Lateral Hooklets Research Articles

Diphyllidean cestodes from the bigeye houndshark Iago omanensis (Norman) (Carcharhiniformes: Triakidae) in the Gulf of Oman, with the description of Coronocestus ehsanentezarii sp. nov. (Echinobothriidae).

A new species of Coronocestus Caira, Marques, Jensen, Kuchta and Ivanov, 2013 is described from Iago omanensis (Norman) from the Gulf of Oman. Coronocestus ehsanentezarii sp. nov. differs from C. musteli (Pintner, 1889) Caira, Marques, Jensen, Kuchta and Ivanov, 2013 in that its ovary is H- rather than U-shape. The new species is easily distinguished from C. diamanti (Ivanov and Lipshitz, 2006) Caira, Marques, Jensen, Kuchta and Ivanov, 2013 by the number of spines per column on the cephalic peduncle (24-36 vs 95-118). It differs from C. hormozganiense (Haseli, Malek, Palm and Ivanov, 2012) Caira, Marques, Jensen, Kuchta and Ivanov, 2013 based on a greater number of spines per column on the cephalic peduncle (24-36 vs 18-21). The new species differs from C. notoguidoi (Ivanov 1997) Caira, Marques, Jensen, Kuchta and Ivanov, 2013 in that of its scolex is craspedote rather than acraspedote. Unlike C. coronatum (Robinson 1959) Caira, Marques, Jensen, Kuchta and Ivanov, 2013, C. ehsanentezarii sp. nov. possesses 29-35 rather than 20 apical hooks in each dorso-ventral group. The new species possesses lateral hooklets with two rows (a and b designations) in each cluster. This character had been presented earlier only for Andocadoncum Abbott and Caira, 2014. Furthermore, a new locality record is presented for C. diamanti from Iago omanensis in the Gulf of Oman. Thus, I. omanensis certainly hosts two diphyllidean species simultaneously in the Gulf of Oman. The generic diagnosis of Coronocestus is also revised to include new data.

Morphology Meets Molecules: A New Genus and Two New Species of Diphyllidean Cestodes From the Yellowspotted Skate,Leucoraja wallacei, from South Africa

Two morphologically disparate undescribed species of diphyllidean cestodes from the Yellowspotted skate, Leucoraja wallacei , from South Africa were included in a recent molecular phylogenetic study aimed at revising diphyllidean classification. From a molecular standpoint, these species were determined to be only distantly related to one another. One (originally referred to as Echinobothrium n. sp. 2) showed affinities with species of the batoid-parasitizing Echinobothrium sensu stricto and is described here as Echinobothrium marquesi n. sp. This species most closely resembles Echinobothrium joshuai, an affinity supported by the previous molecular study, but differs in the form of its "B" hooks and degree of overlap between bothria and cephalic peduncle. The other species (originally referred to as New genus n. sp. 1), although exhibiting the full complement of scolex armature, grouped among primarily shark-hosted genera, most of which lack or exhibit reduced scolex armatures. That unexpected result suggested that erection of a novel genus might be warranted, but morphological grounds supporting the action were not apparent at that time. The present study aimed to explore the morphology of this taxon in more detail. Light and scanning electron microscopy revealed this taxon to be exceptional in that its lateral hooklets, which are arranged in 2 clusters like those of Echinobothrium and Coronocestus, are unique in being arranged in anterior and posterior rows, rather than in a single row. Andocadoncum n. gen. is erected, with Andocadoncum meganae n. sp. as its type, to accommodate this taxon. A minor adjustment to the existing hook formula by presenting counts for the anterior hooklets (a) separately from the posterior hooklets (b) readily accommodates this new form. Leucoraja wallacei is distinctive among skates in hosting 2 different genera of diphyllideans. In the context of the previous molecular phylogenetic analyses, it appears that the presence of Andocadoncum n. gen. in this skate species may be the result of a host-switching event involving a weakly or unarmed shark-hosted taxon moving to a batoid-a shift that was likely accompanied by a return to the fully armed condition seen, for example, in other batoid-parasitizing members of the order.

Two new species of Halysioncum Caira, Marques, Jensen, Kuchta et Ivanov, 2013 (Cestoda, Diphyllidea) from Indo-Pacific rays of the genus Aetomylaeus Garman (Myliobatiformes, Myliobatidae)

Recent collections of cestode parasites from two species of the myliobatid genus Aetomylaeus Garman from several localities in the Pacific Ocean resulted in the discovery of two new species of Halysioncum Caira, Marques, Jensen, Kuchta et Ivanov, 2013. Halysioncum gibsoni sp. n. from Aetomylaeus maculatus (Gray) in the South China Sea off Borneo differs from all of its congeners in having the following combination of characters: 27 apical hooks (14 type A and 13 type B hooks), 11-12 lateral hooklets, 22-28 spines per column on the cephalic peduncle, testes distributed in a single column and an internal seminal vesicle. Halysioncum arafurense sp. n., recovered from Aetomylaeus cf. nichofii 2 (sensu Naylor et al. 2012b) in the Arafura Sea off the Wessel Islands, Northern Territory, Australia, can be distinguished from its congeners based on the following combination of characters: 23 apical hooks (12 type A and 11 type B hooks), the number of lateral hooklets (9-11), the number of spines per column on the cephalic peduncle (20-24), the number and distribution of the testes (13-15 testes in two irregular columns), and the distribution of vitelline follicles (interrupted dorsally at the level of the ovarian lobes). Both species represent the first verified records of diphyllideans from eagle rays of the genus Aetomylaeus and formally extend the host associations of diphyllideans to include a third genus of Myliobatiformes. The myliobatiforms are indeed an understudied group of available hosts for diphyllideans and represent interesting target hosts if the diversity of diphyllidean tapeworms is to be fully estimated and understood.

Phylogenetic analysis and reconfiguration of genera in the cestode order Diphyllidea

The generic boundaries of the Diphyllidea are reassessed based on parsimony and likelihood phylogenetic analyses of 28S rDNA (ribonucleic acid large subunit), 18S rDNA (ribonucleic acid small subunit), and COI (cytochrome oxidase subunit I) sequence data for 31 species representing morphological variation across the order. Trees resulting from these analyses yielded a number of well-supported clades that are congruent with unique morphological features mandating generic revision of the order and erection of at least two new genera. Species originally assigned to Echinobothriumvan Beneden, 1849 but bearing a corona of spines on the region of the scolex anterior to the bothria and posterior to the apical organ armature are transferred to Coronocestus n. gen.; members of this genus typically parasitize triakid sharks, although one report from a hemiscylliid shark exists. Species with lateral hooklets arranged in continuous bands, rather than in two distinct clusters, are transferred to Halysioncum n. gen.; all species parasitize batoids, mostly myliobatids and rhinopterids, but a few records also exist from arhynchobatids, rhinobatids, platyrhinids and urotrygonids. Our analyses support transfer of the five species originally assigned to MacrobothridiumKhalil and Abdul-Salam, 1989 owing to their lack of cephalic peduncle spines to Echinobothrium. As a consequence, Echinobothrium sensu stricto includes species both with and without spines on the cephalic peduncle, but all members of the genus possess lateral hooklets arranged in clusters on either side of the dorsal and ventral apical hooks. With respect to diphyllideans parasitizing catsharks, AhamulinaMarques, Jensen and Caira, 2012 is unique in possessing apical hooks but lacking lateral hooklets and DitrachybothridiumRees, 1959 is unique in entirely lacking scolex armature. By far the majority of species of Echinobothrium sensu stricto parasitize skates of the family Rajidae, guitarfish of the family Rhinobatidae, and stingrays of the dasyatid genera Taeniura Müller and Henle, Dasyatis Rafinesque, and Himantura Müller and Henle, although a single species each has been reported from Anacanthobatidae, Rhynchobatidae, Platyrhinidae and Myliobatidae. It now seems clear that while by far the majority of diphyllideans parasitize batoids, the diphyllideans parasitizing sharks, and catsharks in particular, remain problematic. Additional collections from these carcharhiniform hosts are likely to be particularly illuminating.

Two New Species of Echinobothrium (Cestoda: Diphyllidea) from Batoids off South Africa

Examination of the bycatch from a hake survey off the coast of South Africa in 2010 yielded new diphyllidean tapeworms from 2 species of batoids not previously examined for this cestode order. The spotted skate, Raja straeleni (Rajidae), was found to host Echinobothrium dorothyae n. sp., which differs in hook formula from 37 of its 43 congeners, and can be distinguished from the 6 remaining species in features such as length, number and arrangement of testes, and number of cephalic peduncle spines. The second new species, Echinobothrium dougbermani n. sp., was collected from the lesser guitarfish, Rhinobatos annulatus (Rhinobatidae). This species differs from all but 6 of its congeners in hook formula. With respect to these 6 species, it differs in numbers of cephalic peduncle spines, testes and proglottids, overall size, and ovary shape. Furthermore, it bears lateral hooklets that are more posterior in position relative to the apical hooks than is seen in most of its congeners. Scanning electron microscopy of these 2 species highlights ultrastructural differences that exist among diphyllideans, which, although their complete taxonomic distribution and function(s) are not yet understood, are interesting to consider. These are: the presence or absence of a spinithrix-lacking “V” shaped region on the medial distal bothrial surface, variation in spinithrix form from anterior to posterior on the proximal bothrial surface, and surface elaborations in the form of tiny, ridgelike structures of varying length that may or may not anastomose with one another. The relatively random nature of the selection of the skates and guitarfish hosts sampled here supports the notion that the small percentage of species in these genera that are currently known to host diphyllideans, and likely also their respective families Rajidae and Rhinobatidae, are likely a result of a lack of sampling.

Ahamulina n. gen. (Cestoda: Diphyllidea) from the polkadot catshark, Scyliorhinus besnardi (Carcharhiniformes: Scyliorhinidae), off Brazil

A new genus and species of diphyllidean, Ahamulina catarina n. gen. n. sp., is described from the polkadot catshark, Scyliorhi-nus besnardi, from Santa Catarina, Brazil. The new genus exhibits apical organ armature that is unique among diphyllideans inthe arrangement and shape of the apical hooks as well as in the lack of lateral hooklets. The taxon also exhibits a bipartite cirrussac. This is the seventh diphyllidean reported from a shark, and the third reported from a catshark suggesting that the dearth of cestode data for these particular sharks belies the true extent of diphyllidean diversity they host.

Two new species of Echinobothrium van Beneden, 1849 (Cestoda: Diphyllidea) from the Persian Gulf

Two new species of diphyllidean cestodes are described from the Persian Gulf, Echinobothrium persiense n. sp. from Rhinobatos punctifer Compagno & Randall and Echinobothrium hormozganiense n. sp. from Mustelus mosis Hemprich & Ehrenberg. E. persiense is the first record of a species of Echinobothrium van Beneden, 1849 from R. punctifer and these two new species increase the number of diphyllideans known from the Persian Gulf from one to three. The number of apical hooks of E. persiense (hook formula: {5-6 6/5 5-6}) is distinct from all other species in the genus except for E. affine Diesing, 1863, E. harfordi McVicar, 1976, E. bonasum Williams & Campbell, 1980, E. fautleyae Tyler & Caira, 1999, E. syrtense (Neifar, Tyler & Euzet, 2001) Tyler, 2006 (emend), E. chisholmae Jones & Beveridge, 2001, E. tetabuanense Ivanov & Caira, 2012, E. sematanense Ivanov & Caira, 2012 and E. weipaense Ivanov & Caira, 2012. Echinobothrium persiense can be distinguished from all other species of the genus with 11 apical hooks by a combination of the following features: armed cephalic peduncle, testes arranged in a single column, lateral hooklets arranged in two groups, U-shaped ovary, cephalic peduncle length (124-181 μm), genital pore and cirrus-sac position, and by having 10-14 spines per row on the cephalic peduncle. Echinobothrium hormozganiense has a hook formula of {12-15 16/15 12-15} and is similar to E. musteli Pintner, 1889, E. notoguidoi Ivanov, 1997 and E. diamanti Ivanov & Lipshitz, 2006 by possessing additional spines between the rostellum and the bothria. It differs from E. musteli by having an H-shaped ovary and lateral hooklets arranged in two lateral groups, and the number of spines per row on the cephalic peduncle (18-21) readily differentiates it from E. notoguidoi (24-26) and E. diamanti (95-118). With these two new species, Echinobothrium van Beneden, 1849 now includes 45 valid species.

Three new species of Echinobothrium (Cestoda: Diphyllidea) from Indo-Pacific stingrays of the genus Pastinachus (Rajiformes: Dasyatidae)

Three new species of diphyllidean cestodes are described from stingrays of the genus Pastinachus from the Indian and Pacific Oceans. All three new species differ from all but 10 of the 36 valid species of Echinobothrium van Beneden, 1849 in that they bear lateral hooklets arranged in a continuous band across each lateral surface of the rostellum joining the groups of dorsal and ventral apical hooks, rather than arranged in distinct dorsal and ventral groups, on each side of the apical hooks. Echinobothrium nataliae sp. n. ex Pastinachus solocirostris off Borneo differs from other relatives in the following combination of characters: number of spines in each column on the cephalic peduncle, number of lateral hooklets and number of apical hooks. Echinobothrium reginae sp. n. ex Pastinachus cf. sephen off Madagascar differs from all congeners in the following combination of characters: number of hooklets and number of spines on the cephalic peduncle. Echinobothrium vojtai sp. n. from an undescribed species of Pastinachus off Borneo differs from its congeners in the following combination of characters: number of hooklets, number of apical hooks and number of spines in each column on the cephalic peduncle. The hook formula was modified to accommodate species with lateral hooklets arranged in a continuous band as follows: {(LH) AH(A)/AH(B)}, where (LH) is the total number of lateral hooklets in a band. A table of all nominal species of Echinobothrium, showing their taxonomic status, type host and locality, number of peduncle spines in a column and hook formula, is presented. Macrobothridium djeddensis and Macrobothridium sinensis are transferred to Echinobothrium. In addition, Echinobothrium deeghai is considered as a species inquirenda.

Diphyllidean cestodes of the Gulf of California, México with descriptions of two new species of Echinobothrium (Cestoda: Diphyllidea).

As part of a survey of parasites of elasmobranchs in the Gulf of California, a second and final report of the diphyllidean cestodes resulting from the survey is presented. Of 43 species of elasmobranchs examined for parasites, 7 (Rhinobatos productus, Rhinobatos leucorhynchus, Myliobatis californicus, Myliobatis longirostris, Urobatis halleri, Urobatis maculatus, and Rhinoptera steindachneri) were found to host diphyllidean cestodes, all belonging to Echinobothrium. No species of either of the other 2 diphyllidean genera, Dirrachybothridium or Macrobothridium, were discovered. A greater diversity of diphyllideans was found in 1996 than in 1993. Two new species, Echinobothrium hoffmanorum n. sp. and Echinobothrium rayallemangi n. sp. are described from the spiral intestines of U. maculatus and R. leucorhynchus, respectively. Echinobothrium hoffmanorum is unique in its possession of the following combination of characters: 19-21 apical hooks in each dorsoventral group, 12-22 lateral hooklets in each group, 10-17 cephalic peduncle spines per column, 4-8 testes, 4-10 segments and eggs with a single filament. Echinobothrium rayallemangi is unique in its possession of the following combination of characters: 23 apical hooks in each dorsoventral group, 20-23 lateral hooklets in each group, 2-5 cephalic peduncle spines per column, 4-6 testes, and 4-6 segments. These 2 new species, together with Echinobothrium mexicanum and Echinobothrium fautleyae, brings the total number of diphyllideans known from the Gulf of California to 4. The survey of diphyllidean cestodes of the Gulf of California has resulted in a new host record for Echinobothrium for each of the host species mentioned above, with Rhinobatos and Urobatis representing new host genera and Urolophidae a new host family for Echinobothrium.

Two New Species of Echinobothrium (Cestoidea: Diphyllidea) from Myliobatiform Elasmobranchs in the Gulf of California, Mexico

Two new species of diphyllidean cestodes, Echinobothrium mexicanum n. sp., and Echinobothrium fautleyae n. sp., are described, the former from the spiral intestines of the bat rays Myliobatis californicus and Myliobatis longirostris and the latter from the spiral intestine of the cownose ray Rhinoptera steindachneri, all caught in the Gulf of California, México. Echinobothrium mexicanum is most easily distinguished from the majority of the species of the genus by the number of large apical hooks in each dorsoventral group (23) and from the remainder in the number of lateral hooklets in each group on the scolex. Echinobothrium fautleyae differs conspicuously from all other members of the genus in that the first and last lateral hooklets in each group are distinctly larger than the other hooklets in each group. Serial sections of the scoleces of these 2 new species confirm that the attachment structures on the scolex are bothria, rather than bothridia, as has been described in other species in the genus, suggesting that the attachment structures of the scolex should be examined in more detail in the genus in general. Palmate microtriches of various forms cover the proximal bothrial surfaces of both new species and are also found on the dorsal bothrial surfaces of E. fautleyae. The distal bothrial surfaces of E. mexicanum are covered with slender spiniform and short filiform microtriches. The cephalic peduncles of both species possess short filiform microtriches only. Comparison of these 2 new species with the other 3 species in this genus that have been examined with SEM suggests that the various forms and distributions of these microtriches is unique in each of these 2 species. We believe these features will prove to be taxonomically useful.

Shape Echinobothrium californiense n. sp. (Cestoda: Diphyllidea) from the thornback ray shape Platyrhinoidis triseriata (Chondrichthyes: Rajoidei) and a key to the species in the genus

A new cestode, Echinobothrium californiense n. sp., from the spiral intestine of Platyrhinoidis triseriata, taken in California waters is described. The new species is distinguished from all other species of Echinobothrium by a rostellar armature consisting of 2 apical groups of 20–22 large hooks each, a continuous row of 19–24 hooklets on each lateral surface, 8 rows of 6–7 spines each on the cephalic peduncle, 4–9 segments and 8–11 testes per segment. The new species is most similar to E. coronatum, E. helmymohamedi, E. longicolle, E. acanthocolle and E. pigmentatum. E. californiense can be differentiated from E. coronatum in having fewer spines per row on the cephalic peduncle (32 in E. coronatum), and fewer lateral hooklets (28). It differs from E. helmymohamedi in the number of lateral hooklets (0 in E. helmymohamedi), number of spines per row on the cephalic peduncle (10–12) and number of testes (12–15), and also from E. longicolle in the presence of lateral hooklets (0 in E. longicolle), number of spines per row on the cephalic peduncle (180) and in the number of testes (26–30). E. acanthocolle can be distinguished from the new species in the number of large apical hooks (24 in E. acanthocolle), absence of lateral hooklets and number of testes (23–25). Finally, E. californiense is most similar to E. pigmentatum, in having a similar combination of number of large apical hooks (20–22) and lateral hooklets (19–24 vs. 20–22 in a continuous row), but differs in the number of spines per row in the cephalic peduncle (6–7 vs 9–13 in E. pigmentatum), number of testes (8–11 vs 5–7), body length (1.5–4.5 vs 0.9–1.4~mm), mm), "="?mm), -> ?~number of segments (4–9 vs 3–4), ratio of bothridial length to cephalic peduncle length (1:0.53–0.61 vs 1:1.24–1.71), a notched posterior margin of the bothridium and in the possession of an internal seminal vesicle. E. californiense can also be clearly distinguished from E. raschii and E. euzeti previously reported from the eastern Pacific, in the number of large apical hooks (23–25 in E. raschii and 25 in E. euzeti), number of lateral hooklets (27–36 and 6–7), number of spines per row on the cephalic peduncle (21–26 and 100–107) and number of testes (17–23 and 37–42). An updated key to the species of the genus Echinobothrium is presented.

Echinobothrium raschii n. sp. (Cestoda: Diphyllidea) from Rhinoraja longi (Chondrichthyes, Rajoidei) in the Bering Sea

Echinobothrium raschii n. sp. from the spiral intestine of Rhinoraja longi in the Bering Sea, off the Aleutian Islands of Alaska is described. On the basis of the armature of the rostellum and cephalic peduncle the new species most closely resembles Echinobothrium acanthinophyllum, Echinobothrium acanthocolle, Echinobothrium coronatum and Echinobothrium helmymohamedi. Echinobothrium raschii n. sp. can be differentiated from all but E. coronatum by the possession of a continuous row of 27-36 lateral hooklets per side on the scolex and 21-26 spines per row on the cephalic peduncle. In E. acanthinophyllum there are fewer spines per row on the cephalic peduncle (13) and only 2 groups of 4 lateral hooklets per side instead of a continuous row of lateral hooklets; E. acanthocolle bears only 5 spines per row on the cephalic peduncle and has no lateral hooklets; E. helmymohamedi has 10-12 spines per row on the cephalic peduncle and bears no lateral hooklets. Echinobothrium raschii n. sp. can be distinguished from E. coronatum by number of spines per row on the cephalic peduncle (average 24 vs. 32) and testes number (17-23 vs. 9-11). The combined characters of 2 groups of 23-25 large apical hooks, a continuous alternating row of 27-36 hooklets on each side of the scolex between the groups of large apical hooks, 21-26 spines per row on the cephalic peduncle, and 17-23 testes per segment differentiates E. raschii from all other species of Echinobothrium. The prevalence of infection was 50% and mean intensity of infection was 8.7 worms per host. The current status of the genus Echinobothrium is discussed and a tabulation of the species presented.

Étude de l’oncomiracidium de Diplozoon nipponicum Goto, 1891

Diplozoon nipponicum Goto 1891, a branchial parasite of Cyprinus carpio is mentioned for the first time in France and Western Europe. Carps, along with their Monogenea, were introduced from Hungary. After being obtained experimentally, the oncomiracidium is thoroughly studied (excretory system, ciliated cells, chaetotaxy, haptor). A new haptor for the genus Diplozoon is described: two pairs of larval lateral hooklets are present. The taxonomic and phylogenic implications of these observations are discussed for Diplozoon and Discocotylidae. Mainly as a result of the study of the haptor and the egg structure, it appears that two groups occur, the taxonomic and evolutive significance of which are to be discussed in Diplozoon.