Tetrancistrum nasonis Young, 1967

Kritsky, Delane C., Galli, Paolo & Tingbao, Yang, 2007, Dactylogyrids (Monogenoidea) parasitizing the gills of spinefoots (Teleostei, Siganidae): revision of Tetrancistrum Goto and Kikuchi, 1917, with descriptions of two new species from Siganus spp. of the Red Sea and Celebes, Journal of Natural History 41 (25 - 28), pp. 1513-1551 : 1536-1537

Tetrancistrum nasonis Young, 1967

( Figures 46–51 )

Synonym: Pseudancyrocephalus duplicatus Yamaguti, 1968 .

Measurements. Dimensions of specimens from Hawaii follow in brackets those from Australia. Body 1177 (831–1426; n 54) [1730 (1622–1963; n 55)] long; greatest width 388 (211–535; n 54) [412 (334–517; n 56)] in posterior trunk at level of gonads. Haptor 189 (109–150; n 53) [168 (148–190; n 55)] long, 180 (110–148; n 53) [209 (173–256; n 54)] wide. Pharynx 65 (43–78; n 54) [75 (65–96; n 56)] wide. Copulatory complex 92 (82–99; n 53) [104 (98–111; n 56)] long. Ventral anchor 148 (146–151; n 53) [153 (143–165; n 56)] long; base 43 (40–46; n 53) [56 (53–62; n 54)] wide. Dorsal anchor 134 (132–137; n 53) [139 (125–147; n 56)] long; base 28 (24–31; n 53) [35 (33–38; n 56)] wide. Ventral bar 25 (23–27; n 53) [33 (31–36; n 53)] long; dorsal bar 46 (44–48; n 53) [50 (46–53; n 55)] long. Hook 14 (13–15; n 58) [13–14 (n 52)] long. Germarium 100 (80–111; n 54) [139 (125–154; n 55)] long, 202 (143–258; n 54) [149 (113–173; n 55)] wide; testis 141 (119–181; n 54) [214 (187–243; n 56)] long, 202 (143–258; n 54) [188 (157–227; n 56)] wide.

Type host and locality. Naso annulatus: Heron Island , Queensland, Australia .

Site of infestation. Gills.

Specimens studied. Holotype ( USNPC 61298 ); four paratypes ( USNPC 61299 ) . Holotype, five paratypes of Pseudancyrocephalus duplicatus ( USNPC 63644 ) .

Preυious records. Naso annulatus: Heron Island, Australia ( Young 1967; Lester and Sewell, 1989). N. unicornis : Hawaii as Pseudancyrocephalus duplicatus by Yamaguti (1968); Irabu Island, Okinawa Prefecture, Japan as P. duplicatus by Machida (1979).

Remarks. Young (1967) described the gut of T. nasonis ‘‘without lateral diverticula, united posterior to testis by two or three transverse crura which are connected medially by longitudinal crura’’, while Yamaguti (1968) showed them terminating separately and blindly in the posterior trunk of Pseudancyrocephalus duplicatus . However, the intestinal caeca of the available type specimens of both T. nasonis and P. duplicatus were not visible, and confirmation of their configurations could not be determined. In addition, Yamaguti (1968) confused the dorsoventral positions of the anchors and bars in his description of P. duplicatus , as shown by his references to the ventral anchor with the ‘‘ventral root (superficial root)’’ reduced to a ‘‘stumpy rod’’ and to the dorsal anchor with the ‘‘ventral root (deep root)’’ a little shorter than the ‘‘dorsal root (superficial root)’’. Finally, the specimens of P. dupicatus are somewhat larger in most respects than those of T. nasonis , which are heavily compressed. Nonetheless, the two species are clear synonyms based on the comparative morphology of the copulatory complex and haptoral sclerites, with T. nasonis Young, 1967 having priority.

Figures

Figures 46–51. Copulatory complex and haptoral sclerites of Tetrancistrum nasonis Young, 1967 comb. n. from the whitemargin unicornfish, Naso annulatus, Australia. (46) Copulatory complex (ventral view). (47) Ventral bar. (48) Dorsal bar. (49) Ventral anchor. (50) Hook. (51) Dorsal anchor. Scale bar: 30 Mm.