Progamotaenia aemulans, Beveridge & Shamsi, 2009

Beveridge, I. & Shamsi, S., 2009, Revision of the Progamotaenia festiva species complex (Cestoda: Anoplocephalidae) from Australasian marsupials, with the resurrection of P. fellicola (Nybelin, 1917) comb. nov., Zootaxa 1990, pp. 1-29 : 15-17

Progamotaenia aemulans sp. nov.

( Figs 31–37)

Synonyms: P. festiva ( Rudolphi, 1819) sensu Spratt et al. (1991) , Beveridge et al. 1998, Turni and Smales 2001.

Host: Macropus dorsalis (Gray) (Marsupialia: Macropodidae ).

Site in host: bile ducts.

Types: Holotype, Taunton Stn via Dingo, Queensland (23º 39’ 149º 20’), coll. C. Turni, 1996, SAM 29360 (S); paratypes, same data, SAM 29361 (S), BMNH 2008.6.3.9-10 (S).

Etymology: rivalling or equalling, indicating close similarity to P. fellicola .

Material examined: From Macropus dorsalis : Queensland: types; 1 specimen, 15 km N of Marlborough (SAM 28945, AM 495438 ) ; 1 specimen, 48 km E of Moonie ( SAM 29362) ; 1 specimen, Milman ( SAM 21508) ; 2 specimens, Charters Towers ( SAM 29363) ; 1 specimen, Pallamana Stn via Charters Towers ( SAM 22284) ; 1 specimen, Harvest Home Stn via Charters Towers ( SAM 22283) .

Description: Small, elongate worms, 20–80 (41) long, maximum width 2–5 (4) with 84–192 (136) segments in gravid specimens. Scolex 0.88–1.14 (1.01) in diameter, squat, mildly 4–lobed; suckers circular, 0.293 –0.374 (0.333) in diameter. Neck short. First mature segment 40–70th (51). Mature segments craspedote, 1.01–3.04 (2.02) wide, 0.163 –0.374 (0.245) long. Genital atrium small, in posterior part of lateral segment margin; cirrus sac elongate, extending well beyond osmoregulatory canals, 0.228 –0.423 (0.341) long, 0.052 –0.085 (0.062) wide; cirrus unarmed; internal seminal vesicle occupies approx. 2/3–3/4 of volume of cirrus sac, 0.078 –0.247 (0.147) long, 0.013 –0.059 (0.036) wide; elongate external seminal vesicle, covered with glandular cells, 0.078 –0.293 (0.153) long, 0.026 –0.098 (0.064) wide; vas deferens coils medially, dorsal to uterus; testes arranged in anterior half of segment between osmoregulatory canals; space between canals and testis fields; testes arranged in 2 dorso-ventral layers, almost invariably in single band or more rarely in 2 separate groups separated by small space; segments with single band or 2 groups occur in same specimen; in 10 specimens, 20 of 353 segments had testes in 2 groups. Testes 0.046 –0.078 (0.060) in diameter; testis number 78–109 (89). Vagina tubiform, lacking glandular investment, opens to genital atrium posterior to cirrus sac, leads to ovoid to sub-spherical seminal receptacle 0.150 –0.293 (0.194) x 0.098 –0.247 (0.137). Ovary flabelliform, medial to seminal receptacle 0.052 –0.111 (0.80) x 0.046 –0.111 (0.066), fully developed in c. 12 segments; vitellarium reniform, posterior to ovary, 0.078 –0.195 (0.140) x 0.046 –0.130 (0.082); Mehlis’ gland anterior and medial to vitellarium, c. 0.06 in diameter. Uteri paired in each segment, transverse, tubular; early uterus extends from level of ovary to or slightly beyond proximal pole of cirrus sac; developing uterus extends medially and laterally, lateral extensions crossing osmoregulatory canals dorsally; uteri of each segment do not meet in mid-line. Gravid segments 0.228 –0.569 (0.389) long, 1.84–3.82 (3.08) wide. Egg spherical, shell smooth, 0.024 –0.029 (0.026) in diameter; pyriform apparatus conical, terminating in numerous fine filaments at apex; oncosphere 0.010 –0.015 (0.014) in diameter. Osmoregulatory canals paired; ventral canal generally wider than dorsal, medial to it; ventral canal 0.013 –0.033 (0.022) in diameter, dorsal canal 0.010 –0.033 (0.016) in diameter; transverse canal connects ventral canal at posterior margin of each segment; accessory canals absent.

Remarks. This species most closely resembles P. fellicola in overall size and number of segments, in the cirrus sac projecting well into the medulla and in having a distinctive space between the osmoregulatory canals and the testis fields. It is distinguished from all congeners by these characters. The two species, P.aemulans and P. fellicola , scarcely differ in morphological characters, but are quite distinct genetically and are apparently host specific ( Beveridge et al. 2007). The minor differences observable are in scolex diameter, which is 0.65–0.89 mm in P. fellicola , and 0.89–1.14 mm in P. aemulans and in differences in the rate of maturation of segments, the first mature segment appearing between segments 25–45 (34) in P. fellicola and between 40–70 (51) in P. aemulans . These are quite minor morphological differences and alone would scarcely warrant the erection of a new species. However, the genetic differentiation between the two is based on both MEE and DNA sequence data ( Baverstock et al. 1985; Beveridge et al. 2007), leaving little doubt that the cestodes from these two hosts represent distinct species. The material upon which the new species is based came from the same localities as “ M. dorsalis parasite type 1” of Baverstock et al. (1985) and sequences numbers 27 and 28 in Beveridge et al. (2007). The data of Baverstock et al. (1985) suggested that P. fellicola could also occur in M. dorsalis , although the subsequent study of Beveridge et al. (2007) did not confirm this finding. If the data of Baverstock et al. (1985) are correct then it provides compelling evidence that two species are involved as genetic distinction can be maintained within the same host species. A new species is therefore proposed for the material from M. dorsalis and is differentiated from P. fellicola primarily on the basis of scolex size and rate of maturation of the genitalia.

At several of the localities from which this species was collected, M. dorsalis was also parasitised by P. festiva . However, it proved possible to separate the two species quite readily based on testis distribution and the extent to which the cirrus sac extended into the medulla.