Research Article |
Corresponding author: Supiyanit Maiphae ( supiyanit.m@ku.ac.th ) Academic editor: Hendrik Segers
© 2018 Phuripong Meksuwan, Rapeepan Jaturapruek, Supiyanit Maiphae.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Meksuwan P, Jaturapruek R, Maiphae S (2018) Two new species of genus Limnias from Thailand, with keys to congeners (Rotifera, Gnesiotrocha). ZooKeys 787: 1-15. https://doi.org/10.3897/zookeys.787.28098
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Two new species and two morphological variant taxa of sessile rotifers found during a survey of Thai rotifers are reported upon. Living specimens were collected and identified from twelve sampling sites. The specimens were photographed, and prepared for SEMs of dorsal plates and trophi. Two new species of genus Limnias are recognized. Limnias lenis sp. n. possesses a corona with a relatively shallow ventral sinus, and a dorsal plate without any projection, whereas Limnias novemceras sp. n. carries a corona with a deep and wide ventral sinus, and a dorsal plate with nine projections. Two morphological variants of Limnias melicerta are discussed, which are designated as L. melicerta SH and L. melicerta LH on the basis of the length of the horns on their dorsal plates. Moreover, both a dichotomous key and a formula key are provide including all Limnias species known to date.
corona, dorsal plate, horny process, SEM, sessile rotifers
Limnias Schrank, 1803 is a cosmopolitan genus of sessile rotifers (
Specimens of Limnias species were collected from different localities in Thailand (Supplementary material
Dorsal plate. Each fixed, contracted specimen in 95% ethyl alcohol is extracted from its tube, and placed into a small drop of distilled water on a piece of cover glass. The specimen is oriented dorsally and left until the water is completely evaporated. Dried specimens on cover glasses are coated with gold, followed by examination under SEM.
Trophi. A sorted specimen is placed into a drop of commercial bleach (7% NaOCl). The remaining trophi is picked up and rinsed several times in drops of distilled water on a piece of cover glass. Then, the trophi is air dried, coated with gold and examined under SEM. SEM photographs were processed by a FEI Quanta 400 SEM.
Classification of genus Limnias follows
Holotype. A contracted female in a mounted slide deposited in Princess Maha Chakri Sirindhorn Natural History Museum (
Jik peat swamp, Phuket Province, Thailand: 8°8.683'N, 98°17.983'E. Size of the peat swamp is about 230×140 meters. Individuals of L. lenis sp. n. were found attached to roots of Water hyacinth (Eichhornia crassipes (C.Mart.) Solms). November 15th, 2015.
The species name is an adjective, derived from the Latin “lenis”, meaning “soft, smooth, gentle” and refers to the smooth surface of its dorsal plate.
The species is unique by its corona having a relatively shallow ventral sinus compared to other taxa, and by its smooth dorsal plate, without any projection (Figs
Tube ringed, proximal part smooth, usually transparent. Trunk slender, tapers into slender foot with short stalk (Figs
The species is known only from its type locality.
Holotype. A contracted female in a mounted slide was deposited in Princess Maha Chakri Sirindhorn Natural History Museum (
A stream in Krabi Province, Thailand: 8°12.687'N, 98°46.899'E. Individuals of L. novemceras, sp. n. were found on leaves of Hydrilla verticillata (L.f.) Royle growing in littoral area of the stream. June 2nd, 2011.
The species name is a substantive, and refers to the number of projections (nine, fromthe Latin novem, and horn, from the Greek ceras) on the dorsal plate.
Limnias novemceras sp. n. is easily recognized by its dorsal corona gap being much wider than the tube diameter, by its long ventral antennae that reach beyond the fully extended corona, and by its dorsal plate carrying nine projections. In addition, this species never raises its corona far beyond the tube opening (Figs
Tube ringed, transparent, proximal part smooth, transparent. Trunk slender, tapers into slender foot with short stalk (Figs
The species is known only from its type locality.
We constructed dichotomous and formula keys of all known Limnias species based on investigation of four species, including the two new species, observed in Thailand. In addition to the four species, we reevaluate the identity of L. cornuella, L. myriophylli, L. nymphaea and L. shiawasseensis, based on original publications, the most recent revision of the group by
1 | Tube without ringed structure, usually covered with debris | 2 |
– | Tube with ringed structure, clear or slightly colored (yellow or brownish) and sometimes covered with debris | 4 |
2 | Dorsal plate with seven projections | L. shiawasseensis |
– | Dorsal plate without projection | 3 |
3 | Ventral antennae short, not reaching beyond fully extended corona | L. ceratophylli |
– | Ventral antennae longer than fully extended corona | L. myriophylli |
4 | Dorsal plate without projection | L. lenis sp. n. |
– | Dorsal plate with projections | 5 |
5 | Ventral antennae short | 6 |
– | Ventral antennae long | 7 |
6 | Seven projections on dorsal plate | L. melicerta |
– | Fourteen projections on dorsal plate | L. nymphaea |
7 | Four projections on dorsal plate, tube curved or twisted | L. cornuella |
– | Nine projections on dorsal plate, corona lobes separated by a very wide dorsal gap (nearly twice of truck width) | L. novemceras sp. n. |
1 Ring tube: (a) absent; (b) present (Figs
2 Dorsal plate projections: (a) absent (Figs
3 Ventral antennae length relative to fully extended corona: (a) shorter; (b) longer
L. ceratophylli: 1a, 2a, 3a
L. myriophylli: 1a, 2a, 3b
L. shiawasseensis: 1a, 2c, 3b
L. cornuella: 1b, 2b, 3b
L. melicerta: 1b, 2c, 3a
L. nymphaea: 1b, 2e, 3a
L. lenis sp. n.: 1b, 2a, 3a
L. novemceras sp. n.: 1b, 2d, 3b
The most distinctive features of genus Limnias are the bilobed corona, and apparently, the presence of a rigid dorsal plate. While feeding this plate is located in the neck region on dorsal side of the body. When the rotifers are disturbed, however, they retract the corona into the tube and the dorsal plate is moved into an antero-dorsal position such that the horn-like projections are exposed towards the opening of the tube (Figs
Our keys to species of Limnias, as well as those by
At present, four species of Limnias rotifers have been recorded from Thailand: L. ceratophylli, L. melicerta, L. lenis sp. n. and L. novemceras sp. n. However, we found two additional, clearly distinguishable morphological variants of L. melicerta that both fit the original description of this species. Because no type specimens are known to exist for L. melicerta (see
This work has been supported by Center of Excellence on Biodiversity (BDC), Office of Higher Education Commission (BDC-PG2-161004) and Kasetsart University Research and Development Institute, Kasetsart University. We thank Dr Hendrik Segers for constructive comments on the first version of this manuscript and for spelling of specific names of the new species.
Sampling sites (S1–S12) in Thailand with GPS coordinates.