Mediorhynchus amini

DESCRIPTION General: (based on 2 males, 4 females) Robust worms, medium sized, trunk cylindrical, thick, with shoulders, posterior third expanded in male, slightly tapering at posterior end in female, aspinose (Figs 9, 11). Main lacunar canals with regular lateral branches. Proboscis conical, truncated, in 2 parts; anterior proboscis with rooted hooks, posterior proboscis wider, with spines; hooks and spines embedded in cuticular papillae when proboscis not fully extended. Roots of hooks flask shaped with rounded larger posterior ends, spines slender with either reduced slender flask shaped roots or basal discs. Proboscis armature similar in both sexes, 22 - 24 rows of 5 - 6 hooks, about same number of irregular rows 5 - 6 spines (Fig. 10). Hook lengths, sequence of 2 longitudinal rows measured from anterior, 7 -; 18, 18; 16.5, 16; 22, 12; 13, 12; 13, 8 long; spines 5, 10 long (Figs 13, 14). Neck unarmed, conical, widest at junction with broader trunk. Proboscis receptacle attached anteriorly at junction between anterior and posterior proboscis, about twice as long as proboscis, with cerebral ganglion near mid region (Fig 16). Lemnisci long, slender, equal, inserted at base of neck (Fig. 9). Genital pore, male and female, terminal. Male: (Based on 2 specimens) Trunk 9.1, 11 mm long, 680, 850 wide. Proboscis 470 long, 370 wide; anterior proboscis 290, posterior proboscis 180. Neck 120 long, 300 wide. Proboscis receptacle 850 long, 320 at widest part. Lemnisci 2800 long, 100 wide. Testes ovoid, tandem, contiguous, in posterior third of trunk; anterior testis 680 long, 305 wide; posterior testis 985 long, 440 wide. Cement glands 8 globular, in cluster, each about 100 wide. Saefftigen’s pouch 600 long (Fig. 15). Female: (based on 4 specimens) Trunk 15 - 22 (18.75) mm long, 670 - 1105 (826) wide. Proboscis 415 - 770 (630) long; anterior proboscis 230 - 380 (350) long, posterior proboscis 185 - 385 (373) long; 315 - 375 (337) wide. Neck 105 - 170 (150) long, 370 - 450 (423) wide. Proboscis receptacle 670 - 750 (707) long, 215 - 220 (217) wide. Lemnisci 7500 (1 measurement) long, 110 wide. Reproductive tract, 500, 600 long (Fig. 17). Eggs ovoid, with concentric shells and thin outer membrane; 49.5 - 56.1 (52.8) long, 26.4 - 29.7 (28.0) wide (Fig. 12).

Figs 9 - 17

COMMENTS: Mediorhynchus amini sp. n. demonstrates the characters of the genus as described by Van Cleave (1916) and discussed by Schmidt & Kuntz (1977) and Amin & Dailey (1998). None of the species of Mediorhynchus described to date have spines with markedly reduced, but typically shaped, roots on the posterior proboscis. Consideration of the key of Schmidt & Kuntz (1977) indicated that M. amini with a proboscis armature of 22 - 24 rows of 5 - 6 hooks, largest hooks 18 - 22 was most similar to M. corcoracis Johnston & Edmonds, 1951 with 22 rows of 5 - 6 hooks, largest hooks 14 - 18. Mediorhynchus amini further differs from M. corcoracis in having about the same number of rows of 5 - 6 spines compared with 40 rows of 4 - 5 spines. Mediorhynchus amini, is a much smaller worm (males 9 - 11, compared with 25 - 33 mm long) with smaller testes (680 - 985 compared with 1600 - 2600) than M. corcoracis (Johnston & Edmonds, 1951). Of the species listed or described by Amin et al. (2008) since the key was developed; namely M. channapettae George & Nadakal, 1984, M. fatimaae, Khan, Bilqees & Muti-ur-Rehman, 2004, M. lophurae Wang, 1966, M. mariae George & Nadakal, 1984, M. mattei, Marchand & Vassiliades, 1982, M. nickoli Khan, Bilqees & Muti-ur-Rehman, 2004, M. rajasthanensis Gupta, 1976 and M. lanius Amin, Ha & Heckman, 2008 only M. lanius with 22 rows of 6 - 7 hooks and 29 rows of 4 - 5 spines has a proboscis hook formula approaching that of M. amini. Mediorhynchus amini, however, further differs from M. lanius in being a smaller worm (males 9 - 11 compared with 28. 75 mm long) and having smaller hooks and spines (hooks 7 - 18, spines 5 - 10 long, compared with hooks 35 - 45, spines 30 - 37 long) (Gupta, 1976; Marchand & Vassiliades, 1982; George & Nadakal, 1984; Khan et al., 2004; Amin et al., 2008). An additional 7 species are known including; M. colluricinclae Smales, 2002, (proboscis armature 26 - 28 rows of 7 - 8 hooks and 36 - 38 rows of 3 - 8 spines), M. cisticolae Smales, 2011 (proboscis armature 20 - 22 rows of 5 - 6 hooks and 26 rows of 2 - 3 spines), M. gibsoni Bilqees, Khan, Khatoon & Khatoon, 2007 (proboscis armature 25 rows of 8 - 12 hooks and 10 rows of 8 - 16 spines), M. spinaepaucitas Smales, 2011 (proboscis armature 20 - 22 rows of 4 - 5 hooks and 30 rows of 4 - 5 spines), and M. turdi Smales, 2011 (proboscis armature 24 - 28 rows of 7 - 9 hooks and 35 - 40 rows of 3 - 5 spines) (Bilqees et al., 2007; Smales, 2011). None of the above species have proboscis armature similar to that of M. amini. Mediorhynchus peruensis (proboscis armature 14 - 16 rows of 4 - 6 hooks and a total of 104 - 120 spines) (Moya et al., 2011) is the only species to have been described from South America since Amin et al. (2008) reviewed the genus. The proboscis armature of M. amini (22 - 24 rows of 5 - 6 hooks and 5 - 6 spines), however, does not resemble that of M. peruensis (Moya et al., 2011).

ETYMOLOGY: The species is named to recognize the contribution of Dr Omar Amin to acanthocephalan taxonomy.

MATERIAL EXAMINED: MHNG-INVE- 84833; holotype male, small intestine, Myiarchus ferox (Gmelin, 1789) (Tyrannidae), Paraguay, Route Filadelfia-Teniente, Montana 8 km, 23.11.1993. – MHNG-INVE- 84844; paratype (allotype) female, small intestine, Myiarchus ferox (Gmelin, 1789), Paraguay, Filadelfia-Teniente, Montana 8 km, 23.11.1993. – MHNG-INVE- 38411; 1 male, 2 females, 7 pieces of female, paratypes, small intestine, Myiarchus ferox (Gmelin, 1789), Paraguay, Filadelfia-Teniente, Montana 8 km, 23.11.1993. – MHNG-INVE- 38434; 1 female voucher specimen, small intestine, Myiarchus ferox (Gmelin, 1789), Carapegua, 10.10.1982.