A new species of Acanthobothrium (Cestoda: Tetraphyllidea: Onchobothriidae) from the ocellate river stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in Argentina

Examination of the spiral intestines of 44 freshwater stingrays, Potamotrygon motoro, from tributary rivers of the Parana River in Argentina, allowed for the collection of specimens of an undescribed species of Acanthobothrium. Acanthobothrium ramiroi n. sp. can be distinguished from all other congeners by the combination of the following characters: asymmetrical hooks (medial and lateral hooks conspicuously different in size and form, with axial prong of medial hooks stouter than abaxial prong), hook size (total length of medial hooks up to 242 microm, total length of lateral hooks up to 239 microm), bothridia not fused to the scolex proper at posterior ends, worm size (51-84 mm long), and the presence of a conspicuous vaginal sphincter. The new species is different from all other species of Acanthobothrium in freshwater potamotrygonids, except Acanthobothrium terezae, in having conspicuous asymmetrical hooks. The main differences that allow for the distinction between A. ramiroi and A. terezae include hook size, the way the bothridia are attached to the scolex proper, and the shape of the older gravid segments. The discovery of a new species of Acanthobothrium from a potamotrygonid extends our understanding of the diversity of the genus in freshwater stingrays in South America.     

The development of the rostellar hooks of Taeni pisiformis.

Beveridge I. &; Rickard M. D. 1976. The development of the rostellar hooks of Taenia pisiformis. International Journal for Parasitology6: 55–59. Growth and development of the rostellar hooks of Taenia pisiformis were examined in experimentally infected rabbits. Hook differentiation and the sizes of various parts of the hook were related to the age of cysticerci, the ability of cysticerci to resist the effects of digestive enzymes in vitro and their ability to infect dogs. Hook growth was completed 56 DAI though cysticerci were capable of evaginating in vitro 35 DAI and of infecting dogs 42 DAI. When 42-day old cysticerci were fed to dogs, no further hook growth occurred.     

Phylogenetic position of Acanthobothrium cleofanus (Cestoda: Onchoproteocephalidea) using molecular evidence

Despite the large number of species described to date for the onchoprotepcephalid genus Acanthobothrium (207), only 16 named species have a genetic sequence. With this background, specimens of adult cestodes of the stingray Hypanus longus were collected off San Blas, Nayarit, and onchoproteocephalid larvae in the carangid fish Trachinotus rhodopus from Puerto Ángel, Oaxaca, both located on the Pacific coast of Mexico. The objective of this work is to investigate the phylogenetic position of these adults and larvae using nuclear ribosomal markers (18S rDNA and 28S rDNA). Morphologically, adult specimens were identified as Acanthobothrium cleofanus; larvae were identified only to family level. The phylogenetic position of both taxa was investigated based on the information of two nuclear molecular markers analyzed under Parsimony (PA) and Bayesian Inference (BI) methods. The newly generated sequences of A. cleofanus from Nayarit are identical to the sequences of several samples of Acanthobothrium sp. collected in the Mexican Pacific, which sequence are available in GenBank; DNA sequences obtained from onchoproteocephalid larva clearly place this taxon within Acanthobothrium but representing an independent lineage. In the resulting phylogenetic trees, Uncibilocularis okei was found nested within Acanthobothrium with an unstable position depending on the optimality criteria, indicating the need for more molecular analyzes with a greater number of species of both genera prior to define its phylogenetic relationships.     

Two new species of Acanthobothrium Beneden, 1849 (Tetraphyllidea: Onchobothriidae) from horn sharks in the Gulf of California,Mexico

Between 1993 and 1996, 26 individuals of two species of horn sharks were collected from the upper Gulf of California and their spiral intestines examined for onchobothriid tapeworms. Heterodontus francisci was found to host Acanthobothrium puertecitense n. sp. Based on the criteria of Ghoshroy & Caira (2001), this is a Category 4 species (with >15mm total length, >50 proglottids, >80 testes and a symmetrical ovary). It differs from the four Category 4 species previously reported from either the western Atlantic or eastern Pacific Oceans, including A. bajaense (emend.) which was described from H. francisci, in hook-shape, total length, number of proglottids, number of testes and number of columns of vitelline follicles. H. mexicanus was found to host Acanthobothrium santarosaliense n. sp., which, based on the criteria of Ghoshroy & Caira (2001) is a Category 3 species (with >15mm total length, >50 proglottids, >80 testes and an asymmetrical ovary). A. santarosaliense differs from the five Category 3 species previously reported from either the western Atlantic or eastern Pacific Oceans in its size, euapolytic nature, lack of dark matrix from the bases of the hooks, hook-shape, and distribution and number of testes. In addition to the difference in ovarian symmetry, A. puertecitense possesses fewer testes, fewer proglottids, is a shorter worm, possesses a more anterior genital pore and vitelline follicles which extend further forward anteriorly than in A. santarosaliense. This represents the first report of onchobothriids from H. mexicanus and the first report of onchobothriids from H. francisci in the Gulf of California. The apparent host-specificity of both new species should be viewed with caution until a greater sample of host individuals of both species can be examined. The fact that both new tapeworm species are known only from the Gulf is also considered to be a preliminary result, given the small sample of host individuals examined from these regions to date. This brings the total number of species of Heterodontus known to host Acanthobothrium to four and the total number of Acanthobothrium species described from heterodontiform sharks to five.     

Onchobothrium malakhovi n. sp. (Cestoda: Onchoproteocephalidea) ex Bathyraja (Arctoraja) sexoculata (Rajiformes: Arhynchobatidae) from Kuril Islands (Russia), with comments on the status of the genus Onchobothrium

Onchobothrium malakhovi n. sp. was found in the spiral valve of the softnose skate Bathyraja (Arctoraja) sexoculata off the Simushir Island (Kuril Islands, Russia). The new species has bothridia with three loculi and no additional suckers on bothridia, single-toothed hooks unconnected by their bases, no spines at the bases of the hooks, dense matrix around the hook bases shaped as an unpaired butterfly wing, and a short and wide ovary. Onchobothrium malakhovi n. sp. differs from O. antarcticum and O. magnum in having a smaller total length, cirrus sac and ovary, smaller testes and eggs. Additionally, the new species differs from O. antarcticum by the absence of a vaginal sphincter and shorter bothridia; differs from O. magnum in having fewer proglottids and smaller vitelline follicles. It differs from O. farmeri, O. convolutum, and O. pseudouncinatum, by the absence of a small spine at the base of the hooks and the absence of accessory suckers on bothridia; from O. pseudouncinatum, additionally, by unconnected hooks; from O. schizacanthium, by the number of testes and by the presence of a postvaginal group of testes. Onchobothrium malakhovi n. sp. was placed among other members of the Onchoproteocephalidea with a high support based on the sequence data for the D1-D3 region of the 28S rDNA and cox1 gene. The phylogenetic position of the genus Onchobothrium sensu lato remains ambiguous. We suggest that Onchobothrium sensu lato is a complex genus containing at least two morphologically different groups of species. Onchobothrium farmer, O. convolutum, O. schizacanthium, and O. pseudouncinatum, for which there are no molecular genetic data, are considerably different morphologically from O. malakhovi n. sp., O. antarcticum, and O. magnum. A new genus might have to be established for the latter three species after the accumulation of genetic data.     

Changes in the curvature of sperm apical hooks in murine rodents

Sperm apical hooks in murine rodents play an important role in sperm competition. Apical hooks are more curved and longer in species with relatively larger testes, that is in species with a higher risk of sperm competition. The sperm can form aggregations, ‘trains’, that can move faster than individual sperm, thus reaching the egg earlier as was observed in Apodemus sylvaticus. The apical hook plays an important role for train formation. This study focuses on the changes in the curvature of sperm apical hooks during the final stages of spermiogenesis and stages before fertilization (sperm-life span). Apical hook curvatures of field mice (A. agrarius and A. sylvaticus) vary significantly between dormant and active sperm. In contrast, there are no significant differences among the stages in the eastern house mouse. Since there are high ranges of angle values in all stages, the mean angles of apical hook curvature are not appropriate for evaluating risk of sperm competiton. The ranges of angle values point to a level of flexibility of the apical hooks. The lengths of sperm hooks in individual species do not change during particular stages. The length and flexibility of the sperm apical hooks are important for the formation of sperm aggregations, thus these sperm characters indicate the risk of sperm competition and the sperm strategies in murine rodents.     

Echinococcus granulosus: Hook-muscle systems and cellular organisation of infective oncospheres

The morphology of the oncospheres of Echinococcus granulosus has been reconstructed from thin and semi-thin serial sections. Four major types of oncospheral cells have been identified. These consist of: (1) a bi-nucleate medullary center, (2) glandular regions (eight nuclei) subdivided into three types of oncospheral glands, (3) ten germinative cells, and (4) 34 muscle cells, of which 16 are somatic and 18 are hook muscle cells. The hook muscle cells of each hook are organized functionally into the three following systems: (1) the protraction system, for hook extension, (2) the abduction system for drawing the hooks together toward the median plane of bilateral symmetry, and (3) the retraction system for pulling the hooks back into the body. The interconnections observed between different muscle fibers provide a structural basis for coordinated hook action.     

Involvement of ethylene in responses of etiolated bean hypocotyl hook to coumarin

Coumarin, at concentrations between 1.0 and 0.1 mm, inhibited red light-induced opening of the etiolated bean hypocotyl hook. In addition, anthocyanin synthesis and geotropic bending were inhibited. Coumarin stimulated ethylene synthesis, and ethylene was shown to mediate the inhibitory actions of coumarin. This conclusion was supported by: (a) the parallel concentration dependence and time sequence of hook closing and ethylene synthesis, (b) the restriction of the bulk of coumarin-induced ethylene production to the curved portion of the hook where opening is expressed, (c) the ability of both coumarin and ethylene to reclose partially opened hooks, and (d) the ability of exogenous ethylene, in the amounts produced by coumarintreated hooks, to duplicate the inhibitory effects of coumarin. There was an increasing stimulation of growth of the straight portion of the hypocotyl hook section as coumarin concentrations were increased from 0.1 to 1.0 mm. This action of coumarin was not duplicated by ethylene and occurred regardless of the presence or absence of added ethylene. The results of this study suggest that many actions of coumarin in growth systems are mediated by ethylene produced in response to the coumarin.     

Kinetic analysis of the growth rate of the flagellar hook in Salmonella typhimurium by the population balance method.

The growth rate of flagellar hooks in Salmonella typhimurium was analyzed by computer-aided simulation of the length distributions of mutant hooks of uncontrolled length (polyhooks). The wild-type hook has a relatively well-controlled length, with an average of 55 nm and a standard deviation of 6 nm. Mutations in the fliK gene give rise to polyhooks. A histogram of the lengths of polyhooks from a fliK mutant shows a peak at 55 nm with a long monotonic tail extending out to 1 microm. To analyze the growth rate, we employed the population balance method. Regression analysis showed that the histogram could fit a combination of two theoretical curves. In the first phase of growth, the hook starts with a very fast growth rate (40 nm/min), and then the rate exponentially slows until the length reaches 55 nm. In the second phase of growth, where the hook length is over 55 nm, the hook grows at a constant rate of 8 nm/min. Second mutations in either the fliK or flhB genes, as found in pseudorevertants from fliK mutants, give rise to polyhook filaments (phf). The ratio between the numbers of hooks with and without filament was 6:4. The calculated probability of filament attachment to polyhooks was low so that the proportion of hooks that start filament growth was only 2% per minute. The lengths of polyhooks with and without filaments were measured. A histogram of hook length in phf's was the same as that for polyhooks in single-site fliK mutants, against the expectation that the distribution would shift to a shorter average. The role of FliK in hook length control is discussed.     

Levisunguis subaequalis n. g., n. sp., a tongue worm (Pentastomida: Porocephalida: Sebekidae) infecting softshell turtles, Apalone spp. (Testudines: Trionychidae) in the southeastern United States

A new tongue worm (Pentastomida) belonging to the Sebekidae Sambon, 1922 (Porocephaloidea Sambon, 1922) is described based on exemplars collected from softshell terrapins Apalone spinifera aspera (Agassiz) and Apalone ferox (Schneider) in the southeastern United States; a new genus is erected to accommodate the new species. The new species belongs in the Sebekidae because adults possess four simple hooks arranged in a trapezoid pattern on the ventral surface of the cephalothorax, a mouth opening between the anterior and posterior pairs of hooks, a terminal anus, an elongated uterus with preanal uterine pore, and a Y-shaped seminal vesicle. Nymphs possess geminate hooks, and the new species has an aquatic life-cycle in which nymphs become encapsulated in the body cavity of a freshwater fish and mature in the lungs of a terrapin. The new genus is distinct from other genera in the Sebekidae primarily by differences in hook morphology and the fact that representatives use a terrapin as a definitive host. Nymphs infecting fish and presumed to be the new species matured as postlarval juveniles conspecific with the new species when they were fed to the eastern mud turtle, Kinosternon subrubrum (Lacépède). Nymphs of the new species are anatomically similar to but larger than nymphs of Sebekia mississippiensis Overstreet, Self & Vliet, 1985 found in the mesentery of fishes captured in Florida, U.S.A. Adults of the new species differ from those of S. mississippiensis based on hook features, chloride cell pore pattern on annuli, body size, and use of a turtle rather than crocodilian definitive host. The new species is the third North American member of the Sebekidae.     

Rose Prickles and Asparagus Spines – Different Hook Structures as Attachment Devices in Climbing Plants

Functional morphology and biomechanical properties of hook structures functioning as attachment devices in the leaning climbers Rosa arvensis, Rosa arvensis ‘Splendens‘, Asparagus falcatus and Asparagus setaceus are analysed in order to investigate the variability in closely related species as well as convergent developments of hook structure and properties in distant systematic lineages (monocots and dicots). Prickles and spines were characterised by their size, orientation and the maximum force measured at failure in mechanical tests performed with traction forces applied at different angles. In Rosa arvensis and Rosa arvensis ‘Splendens‘ three types of prickles differing largely in geometrical and mechanical properties are identified (prickles of the wild species and two types of prickles in the cultivar). In prickles of Rosa arvensis no particular orientation of the prickle tip is found whereas in the cultivar Rosa arvensis ‘Splendens‘ prickles gradually gain a downward-orientation due to differential growth in the first weeks of their development. Differences in mechanical properties and modes of failure are correlated to geometrical parameters. In Asparagus falcatus and Asparagus setaceus spines are composed of leaf tissue, stem tissue and tissue of the axillary bud. Between species spines differ in size, orientation, distribution along the stem, tissue contributions and mechanical properties. The prickles of Rosa arvensis and its cultivar and the spines of the studied Asparagus species have several traits in common: (1) a gradual change of cell size and cell wall thickness, with larger cells in the centre and smaller thick-walled cells at the periphery of the hooks, (2) occurrence of a diversity of shape and geometry within one individual, (3) failure of single hooks when submitted to moderate mechanical stresses (F_max/basal area < 35 N/mm²) and (4) failure of the hooks without severe stem damage (at least in the tested wild species).     

Control of Hypocotyl Hook Angle in Phaseolus mungo L. Role of Growth Substances

Effects of growth hormones on the hook angle and light responseof Phaseolus mungo L. hypocotyl hooks are described and theresults are discussed with reference to the functions of otherparts of the seedling in controlling the growth and shape ofthe hook. Apically applied IAA (indolyl acetic acid) prevented hook openingin decapitated seedlings in the dark and in all the red-irradiatedseedlings. [¹⁴C]IAA experiments showed that only a small quantityof IAA (2–6 ?g per hook) was required to produce theseeffects, and that transport of IAA through the hook was negligibleand unaffected by red irradiation. ABA (abscisic acid) had little effect on the hooks or theirlight response. Applied ethylene and IAA-induced ethylene slightly closed thehooks, but only slightly reduced light-induced opening. IAAreduced the effect of ethylene in the dark, but after irradiationthe hooks appeared more sensitive to the ethylene in the presenceof IAA, resulting in light-induced hook closure. Basally applied kinetin (6-furfurylaminopurine) prevented decapitatedhooks from opening in the dark, especially when GA₃ (gibberellicacid) was also present. Some combinations of kinetin and GA₃(with high kinetin concentrations) also prevented light-inducedopening, but combinations with lower kinetin concentrationsallowed almost as much opening as was found in intact hooks. It is proposed that the terminal parts act by regulating thesupply of cytokinins and gibberellins from the basal parts,and that IAA does not mediate this funotion in this species. The results are compared with those reported for other species.     

Electron microscopy and histochemistry of oncospheral hook formation by the cestode Catenotaenia pusilla

Swiderski Z. 1973. Electron microscopy and histochemistry of oncospheral hook formation by the cestode Catenotaenia pusilla. International Journal for Parasitology3: 27–33. Ultrastructure and histochemistry of oncospheral hook development in the cestode C. pusilla are described. The six anlagen of embryonal hooks appear in six specialized hook forming cells (oncoblasts) in the advanced phase of the preoncosphere.Electron microscopy shows a close connection of hook primordium with an abundance of free ribosomes, extended Golgi regions, and mitochondrial aggregations, evidently engaged in the hook morphogenesis. The shank completion occurs simultaneously with the progressive degeneration of hook forming cells, which completely disappears in the last phase of hook development. The mature oncospheral hook is a heterogeneous, bipartite structure composed of a dense outer sheath or cortex and a less dense inner core.Histochemistry shows evident changes in the reactivity for —SH, and —S—S— groups through the consecutive stages of hook development. The early hook anlage shows strongly positive reaction for sulfhydryl (—SH) groups (unconsolidated prekeratin), which remains in the subsequent stages mainly in the zone of keratinization, undergoing continuous displacement toward the base during hook maturation.The sulfhydryl groups of prokeratin through the oxidation process form bisulfite (—S—S—) links of mature hook keratin; reactivity for —SH groups completely disappears. The difference in electron density between the outer and inner part of the hook corresponds to a different reactivity for —S—S— links; the outer sheath shows evidently stronger reaction than the inner core.     

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) from the freshwater stingray Himantura chaophraya (Batoidea: Dasyatidae) in Malaysian Borneo

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) are described from the spiral intestine of the Freshwater whipray, Himantura chaophraya, in the Kinabatangan River in Malaysian Borneo. Based on criteria set forth in a previous categorization scheme for species of Acanthobothrium, these consist of 3 Category 1 species, Acanthobothrium asnihae n. sp., Acanthobothrium saliki n. sp., and Acanthobothrium zainali n. sp.; a Category 8 species, Acanthobothrium etini n. sp.; and a Category 2 species, Acanthobothrium masnihae n. sp.. Acanthobothrium asnihae n. sp. differs from all Category 1 species in its possession of a horizontal band of weak musculature that divides the posterior loculus in half. Among Category 1 species, A. saliki n. sp. differs from all but Acanthobothrium southwelli in its possession of postovarian testes. It differs from A. southwelli in its possession of fewer testes and a greater number of proglottids. Acanthobothrium zainali n. sp. differs from the 25 other Category 1 species in a combination of overall size, muscular pad and hook shape, arrangement and number of testes, ovary configuration in cross section, position of ovarian isthmus, and genital pore position. Acanthobothrium etini n. sp. is distinguished from all 5 other Category 8 species in its lack of testes from the proglottid antiporal and postporal regions and in testis number. Acanthobothrium masnihae n. sp. differs from the 35 other Category 2 species in its possession of fewer testes, postporal testes, or a greater number of proglottids. A key to Acanthobothrium species parasitizing H. chayophraya is presented. This represents the first report of Acanthobothrium from freshwater stingrays belonging to a family other than the Potamotrygonidae.     

Three new species of the carnivorous snail genus Perrottetia Kobelt, 1905 from Thailand (Pulmonata,?Streptaxidae)

Three new species of the streptaxid snail genus Perrottetia are described from north and northeastern Thailand, Perrottetia aquilonaria sp. n., Perrottetia dermapyrrhosa sp. n. and Perrottetia phuphamanensis sp. n. Each species is endemic to a single or a few limestone mountain ranges. The species are characterized by the morphology of their genital organs, as well as by shell characters. Perrottetia aquilonaria sp. n. has a club shaped distal penis and large penial hooks are present and penial papillae cover almost the entire penial hook portion; adjacent areas possess low reticulated folds. Perrottetia dermapyrrhosa sp. n. has a long genital atrium and the penial sheath is about two-thirds of the penis length. Penial hooks are long, scattered and sunken into deep ovate hollows; vaginal hooks are present. Perrottetia phuphamanensis sp. n. has a rounded and protruded shell periphery. The aperture is subcircular, peristome is thick and the second parietal lamella is adjacent to the first parietal lamella; a basal lamella is the smaller than in the other Thai species.     

A new species of Calliobothrium (Tetraphyllidea: Onchobothriidae) from the whiskery shark, Furgaleus macki, in Australia

Calliobothrium pritchardae n. sp. is described from the whiskery shark, Furgaleus macki (Whitley, 1943), collected from Young Rocks in South Australia. This species differs from the 7 other known species of Calliobothrium in its possession of 2 rather than 3 posthook loculi. It is a further distinguished from all other Calliobothrium species except Calliobothrium evani in its possession of asymmetrical hooks. The lack of an accessory piece between the bases of the axial hooks and medial axial hook bases that are longer than the lateral axial hook bases further distinguish the new species from C. evani in which an accessory piece is present and the relative lengths of the medial and lateral axial hook bases are reversed. Scanning electron microscopy reveals spiniform microtriches on the neck and proximal bothridial surfaces, filiform microtriches on the apical bothridial surfaces, and a combination of the 2 microthrix types on the distal bothridial surfaces. The extended bases of the axial hooks are densely covered with spiniform microtriches. In addition, the number of testes within worms decreases substantially in progressively posterior (older) segments. The generic diagnosis of Calliobothrium is emended to include this species with 2 rather than 3 posthook loculi.