form colonies in this species has been reported by ( Wallace 1987). Cosmopolitan.]

4(3) Mucron tips bifid, (noted above); tube with loosely packed, round pellets; peduncle long ( Fig. 5 )........ bifida Segers, 1997 [Tube resembles that of F. bifida and F. ringens ( Segers 1997) . The adult (contracted) and trophi (asymmetric) have been documented by Segers (1997). The bifid dorsal hooks are apparently variable ( Segers et al. 2010). Thailand. South America.]

4’ Mucrons variable: large with two, strong, lateral spines, slightly incurved or almost straight pointing ventrally or with accessory projections near ends; pellet tube comprising loosely packed, round pellets; peduncle short ( Fig. 6 ).... armata Segers, 1997 [Tube resembles that of F. ringens and F. bifida ( Segers 1997) . The adult (contracted) and trophi (asymmetric) have been documented by Segers (1997). Thailand. South America.]

5(2) Tube composed of densely packed pellets; peduncle short or long.............................................. 6

5’ Tube composed solely of firm gelatinous material (clear or colored), embedded and/or covered by algae, bacteria, or debris partly obscuring the animal; labium and modulus broad; total body length ≤1600 µm; solitary ( Fig. 7 )............................................................................................... melicerta (Ehrenberg, 1832) [The trophi are illustrated by ( Koste & Böttger 1989). Drawings showing the layers in the gelatinous tubes were published by ( Hudson 1875). The layers of jelly are laid down by the animals as described above. Cosmopolitan.]

6(5) Tube composed of densely packed, clear, hexagonal, bullet-shaped pellets; dorsal hooks large, slightly curved; peduncle short; total body length ~500 µm; solitary or colonies of a few individuals ( Fig. 8 ).................. decora Edmondson, 1940 [This species uses little particulate material in forming its clear pellets; these are large and hexagonal in shape at the anterior, but are flattened at the base. To our knowledge, the trophi have not been figured. Thailand. North America.]

6’ Tube composed of densely packed round pellets; labium long or short; peduncle long or short........................ 7

7(6’) Quadridigitate, cuticular processes located on sides of neck; below the labium two conical processes, with a smaller knob in between, below another median knob; labium short, round; peduncle long; total body length ~750 µm; solitary, perhaps colonial ( Fig. 9 ) …....................................................................... pedunculata ( Joliet, 1883) [See Koste (1978) Tafel 199, figure 4a–d for additional figures. Figure 116 in Remane (1929 –1933) illustrates the long peduncle. W.T. Edmondson (pers. commun.) notes that this species “… has a great resemblance to F. ringens .” Indeed Joliet (1883) states much the same: “Cette différence dans la forme du tube des deux espèces correspond à un détail anatomique qui constitue à lui seul à peu près toute la différence qui existe entre elles.” Nevertheless, these species may be separated based on the presence of the quadridigitate processes and the conical processes, as well as the relative length of their peduncles. To our knowledge, the trophi have not been figured. India. Thailand. North and South America.]

7’ Quadridigitate processes absent; conical processes absent; peduncle long; labium long or short....................... 8

8(7’) Labium short, blunt; unci teeth weekly differentiated; total body length 500–1900 µm; solitary or colonies of a few individuals ( Fig. 10 ) ……………............................................................... ringens (Linnaeus, 1758) [The mucrons resemble that of F. decora ( Figs. 2C , 8B,C ). The trophi have been documented by Fontaneto et al. (2003), Koste and Poltz (1987), and Segers (1997). Several workers have reviewed the life history of this species, including tube building ( Bedwell 1877; Fontaneto et al. 2003; Gosse 1852; Santo et al. 2005; Tiefenbacher 1972; Wright 1950). Tiefenbacher (1972) studied animal growth, pellet and colony formation and regeneration of the dorsal lobe. Charles Krebs submitted a winning photomicrograph of F. ringens in the 2011 Olympus BioScapes Digital Imaging Competition (https://www.washingtonpost.com/ national/health-science/olympus-bioscapes-2011-winners-gallery/ 2011/11/28 /gIQAGqys8N_gallery.html). Cosmopolitan.]

8’ Labium elongate; unci teeth weekly differentiated; solitary or small, allorecruitive colonies; total body length ~1800 µm; ( Fig. 11 )......................................................................... wallacei Segers & Shiel, 2008 [Specimens of Floscularia wallacei were hatched and cultured from rehydrated dry sediments isolated from a billabong in Victoria ( Australia) by Segers and Shiel (2008) who also documented its trophi. This species was also reported in Thailand by ( Meksuwan et al. 2011). Australia. Thailand.]

Figures

FIGURE 2. Examples of critical characteristics used in differentiating Floscularia species. (See Table 1 for additional information.) A, B. Anterior ends showing features of the corona.A. Corona lateral view of F. conifera: tripartite pellet-forming organ (encircled with dotted line) with a pellet (p) in the modulus; B. Corona ventrolateral view of F. melicerta. C. Presence (F. conifera and F. decora) or absence (F. janus) of mucrons. D. Long peduncle of F. pedunculata; Insert: illustrations of two Floscularia spp. lacking peduncles. E. Examples of trophi showing weekly and strongly differentiated unci teeth. F. Examples of allorecruitive colony formation (three small colonies). Tubes in the upper left colony with rings (Edmondson 1945) for details. Symbols: d = debris; dl = dorsal lobe; f = foot; gt = gelatinous tube: dotted line indicates tube; i = insertion point of peduncle to foot; m = mouth; pd = peduncle; pt = pellet tube; s = substratum; sf = stem female of colony; tr = trophi in mastax; vl = ventral lobe; vla = ventrolateral antenna. A, C = Reproduced from original art courtesy of W.T. Edmondson; D. After. Joliet 1883; E. (Reproduced with permission from the copyright holder [Hydrobiologia 354: 165–175; (Segers 1997)).

FIGURE 3. Floscularia janus. A. Dorsal view of an animal in its tube. B. Lateral view of an animal in its tube. C. Lateral view of an animal removed from its tube. D. Dorsal view of the corona showing medial notch in the labium. Symbols: arrows = modulus; a = antenna; an = anus; fp = fecal pellet; gt = elements of the gelatinous tube; lb = labium; m = mouth; S = substratum. Bar = 500 µm. (B = From Hudson, 1881; C = Reproduced from original art courtesy of W.T. Edmondson.)

FIGURE 4. Floscularia conifera. A. Lateral view of the anterior end. B. Small colony with three individuals attached to a stem female (sf). C. Rings of dark pellets formed after three successive rain storms that took place over approximately three days: consult Edmondson (1945). D. Damaged tube of a solitary individual. Symbols: arrow = modulus with a dark pellet being formed; a = antenna; cm = colony mates; d = damaged region; lb = labium; m = mouth; mx = mastax; pt = pellet tube; r = rings of dark pellets; S = substratum; sf = stem female (previously solitary). Bars = 500 µm. (A. Reproduced from original art courtesy of W.T. Edmondson.)

FIGURE 5. Floscularia bifida. A. Trophi, caudal view. B. Apical region, ventral view showing mucrons and ventrolateral antennae. Scale bars: as indicated. (Reproduced with permission from the copyright holder [Hydrobiologia 354: 165–175] and the author (Segers 1997)).

FIGURE 6. Floscularia armata. A. Trophi (caudal view). B. Apical region, ventral view showing mucrons and ventrolateral antennae.Dotted oval: variations of the mucrons and accessory projections may occur in different specimens: consult the original descriptions in Segers (1997). Scale bars: as indicated. (Reproduced with permission from the copyright holder [Hydrobiologia 354: 165–175] and the author (Segers 1997)).

FIGURE 7. Floscularia melicerta. A. Anterio-ventral view. B. 3/4th Anterio-ventral view. C. Lateral view with little debris incorporated into its gelatinous tube; D. lateral view—tube with copious amounts of debris obscuring the gelatinous tube.A and B: Dashes outline the periphery of the gelatinous tube. Symbols: a = antenna; d = small bit of debris in the tube; gt = gelatinous tube; m = modulus; S = substratum. Bars: A, B = 100 µm; C, D = 500 µm. (C = From Hudson 1875.)

FIGURE 8. Floscularia decora. A. Ventral anterior view. B and C. Mucrons. B. Lateral view. C. Ventral view. Symbols: a = antenna (right side); hp = hexagonal, bullet-shaped pellets; la = labium; mo = modulus. (Reproduced from original art courtesy of W.T. Edmondson).

FIGURE 9. Floscularia pedunculata. A. Corona, dorsal view. B. Corona, lateral view. C. Corona closed, ventral view. D. Long peduncle. Symbols: arrow = modulus; a = antennae; cop = conical processes; f = foot; m = mouth; pd = peduncle; qcp = quadridigitate, cuticular processes. Bars = 100 µm. (Reproduced from original art courtesy of W.T. Edmondson.)

FIGURE 11. Floscularia wallacei. A. From culture, young (left) and adult (right).B. Corona, lateral view.C. Corona, dorsal view. D. Mucrons, lateral view. E. Trophi, frontal view. F. Trophi, caudal view. Scale bars: A ~500 µm; D, E, F = 10 µm. (©Magnolia Press, reproduced with permission from the copyright holder [Zootaxa 1750: 19–31] and the authors (Segers & Shiel 2008).)

FIG. 10. Floscularia ringens. A. Ventral view of an adult. B. Frontal view of trophi. C. Caudal view of trophi. Symbols: a = antenna; lb = labium; m = mouth pt = pellet tube; pt = pellet tube; slb = sublabium; Bars: as indicated. (Reproduced with permission from the copyright holder [Invertebrate Biology 122:231–240] and the authors (Fontaneto et al. 2003).)