Haplocelis dichona ( Marcus, 1954 )

Hooge, Matthew D. & Rocha, Carlos E. F., 2006, Acoela (Acoelomorpha) from the northern beaches of the state of São Paulo, Brazil, and a systematic revision of the family Otocelididae, Zootaxa 1335, pp. 1-50 : 37

Haplocelis dichona ( Marcus, 1954)

( Fig. 24 )

Otocelis dichona: Marcus 1954 (p 429).

Haplocelis dichone: Dörjes 1968 (p 102).

Haplocelis dichona: Dörjes and Karling 1975 (p 180); Ehlers and Dörjes 1979 (p 34).

Material. MZUSP PL. 192, one set of 1.5-µm-thick serial sagittal sections of epoxyembedded specimen stained with toluidine blue; living specimens in squeeze preparation; whole mounts for fluorescence imaging of musculature.

Locality. Praia São Francisco, São Sebastião, São Paulo, Brazil, from intertidal coarse sand (23°45’45.1”S, 45°24’27.1”W).

Description. Living specimens ~ 950 m long and ~ 250 m wide ( Fig. 24 A). Body without coloration in transmitted light. Rhabdoids scattered across body. Mouth opening on ventral surface, middle of body.

Ovaries and testes paired. Common gonopore terminal at posterior end; opens dorsally to vagina and ventrally to male copulatory organ. Vagina leads to bursa with one or two winding bursal nozzles ( Fig. 24 B). Long, coiled, muscular, glandular penis invaginated into muscular seminal vesicle containing sperm ( Fig. 24 B).

Remarks. This species can be distinguished from all other species of acoels by its winding curlicue bursal nozzle and penis. Marcus (1954) described his specimens of H. dichona , collected from Ilhabela, as having two bursal nozzles; however, all of our specimens possessed only a single nozzle.

Figures

FIGURE 24. Haplocelis dichona; photomicrographs of living specimen. A. Dorsal view of squeezed specimen. B. Copulatory organs.