Two new species and a new phyllobothriid cestode genus from sharks of the genus Negaprion Whitley (Carcharhiniformes)

Alexandercestus n. g. (Cestoda: Tetraphyllidea) is erected for two cestode species found parasitising the two known species of lemon sharks (Carcharhiniformes: Negaprion spp.). This new genus differs from all other phyllobothriid genera except for Hemipristicola Cutmore, Theiss, Bennett & Cribb, 2011, Marsupiobothrium Yamaguti, 1952, Nandocestus Reyda, 2008, Orectolobicestus Ruhnke, Caira & Carpenter 2006, Orygmatobothrium Diesing, 1863, Paraorygmatobothrium Ruhnke, 1994 and Phyllobothrium van Beneden, 1849 in possessing uniloculate bothridia with an apical sucker and neck scutes. Alexandercestus differs from Orectolobicestus and Nandocestus in lacking marginal loculi on the bothridia, from Paraorygmatobothrium in possessing uninterrupted vitelline follicles at the level of the ovary and from Phyllobothrium in being euapolytic as opposed to anapolytic and in lacking posteriorly bifid bothridia. The new genus lacks the central accessory bothridial organ seen in specimens of Orygmatobothrium, and lacks the central bothridial accessory sucker of specimens of Marsupiobothrium. Alexandercestus spp. compare most favourably with specimens of Hemipristicola, especially with respect to aspects of proglottid morphology, but differ in possessing aristate gladiate spinitriches rather than serrate gladiate spinitriches on the proximal bothridial surface. In addition, the bothridia of Alexandercestus spp. are comparatively more fleshy and foliose than those in specimens of Hemipristicola. Two new species of Alexandercestus n. g. are described, Alexandercestus gibsoni n. sp. from Negaprion acutidens, collected from off northern Australia and the Marshall Islands, and Alexandercestus manteri n. sp. from N. brevirostris, collected off the islands of Bimini and the Florida Keys. The two new species differ in total length and vitelline follicle distribution. Bayesian inference and parsimony analysis of the D1–D3 region of the large nuclear ribosomal DNA of 17 published and seven novel sequences placed A. gibsoni as the sister taxon to a clade containing Hemipristicola gunterae Cutmore, Theiss, Bennett & Cribb, 2011 and species of Paraorygmatobothrium. This result supports the erection of Alexandercestus as a genus separate from Hemipristicola and Paraorygmatobothrium. At the present time, species of Alexandercestus are known only from hosts of the carcharhinid genus Negaprion Whitley; examination of extensive survey data suggests this may be the extent of the host distribution of this genus.     

Orectolobicestus n. g. (Cestoda: Tetraphyllidea), with the description of five new species and the transfer of Phyllobothrium chiloscyllii to the new genus

ORECTOLOBICESTUS N. G. (CESTODA: Tetraphyllidea) is erected for six cestode species parasitising bamboo sharks (Orectolobiformes: Chiloscyllium). Members of this genus differ from all other phyllobothriid genera in possessing modified maisiform spinitriches on their distal bothridial surfaces. In addition, they are easily recognised in that they share the following unique combination of characters: their vitelline fields are interrupted by the ovary, their necks are scutellate, and their bothridia bear an apical sucker and marginal loculi. Five new species of Orectolobicestus are described, including O. tyleri n. sp. from Chiloscyllium punctatum off Borneo, O. lorettae n. sp. from C. cf. punctatum off Australia, O. mukahensis n. sp. and O. kelleyae n. sp. from C. indicum off Borneo, and O. randyi n.sp. from C. hasselti also from off Borneo. In addition, Phyllobothrium chiloscyllii Subhapradha, 1955 is transferred to the new genus. O. chiloscyllii (Subhapradha, 1955) n. comb. is readily distinguished from all five new species in its greater total length. In addition to a number of proglottid features, O. kelleyae n. sp. and O. randyi n. sp. clearly differ from the other three new species in their possession of trifid, rather than fully serrate, spinitriches on their proximal bothridial surfaces. The latter two species conspicuously differ from one another in total number of proglottids (11-21 vs 27-38). O. tyleri n. sp. generally has fewer proglottids than O. lorrettae n. sp. (7-17 vs 13-23) and, like O. mukahensis n. sp., possesses scutes that are spathate rather than elongate. O. tyleri n. sp. is readily distinguished from O. mukahensis n. sp. in its possession of fewer proglottids (7-17 vs. 19-29). The five new species of Orectolobicestus share derived bothridial microthrix features with Phyllobothrium squali Yamaguti, 1952, Thysanocephalum sp., Orygmatobothrium sp., Ruhnkecestus Caira & Durkin, 2006 and species of Paraorygmatobothrium Ruhnke, 1994. Among these taxa, Orectolobicestus most closely resembles Paraorygmatobothrium and Ruhnkecestus in its vitelline fields being interrupted by the ovary and the possession of a scutellate neck.     

Comparison of microthrix ultrastructure and morphology on the plerocercoid and adult scolex of Calliobothrium cf. verticillatum (Tetraphyllidea: Onchobothriidae)

The distal bothridial surfaces of adult triloculate onchobothriids are covered with short structures that have been tentatively classified as very short filitriches, but this hypothesis has never been tested. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate microthrix morphology in the plerocercoid and adult forms of Calliobothrium cf. verticillatum, a triloculate onchobothriid tapeworm from Long Island Sound (Connecticut). Plerocercoids of C. cf. verticillatum were collected from the anterior midgut ceaca of Pagurus pollicaris Say, 1817 (flat-clawed hermit crab), and adults were collected from the spiral intestine of the dusky smooth hound Mustelis canis (Mitchell, 1815). Two plerocercoids and 2 adults were examined using SEM; 2 plerocercoids and 2 adults were examined using TEM. Microthrix distribution and morphology (including measurements of total length, base length, shaft length, and base width) were investigated on all surfaces of the plerocercoid and adult scolex. Slender filitriches and large bladelike spinitriches were observed extending from the tegument of plerocercoid and adult forms. The filitriches were found to have significantly narrower bases than the spinitriches (65-167 nm vs. 466-1,936 nm, respectively). The scolex proper of the plerocercoid and adult forms were found to have filitriches of medium-length and bladelike spinitriches. The distal bothridial surfaces differed dramatically in microthrix morphology between plerocercoid and adult forms; on the distal surfaces of the plerocercoids were long filitriches and bladelike spinitriches. However, the distal surfaces of the adults had short structures (previously hypothesized to be short filitriches) and a few bladelike spinitriches. Serial transverse sections revealed that the short structures on the distal bothridial surfaces of the adults were homologous with filitriches. They included all of the structural components of a filithrix as well as a base width that conformed to the filitriches found on other surfaces. The bothridial margins of the plerocercoid and adult forms had a microthrix pattern similar to that seen on the proximal bothridial surfaces except that the filitriches on the margins were significantly longer than those found anywhere else on the bothridia. The most dramatic difference between the plerocercoid and adult forms occurred on the distal bothridial surfaces, where the filitriches of the adult cestodes were significantly shorter and narrower, and the spinitriches were almost entirely lacking.     

A new tetraphyllidean genus and species, Caulopaterapagei n. g., n. sp. (Tetraphyllidea: Phyllobothriidae), from the grey carpetshark Chiloscyllium punctatum Müller & Henle (Orectolobiformes: Hemiscylliidae)

A new genus and species of tetraphyllidean cestode, Caulopatera pagei n. g., n. sp., is described from the grey carpetshark Chiloscyllium punctatum Müller & Henle in Moreton Bay, Australia. The new genus is placed in the Phyllobothriidae, subfamily Phyllobothriinae. Caulopatera n. g. is distinct from all other phyllobothriine genera in having stalked, circular, non-loculate bothridia that lack an apical sucker, testes that are restricted to the region anterior to the cirrus-sac and circum-medullary vitelline follicles. The new genus most closely resembles Carpobothrium Shipley & Hornell, 1906, with which it shares non-loculate, stalked, unhooked bothridia without an accessory sucker and testes that are entirely anterior to the cirrus-sac, but differs from it in that it lacks a slit-like opening in each bothridium and flaps surrounding the opening. The possession of bothridial stalks is consistent with two cestode orders, the Tetraphyllidea and the Rhinebothriidea. The morphology of the bothridial stalks is consistent with other tetraphyllidean genera, in that Caulopatera possesses triangular bothridial stalks surrounding the back of the bothridia, indicating that it belongs in the Tetraphyllidea senso stricto, rather than in the recently recognised Rhinebothriidea.     

Head Morphology and Electrosensory Pore Distribution of Carcharhinid and Sphyrnid Sharks

Selection to maximize electroreceptive search area might have driven evolution of the cephalofoil head morphology of hammerhead sharks (family Sphyrnidae). The enhanced electrosensory hypothesis predicts that the wider head of sphyrnid sharks necessitates a greater number of electrosensory pores to maintain a comparable pore density. Although gross head morphology clearly differs between sphyrnid sharks and their closest relatives the carcharhinids, a quantitative examination is lacking. Head morphology and the distribution of electrosensory pores were compared between a carcharhinid, Carcharhinus plumbeus, and two sphyrnid sharks, Sphyrna lewini and S. tiburo. Both sphyrnids had greater head widths than the carcharhinid, although head surface area and volume did not differ between the three species. The raked head morphology of neonatal S. lewini pups, presumably an adaptation to facilitate parturition, becomes orthogonal to the body axis immediately post-parturition whereas this change is much less dramatic for the other two species. The general pattern of electrosensory pore distribution on the head is conserved across species despite the differences in gross head morphology. Sphyrna lewini has a mean of 3067 ± 158.9 SD pores, S. tiburo has a mean of 2028 ± 96.6 SD pores and C. plumbeus has a mean of 2317 ± 126.3 SD pores and the number of pores remains constant with age. Sphyrnids have a greater number of pores on the ventral surface of the head whereas C. plumbeus has an even distribution on dorsal and ventral surfaces. The greater number of pores distributed on a similar surface area provides S. lewini pups with a higher density of electrosensory pores per unit area compared to C. plumbeus pups. The greater number of ampullae, the higher pore density and the larger sampling area of the head combine to provide hammerhead sharks with a morphologically enhanced electroreceptive capability compared to comparably sized carcharhinids.     

A revision of Platybothrium Linton, 1890 (Tetraphyllidea: Onchobothriidae), with a phylogenetic analysis and comments on host-parasite associations

A revision of Platybothrium Linton, 1890 is presented, based on available type and voucher material, as well as extensive new collections from elasmobranchs belonging to the Carcharhinidae (requiem sharks) and Sphyrnidae (hammerhead sharks). All 10 nominal Platybothrium species are treated or redescribed herein. Four of these 10 nominal species, in addition to one former member of Dicranobothrium Euzet, 1953, are considered valid members of Platybothrium. Five new Platybothrium species are described: P. angelbahiense n. sp. ex Carcharhinus leucas, P. coshtaprum n. sp. ex C. plumbeus, P. jondoeorum n. sp. ex Negaprion acutidens and C. melanopterus, P. kirstenae n. sp. ex C. obscurus, and P. tantulum n. sp. ex Sphyrna lewini and S. zygaena. Sixty-three morphological characters were employed in cladistic analyses of nine Platybothrium species and five outgroup species. Coding and analysis strategies were varied to assess the effects of coding inapplicable characters as missing or as a separate character state, and of excluding characters for which data are missing in more than 10% of the taxa. The analysis in which inapplicable characters were coded as a separate character state and no characters were excluded produced the best-supported and most conservative estimate of the interrelationships of Platybothrium spp. Platybothrium appears to be a monophyletic assemblage, with the most basal species being P. spinulifera Southwell, 1912. The group of species possessing an accessory piece between the hooks forms a clade within the genus. Species lacking an accessory piece, which had previously been placed in Dicranobothrium Euzet, 1953, do not appear to be each other's closest relatives; thus, Dicranobothrium is considered a synonym of Platybothrium. An examination of host associations indicated that Platybothrium species are broadly distributed among, and entirely restricted to, carcharhinid and sphyrnid shark species. Most Platybothrium species exhibit oioxenous host-specificity, with all but two species each parasitising only a single host species. In several host species, multiple Platybothrium congeners parasitise the same host individual, a phenomenon not previously reported for Platybothrium.     

A new genus and species of cestode (Rhinebothriidea) from Mobula kuhlii (Rajiformes: Mobulidae) from Malaysian Borneo

The cestode fauna of the shortfin devilray, Mobula kuhlii (Müller & Henle, 1841) was examined for the first time. The work resulted in the discovery of a new genus and species of rhinebothriidean tapeworm. Crassuseptum pietrafacei, n. gen. n. sp. is erected here on the basis of its unique scolex and proglottid morphology. Histological sections and examination by light and scanning electron microscopy demonstrated that this new genus differs from all other rhinebothriidean genera in its possession of bothridia in which the proximal and distal sides are confluent, i.e., not separated by a rim of tissue, and in its possession of testes that extend to the posterior margin of the ovary. This new species is characterized in part by its possession of stalked, elongate bothridia lacking lateral constrictions, with 13-15 prominent transverse bothridial septa and 4 reduced transverse septa, craspedote proglottids, each with 2-3 layers of testes in cross section, and a vas deferens that joins the cirrus sac at its anterior margin. Histological and optical sections through bothridial septa revealed that the transverse septa are formed by septal muscles separate from bothridial radial musculature, extending from the anterior side to the posterior side of each septum. This is only the second species rhinebothriidean cestode reported from mobulids. This study adds to the number of new species and genera of elasmobranch cestodes discovered off of the island of Borneo.     

Two new species of Paraorygmatobothrium (Cestoda: Tetraphyllidea) from weasel sharks (Carcharhiniformes: Hemigaleidae) of Australia and Borneo

Two new species of Paraorygmatobothrium Ruhnke, 1994, P. janineae n. sp. and P. kirstenae n. sp., are described from the spiral intestine of 2 shark species of the Family Hemigaleidae: Hemigaleus microstoma and Hemipristis elongata. The 2 new cestode species differ from other members of Paraorygmatobothrium in vitelline follicle distribution and possession of a cephalic peduncle. The 2 new species differ from 1 another in total length, maximum width, scolex size, number of proglottids per strobila, and number of testes per proglottid. The generic diagnosis of Paraorygmatobothrium is emended to include the new species. The results of this study extend the distribution of Paraorygmatobothrium to include the carcharhinid shark family Hemigaleidae.     

Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa

Mello, W.C., de Carvalho, J.J., Brito, P.M.M. 2011. Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa. —Acta Zoologica (Stockholm) 00 : 1–7. This study uses scanning electron microscopies to investigate and describe the microstructural diversity of dermal denticles in the family Sphyrnidae, which comprises all living hammerhead shark species, comparing them to other related taxa (i.e. Carcharhinus dussumieri, Carcharhinus plumbeus, Carcharhinus acronotus, Rhizoprionodon acutus, Negaprion brevirostris and Hemigaleus microstoma). The results reveal that sphyrnids present noticeable microstructures in the dermal denticles, distinguishing them from the other related species investigated. Additionally, scale patterns are the same in three distinct body regions (i.e. cephalic, branchial and dorsal fin). Species of Sphyrnidae that reach bigger total lengths and that are widely distributed (i.e. Sphyrna lewini and Sphyrna mokarran) presented more, smaller and nearly hexagonal microstructures that do not cover the entire scale surface, unlike species reaching smaller sizes and restricted to coastal habits (i.e. Sphyrna tiburo, Sphyrna tudes, Sphyrna media and Eusphyra blochii). The sphyrnid scales are similar to R. acutus and C. dussumieri rather than to the other species, but it is not possible to identify the sphyrnid species only by scale features. It is clear that a similar morphology of scales is not necessarily related to similar life habits, and that they are candidates to provide new characters in phylogenetical studies among sphyrnids.     

Five new species of Pedibothrium (Tetraphyllidea: Onchobothriidae) from the tawny nurse shark, Nebrius ferrugineus, in the Pacific Ocean

The spiral intestines of 7 Tawny nurse sharks (Nebrius ferrugineus; Rhincodontidae) from Australia and French Polynesia were examined for tapeworms. These sharks hosted 5 new species of Pedibothrium. The 5 species were prepared for light and scanning electron microscopy. Whereas 3 of the species exhibit the bipronged hooks typical of members of Pedibothrium, 1 species was found to possess tiny unipronged hooks or to lack some, or all, hooks, and all individuals of the fifth species appeared to lack bothridial hooks entirely. Nonetheless, the otherwise remarkable similarities between these species and the species of Pedibothrium bearing bipronged hooks were considered to be sufficient to justify the placement of these 2 species in this genus. All 5 species possess proglottid features typical of Pedibothrium, including a uterus that extends anteriorly only to the level of the cirrus sac and a cirrus sac that is bent anteriorly and is crossed by the vagina. All 5 species also exhibit uniloculated bothridia. Of particular note was the fact that all 5 species exhibit bladelike spinitrichs with elongated distal tips, a form of microthrix currently known only from species of Pedibothrium. As a consequence, these species were treated as possessing modified hooks or as having lost hooks. The diagnoses of Pedibothrium and Onchobothriidae were emended to include these species. Each of the 5 new species bears a strong resemblance to 1 or more species of Pedibothrium hosted by a species of rhincodontid shark other than N. ferrugineus. Much of Southwell's type and voucher material of Pedibothrium was located and used to verify the identity of Pedibothrium kerkhami and many of the hosts from which Southwell's material of Pedibothrium was collected. This material suggests that P. kerkhami parasitizes Stegostoma fasciatum and not N. ferrugineus.     

Scyphophyllidium uruguayense n. sp. (Eucestoda: Tetraphyllidea) in Mustelus mento (Cope, 1877) (Chondrichthyes: Carcharhiniformes: Triakidae) from La Paloma, Uruguay.

A new species of Scyphophyllidium inhabits Mustelus mento near La Paloma, Uruguay. It resembles Scyphophyllidium giganteum from the Atlantic Ocean and specimens identified as S. giganteum from California by having anapolytic strobilae 155-258 mm long, 250-300 craspedote proglottids, scoleces 1.2-1.4 mm wide, necks 34-41 mm long, immature and mature proglottids wider than long, gravid proglottids wider than long to longer than wide, genital pores averaging 28% of proglottid length from the anterior end, relatively flat ovaries with digitiform lobes reaching the lateralmost extent of the testicular field, vitellaria in 2 fields converging toward the proglottid midline, straight and short cirrus sacs, and postvaginal vas deferens. The bothridia of the new species have accessory bothridial suckers that are smaller than those of California specimens; European specimens reportedly lack accessory bothridial suckers. The new species possesses a uterine duct that joins the uterus at the level of the genital atrium and ventral osmoregulatory ducts medial rather than lateral to the dorsal ducts, an arrangement described for Californian but not European specimens. It differs from both European and Californian specimens by having longer cirri, more testes per proglottid, prominent scales covering the neck, and vaginae and uterine ducts coiled immediately preovarially. Pithophorus, Marsupiobothrium, and Scyphophyllidium may form a clade.     

Microtriches of tetraphyllidean metacestodes from Western Mediterranean striped dolphins (Stenella coeruleoalba)

The tegumental structures of two types of tetraphyllidean plerocercoids and two types of merocercoids (Phyllobothrium delphini and Monorygma grimaldii) from Mediterranean striped dolphins, Stenella coeruleoalba, are described for the first time using scanning electron microscopy. The tegument of all of the specimens was fully covered with microtriches. Four basic types were found: filitriches, blade-like spinitriches of different sizes and shapes, cone-shaped spinitriches (with two parallel small projections of equal length at the apex), and crowned cylindrical spinitriches (with 6-7 small papillae forming a crown at the apex); the two latter types are newly described. The two types of plerocercoids had a similar morphology and distribution of microtriches; in addition, cilium-like projections appeared interspersed among the microtriches on the apical sucker, accessory suckers, and distal bothridial loculus. Merocercoids exhibited a greater variety of tegumental structures, especially on the distal bothridial loculus. Both merocercoid types had regularly spaced papillae or "buttons" on the accessory suckers and the distal bothridial loculus that were composed of a central cilium-like projection surrounded by numerous filitriches. However, crowned cylindrical spinitriches were specific to P. delphini and cone-shaped spinitriches were specific to M. grimaldii. Differences in the morphology and distribution of scolex microtriches of adult cestodes have been considered useful for species identification. A previous molecular study has suggested that P. delphini and M. grimaldii are actually different congeneric species. Our study has shown that significant differences in the morphology and distribution of microtriches occur between these species at the merocercoid stage.     

A new genus and two new species of Aporhynchidae (Cestoda: Trypanorhyncha) from catsharks (Carcharhiniformes: Scyliorhinidae) off Taiwan

New collections of cestodes from the spiral intestines of catsharks (Carcharhiniformes: Scyliorhinidae) off Taiwan have led to the discovery of a new genus and 2 new species of trypanorhynchs. These taxa are relatively unique among trypanorhynchs in their lack of all elements of the rhyncheal apparatus. The new genus, Nakayacestus n. gen., is considered to belong with Aporhynchus in the Aporhynchidae. In addition to lacking the rhyncheal apparatus, these 2 genera share circum-medullary vitelline follicles, post-ovarian testes, and complex terminal genitalia consisting of accessory, external, and internal seminal vesicles. The 2 genera differ conspicuously in spinithrix configuration; whereas both species of Nakayacestus n. gen. bear scolex spinitriches that are bifid, trifid, or pectinate, species of Aporhynchus either lack scolex spinitriches entirely or possess spathulate spinitriches. The configuration of the bothria of the 2 genera also differ conspicuously. Whereas the bothria of Aporhynchus are sessile and generally do not extend beyond the lateral margins of the cephalic peduncle, those of Nakayacestus bear only a tenuous connection with the scolex proper, being conspicuously free both anteriorly and posteriorly and extending conspicuously beyond the cephalic peduncle. Futhermore, the boundary between the scolex and the strobila of members of the new genus is clearly delineated, whereas this distinction is ill-defined in species of Aporhynchus. Nakayacestus takahashii n. sp., the type of the new genus, was collected from the Broadmouth catshark, Apristurus macrostomus, and differs from Nakayacestus tanyderus n. sp., collected from the Blacktip sawtail catshark, Galeus sauteri, in being shorter, bearing a longer pedunculus scolecis, an ovary that is more posterior in the proglottid, and fewer post-ovarian testes. Furthermore, the 2 new species differ conspicuously from one another in the configuration of their scolex spinitriches.     

Anthobothrium lesteri n. sp. (Cestoda: Tetraphyllidea) in Carcharhinus melanopterus from Heron Island, Australia, with comments on its site, mode of attachment, reproductive strategy and membership of the genus

Anthobothrium lesteri n. sp. in Carcharhinus melanopterus from Heron Island, Australia is described and figured. A combination of characters, namely the number of testes, a weakly laciniate strobila and mature proglottis which is conspicuously longer than wide distinguishes it from other species that appear to be consistent with van Beneden's original concept of Anthobothrium . The scolex and the peduncle are relatively small and frail when compared with the rest of the strobila and with the detached proglottis. A myzorhynchus is absent and the stalked, undivided, simple bothridia have thickened margins. Two circular areas of muscles, which resemble accessory suckers, occur in the centre of each bothridium. There is a distinct cephalic peduncle with spiniform blade-like microtriches followed by craspedote proglottides which have a posterior four-lobed velum. Apolysis is well developed and the oncosphere has a polar filament and a dense covering of spines. Comments are made on the site, the mode of attachment, an aspect of the reproductive strategy of the new species in relation to intestinal eversion in some sharks, and membership of the genus.     

The use of an unoccupied aerial vehicle to survey shark species over sand and rocky-reef habitats in a marine protected area

Cabo Pulmo National Park was established in 1995 and has since seen a large increase in fish biomass. An unoccupied aerial vehicle (UAV) was used to survey shallow coastal habitat in which lemon sharks (Negaprion brevirostris), bull sharks (Carcharhinus leucas) and Pacific nurse sharks (Ginglymostoma unami) were recorded. Sharks were more common in the afternoon, potentially using warmer shallow areas to behaviourally thermoregulate. This study highlights UAV surveying to be a viable tool for species identification, a limitation of previous terrestrial surveys conducted in the area.