Mediorhynchus micracanthus (Rudolphi, 1819)

Smales, L. R., 2014, Acanthocephala, including the descriptions of two new species of Mediorhynchus (Gigantorhynchidae) from birds from Paraguay, South America, Revue suisse de Zoologie 121 (2), pp. 261-276 : 266-269

Mediorhynchus micracanthus (Rudolphi, 1819)

Figs 2-8

MATERIAL EXAMINED: MHNG-INVE-38383 male, small intestine Paroaria capitata (d’Orbigny & Lafresne, 1837) (Emberezidae) , Paraguay, Rio Aguary-Guazu , 22.10.1987. – MHNG-INVE-38391 , INVE-38382 ; 1 male, 2 pieces females, small intestine, Molothrus bonariensis (Gmelin, 1789) (Icteridae) , Paraguay, Transchaco 293, 03.11.1988. – MHNG-INVE- 3851 ; 3 females, small intestine, Psarocolius decumanus (Pallas, 1769) (Icteridae) , Paraguay, Estrellas , 16.10.1979. – MHNG-INVE-38394 ; 2 pieces male, 1 female, small intestine, undetermined bird, Paraguay, Transchaco 293, 04.11.1988.

REVISED DESCRIPTION

General: (based on 1 male, 3 females and 5 pieces males, 4 pieces females, including anterior and posterior ends) Robust worms, medium sized, trunk cylindrical, thick, with heavy shoulders, slightly tapering at posterior end, aspinose (Figs 2, 5). Main lacunar canals with regular lateral branches. Proboscis conical, truncated, in 2 parts; anterior proboscis with rooted hooks, posterior proboscis wider with rootless spines (Fig 5). Hook roots flask shaped with rounded larger posterior ends with scalloped outer edges, spines slender with stubby basal discs (Fig. 3). Proboscis armature similar in both sexes, 16-18 rows of 4-5 hooks, 2-3 spines. Neck unarmed, conical, widest at junction with broader trunk. Proboscis receptacle attached anteriorly at junction between anterior and posterior proboscis, with cerebral ganglion near mid region, about twice as long as proboscis (Fig. 7). Lemnisci long, slender, equal, inserted at base of neck (Fig. 2). Genital pore male sub terminal; female terminal without papillae.

Male: (based on 1 complete specimen, 1 anterior end, 2 posterior ends) Trunk 12.5 mm long 0.5 mm wide. Proboscis 560, 460 long, 490, 280 wide; anterior proboscis 360, 295 long, posterior proboscis 200, 165 long. Hook lengths, sequence of 1 longitudinal row measured from anterior 10, 11, 20, 20, 15; spines 5 long. Neck 80, 140 long, 480, 300 wide. Proboscis receptacle 950, 490 long, 330 wide. Lemnisci extend to anterior testis, 2890, 3560 long 110 wide. Testes oblong, tandem, contiguous, in mid third of trunk; anterior testis 1660, 1870 long, 700, 595, wide; posterior testis 2000, 1615 long, 750, 500 wide. Cement glands 8 globular, in cluster, each gland 268- 350 (302) wide. Saefftigen’s pouch 1000, 765, 500 long (Fig. 4).

Female: (based on 3 complete specimens, 2 anterior ends) Trunk 20-21 (20.33) mm long, 1360-1530 (1457) wide. Proboscis 350, 390 long, 335 wide; anterior proboscis 240, 280, posterior proboscis 110, 120. Hook lengths, sequence of 1 longitudinal row measured from anterior 20.5, 24, 22, 24; spines 5-7 long. Neck 120, 200 long, 535, 470 wide. Proboscisreceptacle 670-871 (737) long, 210-510 (360) wide. Lemnisci 2250 - 5610 (3583) long, 100, 200 wide. Reproductive tract, 500, 550 long, about 25-26% trunk length (Fig. 8). Eggs ovoid, with concentric shells and thinoutermembrane, 47.6-59.4 (53.6) long, 26.4-39.6 (32.8) wide (Fig. 6).

COMMENTS: A more comprehensive description of M. micracanthus is given here because the most recent redescription ( Petrochenko, 1958) is rather brief. The proboscis armature and hook size of the specimens from Paraguay, 16-18 longitudinal rows of 4-5 hooks up to 25 long, and 2- 3 spines is consistent with the description of the proboscis of M. micracanthus as given by Petrochenko (1958, fig. 136), although the figure is difficult to interpret. Further, the specimens, total hook number 64-90, fall out as M. micracanthus , total hook number 64-96, in the key of Schmidt & Kuntz (1977). The descriptions of the proboscis armature of M. micracanthus and its synonym, M. armenicus Petrochenko, 1958 are given in spiral rows by Petrochenko (1958). An analysis by Schmidt & Kuntz (1977) demonstrated that although the proboscis hook patterns of species of Mediorhynchus may appear irregular basically they are arranged in longitudinal rows. Accordingly they reexamined all known species and converted the hook formulae to longitudinal rows. This revealed the synonymy of M. micracanthus and M. armenicus to which was assigned the hook formula of 20-24 rows of 3-4 hooks. Therefore the specimens from Paraguay can be identified as M. micracanthus . The morphology and morphometrics of the specimens from Paraguay were also consistent with those of M. micracanthus syn M. armenicus ( Petrochenko, 1958) ( Table 2 ).

The geographical distribution of M. micracanthus in South America can now, therefore, be extended from Brazil to Paraguay and the host range to include Paroaria capitata , Molothrus bonariensis , Psarocolius decumanus as well as the undetermined bird species.