Gieysztoria iberica, Steenkiste, Niels Van, Tessens, Bart, Krznaric, Kathleen & Artois, Tom, 2011

Steenkiste, Niels Van, Tessens, Bart, Krznaric, Kathleen & Artois, Tom, 2011, Dalytyphloplanida (Platyhelminthes: Rhabdocoela) from Andalusia, Spain, with the description of four new species, Zootaxa 2791, pp. 1-29 : 23-24

Gieysztoria iberica n. sp.

( Figs. 9 A–9C)

Localities. Doñana National Park, Provincia de Huelva, Spain (37°03’00”N, 6°16’42”W). Veta de Rivera: creek full of vegetation with a high diversity of macrobenthos (18/03/2008) (type locality).

Doñana National Park, Provincia de Huelva, Spain (36°54’50”N, 6°17’48”W). La Montaña del Rio: green algae in shallow brackish pool (29/03/2008; 06/04/2008).

Material. Observations on several live animals. Three whole mounts, one of which designated holotype ( MNCN, no. 4.01/56), the other two paratype (HU, nos. 427–428). Two serially-sectioned specimens of rather poor quality.

Etymology. The species epithet refers to Iberia (Gr.: Iβηρία), a toponym used by the Ancient Greeks to designate the Iberian Peninsula (Lat.: Paeninsula Iberica ), currently occupied by Spain and Portugal.

Description. Animals measure ± 0.7 mm and have a reddish-brown colour (parenchymatous). Two eyes are present. The pharynx doliiformis is about 1/3–1/4 of the body length long. As far as could be observed in the serial sections, the internal organization of the genital system seems to be similar to that of other species of Gieysztoria (see Luther 1955).

Two testes were observed in the live animals and are situated in the caudal body half. The ovary lies on the right side. The vitellaria are smooth without protrusions (papillae) and distally merge near the ovary.

The relatively elongated, pyriform prostate vesicle is 200–260 µm long (x = 225 µm; n = 3), when measured on the whole mounts, and surrounded by well-developed circular muscles. The copulatory organ is situated on the left side of the body. Distally it ends in a straight stylet, which is 95–108 µm long (x = 102 µm; n = 3). The exceptionally long, half open girdle has a length of 76–87 µm (x = 82 µm; n = 3) and consists of a branching network of lengthwise-orientated fibres. Proximally, the bundle of fibres fans out with straight or curved tips. Distally the stylet bears a half open ring of 14–16 spines. The distal parts of the outer lateral spines bend more inwards than those of the inner spines. The outer spines (± 10 µm long) are also shorter than the inner ones (17–20 µm long). The proximal parts of the spines are firmly fixed on the curved girdle rim. The ratio girdle/entire stylet is ± 0.8.

A muscular bursa is situated between the male and female system and ends in the common genital atrium. Both circular and longitudinal muscles surround the bursa. The female duct was not clearly visible in the serial sections, but conspicuous glandular tissue and a sperm-filled seminal receptacle indicate its presence near the ovary. Vitellaria do not have digitiform protuberances. The uterus often contains a single egg.

Diagnosis. Species of Gieysztoria with a stylet consisting of a 76–87 µm-long girdle composed of a branching network of lengthwise-orientated fibres and a distal half open ring of 14–16 spines. Outer spines shorter and bending more inwards. Ratio girdle/entire stylet ± 0.8.

Discussion. Gieysztoria Ruebush and Hayes, 1939 is a cosmopolitan and species-rich taxon. Based on stylet morphology, Luther (1955) split the genus into the “Aequales”, having stylets with equal spines, and the “Inaequales”, having stylets with spines of different shapes and sizes. The latter group is subdivided in the “Fenestratae” (F) (with round to oval openings in the girdle), the “Radiata” (R) (stylet radially symmetric without openings in the girdle) and the “Aberrantes” (A) (irregular construction of the stylet). A recent phylogenetic analysis based on morphological characters of a number of taxa belonging to both “Aequales” and “Inaequales” (see Brusa et al. 2003), confirms the monophyly of the genus, but also shows that the “Aequales” are interspersed among the “Inaequales”, suggesting these groups do not reflect phylogenetic relationships. A thorough cladistical analysis of the Dalyelliidae Graff, 1908 and the taxon Gieysztoria in particular should further clarify the position of its representatives.

When following Luther’s classification, Gieysztoria iberica n. sp. can be placed in the “Inaequales”, subgroup “Radiata”, because of the difference in size and shape between the outer and inner spines of the stylet and the lack of an opening in the girdle. It is, however, the relative length of the girdle that makes this taxon unique within Gieysztoria . Only nine taxa of Gieysztoria have a girdle, which is at least as long as the length of the spines. Four belong to the “Aequales”: G. japonica ( Okugawa, 1930) Ruebush & Hayes, 1939 , G. k n i p o v i c i ( Beklemischew, 1953) Luther, 1955, G. taurica ( Nasonov, 1923) Ruebush & Hayes, 1939 and G. rubra subsp. caucasica ( Nasonov, 1919) Ruebush & Hayes, 1939; five are “Inaequales”: G. f a u b e l i Artois et al., 2004 (R), G. beltrani ( Gieysztor, 1931) Ruebush & Hayes, 1939 (F), G. pavimentata ( Beklemischew, 1926) Ruebush & Hayes, 1939 (F), G. sasa Damborenea et al., 2005 (A) and G. virgulifera ( Plotnikow, 1906) Ruebush & Hayes, 1939 (F). However, none of them has a girdle of this impressive size, clearly distinguishing G. iberica n. sp. from all other taxa within Gieysztoria .

Figures

FIGURE 9. Gieysztoria iberica n. sp. (A) Habitus from a live animal. (B – C) Stylet from the holotype.