REVISION OF THE LECANICEPHALIDEAN GENUS FLAPOCEPHALUS DESHMUKH, 1979 (EUCESTODA) FROM COWTAIL RAYS (GENUS PASTINACHUS RÜPPELL) (MYLIOBATIFORMES: DASYATIDAE JORDAN AND GILBERT) WITH THE DESCRIPTION OF FOUR NEW SPECIES
The genus Flapocephalus Deshmukh, 1979, is a little-known group of lecanicephalidean cestodes parasitizing cowtail rays (genus Pastinachus Rüppell) mainly in the Indo-Pacific region. Since the erection of the genus, with Flapocephalus trygonis Deshmukh, 1979, as the type species, and the description of a second species, Flapocephalus saurashtri Shinde and Deshmukh, 1979, both from Pastinachus sephen (Fabricius) from India, reports of this genus have been restricted mainly to brief mentions or discussion of its validity and taxonomic placement. More recently, phylogenetic analyses based on molecular sequence data that included specimens of Flapocephalus have supported Flapocephalus as a distinct genus allied with the Polypocephalidae Meggitt, 1924. Limited by the amount of detail provided in the original descriptions, the unavailability of type material, and the lack of a detailed generic diagnosis, we aimed to fully characterize the genus based on newly collected specimens. A total of 38 specimens of Pastinachus, representing 3 of the 5 described species and 1 undescribed species, from throughout the Indo-Pacific region were examined for specimens of Flapocephalus. Worms were prepared for examination with light and scanning electron microscopy and as histological sections. A subset of specimens was included in a phylogenetic analysis based on data for a portion of the 28S rDNA gene. Overall, these specimens were found to include the type species, 4 new species that are described herein (Flapocephalus monostylorchis Hanselman and Jensen n. sp., Flapocephalus capitonis Hanselman and Jensen n. sp., Flapocephalus rudkinorum Hanselman and Jensen n. sp., and Flapocephalus infundibulapex Hanselman and Jensen n. sp.), and 4 putative new species. Flapocephalus trygonis is redescribed from specimens from Pastinachus ater (Macleay) from Sri Lanka, and a neotype is designated. The newly described species are distinct genetically and can be distinguished morphologically from the existing species and one another based on a combination of total length, the shape of the apical organ, and the arrangement of testes and vitelline follicles. A revised diagnosis of the genus and a key to the described species are presented, as is a hypothesis of the interrelationships resulting from a maximum likelihood analysis including 4 of the 5 described species and the 4 putative new species. The presence of 4 glandular, sac-like structures surrounded by scolex proper, with channels that open to the outside at the base of the apical organ, is reported in lecanicephalidean tapeworms for the first time.ABSTRACT
Maximum-likelihood tree based on sequence data for the D1–D3 region of the 28S rDNA gene of specimens of Flapocephalus Deshmukh, 1979, color coded by host species. Nodal support is indicated by standard bootstrap (SBS) values; only SBS values ≥70% are shown on the tree. Taxon labels are given as the species name followed in parentheses by the GenBank accession, unique worm specimen and hologenophore accession numbers, and the unique host specimen number in separate parentheses. Taxa for which sequence data were generated as part of this study are indicated in bold. Scale bar indicates number of nucleotide substitutions per site. Color version available online.
Line drawings of Flapocephalus trygonis Deshmukh, 1979. (A) Whole worm (voucher; USNM 1456349). (B) Scolex (neotype; BRT-P 006). (C) Terminal mature proglottid (voucher; QM G241949); arrows indicate level of sections in Figure 4A, B. (D) Terminal genitalia (voucher; QM G241949).
Scanning electron micrographs of Flapocephalus trygonis Deshmukh, 1979 (A–F) and Flapocephalus monostylorchis Hanselman and Jensen n. sp. (G–L). (A) Scolex; small letters indicate location of details in B, C, E, and F; rectangle indicates region shown in D. (B) Surface of scolex proper. (C) Proximal surface of anterior region of apical organ. (D) Transition between anterior and posterior regions of apical organ. (E) Surface of posterior region of apical organ. (F) Surface of strobila. (G) Scolex; small letters indicate location of details in H, I, K, and L; rectangle indicates region shown in J. (H) Surface of scolex proper. (I) Proximal surface of apical organ. (J) Transition between apical organ and apical modification of scolex proper. (K) Distal acetabular surface. (L) Surface of strobila.
Light micrographs of histological sections of Flapocephalus trygonis Deshmukh, 1979 (A–C) and whole mounts of Flapocephalus monostylorchis Hanselman and Jensen n. sp. (D, E). (A) Proglottid cross section at level of testes. (B) Proglottid cross section at level of ovarian isthmus. (C) Scolex sagittal section. (D) Scolex in lateral view (paratype; USNM 1456341). (E) Terminal genitalia (holotype; QM G241937). Abbreviations: AO, apical organ; CS, cirrus sac; OV, ovary; SU, sucker; T, testis; UT, uterus; VA, vagina; VD, vas deferens; VF, vitelline follicle; VS, vaginal sphincter. Color version available online.
Line drawings of Flapocephalus monostylorchis Hanselman and Jensen n. sp. (A) Whole worm (holotype; QM G241937). (B) Scolex (paratype; QM G241941). (C) Subterminal mature proglottid (paratype; LRP 11101). (D) Terminal mature proglottid (paratype; QM G241942).
Line drawings of Flapocephalus capitonis Hanselman and Jensen n. sp. (A) Whole worm (holotype; MZBCa 221); arrow indicates level of mature proglottid in C. (B) Scolex (paratype; USNM 1456335). (C) Mature proglottid (holotype; MZBCa 221).
Scanning electron micrographs of Flapocephalus capitonis Hanselman and Jensen n. sp. (A) Scolex; small letters indicate location of details in B–D. (B) Proximal surface of apical organ. (C) Surface of scolex proper. (D) Surface of strobila.
Line drawings of Flapocephalus rudkinorum Hanselman and Jensen n. sp. (A) Whole worm (holotype; BRT-P 008); arrow indicates level of mature proglottid in C. (B) Scolex (paratype; LRP 11115). (C) Mature proglottid (holotype; BRT-P 008). (D) Terminal mature proglottid (paratype; USNM 1456342). (E) Terminal genitalia (holotype; BRT-P 008).
Scanning electron micrographs of Flapocephalus rudkinorum Hanselman and Jensen n. sp. (A–E) and Flapocephalus infundibulapex Hanselman and Jensen n. sp. (F–K). (A) Scolex; small letters indicate location of details in B, D, and E; rectangle indicates region shown in C. (B) Distal surface of apical organ, towards center. (C) Enlarged view of distal surface of apical organ. (D) Surface of scolex proper. (E) Surface of strobila. (F) Scolex; small letters indicate location of details in G, H, J, and K; rectangle indicates region shown in I. (G) Distal surface of apical organ, towards center. (H) Proximal surface of apical organ, near rim. (I) Enlarged view of acetabulum. (J) Surface of scolex proper. (K) Surface of strobila.
Light micrographs of histological sections of Flapocephalus rudkinorum Hanselman and Jensen n. sp. (A, B) and Flapocephalus infundibulapex Hanselman and Jensen n. sp. (C–H). (A) Scolex frontal section through center showing pair of glandular sac-like structures opening to outside at base of apical organ. (B) Scolex frontal section at level of acetabula showing 1 of 4 glandular sac-like structures; inset shows enlarged view of content of channels of glandular sac-like structure. (C) Scolex cross section at level of acetabula. (D) Scolex cross section at level of scolex proper posterior to acetabula near base of apical organ. (E) Scolex cross section at level of glandular sac-like structures opening to outside at base of apical. (F) Proglottid cross section at level of testes. (G) Proglottid cross section at level of genital pore. (H) Proglottid cross section at level of ovary. Abbreviations: AC, acetabulum; AO, apical organ; CS, cirrus sac; GS, glandular structure; MG, Mehlis gland; OV, ovary; T, testis; UT, uterus; VA, vagina; VD, vas deferens; VF, vitelline follicle. Color version available online.
Line drawings of Flapocephalus infundibulapex Hanselman and Jensen n. sp. (A) Whole worm (holotype; MAGNT D001952). (B) Scolex (holotype; MAGNT D001952); arrows indicate level of proglottid cross sections in Figure 10C–E. (C) Terminal mature proglottid (paratype; QM G241944); arrows indicate level of proglottid cross sections in Figure 10F–H. (D) Terminal genitalia (holotype; MAGNT D001952).
Contributor Notes
Version of Record, first published online with fixed content and layout, in compliance with ICZN Arts. 8.1.3.2, 8.5, and 21.8.2 as amended, 2012. ZooBank publication registration: urn:lsid:zoobank.org:pub:76D1176F-135E-43E9-B895-7C27DA7AC026.