Gyrodactylus bullatarudis Turnbull, 1956

Richards, G. R., Veltkamp, C. J. & Chubb, J. C., 2000, Di erentiation of Gyrodactylus bullatarudis Turnbull, 1956 and G. rasini Lucky, 1973 (Monogenea) with reassignment of Gyrodactylus bullatarudis Turnbull, 1956 sensu Harris (1986) to G. rasini, Journal of Natural History 34 (3), pp. 341-353 : 347-349

Gyrodactylus bullatarudis Turnbull, 1956

( Figures 3B , 6 , 7 , 8A ±C, 9C, D)

Voucher specimens: The Natural History Museum, London (BM(NH) 1994.11.24.1 ±6).

Host: Poecilia reticulata imported into UK from ornamental ®sh farms in Singapore. Site: external surface, anterior of ®sh, particularly head and opercula regions. A`very small’ species according to scheme of Harris (1985). Body length of moderately contracted living specimens under 400 m m. Anterior of the pharynx (see Kritsky, 1971) consisted of eight cells arranged in a ring which were fused to each other along their lateral borders. The anterior and posterior pharyngeal bulbs of ¯attened specimens were of approximately equal width. Pharynx measurements were not taken. Measurements of attachment hooks and bars are given in table 1. The most distinctive elements were the connecting bars and the marginal hooks (see ®gures 6 and 7). The ventral bar had relatively long antero-lateral processes and a membrane which tapered slightly posteriorly. The dorsal bar had an obvious notch at the mid point with two swellings on either side (®gure 6). The marginal hook blade was bent at an angle of about 90ss with a straight point not extending as far as the toe. The cirrus had one large spine with the base on each side curved behind and joined (®gure 3B) and a single row of four to seven small spines (®gure 8).

Gyrodactylus bullatarudis from P. reticulata infected and reproduced on seven Xiphophorus hybrids. An increasing G. bullatarudis infrapopulation caused the death of one Xiphophorus , but six infrapopulations went extinct between one and ten days af ter infection (®gure 10).

Figures

FIG. 3. Schematic representations of the large cirrus spines of: (A) G. rasini from Xiphophorus hybrids; and (B) that of G. bullatarudis from P. reticulata. The three-dimensional curvature of these structures is not shown. The main di€erence between the two species is that each side of the base of the large cirrus spine of G. bullatarudis appears to join to form a ring whereas those of the large spine of G. rasini diverge and do not appear to join.

FIG. 6. Attachment hooks and bars of G. bullatarudis from a Poecilia reticulata. Note the shorter ventral bar processes and di€erent marginal hook sickle morphology in comparison to ®gure 1.

FIG. 7. Marginal hook of a G. bullatarudis detached from a P. reticulata. Note the absence of curvature near the point (arrowed). (1 marker= 1 mm).

FIG. 8. (A±C) Cirrus armature of G. bullatarudis from P. reticulata ®xed and mounted in ammonium picrate±glycerin, viewed with a phase contrast microscope and drawn with the aid of a camera lucida.