Acanthobothrium guanghaiense Yang, Sun, Zhi, Iwaki, Reyda & Yang, 2016, n. sp.

Acanthobothrium guanghaiense n. sp.

(Figs 16 – 21)

Type host. Dasyatis akajei (Müller & Henle).

Site of infection. Spiral intestine.

Type locality. Off Guanghai Port (21°95′N, 112°80′E), Taishan, Guangdong Province, China.

Deposited Specimens. Holotype (MPM 21229) and 5 paratypes (MPM 21230), 4 paratypes (SYSU 20140818-1-4).

Etymology. This specific name refers to the location, Guanghai port, Taishan Guangdong Province, China.

Morphological description. [Based on 15 whole mounts (10 mature and 5 immature) and 5 worms examined with SEM]: Worms euapolytic, 2.97 – 7.67 mm (5.39 ± 1.71; 10) long; greatest width at level of scolex; with more than 13 – 28 (20 ± 5; 15) proglottids per worm, excluding some too immature to count clearly; genital pores marginal, irregularly alternating, 38 – 49% (42 ± 4; 15) of proglottid length from posterior end. Scolex consisting of scolex proper and conspicuous cephalic peduncle. Scolex proper with 4 linguiform bothridia; bothridia 274 – 459 (367 ± 58; 7) long by 110 – 174 (134 ± 27; 7) wide, joined by velum at anterior septum; free posteriorly. Each bothridium with 3 loculi, muscular pad and apical sucker, muscular pad and apical sucker conspicuous with SEM (Fig. 19). Muscular pad triangular, 94 – 122 (107 ± 14; 5) long by 64 – 95 (81 ± 14; 5) wide. Apical sucker rounded, 28 – 32 (30 ± 2; 5) in diameter. Anterior loculus 199 – 325 (286 ± 47; 7) long, middle loculus 38 – 60 (48 ± 9; 7) long, and posterior loculus 38 – 64 (48 ± 12; 7) long; loculi length ratio 1:0.13 – 0.22:0.12 – 0.26 (1:0.17:0.18 ± 0.10:0.04:0.05; 7); maximum width of bothridia at level of anterior loculus. Hooks bipronged, hollow, internal channel smooth; axial prongs are almost as long as abaxial prongs. Axial prong fenestrated in proximal part. Hooks on each bothridium closely linked in proximal portions. Lateral and medial hooks approximately equal in size. Lateral hook measurements (n=15): Hook base length 48 – 68 (58 ± 6; 15), axial prong length 95 – 127 (117 ± 8; 15), abaxial prong length 94 – 124 (110 ± 8; 15), total lateral hook length 137 – 188 (169 ± 14; 15). Medial hook measurements (n=15): Hook base length 42 – 69 (58 ± 7; 15), axial prong length 94 – 136 (114 ± 11; 15), abaxial prong length 94 – 122 (109 ± 9; 15), total medial hook length 135 – 193 (168 ± 15; 15). Ratio of total hook length (both medial hook and lateral hook) to bothridial length: 1:1.73 – 2.90 (2.25 ± 0.39; 7). Cephalic peduncle conspicuous, 421 – 3157 (1437 ± 1006; 10) long by 133 – 238 (191 ± 31; 10) wide.

Distal bothridial surfaces covered with acicular filitriches (Fig. 20). Bothridial surfaces at lateral margin covered with acicular filitriches interspersed with capilliform filitriches from mid-level of anterior loculus to posterior loculus (Fig. 21). Detail of proximal portion not observed.

Proglottids acraspedote. Immature proglottids 8 – 18 (15 ± 4; 8) in number, mature proglottids 3 – 11 (6 ± 4; 10) in number; 432 – 886 long by 207 – 365 wide and with length-to-width ratio 1:0.35 – 0.85 (0.55 ± 0.18; 10); gravid proglottids not seen; terminal proglottids length-to-width ratio 1:0.22 – 0.71 (0.45 ± 0.17; 10). Testes irregularly oval in dorsal or ventral view, 40 – 74 long by 25 – 41 wide, arranged in two staggered columns anterior to ovarian isthmus, one or two layers deep, 35 – 63 (46 ± 8; 10) in total number in mature proglottid, 14 – 24 (18 ± 3; 10) prevaginal; 2 – 7 (5 ± 2; 10) post-vaginal; 18 – 33 (24 ± 5; 10) in aporal side. Vas deferens originates in anterior quarter of segment, sinuous, descending posteriorly in mid-line and entering proximal portion of cirrus pouch. Cirrus sac straight, post-equatorial, 95 – 132 (109 ± 15, 5) long by 35 – 64 (51 ± 11, 5) wide, containing coiled cirrus; cirrus expanded at base; proximal and part of distal portion with spinitriches. Vagina opening into genital atrium immediately in front of cirrus, thick walled, extending from ootype along medial line of proglottid to anterior margin of cirrus sac to common genital atrium; vaginal sphincter not observed; seminal receptacle not seen. Ovary asymmetrical H-shaped in dorsoventral view, not seen in cross-section, located at or near posterior end of proglottid, each lobe lobulated, maximum width 121 – 212 (181 ± 42; 5); poral lobe 120 – 367 (215 ± 93; 5) and aporal lobe 171 – 470 (267 ± 120; 5) long; poral lobe extending to (or slightly overlapping) cirrus sac; ovarian isthmus located at approximate mid-point of ovary. Mehlis’ gland posterior to ovarian isthmus. Vitellarium follicular form narrow lateral bands, each with 1 – 2 rows of follicles, extending from post-ovarian extremity to near anterior extent of testes, interrupted by vagina and cirrus sac dorsally and ventrally, not interrupted by ovary. Uterus linear, median, tubiform, extending from ovarian isthmus to near anterior margin of testicular field. Gravid proglottids and eggs not observed.

Remarks. Acanthobothrium guanghaiense n. sp. belongs to category 2 of Acanthobothrium suggested by Ghoshroy & Caira (2001) because of its characteristics of ≤ 15 mm in total length, ≤ 50 proglottids, ≤ 80 testes, and with an asymmetrical ovary. Forty-one species of Acanthobothrium belongs to the species category 2 (Fyler & Caira 2006; Reyda & Caira 2006; Fyler et al. 2009; Tazerouti et al. 2009; Fyler & Caira 2010; Maleki et al. 2013). Acanthobothrium guanghaiense n. sp. has more testes (35–63) which discriminates it from A. annapinkiense Carvajal & Goldstein, 1971 (23–34), A. atahualpai Marques, Brooks & Barriga, 1977 (20–30), A. brachyacanthum Riser, 1955 (33–34), A. brevissime Linton, 1908 (20–21), A. campbelli Marques, Brooks & Monks, 1995 (15–23), A. chisholmae Campbell & Beveridge, 2002 (23–27), A. edwardsi Williams, 1969 (23–26), A. lasti Campbell & Beveridge, 2002 (14–21), A. masnihae Fyler & Caira, 2006 (6–12), A. mooreae Campbell & Beveridge, 2002 (12– 17), A. quadripartitum Williams, 1968 (up to 18), A. rajivi Ghoshroy & Caira, 2001 (9–13), A. stevensi Campbell & Beveridge, 2002 (14–18), A. tasajerasi Brooks, 1977 (19–33), A. tetabuanense Reyda & Caira, 2006 (6–12), A. thomasae Campbell & Beveridge, 2002 (12–18), A. tripartitum Williams, 1969 (13–16), A. urotrygoni Brooks & Mayes, 1980 (24–33), A. vargasi Marques, Brooks & Monks, 1995 (22–29), A. walkeri Campbell & Beveridge, 2002 (9–13), A. minus Tazerouti, Kechemir-Issad & Euzet, 2009 (17–25) and A. sphaera Maleki, Malek & Palm, 2013 (10–14). The new species also has more aporal testes than those of A. dujardini van Beneden, 1850 (18–33 vs. 13–16). A. guanghaiense n. sp. can be distinguished from A. popi Fyler, Caira & Jensen, 2009 and A. bobconniorum Fyler & Caira, 2010 by lacking post-ovarian testes. A. guanghaiense n. sp. is distinguished from A. batailloni Euzet, 1955, A. bullardi Ghoshroy & Caira, 2001, A. coquimbense Carvajal & Jeges, 1980 and A. zapterycum Ostrosski de Nunez, 1971 in possessing a post-equatorial rather than pre-equatorial genital pore. Acanthobothrium guanghaiense n. sp. differs from A. brayi Campbell & Beveridge, 2002, A. gloveri Campbell & Beveridge, 2002 and A. ocallaghani Campbell & Beveridge, 2002 by the position of ovary; the aporal ovarian lobes in A. guanghaiense n. sp. reach the cirrus sac, whereas in A. brayi, A. gloveri and A. ocallaghani the lobes of ovary never reach the cirrus sac. Acanthobothrium guanghaiense n. sp. differs from A. olseni Dailey & Mudry, 1968 by having post-vaginal testes. It differs from A. cimari Marques, Brooks & Monks, 1995, A. costarricense Marques, Brooks & Monks, 1995 and A. puntarenasense Marques, Brooks & Monks, 1995 in its locular ratio (1:0.13–0.22:0.12–0.26 vs. 1:0.5:0.6, 1:0.6:0.6, 1:0.3:0.5 respectively). Acanthobothrium guanghaiense n. sp. can be differentiated from A. dasi Ghoshroy & Caira, 2001 and A. woodsholei Baer, 1948 by greater total hook length (135–193 vs. 68–128, 129 respectively), and from A. lilium Baer & Euzet, 1962 by its longer abaxial prong length (94–124 vs. 60–80). It also differs from A. unilateralis Alexander, 1953 by its arrangement of testes (arranged in two staggered columns vs. randomly arranged). Acanthobothrium guanghaiense n. sp. resembles A.

semnovesiculum Verma, 1928 mostly in total length (2.24–7.67 mm vs. 3.50–9.90 mm), bothridial length (274–459 vs. 330–440), testes number (35–63 vs. 43–54), locular length ratio (1:0.13–0.22:0.12–0.26 vs. 1:0.24–0.27:0.19– 0.22), but can be distinguished from the latter by the arrangement of testes (arranged in two staggered columns vs. arranged in two tandem columns). In addition, the abaxial prong in A. guanghaiense n. sp. is nearly straight while the corresponding structure in A. semnovesiculum is obviously curved in its proximal portion.

Acanthobothrium guanghaiense n. sp. is the first species of category 2 reported from the host D. akajei.