Catenotaenia dendritica ( Goeze, 1782 )

Haukisalmi, Voitto, Hardman, Lotta M. & Henttonen, Heikki, 2010, Taxonomic review of cestodes of the genus Catenotaenia Janicki, 1904 in Eurasia and molecular phylogeny of the Catenotaeniidae (Cyclophyllidea), Zootaxa 2489, pp. 1-33 : 8-10

Catenotaenia dendritica ( Goeze, 1782)

(Fig. 3)

Synonym: Catenotaenia ris Yamaguti, 1942 . For other synonyms, see Spasskii 1951.

Material examined: Two gravid specimens from a single individual of the Eurasian red squirrel Sciurus vulgaris Linnaeus (Sciuridae) from Finland. Additional data on the relative position of the genital pore and vitellarium, and the number of uterine branches were extracted from the illustrations of Joyeux & Baer (1945), Spasskii (1951) and Genov (1984), all from cestodes found in S. vulgaris .

Site: Small intestine.

Deposited voucher specimen: USNPC 102581, from S. vulgaris from Sipoo, southern Finland (60o23' N, 25o14' E).

Description (main features): Mature and subsequent proglottids slightly craspedote (velum short), elongate, of rather uniform width, usually widest at genital pore. Genital pores positioned slightly posterior to border between anterior and middle thirds of proglottid margin; relative anterior distance of genital pore 0.36– 0.40 (0.38, n=5). Marginal bulge associated with genital pore present.

Testicular field divided partly or completely (longitudinally). Antiporal testes reaching level of midvitellarium, usually not overlapping ovary. When cirrus withdrawn, cirrus sac overlaps longitudinal canal or extends slightly across it.

Ovary asymmetrical, short relative to proglottid length (<40%). Posterior part of ovary extends to level of mid-vitellarium or slightly more posteriad. Long (500–670, n=2) free space separating ovary from anterior margin of proglottid always present. Vitellarium slightly longer than wide. Midpoint of vitellarium positioned at midline of proglottid; relative longitudinal position 0.48–0.53 (n=4). Vagina slightly curved, merging seminal receptacle antero-porally. Seminal receptacle positioned anterior to Mehlis' gland. Uterus in pregravid proglottids with 43–53 (47.5, n=8) primary branches on each side; secondary branches frequent. Outer egg membrane ovoid.

FIGURE. 3. Catenotaenia dendritica from Sciurus vulgaris . A. Mature proglottid (symbols: AD, distance of anterior “free” space; PD, poral distance of genital pore; VD, poral distance of vitellarium; OL, length of ovary; TL, length of testicular field) (scale bar 0.50 mm). B. Outline of mature proglottids (scale bar 1.0 mm). C. Uterus in pregravid proglottid (scale bar 1.0 mm). D. Scolex and neck (scale bar 0.20 mm). E. Egg (scale bar 0.010 mm).

Remarks: Catenotaenia dendritica is generally regarded as a host-specific parasite of Sciurus vulgaris (e.g. Joyeux & Baer 1945, Spasskii 1951, Tenora & Murai 1975, Genov 1984). It occurs commonly in the red squirrel in Europe (e.g. Genov 1984, Shimalov & Shimalov 2002, present study) and evidently has a wide Eurasian distribution ( Spasskii 1951, Ryzhikov et al. 1978). According to Joyeux & Baer (1945), Spasskii (1951) and Quentin (1971), C. dendritica also occurs in arboreal sciurid rodents in (eastern) Africa, although no data or references were given.

Catenotaenia dendritica is morphologically distinctive, being characterized by elongate proglottids of rather uniform width, numerous uterine branches and a tendency toward longitudinal division of the testicular field. Additional diagnostic characteristics are the prominent "free space" anterior to ovary, short ovary in relation to the proglottid length (<40%; usually>50% in other species), slightly curved vagina that merges with the seminal receptacle antero-porally (anteriorly or antero-medially in other species except C. pusilla ) and a seminal receptacle that is positioned anterior to Mehlis' gland (usually between Mehlis' gland and the longitudinal canal in the other species).

Catenotaenia ris Yamaguti, 1942 from Sciurus lis Temminck from Japan is very similar to C. dendritica . According to Yamaguti (1942), C. ris differs from the latter species by the size of the apical sucker (absent or small in C. dendritica ) and number of testes. The presence/absence of the apical sucker is variable within some other Catenotaenia species, and is not considered to be of high taxonomic value. Joyeux & Baer (1945) have demonstrated that the apical sucker is functional in metacestodes of Catenotaenia pusilla and degenerates in adult specimens. The number of testes in C. ris (140–190) is indeed slightly lower than reported for C. dendritica by Riggenbach (1895) (200–250), but other studies (including the present one) show that there are usually 140–233 testes in the latter species. Perhaps the most significant difference between C. ris and C. dendritica concerns the number of uterine branches (30–40 in the former, 35–60 in the latter), but considering the high intraspecific variability of this feature, it cannot be used to differentiate two otherwise similar species. Following Joyeux & Baer (1945) and Spasskii (1951), C. ris is considered here a synonym of C. dendritica .