Corresponding author: Hendrik Segers (
Academic editor: Lyubomir Penev
Following previous reports indicating a remarkable high diversity of sessile rotifers in Southeast Asian freshwaters, we report on an extensive study of the diversity of
Family
To date, comparatively little is known on the distribution and diversity of sessile rotifers in general and of
We explored 15 freshwater habitats in 12 provinces of Thailand for
Sampling sites in Thailand. S, C, N and NE represent sampling sites in the Southern, Central, North and Northeast part of Thailand, respectively. Map from GIS center, PSU.
The samples examined contained 13 species and two infraspecific variants of
List of
Family |
Genus |
Genus |
* = new to Oriental region and Thailand;
** = new to Thailand
1recorded by
The morphological characters of our specimens agree closely with the description of the species by
Thale Noi Lake, Phatthalung Province, Thailand:
Holotype female mounted in permanent microscope slide, in Princess Maha Chakri Sirindhorn NaturalHistory Museum, Prince of Songkla University, Songkhla, Thailand, PSUZC-PK5PM2-1. Original label: “
The presence of a five-lobed corona separates the new species from most of the known members of genus
Habitus (
Trophi (
Females total length ca. 340 µm. Length of infundibulum plus proventriculus ca. 190 µm, trunk ca. 100 µm, foot ca. 50 µm. Trunk width ca. 70 µm. Infundibulum width ca. 180; dorsal lobe length ca. 75 µm, width ca. 30 µm; ventral lobe width ca. 120 µm, ventral sinus depth ca. 30 µm.
The species name –
The species is known from its type locality only.
This taxon (
Specimens were found in Khlong Lam Chan Non-Hunting Area, Trang province (
We found a single specimen of a species that we could not identify (
The uncinate trophi of
Genus
We believe that the diagnosis of
We found specimens matching the descriptions of two taxa in
Because the morphological characters of these two taxa enable a reliable diagnosis and because the two have wide and overlapping distribution ranges, we argue that these two taxa are distinct species, in contrast to
The uncinate trophi type is one of nine trophi types recognized in phylum
We found that, in all species examined, the uncinate trophi are composed of two pairs of large and sturdy unci teeth, whereas manubria, rami and fulcrum are less developed components (
As illustrated here, the uncinate trophi, in particular the unci, do exhibit features that might be useful for taxonomic analysis. We suggest that 1) shape of the head of the unci; 2) shape of the unci teeth; and 3) relative size of the two pairs of unci teeth might be registered in future studies of
As mentioned above,
The keys presented here include all species recorded hitherto from Southeast Asia (Brunei, Cambodia, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Thailand, Timor Leste, Vietnam), as included in
1 | Length of corona lobe(s) shorter than trunk ( |
(genus |
– | Length of corona lobes in adult specimens as long as, or longer than trunk ( |
(genus |
2(1) | Animals free-living (planktonic) | 3 |
– | Animals fixosessile, permanently attached to a substratum | 5 |
3(2) | Corona edge circular, smooth; inner side of infundibulum with five rudimentary lobes |
|
– | Corona with projections bearing groups of cilia | 4 |
4(3) | Corona with a single dorsal lobe carrying one group of long cilia |
|
– | Corona with five knob-shaped projections, the dorsal one on a triangular lobe; all bearing a group of long cilia ( |
|
5(2) | Corona with well-defined, rounded or club-shaped knobs ( |
6 |
– | Corona circular or with broad lobes, no knob(s) ( |
8 |
6(5) | Corona with seven knobs, the dorsal on a small, triangular lobe ( |
|
– | Corona five projections ( |
7 |
7(6) | Corona with equal, elongated lobes terminating in club-shaped knobs ( |
|
– | Corona lobes unequal and/or less than three times their width ( |
|
Within this species two infrasubspecific variants have been recorded from Southeast Asia. One ( |
||
8(5) | Corona circular, smooth, bearing only short cilia |
|
– | Corona with broad lobes | 9 |
9(8) | Corona with one large dorsal and one smaller ventral lobe, dorsal lobe with a group of elongate, parallel cilia ( |
|
– | Corona with a dorsal lobe and a ventral sinus ( |
10 |
10(9) | Corona with three lobes separated by clear, smoothly concave sinuses between the dorsal and ventral lobes ( |
11 |
– | Corona with five lobes, the lateral ones may be only indicated ( |
12 |
11(10) | Corona consisting of homogeneous rows of cilia ( |
|
– | Corona consisting of transversal sets of short, stiff cilia ( |
|
12(9) | Lateral corona lobes larger than ventral lobes, these set close together and separated by a shallow and narrow V-shaped sinus ( |
|
– | Lateral corona lobes smaller than ventral lobes ( |
13 |
13(12) | Lateral corona lobes well-develloped, thumb-shaped; ventral lobes large, rounded ( |
|
– | Lateral corona lobes lower than wide or only indicated ( |
14 |
14(13) | Ventral sinus deep, broadly U-shaped, wider than the width of the ventral lobes ( |
|
– | Ventral sinus shallow ( |
15 |
15(14) | Ventral lobes triangular with rounded tip, dorsal lobe relatively narrow ( |
|
– | Ventral lobes rounded, dorsal lobe broad ( |
|
Within this species one infrasubspecific variant has been recorded from Southeast Asia. |
||
16(1) | Corona lobes stout and robust, carrying parallel, transversal sets of robust cilia ( |
|
– | Corona lobes slender, carrying dense, longitudinal rows of fine, cilia ( |
|
Species (a) free-living (pelagic); (b) living attached to a substratum (fixosessile)
Corona edge: (a) circular, smooth; (b) with well-defined knobs (
Number of corona projections: (a) one dorsal; (b) two: one dorsal, one ventral (
Length of corona projections: (a) much shorter than trunk (
Diversification of corona projections: (a) none, all projections more or less equal (
Lateral corona lobes: (a) absent (3E); (b) indicated (sinus between dorsal and ventral lobe is not smoothly concave or indicated by presence of a distinct group of particularly long cilae:
Ventral corona projections: (a) with one midventral lobe, (b) with two knobs (
Ventral corona sinus: (a) shallow, narrow (
Special features: (a) elongate projection dorsally on dorsal corona lobe (
This research was supported by Ph.D. thesis supporting grant, Graduate school, Prince of Songkla University to PM. Part of this work was done during a visit of HS to Prince of Songkla University, supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission. We further wish to acknowledge Prof. Dr WH De Smet and two anonymous reviewers for their suggestions and corrections on the manuscript of this paper.