Collotheca algicola (Hudson),

Meksuwan, Phuripong, Pholpunthin, Pornsilp & Segers, Hendrik, 2011, Diversity of sessile rotifers (Gnesiotrocha, Monogononta, Rotifera) in Thale Noi Lake, Thailand, Zootaxa 2997, pp. 1-18: 6-7

publication ID 10.5281/zenodo.207999

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Collotheca algicola (Hudson)


Collotheca algicola (Hudson)  ( Figs 2View FIGURES 2 A – 2 I d – 2 f) and Collotheca ambigua (Hudson)  ( Figs 2View FIGURES 2 A – 2 I g – 2 i)

We tentatively consider these two taxa as separate species, even though the most recent checklist of the group considers C. algicola (Hudson)  a synonym of C. ambigua (Hudson) (Segers 2007)  . Our material matches well the original description of both species ( Hudson & Gosse 1886). We found three morphological characters that distinguish the two ( Table 3):

● the dorso-lateral corona lobes are more prominent in C. algicola  than in C. ambigua  ● the separation between foot and trunk is more pronounced in C. ambigua  than in C. algicola  ; ● they differ significantly in size, with C. ambigua  being the larger of the two.

Species Characters C. algicola (Hudson)  C. ambigua (Hudson)  C. campanulata  C. trilobata (Collins) 


Corona lobes Five Five Five Three

Separation between foot and Less distinct Distinct Distinct Distinct


That the relatively small C. algicola  is not a young, immature and therefore not fully grown specimen is indicated by the accumulation of excretophores ( Fig. 2View FIGURES 2 A – 2 I e), a phenomenon which is commonly observed in old specimens of many species of Collotheca  , but not in young ones ( Koste 1978). We nevertheless refrain from concluding on the matter as we observed only low numbers of both of the taxa concerned. In particular, we found only a single specimen of what we identify as C. algicola  .

Collotheca ambigua  could also be confused with C. campanulata (Dobie)  ( Figs 3 a – 3View FIGURES 3 A – 3 F c) or C. trilobata (Collins)  ( Figs 3View FIGURES 3 A – 3 F d – 3 f). However, they can be distinguished from C. campanulata  by having a deeper and wider sinus separating the ventral corona lobes (compare Fig. 2View FIGURES 2 A – 2 I i and 3 c), and by shape of its relatively narrower dorsal corona (compare Figs 2View FIGURES 2 A – 2 I h – 2 i and 3 b – 3 c). C. ambigua  can further be separated from C. trilobata  by having small dorso-lateral corona lobes (absent in C. trilobata  ) and relatively small ventro-lateral corona lobes when compared to C. trilobata  (compare Figs 2View FIGURES 2 A – 2 I h – 2 i and 3 e – 3 f; see also Table 3).

TABLE 3. Comparison of diagnostic features of four species of Collotheca (after Koste, 1978)

  Gradually narrow onto Gradually narrow the tip end onto the tip end Rather parallel with rounded tip