Aberrapex panamensis sp. nov.

(Figs. 1, 2, 3A, 4A, B, 5, 6A, B)

Type host: Aetomylaeus asperrimus (Gilbert), rough eagle ray ( Myliobatiformes: Myliobatidae).

Type locality: off Mariato, Comunidad De Palo Seco (7°36’06.3” N, 80°59’33.7” W), Veráguas, Panama, northeastern Pacific .

Site of infection: Spiral intestine.

Specimens deposited: Holotype (mature worm) MIUP H-0085, 19 paratypes (16 mature worms and three detached gravid proglottids) MZUSP 8050 a–8050s, two SEM strobilar vouchers MZUSP 8051, 8052, one voucher of proglottid cross-section series MZUSP 8053 a, proglottid cross-section series MZUSP 8053 b–8053d and 16 paratypes (14 mature worms and two detached gravid proglottid) HWML 217583–217598.

Etymology: The specific epithet, panamensis, refers to the type locality of this species registered in Mariato, Panama.

Description. Based on 31 complete mature worms, five detached gravid proglottids, one cross-sectioned worm and two specimens prepared for SEM.

Worms 2.37–6.02 mm (3.73 mm ± 0.92 mm; 31) long, maximum width at level of terminal proglottid (Fig. 3A), euapolytic, 30–51 (37 ± 4.6; 31) proglottids per worm. Scolex 71–102 (89 ± 8.6; 18) long, 104–169 (139 ± 18.2; 21) wide, consisting of four bothridiate acetabula; apical modification of scolex proper and apical organ absent (Figs. 1A, 2A–C). Acetabula cup-shaped, 79–104 (90 ± 5.7; 24; 28) long, 59–79 (67 ± 4.6; 24; 28) wide (Figs. 1A, 2A–C). Cephalic peduncle absent.

Apex of scolex covered with capilliform filitriches (Fig. 2D). Proximal and distal acetabular surface covered with hastate spinitriches and acicular filitriches (Fig. 2E, F); hastate spinitriches covering all distal acetabular surface (Fig. 2B). Immature proglottids covered with acicular filitriches (Fig. 2G).

Proglottids craspedote, laciniate, with four laciniations (two dorsal, two ventral), less evident in mature proglottids (Figs. 1B, 3A). Immature proglottids 28–49 (35 ± 4.6; 31) in number, initially wider than long, becoming longer than wide with maturity; posterior-most immature proglottid 202–492 (354 ± 74.6; 31) long, 110–313 (210 ± 45.6; 31) wide. Mature proglottids 1–2 (N = 31) in number, terminal mature proglottids in which testes are not degenerated 708–1170 (886 ± 98.4; 19) long, 142–312 (238 ± 39.4; 19) wide (Fig. 1B); terminal fully mature proglottids in which most testes are degenerated 884–1434 (1126 ± 154.7; 12) long, 184–329 (266 ± 53.9; 12) wide (Fig. 4A).

Testes 24–42 (35 ± 4.1; 31) in number, 37–59 (50 ± 5.2; 31; 52) long, 64–96 (83 ± 7.6; 31; 52) wide in mature proglottids, arranged in 2–4 irregular columns in dorsoventral view (Fig. 1B), in single field extending from anterior margin of proglottid to ovary, slightly overlapping anterior margins of ovary, one row deep in cross-section (Fig. 6A), degenerated in some terminal mature proglottids (Fig. 4A). Vas deferens in maturing proglottids in form of thin tube, sinuous, extending along lateral margin of proglottid from level of ootype to cirrus sac, entering cirrus sac at distal end (Fig. 1B, C); vas deferens in proglottids in which testes are degenerated enlarged to form conspicuous external seminal vesicle (Fig. 4A). External seminal vesicle extensive, sinuous, extending more or less along midline of proglottid from ootype to near the anterior margin of cirrus sac. Internal seminal vesicle absent. Cirrus sac pyriform, slightly angled anteriorly, 67–153 (97 ± 21.4; 17) long, 36–106 (58 ± 16.8; 17) wide in mature proglottids with testes; 112–208 (157 ± 32.7; 12) long, 73–126 (101 ± 16.8; 12) wide in mature proglottids in which testes are degenerated, containing coiled unarmed cirrus (Fig. 1B).

Ovary H-shaped in dorsoventral view (Fig. 1B, C), tetralobed in cross-section (Fig. 6B), lobulated, symmetrical, 93–281 (170 ± 45.6; 17) long, 87–183 (129 ± 28.3; 18) wide in mature proglottids with testes; 205–356 (282 ± 44.6; 12) long, 119–203 (147 ± 24.0; 11) wide in mature proglottids in which testes are degenerated; ovarian isthmus at middle of ovary. Mehlis’ gland at posterior margin of ovary (Fig. 1B, C). Vagina sinuous, extending along lateral margin of proglottid from ootype to genital atrium, opening into genital atrium posterior to cirrus sac (Fig. 1B, C). Genital pores lateral, irregularly alternating, 70–81% (75% ± 2.5%; 19) of proglottid length from posterior margin in mature proglottids with testes, 77–80% (79% ± 1.3%; 10) in mature proglottids with degenerated testes.

Uterus saccate, sinuous, extending along median line of proglottid from anterior margin of ovary to the level of anterior margin of cirrus sac (Fig. 1B, C); uterine duct not observed. Vitelline follicles in four columns (two dorsal, two ventral) on each lateral margin of proglottid, extending entire length of proglottid, interrupted by ovary and cirrus sac, slightly overlapping anterior and posterior margins of ovary (Fig. 1B, C); vitelline follicles 5–18 (11 ± 2.6; 19; 35) long, 10–33 (21 ± 5.9; 19; 35) wide in mature proglottids with testes, 12–21 (17 ± 3.3; 11; 20) long, 32– 82 (49 ± 15.9; 11; 20) wide in mature proglottids with degenerated testes. Gravid detached proglottids 1606–2503 (2177 ± 396.2; 4) long, 301–492 (415 ± 81.2; 4) wide (Fig. 4B). Eggs unembryonated, broadly dolioform, 17–22 (18 ± 2.2; 4; 8) long by 12–15 (13 ± 1.5; 4; 8) wide, arranged in tandem in cocoons; cocoons in form of continuous strand of hundreds of eggs (Fig. 5A, B). Single pair of excretory ducts.

Remarks. Aberrapex panamensis sp. nov. is the second species of its genus reported in the eastern Pacific Ocean. It can be easily distinguished morphologically from its congeners by a series of morphometric and/or morphological attributes. Aberrapex panamensis sp. nov. possesses a greater number of testes than A. sanmartini, A. vitalemuttiorum, A. manjajiae, and A. weipaensis (24–42 vs 11–16, 15–21, 10–19 and 10–17, respectively). In addition, in A. panamensis sp. nov. the eggs are arranged in tandem in large number in strand-like cocoons, whereas in A. sanmartini the eggs are grouped in oval cocoons with 16– 22 eggs each. Aberrapex panamensis sp. nov. can further be distinguished from A. manjajiae, and A. weipaensis as it follows by the microthrix pattern. Hastate spinitriches are covering the entire distal acetabular surface in A. panamensis sp. nov., rather than restricted to the central acetabular region as in the case of A. manjajiae or absent in that surface as in the case of A. weipaensis . Aberrapex panamensis sp. nov. differs from A. arrhynchum, A. senticosus, and A. ludmilae in the length of the scolex (71–102 vs 165–205, 100–130, and 160–190, respectively). In addition, in A. panamensis sp. nov. the uterus extends from anterior margin of ovary to the level of anterior margin of the cirrus sac rather than extending from level of anterior margin of ovary to the posterior margin of the cirrus sac and curving porally as in the case of A. arrhynchum or in A. senticosus which extends from level of ootype to near the anterior margin of proglottid. Finally, A. panamesis also differs from A. ludmilae in having external seminal vesicle rather than lacking.