Aploparaksis (Aploparaksis) shigini Bondarenko and Kontrimavichus, 2006

Bondarenko, Svetlana & Kontrimavichus, Vytautas, 2006, Cestodes of the genus Aploparaksis Clerc, 1903 (Cyclophyllidea, Aploparaksidae) reported from gulls, with a description of new species, Journal of Natural History 40 (47 - 48), pp. 2589-2610 : 2597-2602

Aploparaksis (Aploparaksis) shigini Bondarenko and Kontrimavichus n. sp.

( Figures 5–7 )

Type host. Larus ridibundus Linnaeus.

Other hosts. Larus canus Linnaeus , L. delawarensis Ord , Sterna hirundo Linnaeus , Larus sp.

Site . Small intestine.

Type locality. The Rybinsk Reservoir (Zabolotnoe, Yaroslavlskaya oblast’, Russia) .

Other localities. The Urals, Siberia (Yakutiya, the Ob’ River , the Kolyma River and Primorskiy Kray, Russia), North America (Madison, Wisconsin, USA) .

Type specimens. Holotype: INPA, Moscow No 903, from L. ridibundus , the Rybinsk Reservoir. Paratypes: INPA, Moscow No. 904, from L. ridibundus , the Rybinsk reservoir, No. 905, the Kolyma River, Russia; the Natural History Museum, London (BMNH), No. 2004.7.28.3, from L. ridibundus , the Rybinsk reservoir, No. 2004.7.28.4, from L. ridibundus from the Kolyma River, Siberia, No. 2004.7.28.5 from L. ridibundus , from the Ob’ River, Siberia; USNPC, No. 94901, from L. ridibundus from the Rybinsk reservoir, No. 94902, from L. ridibundus from the Kolyma River, Siberia, No. 94903 (2 slides), from L. delawarensis from Madison, Wisconsin, USA. The remaining paratypes are in the collection of S. Bondarenko.

Etymology. The new species is named in memory of Dr A.A. Shigin who was the first to describe specimens from L. ridibundus from the Rybinsk reservoir and kindly provided part of them for our investigation.

Material studied. This study is based on both the original material collected from gulls of Siberia, specimens from museum collections (INPA, Moscow), and specimens collected by Dr. A. Shigin in the Rybinsk reservoir from L. ridibundus No. 107, 15 May 1953 (Zabolotnoe, Jaroslavskaya Oblast’, Russia) and fragments of one specimen collected by Dr. Z. Smetanina in Primorskiy Kray (Lake Hanka) from L. ridibundus No. 243, 13 June 1968. One of the Siberian specimens was collected from young L. ridibundus in the lower reaches of the Ob’ River in 1982 by S. Bondarenko and 20 specimens were collected from the same host in the Kolyma River basin (Ten’ka River, Magadan Region) by Mr. S. Leonov. In addition, we used 11 specimens from one L. delawarensis Ord. collected in Madison (Wisconsin, USA, 21 November 1946) by Dr. R. Rausch. The re-examined voucher specimens identified as A. cirrosa or A. fusus (5 A. larina ) by Spasskaya (1956, 1957) and Spasskaya and Spassky (1960) are in the INPA collection as follows: Nos. 199 and 366, L. canus ; Nos. 82, 86b, 90b, 109, 324a, 366a and 413a, L. ridibundus ; Nos. 3 and 16, Larus sp. ; Nos. 159, 162, 163, 206, 210 and 240, S. hirundo from Yakutiya.

For a long time Aploparaksis schigini n. sp. was reported under different names: as A. cirrosa of Clerc (1903), Dubinina (1953), Spasskaya (1957 in part) nec Taenia cirrosa Krabbe, 1869 ; as A. fusus of Joyeux and Baer (1928), Skrjabin and Mathevossian (1945), Spasskaya (1956 in part), Spasskaya and Spassky (1960) nec Taenia fusus Krabbe, 1869 ; as A. larina of Schigin (1961), Spassky (1963 in part), Spasskaya (1966 in part), nec A. larina Fuhrmann, 1921 . Aploparaksis larina is considered here as a synonym of A. brachyphallos (see above).

Description (the measurements given before the parenthesis are those of the holotype). Length of mature specimen 87 (45–70) mm, maximum width 1.06 (0.54– 0.95) mm. Scolex with evaginated rostellum 180×143 (135–230×120–190) mm. Rostellum small, 65×41 (66–90×45–49) mm, rostellar sheath 143×49 (180–230×60– 78) mm. Rostellar hooks 10, with typical aploparaksoid shape ( Figures 5B and 6B ), blade long and thin, significantly longer than guard, handle rudimentary. Total length of hook 23–24 (24.8–25.6) mm; length of blade 16–17.6 mm; length of base with guard 15–16 (14– 17) mm. Suckers prominent, muscular, 57–65×53–57 (62–90×60–80) mm. Neck 1. 67 (0.40–0.86) mm long and 45 (60–90) mm wide immediately posterior to scolex. Internal segmentation observed earlier than external ones, approximately 0.88 mm from scolex. Strobila delicate, band-like. Proglottides numerous (1340 in holotype), first proglottides significantly wider than long. Osmoregulatory canals in hermaphroditic proglottides move towards centre of median field, dividing proglottis approximately into three equal parts, in pre-gravid proglottides it passes laterally; transverse anastomoses not observed. Single testis ( Figures 5C, F ) 70–90×45–50 (70–139×45–82) mm, oval or rounded, sometimes slightly lobed or even divided by transverse septum into two parts; in centre of relaxed proglottides but frequently displaced antiporally in contracted ones. Cirrus-sac cylindrical, 176– 229×32–33 (170–250×33–45) mm, with powerful muscular walls, crosses median line or reaches antiporal osmoregulatory canals; when muscles in walls contract it becomes cigarshaped. Cavity of cirrus-sac 21–29 mm in diameter. Internal seminal vesicle 140–160× 21– 25 mm, external seminal vesicle 70–80× 45–53 mm, opposite antiporal region of cirrus-sac or overlying its dorsal surface. Evaginated cirrus ( Figures 5D, E and 6D ) 80–104 (43–79) mm long, with parabasal swelling 14 (11–16) mm long and 13 (12–16) mm wide taking into account length of spines covering it. Basal part of cirrus 25–33×6.0–6.5 (25–30×6–8) mm, cylindrical and distal part 50 mm long with diameter at base 3 mm. Basal part and parabasal swelling armed with spines. Spines differ in size, smaller spines cover base of cirrus, and largest one cover surface of swelling where its become triangular-shaped (ca. five to six spines per diagonal row on each side of cirrus). Several very small spines visible at base of distal part of cirrus, rest of surface smooth.

Ovary 143 (120–200) mm wide, usually trilobed, in centre of median field, ventral to male organs, sometimes, when fully developed, occupies entire median field. Vitellarium compact, oval, 41×20 (37–53×21–49) mm, median, posterior to ovary. Seminal receptacle elongated-oval or rounded depending on filling by sperm, 90×41 (45– 120×48–74) mm (in holotype not well outlined and visible only in gravid proglottides). Vagina 60–99 mm long, thin-walled, tubular, sometimes slightly twisted in conductive part, runs parallel with and dorsal to cirrus sac, under or rarely over it. Copulatory part of vagina 41–49× 6–8 mm, walls weakly sclerotised; conductive part to 58 mm long. Uterus first appears in hermaphroditic proglottides as transverse tube and with further maturation it acquires the form of a slightly lobed sac and occupies entire proglottis. Young eggs evenly distributed throughout uterus; with maturation, eggs were enveloped by a layer of substance, forming a package in the centre of the uterus. Eggs with thin outer shell, 66– 107× 49–82 mm ( Figure 5G ). Granular internal envelope is hardly discernible. Embryophore 29–33×33–37 (25–29×29–32) mm, wall smooth, about 1 mm thick. Oncosphere 21×25–27 (23×25) mm, embryonic hooks 12 mm long. Packet leaves uterus through rupture of lateral uterine and proglottis walls.

Morphological variability. Fragments of the specimen from Smetanina’s collection possess a slightly larger testis and a shorter (20 mm long) base of the cirrus. The distal end of the cirrus-sac is surrounded by numerous glandular cells, which are not found in other specimens. Glandular cells are also seen in the uterus wall. The package in a uterus of specimens from L. delawarensis looks as if it is hung in the centre of a uterus by filaments attached to walls of the uterus ( Figure 6E ). Size of packets 230–250× 340–370 mm. Number of eggs in them variable, and can reach 100 and perhaps a little more.

Live eggs ( Figure 7 ) were studied in a specimen from L. ridibundus from the Ob’ River. The packet from 0.70×0.59 to 1.01× 0.73 mm; number of eggs 33–80. Outer envelope of egg 55× 38 mm, granular envelope 46× 27 mm, embryophore 27× 34 mm, oncosphere 21× 29 mm, embryonic hooks of central and lateral pairs identical in shape and length, 12 mm long.

The life cycle A. shigini is unknown.

Remarks

The first detailed description of specimens from gulls under the name A. larina from the Rybinsk Reservoir was published by Shigin (1961). That description was included in the monographs by Spassky (1963) and Spasskaya (1966). Prudhoe (1969) mentioned this species as recorded in gulls in many regions from the Antarctic to the Arctic. However, any cestodes with a bulbous-like swelling on the cirrus were assigned to A. larina , and as a consequence, this species would represent a composite of what may be several independent taxa. The reported host spectrum of A. larina is wide and includes 16 species of birds (Tolkatcheva in Ryzhikov et al. 1985).

The re-examination of voucher specimens from gulls of Yakutiya, which were at first determined as A. cirrosa by Spasskaya (1957), as A. fusus by Spasskaya (1956), Spasskaya and Spassky (1960) and finally as A. larina by Spassky (1963) and Spasskaya (1966), and specimens collected by A. Shigin, showed that they were identical, although different to A. larina from the Antarctic (see above) described by Fuhrmann (1921). On the basis of the comparison with the present results, we consider the previous records of A. larina by Spassky (1963), Spasskaya (1966) and Shigin (1961) as belonging to A. shigini n. sp.

Aploparaksis shigini belongs to a quite large group of Aploparaksis with a parabasal swelling on the cirrus and relatively small hooks, the length of which differs insignificantly. They are: A. brachyphallos ; A. clavata Spasskaya, 1966 ; A. gallinagii Bondarenko, 1979 ; A. mamaevi ( Bondarenko, 1966) ; A. schilleri Webster, 1955 ; A. sachalinensis Krotov, 1952 and A. spinosus ( Bondarenko, 1966) .

Aploparaksis shigini n. sp. is especially similar to A. spinosus , parasitising shorebirds, mainly snipes. One of the most distinguishing characters of the new species is the presence of a single packet (‘‘pseudocapsules’’), according to Belopolskaya and Kulachkova (1968), of eggs in the uterus, formed by secretion produced by the uterus walls. Analogous packets, only in larger quantities (two to five), are also present in the uterus of A. spinosus , but this species differs by smaller rostellar hooks (18–20 mm long), as compared to those (22–26 mm long) of A. shigini , and a larger cirrus (70–126× 18–21 mm and 61–90× 12–16 mm, respectively), the armament of the cirrus being similar.

Egg packets are formed in the uterus of A. mamaevi also, however their number reaches 10. Moreover, rostellar hooks in this species are smaller (17 mm) and the cirrus, up to 74 mm long, has a bulbous swelling, up to 8–10 mm in diameter, armed with smaller spines.

Aploparaksis sachalinensis is also close to the new species in size (20–24 mm) and shape of the hooks and the length of the cirrus (up to 120 mm), but the bulbous-like swelling of the cirrus of the latter is considerably larger (24.6× 24.6–30 mm), almost spherical, and armed with very fine, evenly and densely distributed spines (our unpublished data). Rostellar hooks of the rest of the above-mentioned species are 17–20 mm long and the cirrus differs in its armament. The study of fragments labelled by Clerc (1903) as A. cirrosa (ZIN, vial 312, Larus sp. , the Urals, 1901) showed that their morphological characters correspond well to the characteristics of A. shigini n. sp., therefore, we consider A.cirrosa sensu Clerc, 1903 as a synonym of A. shigini .

Figures

Figure 5. Aploparaksis shigini n. sp. Holotype from Larus ridibundus, the Rybinsk reservoir, Russia: (A) scolex, (B) hook, (C) hermaphroditic proglottis. (D) Cirrus paratype from Larus sp., Yakutiya (Spasskaya’s collection, INPA, determinate as A. fusus (Krabbe, 1869): (E) cirrus, (F) hermaphroditic proglottis. Paratype from L. ridibundus from Kolyma river: (G) egg. Scale bars: 100 mm (A, C, F), 20 mm (B, D, E, G).

Figure 6. Aploparaksis shigini n. sp., paratype from Larus delawarensis from Alaska: (A) scolex, (B) hooks, (C) hermaphroditic proglottis, (D) cirrus, (E) egg-packet, (F) egg. Scale bars: 100 mm (A, C, E, F), 20 mm (B, D).

Figure 7. Aploparaksis shigini n. sp., paratype from L. ridibundus, Siberia: (A) live egg-packet; (B, C) live eggs. Scale bars: 200 mm (A), 30 mm (B, C).