First description of Chloromyxum squali Gleeson and Adlard, 2012 (Myxozoa) in the Mediterranean Sea in a new host Squalus blainville (Chondrichthyes: Squalidae): morphological, ultrastructural and phylogenetic data.

Chloromyxum squali Gleeson and Adlard, 2012 originally described from Squalus acanthias Linnaeus, 1758 is reported for the first time from the gallbladder of Squalus blainville (Risso, 1827) caught from the eastern coast of Tunisia. In the present study, this chloromyxid was described based on morphological and ultrastructural features combined with molecular analysis of 18S rDNA. Young plasmodia were found attached to the gallbladder, while mature plasmodia and myxospores were observed floating free in the bile. Mature plasmodia were polysporic, subspherical in shape, measured 97.8 ± 0.5 µm long and 63.4 ± 0.4 µm wide. Mature myxospores were ovoid with a pointed anterior end, measuring 10.2 ± 0.5 µm long and 8.3 ± 0.5 µm wide. Two asymmetrical shell valves adhered together along an S-shaped suture line. Each valve has 5-7 elevated surface ridges parallel to suture line. A bundle of long caudal filaments extended from the basal end of shell valves. Four pyriform polar capsules equal in size, measuring 3.1 ± 0.4 µm long and 2.5 ± 0.3 µm wide, were situated at the same level in the anterior pole of the myxospore, each with a polar filament coiled in 7-8 turns. Pairwise comparisons among the SSU rDNA sequences revealed significant similarity between Chloromyxum squali infecting S. acanthias with the sequence obtained in this study. Phylogenetic analysis revealed that C. squali clustered in the clade of Chloromyxum species infecting the gallbladder of marine Chondrichthyes. Chloromyxum squali showed a seasonal variation of prevalence with significantly higher prevalence noted in summer and in autumn and absence of infection in winter.

A new species of Pseudopandarus Kirtisinghe, 1950 (Copepoda: Siphonostomatoida: Pandaridae) from sharks of the genus Squalus L. in New Caledonian waters.

Both sexes of a new species of pandarid copepod are described from sharks of the genus Squalus L. (Squaliformes: Squalidae). Specimens of Pseudopandarus cairae n. sp. were collected from Squalus bucephalus Last, Séret & Pogonoski and S. melanurus Fourmanoir & Rivaton in New Caledonian waters, the first parasitic copepod to be described from either host species. This is the eighth nominal species of Pseudopandarus Kirtisinghe, 1950 and the first to be described from a shark of the order Squaliformes. Pseudopandarus cairae n. sp. is easily distinguished from P. australis Cressey & Simpfendorfer, 1988, P. longus (Gnanamuthu, 1951) Cressey, 1967, and P. pelagicus Rangnekar, 1977 in having the female genital complex concealed beneath an elongate dorsal genital shield with a trilobed posterior margin. It can be distinguished from P. gracilis Kirtisinghe, 1950 and P. scyllii Yamaguti & Yamasu, 1959 by the armature of the leg 4 endopod and by the proportions of the dorsal genital shield. The new species is unique among known species of Pseudopandarus in its possession of only 1 setal element on the distal endopod segment of leg 4. In addition to describing the new species, the host associations of all species of Pseudopandarus are reviewed and observations are made regarding sexual dimorphism and mode of attachment. A key to the species considered valid is provided.

Trebius benzi n. sp. (Siphonostomatoida: Trebiidae) infecting Squalus acutipinnis Regan off South Africa.

Trebius Krøyer, 1838 currently consists of 15 accepted species all infecting elasmobranchs. Apart from two species, i.e. T. caudatus Krøyer, 1838 and T. latifurcatus Wilson, 1921, that have been reported from ten and eight host species, respectively, the other 13 species have each been reported from only one or two host species. Trebius benzi n. sp., collected from Squalus acutipinnis Regan, is described and illustrated after examination through stereo- and compound microscopes. This species can be distinguished from the other known species by a combination of characters including an abdomen that is shorter than the genital complex, a maxillule with an endite that consists of a single-tined dentiform process, sternal furca tines that are blunt and as long as the base, and the innermost spine of the last exopodal segment of leg 1 the shortest.

Interactions of warming and exposure affect susceptibility to parasite infection in a temperate fish species.

Predicting how elevated temperatures from climate change alter host-parasite interactions requires understandings of how warming affects host susceptibility and parasite virulence. Here, the effect of elevated water temperature and parasite exposure level was tested on parasite prevalence, abundance and burden, and on fish growth, using Pomphorhynchus laevis and its fish host Squalius cephalus. At 60 days post-exposure, prevalence was higher at the elevated temperature (22 °C) than ambient temperature (18 °C), with infections achieved at considerably lower levels of exposure. Whilst parasite number was significantly higher in infected fish at 22 °C, both mean parasite weight and parasite burden was significantly higher at 18 °C. There were, however, no significant relationships between fish growth rate and temperature, parasite exposure, and the infection parameters. Thus, whilst elevated temperature significantly influenced parasite infection rates, it also impacted parasite development rates, suggesting warming could have complex implications for parasite dynamics and host resistance.

A new hyperapolytic species, Trilocularia eberti sp. n. (Cestoda: Tetraphyllidea), from Squalus cf. mitsukurii (Squaliformes: Squalidae) off South Africa with comments on its development and fecundity.

A new species of tetraphyllidean cestode in the genus Trilocularia is described from an undescribed shark species, Squalus cf. mitsukurii, off the coast of South Africa. Trilocularia eberti sp. n. is the second known member of its genus, and like its congener, T. gracilis (Olsson, 1866-1867) Olsson, 1869, is extremely hyperapolytic, dropping proglottids from its strobila while they are still very immature. Characteristic of the genus, it possesses a distinctive scolex with triloculated bothridia, but differs conspicuously from its congener in its possession of an anterior loculus that is much larger in width relative to the paired posterior loculi, and also in its possession of an anterior, enlarged region of its free proglottids that is triangular with a slit-like ventral aperture, rather than rounded and cup-like. This anterior region of the free proglottid is used in attachment, and its development is described. For assessment of fecundity, an attempt was made to record all free proglottids of all ages found in both host individuals, and yielded an average estimate of 362 free proglottids being produced per individual worm of T. eberti sp. n. Both Trilocularia species parasitize sharks of the genus Squalus, and given the host specificity typically exhibited by tetraphyllideans and preliminary examinations of other members of this shark genus, it is likely that other Squalus species will be found to host additional new Trilocularia species.

A new species of Calicotyle Diesing, 1850 (Monogenea: Monocotylidae) from the shortspine spurdog Squalus mitsukurii Jordan & Snyder and the synonymy of Gymnocalicotyle Nybelin, 1941 with this genus.

Calicotyle japonica n. sp., collected from the uterus, rectal gland, archinephric duct and cloaca of the shortspine spurdog Squalus mitsukurii Jordan & Snyder (Squaliformes) off the Pacific coast of Japan, is described. The new species can be distinguished from C. inermis Woolcock, 1936 by the shape of the male copulatory organ; in C. japonica this is directed anteriorly, is sharply bent in the middle and then increases in width toward the tip, whereas it is long, coiled and uniform in width throughout its entire length in C. inermis. Furthermore, the intestinal caeca have many irregular diverticula on both sides and the vaginal apertures are at the level of the common genital pore in C. japonica, whereas in C. inermis the intestine is smooth and the vaginae open at the level of the oötype. A phylogeny constructed using LSU rDNA data indicates that the new species is grouped with other Calicotyle species; based on this, Gymnocalicotyle Nybelin, 1941 is synonymised with Calicotyle Diesing, 1850. Calicotyle is divided into two major clades, with the new species being grouped with Calicotyle species infecting sharks and the second clade consisting of Calicotyle spp. infecting rays. This suggests that the loss of the hamuli in C. japonica and C. inermis, both parasites of sharks, is a comparatively recent event in the evolution of the genus.

A new species of Triloculotrema Kearn, 1993 (Monogenea: Monocotylidae) from a deep-sea shark, the blacktailed spurdog Squalus melanurus (Squaliformes: Squalidae), off New Caledonia.

Triloculotrema chisholmae n. sp. is described from three specimens collected from the nasal tissues of a deep-sea shark, the blacktailed spurdog Squalus melanurus Fourmanoir & Rivaton, caught off New Caledonia, South Pacific. The new species is distinguished from the only other and type-species of the genus, T. japanicae Kearn, 1993, by the morphology of the sclerotised male copulatory organ (shorter and straight versus curved) and shorter hamuli.

Two new species of hexabothriid monogeneans from the ginzame Chimaera phantasma and shortspine spurdog Squalus mitsukurii.

Descriptions are given for two new species of hexabothriid monogeneans, one collected from the gills of shortspine spurdog Squalus mitsukurii and the other from the gills of the ginzame Chimaera phantasma in Sagami Bay on the Pacific coast of Japan. Squalonchocotyle mitsukurii n. sp. from Squalus mitsukurii can be distinguished from Squalonchocotyle squali MacCallum, 1931, the most closely related species, by the inwardly curved vagina. Callorhynchocotyle sagamiensis n. sp. from Chimaera phantasma can be distinguished from all the known species of Callorhynchocotyle Suriano & Incorvaia, 1982 by the structure of the cirrus; in the new species, the cirrus is entirely muscular with a widened opening, while in the four known species it comprises a tubular proximal part and a bulbous distal part.