Flosculariidae Remane, 1933

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 : 508-512

Family Flosculariidae Remane, 1933

Flosculariidae is a cosmopolitan family comprising nine genera ( Beauchampia , Floscularia , Lacinularia , Lacinularoides , Limnias , Octotrocha , Pentatrocha , Ptygura , Sinantherina ) with approximately 60 named species and subspecies. The etymon of the family is as for the order.

Diagnosis. Symmetrical or asymmetrical, malleoramate trophi; typically with elongate bodies and large, circular (slightly elliptical) to lobate, heart-shaped, or ear-like corona. Animals live in a tube formed in various ways or in a secreted gelatinous matrix. They may be solitary or colonial: colonies may be intra- or interspecific. Mostly species are sessile, some are planktonic, two are facultatively sessile.

1 Single dorsal antenna, visible when animal contracts, conspicuously long (> body width); gelatinous matrix embedded with debris; sessile; solitary; body length ≤1000 µm; oviparous; monospecific ( Fig. 7 ).................................................................................................... Beauchampia crucigera (Dutrochet, 1812)

1’ Two dorsal antennae, not visible when animal contracts, not conspicuously long; gelatinous matrix present or absent...... 2

2(1) Adults with oviferon below anus......................................................................... 3 [The oviferon, a specialized egg-bearing structure where eggs attach ( Fig. 8 ) ( Segers & Shiel 2008).]

2’ Adults without oviferon; gelatinous matrix or constructed tube present........................................... 4

3(2) Corona with five large lobes; transparent, amorphic, gelatinous matrix; sessile; typically solitary, occasionally small colonies (<3 animals); body length 3000–3500 µm; oviparous; monospecific........... Pentatrocha gigantea Segers & Shiel, 2008 [Specimens of this monospecific genus were hatched from dry sediments of a temporary waterbody in Australia ( Segers and Shiel 2008). The original description provides illustrations of the adult and SEM photomicrographs of the trophi. Being extremely large and with a corona of five lobes Pentatrocha cannot be mistaken for Sinantherina or any other sessile rotifer ( Meksuwan et al. 2011).]

3’ Corona not as above (heart-shaped); gelatinous matrix is absent; sessile or planktonic; solitary or colonial; body length 750– 2500 µm; oviparous. ( Fig. 8 )............................................. Sinantherina Bory de St. Vincent, 1826 [Three species possess bulbous structures called warts ( Wallace et al. 2023) on their anterio-ventral; one species has spines. Five species.]

4(2’) Adults in a flexible straight or slightly curved pipe of hardened secretions (either as a stack of semitransparent rings or granular, stucco-like and opaque); sessile; usually solitary (occasional small, branching, colonies, typically ≤15); body length ≤ 1000 µm; oviparous. ( Fig. 9 )............................................................... Limnias Schrank, 1803 [Corona width greater than height, with one pair of lobes; corona with wide dorsal gap and ventral depression. Two groups of Limnias are easily recognized by their tubes. (1) The melicerta -group (3 species) possess a tube with a ringed structure ( Wright 1954; Yang & Hochberg 2018). (2) The ceratophylli -group (5 species) lacks rings, its tube resembles a stucco surface. Identification of species requires observations of the shape of the corona and the number and shape of outgrowths (horny processes or projections) on a dorsal plate just beneath the corona ( Meksuwan et al. 2018). One species, Limnias ceratophylli Shrank, 1803 has been reported as epizoic on the Amazonian crocodile, Melanosuchus niger ( Magnusson 1985) . The etymon of this genus (L., limnos, lake) apparently refers to the general habitat of these animals. Keys to species of Limnias are given by Meksuwan et al. (2018) and Wallace et al. (2018).]

4’ Not as above......................................................................................... 5

5(4) Corona with distinct lateral lobes......................................................................... 6

5’ Corona without distinct lateral lobes...................................................................... 8

6(5) Corona with four pairs of lateral lobes (= 8 lobes) one pair smaller; gelatinous tube; solitary; body length 1500–2000 µm; oviparous; monospecific. ( Fig. 10 )............................................. Octotrocha speciosa Thorpe, 1893 [Information on this monospecific genus is provided by Koste & B̂ttger (1989) and Segers & Shiel (2008).]

6’ Corona otherwise..................................................................................... 7

7(6) Corona with 7 lobes (2 small and 5 prominent lateral lobes); sessile in a tough gelatinous tube; solitary (stem female?) or colonial; foot long; body length ≤1300 µm; oviparous; monospecific. ( Fig. 11 )..................................................................................................... Lacinularoides coloniensis (Colledge, 1918) [The corona resembles that of Pentatrocha , but this species lacks an oviferon; the corona is not as elaborate as in Octotrocha . The genus name was derived from the genus Lacinularia ; a review of this monospecific genus was done by Meksuwan et al. (2011).]

7’ Corona with 4 lobes (2 pairs of distinct lateral lobes); sessile; solitary or colonial; tube composed of formed pellets, or gelatinous matrix; body length 500–2000 µm; oviparous. ( Fig. 12 ).................................... Floscularia Cuvier, 1798 [Two species ( Floscularia conifera (Hudson, 1886) and Floscularia ringens (Linnaeus, 1758) are known to form allorecruitive colonies. Nine species.]

8(5’) Corona round to slightly elliptical; animals in gelatinous matrix, often with debris (one species with fecal pellets in the matrix); usually solitary, occasionally in intra- or interspecific colonies; body length 200–1400 µm; oviparous. ( Fig. 13 )........................................................................................... Ptygura Ehrenberg, 1832 The taxonomic history of Ptygura is complicated; the genus is in need of a comprehensive review (Meksuwan 2015). [30 species.]

8’ Corona heart-shaped; animals embedded in common, flocculent gelatinous matrix; sessile or planktonic; usually colonial (usually <200); body length 900–2000 µm; oviparous. ( Fig. 14 )........................ Lacinularia Schweigger, 1820 [In field samples, colonies of 1000s of individuals have been seen (EJW, pers. obs. Seven species.]

Figures

FIGURE 7. Beauchampia crucigera attached to filamentous algae. A. Corona retracted; B. corona expanded. Bar = 500 µm.

FIGURE 8. Scanning electron photomicrograph (SEM) of part of a colony of Sinantherina socialis. The two individuals in the center show the oviferon (OV) below the cloaca (CL). A gelatinous matrix is absent in this genus. (Bar ~ 250 µm.)

FIGURE 9. Examples of species in the genus Limnias: A-B. solitary Limnias ceratophylli-group; C. solitary Limnias melicerta- group; D. colonial L. ceratophylli-group; E. colonial L. melicerta-group. Symbols: a = algae; e = embryo; S = substratum. Bars ~ 100 µm.

FIGURE 10. Octotrocha speciosa. A. dorsal view; B. partial side view which illustrates the elaborate coronal lobes. Symbol: g = gelatinous matrix (tube). Bar = 250 µm.

FIGURE 11. Lacinularoides coloniensis: schematic dorsal view of the corona. Ciliation is indicated for only a small portion of the coronal margin. Bar = 250 µm. (Modified after Colledge, 1918).

FIGURE 12. Examples of Floscularia species. A. Floscularia melicerta B. F Floscularia conifera (lateral view). Symbols an = antennae; c = corona; e = embryo; gt = gelatinous tube; pt = pellet tube; * = colony mates (out of focus). Bars = 500 µm.

FIGURE 13. Examples of Ptygura species. A. Ptygura beauchampi Edmondson, 1940; B. Ptygura libera Myers, 1934; C. Ptygura brachiata (Hudson, 1886); D. Ptygura mucicola (Kellicott, 1889); E. Ptygura pilula (Cubitt, 1872). Symbols: an = antennae; c = corona; e = embryo; gt = gelatinous tube; fp = fecal pellets (embedded in gt); gl = Gloeotrichia sp. (cyanobacteria) attached to a vascular hydrophyte; S = substratum.. Bars = 100 µm.

FIGURE 14. Examples of Lacinularia. A. SEM dorsal view; B. Complete colony attached to Ceratophyllum demersum Linnaeus, 1753; C. Closeup of a colony. Symbols: a = algal filament; b = body; c = corona; gm = gelatinous matrix (embryos are embedded within); m = mouth; S = substratum. Bars = 1,000 µm.