Gordius gonzalezi, Schmidt-Rhaesa, Andreas & Martínez, Jesús, 2016

Schmidt-Rhaesa, Andreas & Martínez, Jesús, 2016, Gordius gonzalezi, a new species of horsehair worms (Nematomorpha) from Spain, Zootaxa 4103 (1), pp. 63-67 : 64-66

Gordius gonzalezi n. sp.

Type locality. Guijo de Sta. Bárbara. Comarca de La Vera, arroyo de la Gazapierna. Sierra de los Tormantos, 759 m, Cáceres, Extremadura, Spain, 40°9´0.57´´N / 5°40´0.30´´W.

Holotype. One male, Zoological Museum Hamburg ZMH V13368

Paratype. One male, Zoological Museum Hamburg ZMH V13369

Etymology. The species name “ gonzalezi ” honours Prof. Dr. Marcos González from the Universidad de Santiago de Compostela, advisor of the second author.

Further information. Collected on July 23, 2010 in a light trap together with a cricket, which might have been the host. Collected by J. Martínez and M. González.

Description. The specimens are 235 mm (holotype) and 220 mm (paratype) long, and both measure 1 mm in diameter. They are a medium shade of brown in color and have a white cap and a dark collar at the anterior end, as is usual in the genus Gordius . There is a faint dorsal and a ventral longitudinal line of darker coloration, and white spots are present on the cuticle.

SEM investigation shows that the cuticle forms folds or cords of irregular structure ( Fig. 1 C). These cords have alternating broader and narrower regions and they are arranged perpendicular to the longitudinal axis of the worm. Under higher magnification their surface is rough and composed of fibres ( Fig. 1 D, E). Abundant spine-like extensions are present on the cuticle, estimated to be a few micrometers in length ( Fig. 1 A–D). They occur on almost the entire cuticle with an irregular distribution ( Fig. 1 D), but in a regular pattern on either the ventral or the dorsal side ( Fig. 1 B, C). There they occur in two lines on both sides of a 60 µm broad band of cuticle that is devoid of spines ( Fig. 1 B, C). The region between the lines of spines is structured into polygonal structures, mostly hexagons of irregular shape and size of their sides. The spines have a diameter of about 5µm on their base and decrease towards their apex ( Fig. 1 E, F). The spines resemble the cuticular fine structure and have a fibrillary appearance rather than a smooth surface.

The posterior end has a parabolic postcloacal crescent that extends onto the tail lobes ( Fig. 2 A, C). The cloacal opening could not be observed and is probably covered by dirt or other material. The spine-like extensions described above extend in the posterior end onto the outer side of the tail lobes ( Fig. 2 A–C). In the holotype, further spines are present on the inner side of the tail lobes ( Fig. 2 C-E). These spines are more slender than the “spine-like extensions” and are curved apically ( Fig. 2 E). They were not observed in the paratype.

Remarks. In the majority of freshwater nematomorphs the cuticle is formed into elevated substructures called areoles. These may be flat polygonal structures or may be more elevated and more diverse in structure. In the genus Gordius , only flat areoles are present or the cuticle is smooth. The observed cords on the cuticle might represent strongly modified areoles, because of their alternating diameter. There is some resemblance to the cuticular pattern as described for G. plicatissimus , figured by SEM for an undescribed species named “ cf. plicatissimus ” by Schmidt-Rhaesa (2010). The fibrous substructure of the cuticle has been observed by SEM investigation of several specimens (see Schmidt-Rhaesa 2010) and it is still not clear if this represents the native surface of the cuticle or if there has been some ageing or abrasion of a cuticular surface layer that creates this fibrous character.

Structures described here as spines are present on few other Gordius species. Spine-like structures have been reported on two Asian species (from Uzbekistan and Tajikistan), G. bivittatus and G. t e s t a c eu s, both described by Kirjanova (1950), and on two South American species, G. deltaensis and G. spinosus , both described by De Miralles & De Villalobos (1996a, b). In all four species, the documentation is not optimal, but the presence of spines is reported as being scarce and a regular arrangement into lines was never reported. Therefore we assume that the specimens represent a new species of the genus Gordius .

Figures

FIGURE 1. Gordius gonzalezi, n. sp., showing cuticular structure. A. Overview on the cuticle of the holotype. B. Magnification showing the distribution of spine-like extensions into two lines (arrows). C. In the paratype, the lines (arrows) are present, but not as obvious as in the holotype. D. Irregular distribution of spine-like extensions on the regions of the cuticle other than the ventral side. E, F. Magnification of spine-like extensions in the holotype (E) and the paratype (F).

FIGURE 2. Gordius gonzalezi, n. sp., ventral views on the posterior end. A. Posterior end of the paratype with postcloacal crescent (pcc); cloacal opening is not visible. Marked oval area indicates location of structures shown in B. B. Spine-like extensions on the outer side of the tail lobes. C. Posterior end of the holotype, labelled as in A. Marked area shows location of spines on the inner side of the tail lobes. D. Spines on the inner side of the tail lobes as marked in C. D. Magnification of slender and curved spines.