Turbellarian taxonomic database

Isodiametridae Haplocelis Notes

Hooge M.D. & Rocha C.E.F. 2006 (citation) - P. 47 "Reassignment of the genera Haplocelis Dörjes, 1968 and 
Otocelis Diesing, 1862 (Otocelididae) to the Family Isodiametridae

Members of the family Otocelididae diagnostically have their vagina positioned posterior to the male 
copulatory organ (Westblad 1948). Hooge and Tyler (2005) showed this to be a homoplasious character that 
occurs in several unrelated lineages, a conclusion supported by molecular sequence analysis (Hooge et al. 
2002) and the presence of more than one type of sperm morphology in the family (Petrov et al. 2004). In fact, 
many of the 20 Otocelididae species have no similarity to each other apart from the relative positions of the 
vagina and male copulatory organ (see Tyler et al. 2006), and as such, five of the eight genera are monotypic. 
For many species, the diagnostic characters that would place them in a valid acoel family are not yet known.
Two genera of Otocelididae, Haplocelis and Otocelis, contain well-described species with easily discerned 
taxonomic characters. The genus Haplocelis is monotypic (H. dichona), while Otocelis contains six species: O. 
erinae sp. nov., O. luteola (Kozloff, 1965), O. phycophilus Ehlers and Dörjes, 1979, O. rubropunctata 
(Schmidt, 1852), O. sachalinensis Ivanov, 1952, O. sandara Hooge and Tyler, 2003, and O. westbladi Ax, 1959. 
We  have examined the type material of Otocelis westbladi, fluorescence preparations and histological sections 
of O. erinae and H. dichona, and reviewed the relevant literature on the other species of Otocelis, 
particularly for that of the type species, O. rubropunctata (see Dörjes 1968, Kozloff 1998). Our investigation 
reveals that species of Haplocelis and Otocelis possess the diagnostic features of the Isodiametridae—a 
muscular, isodiametric penis, with non-anastomosing longitudinal muscles, that is invaginated into a muscular 
seminal vesicle (Fig. 26B). We herein reassign the genera Haplocelis and Otocelis to the family 
One of these species, Otocelis sandara, remains problematic, and is likely to be unrelated to the other 
Otocelis species.  We cannot confirm from the material available to us that O. sandara possesses an 
isodiametrid-type penis. In an 18S rDNA sequence analysis of acoels, the sequence of O. sandara did not group 
with Isodiametridae taxa (Hooge et al. 2002). Finally, while the sperm axonemes of O. sandara have the same 9 
+ 2 microtubule configuration found in the Isodiametridae, other microtubules in their sperm have a 
configuration that differs from the isodiametrids (Petrov et al. 2004). For now, we choose to leave O. sandara 
in the genus until more information can be gathered on its true phylogenetic position."

Notes from synonyms

Notes for Otocelididae Haplocelis

Dorjes J 1968 (citation)- sets up this genus for Marcus' species Otocelis dichona (Marcus 1954).
	p 102 definition, lists 1 species- type H. dichona.
Ehlers U, Doerjes J 1979 (citation)- in comparison p 34, discussion p 48.

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