Gieysztoria hymanae ( Marcus 1946 ) Luther 1955

Brusa, Francisco, Damborenea, Cristina & Noreña, Carolina, 2008, “ Dalyellioida ” (Platyhelminthes, Rhabdocoela) from the Río de la Plata estuary in Argentina, with the description of two new species of Gieysztoria, Zootaxa 1861, pp. 1-16 : 10

Gieysztoria hymanae ( Marcus 1946) Luther 1955

Figures 5 , 7 A, B

Material and locality. Live specimens studied by squash method. Two specimens sectioned sagittally MLP 5359. Atalaya (2­8­01; 27­1­04). This is the first record of the species in Argentina.

Comments. The specimens studied here are similar to those described by Marcus (1946) from Brazil. However, subtle differences between both populations can be observed. Fixed studied specimens were 250– 290 µm long, with the pharynx 85 µm long and 57 µm wide.Within the male genital system, Marcus (1946) mentioned that the vasa deferentia arose from the rostral region of the testes and the seminal vesicle was small, in contrast with the morphology observed in our materials in which the vasa deferentia issue from the medial­posterior region of testes, first extending anteriorly and then merging together before entering a large seminal vesicle at its medial region (figure 5B).

The morphology and size of the stylet agree with Marcus´description ( Marcus 1946). The stylet was 60 µm in total length, with a belt with two rings joined by several bridges (figure 5A). It bears four thick spines with three groups of 4–6 thin spines interspersed, and two thin spines on each side between the thick lateral spines and the opening of the belt, all arising from the distal ring in a single row.

In specimens observed in vivo, spermatozoids are found in the peripheral region of the testes, while none are present in the central region.

The morphology of ovary, seminal receptacle and vitellaria agree with Marcus´descriptions. According to Marcus (1946), the bursa copulatrix of some specimens has a pseudocuticle formed by the basilar walls of the epithelium, which was not observed in our material. On the other hand, a sinuosity was observed in the peduncle of the bursa, and a pair of lateral projections in the main region of the bursa (figure 5C). These were very evident in our material, but are not mentioned in the original description of this species.

Previously known distribution. Brazil: São Paulo, a stream near Pirajussára River and a marsh in Brooklyn Paulista ( Marcus 1946). This last locality where the material was originally collected has disappeared because of the expansion of São Paulo city. It is worth noting that this is the first record of this species since its description.

Figures

FIGURE 5. Gieysztoria hymanae. A, detail of the copulatory apparatus. B, general view in vivo. C, sagittal reconstruction. Scale A – C: 100 m. For abbreviations see Figure 8.

FIGURE 7. Microphotographs of sagittal sections of Gieysztoria hymanae. A, general view. B, detail of genital region. Microphotograps of Gieysztoria atalaya sp. n. Sagittal sections. C, general view. D, detail of digestive system. E, detail of genital region. F: horizontal section of stylet region. Scale A – F: 50 m. For abbreviations see Figure 8.