New species of Spinuris (monogenea: monocotyladae) from Zapteryx exasperata (elasmobranchii: rhinobatidae) from Baja California Sur, Mexico.

Monocotylid monogeneans were collected from the gills of 2 Rhinobatos productus and 5 Zapteryx exasperata in Bahia Almeja, Baja California Sur, Mexico. All are parasitized by monocotylids of the genus Spinuris, 9 specimens of Spinuris lophosoma Doran on Rhinobatos productus (new record) and 27 specimens of Spinuris zapterygis n. sp. on Z. exasperata. This new species differs from the other species in the genus Spinuris by the number of dorsal haptoral sclerites, morphology of hooks, and male copulatory apparatus. The generic diagnosis of the genus Spinuris is revised.     

Weight–length relationships of six batoids in the Ecuadorian Pacific

Weight–length relationships (WLR) were estimated for six batoids, namely: Urotrygon chilensis, Narcine entemedor, Rhinobatos leucorhynchus, Rhinobatos planiceps, Rhinobatos prahli and Urobatis tumbesensis captured in the Ecuadorian Pacific. Data were collected between October 2013 and August 2014 in two artisanal fishing ports. In addition, this represents the first WLR estimations for five of the species.     

Two new species of Macrobothridium (Cestoda: Diphyllidea) from rhinobatid elasmobranchs in the Gulf of Gabès, Tunisia, with notes on the status of the genus.

As a result of an investigation of metazoan parasites of elasmobranch fishes in the Gulf of Gabès, Tunisia, we discovered 2 new species of diphyllidean cestodes. Macrobothridium euterpes n. sp. is described from the spiral intestine of Rhinobatos rhinobatos, and Macrobothridium syrtensis n. sp. from the spiral intestine of Rhinobatos cemiculus. Macrobothridium euterpes is distinguished from the only other species in the genus (Macrobothridium rhynchobati) by the number of rostellar hooks, size, genital pore position, vagina position, and ovary shape. Macrobothridium syrtensis is distinguished from M. rhynchobati by the hook morphology, testis number, and overall size, and from M. euterpes by the number of rostellar hooks, testis number, genital pore position, vagina position, and ovary shape. These are the first 2 species added to the genus since its establishment in 1989. A standardized formula for representing the number and arrangement of rostellar hooks in diphyllidean species is presented.     

Preliminary data on elasmobranch gillnet fishery in the Gulf of Gabès,Tunisia

Elasmobranchs are an important catch component in Tunisian artisanal fisheries. Generally, species‐specific information is largely unavailable for artisanal fisheries; an increase in knowledge thereof is essential to ensure proper management of these species. The study analyzed the gillnet fishery elasmobranch catches in the Gulf of Gabès, whereby 45 fishing trips were conducted from April to June 2007 and 2008 for the capture of a total of six species: three Rajiformes and three Carchariniformes. Rhinobatos cemiculus was the most important species (52%; 4.588 ind km^?2 net per day). Among shark species, Mustelus mustelus was the most important (66.8%; 2.21 ind km^?2 net per day). Discards represented 6.87% of total catch in weight and 14.28% in number of specimens caught. Size composition of captures varied by species, but usually mature, mainly gravid females were abundant. Further investigations are needed to obtain more information on such fragile species for the development of protective measures.     

Diet of two selachians common to the Gulf of Gabes (Tunisia): Rhinobatos rhinobatos (Linnè, 1758) and Rhinobatos cemiculus (Geoffroy Sainte-Hilarie, 1817)

Rhinobatos rhinobatos and Rh. cemiculus are two digging species with a malacophagic and, accessorly ichthyophagic diet. Rh. rhinobatos' main prey is Hermione hystrix. Rh. cemiculus' one is Citharus macrolepidotus. This study points out that it exists few seasonal changes about the diet of these Selacians.     

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.     

Length–weight relationships for nine species of batoids from the Iskenderun Bay,Turkey

Presented are length–weight relationships for Rhinobatos rhinobatos, Rhinobatos cemiculus, Gymnura altevela, Dasyatis pastinaca, Rhinoptera marginata, Pteromylaeus bovinus, Torpedo nobiliana, Raja miraletus and Raja clavata captured by gillnet, longline and bottom trawl fishing between May 2010 and July 2011 off the east coast of Iskenderun Bay, Turkey.     

Prochristianella spinulifera n. sp. (Cestoda: Trypanorhyncha) from Australian dasyatid and rhinobatid rays

Prochristianella spinulifera n. sp. (Cestoda: Trypanorhyncha: Eutetrarhynchidae) is described from the spiral valves of the rays Rhinobatos typus (Rhinobatidae) and Himantura fai (Dasyatidae) from Heron Island, Queensland, Australia. The new species is distinguished from all congeners by the deltoid microtriches covering the anterior 80% of the scolex and the presence of a dorsoventrally elongate genital atrium. The species occurred in the anteriormost section of the spiral valve of R. typus. The orientation of the armature of this and other congeners is such that principal rows of hooks begin on the bothridial surface of the tentacle and end on the antibothridial surface.     

Length–weight relationship of Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) off Brazil,southwestern Atlantic Ocean

This study reports the length–weight relationships (LWRs) for two elasmobranch species, Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) collected from the southwestern Atlantic, off Brazil. Both are considered endangered species. The LWR data can be taken into consideration for further management and conservation plans.     

A new species of <Emphasis Type="Italic">Neoheterocotyle</Emphasis> Hargis, 1955 (Monogenea: Monocotylidae) from the gills of <Emphasis Type="Italic">Rhinobatos annulatus</Emphasis> Müller &; Henle (Rhinobatidae) off the southern tip of Africa

Neoheterocotyle robii n. sp. is described from the gills of four female Rhinobatos annulatus Müller & Henle caught as bycatch during routine demersal research trawls off the Southern Cape coast of South Africa. The new species can be distinguished from all other members of Neoheterocotyle Hargis, 1955 by the morphology of the accessory piece associated with the male copulatory organ, the presence of a distinct horseshoe-shaped muscle associated with the male copulatory organ and the presence of a sclerotised structure in the proximal portion of the vagina. This is the first Neoheterocotyle species described from South African waters.     

Feeding habits of the speckled guitarfish Rhinobatos glaucostigma (Elasmobranchii: Rhinobatidae)

The stomachs of 464 speckled guitarfish Rhinobatos glaucostigma were sampled from the south‐eastern Gulf of California (GC) to determine diet composition. Numerical indices and prey‐specific index of relative importance (%I_PSIR) were used to determine the feeding strategy of the species. An analysis of similarity (ANOSIM) was used to determine differences in diet with respect to sex, season (dry or rainy) and maturity stages (immature or mature). The diversity and niche breadth (by sex, season and maturity) and a general trophic level were determined. The overall diet was dominated by shrimps (%I_PSIR = 43·47), amphipods (%I_PSIR = 18·89) and crabs (%I_PSIR = 18·07). ANOSIM demonstrated differences in the diet by maturity and season, but not by sex. Rainy and dry season diets were dominated by shrimps and amphipods, respectively. Immature specimens fed mainly on amphipods, whereas mature fish preferred shrimps and crabs. Rhinobatos glaucostigma showed a narrow niche breadth with an intermediary trophic level (T_L = 3·72) and can be considered as a secondary consumer in the soft‐bottom demersal community of the south‐east GC. Understanding the feeding habits and trophic level of R. glaucostigma is vital to help identify the segments of the population vulnerable to overfishing by artisanal and industrial fisheries, and to aid in conservation and management of this elasmobranch.     

Inter- and intraspecific variation in the distribution and number of pit organs (free neuromasts) of sharks and rays

The distribution of pit organs (free neuromasts) has previously been documented for several species of pelagic sharks, but is relatively poorly known for rays and bottom-dwelling (demersal) sharks. In the present study, the complete distribution of pit organs was mapped in the demersal sharks Heterodontus portusjacksoni, Orectolobus maculatus, Hemiscyllium ocellatum, Chiloscyllium punctatum, and Asymbolus analis, and the rays Rhinobatos typus, Aptychotrema rostrata, Trygonorrhina sp. A, Raja sp. A, and Myliobatis australis. All of these species had pit organs scattered over the dorsolateral surface. The sharks also had "mandibular" pit organs (and "umbilical" pit organs in C. punctatum and A. analis) on the ventral surface, while pit organs were sparse or absent on the ventral surface of rays. All of the species examined here, except for M. australis, also had a "spiracular" group of pit organs adjacent to the eye and/or spiracle. Spiracular pit organs were also recorded for the sawshark Pristiophorus sp. A and the skate Pavoraja nitida, although the remainder of pit organs were not mapped in these species. The distribution and number of pit organs varied both within and among species. Pit organ distribution was asymmetrical in each individual examined, but no particular trend towards left or right "handedness" was observed in any species. Although rays have been thought to have fewer pit organs than sharks in general, this was not the case in the present study. All of the species examined here had few pit organs compared to the pelagic sharks previously documented, but it is not clear whether this is due to ecological or phylogenetic causes.     

Two new species of Pseudochristianella Campbell & Beveridge, 1990 (Cestoda: Trypanorhyncha) from elasmobranch fishes from the Gulf of California, Mexico

Pseudochristionella elegantissima sp. nov. (Cestoda: Trypanorhyncha) is described from the spiral valves of the rays Dasyatis brevis (Garman, 1880) and D. longus (Garman, 1880), from the Gulf of California, Mexico. Also described is P. nudisculo sp. nov. from rays Rhinobatos productus Ayres, 1854, D. longus, Myliobatis longirostris Applegate & Fitch, 1964 and Zapteryx exasperat (Jordan & Gilbert, 1880) from the same location. The species are distinguished from one another and from the only existing species within the genus, P. southwelli Campbel & Beveridge, 1990, by differences in the arrangement of bill-hooks on the external surface of the basal swelling of the tentacle and by the number of hooks in each row of the metabasasl armature.     

Some ascaridoid nematodes of fishes: Paranisakis and Mawsonascaris n. g.

As a result of examination of type-material and other specimens representing species previously assigned to Paranisakis Baylis, 1923, it is proposed that this genus be reduced to one species, namely P. squatinae Baylis, 1923. The other species are distributed as follows: pastinacae Rudolphi, 1819, australis Johnston & Mawson, 1943 and laymani Mozgovoy, 1950 are assigned to a new genus Mawsonascaris. The main features differentiating Mawsonascaris from Paranisakis are: dentigerous ridges on the lips (absent in Paranisakis), digitiform extensions of the labial pulp (absent in Paranisakis), excretory pore posterior to the nerve-ring (anterior to the nerve-ring in Paranisakis) and long filiform spicules (short and stout in Paranisakis). The following new host records are reported: Rhinobatos cemiculus for P. squatinae; and Aptychotrema banksii, Rhinobatos batillum, Rhynchobatus dijddensis and Taeniura lymma for M. australis. Specimens were not available from teleosts. It is considered that the proposal of Yamaguti (1961) to raise the subgenus Ortoanisakis Mozgovoy, 1951 to full generic status be upheld provisionally, Ortoanisakis containing species from teleosts, formerly in Paranisakis, but described as having no dentigerous ridges and no gubernaculum. These include O. lophii (Yamaguti, 1935), O. halieutaeae (Yamaguti 1941), O. muraenesocis (Yamaguti, 1935), O. lophii hoplobrotulae (Yamaguti, 1941) and O. sciaenae Khan & Begum, 1971. The remaining species formerly in Paranisakis are relegated to the status of species inquirendae.     

Early development and microhabitat of the monogenean Horricauda rhinobatidis, with observations on the related Troglocephalus rhinobatidis, from Rhinobatos batillum from Queensland,Australia

The small monocotylid monogenean Horricauda rhinobatidis is abundant on the gills of its host Rhinobatos batillum, whereas the larger, related monogenean Troglocephalus rhinobatidis is comparatively uncommon. Young specimens of Horricauda live between the host's secondary gill lamellae. Post-oncomiracidia have 14 marginal booklets but as the larvae develop these are supplemented first by a pair of hamuli and then by muscular ventral loculi followed by six forwardly-directed, dorsal spines. By impaling secondary gill lamellae these spines may serve to prevent parasites from being dislodged by gill ventilating currents. Before reaching sexual maturity the parasites leave the secondary gill lamellae and establish themselves in the septal canals. It is uncommon to find more than one adult specimen of Horricauda in each septal canal. The significance of this in relation to sperm exchange is discussed. Like Troglocephalus, Horricauda has eight head sacs, and the suggestion is made that these sacs may play a part in feeding.     

Length–weight relationships for 10 elasmobranch species from the Oman Sea

Length–weight relationships (LWRs) were estimated for ten elasmobranch species from Iranian waters of the Oman Sea. All specimens were collected by bottom trawl (mesh size 80 mm in the cod end) between May and December 2014. A total of 509 individuals (107 Torpedo sinuspersici, 68 Rhinobatos punctifer, 63 Chaenogaleus macrostoma, 72 Himantura walga, 80 Himantura gerrardi, 58 Gymnura poecilura, 4 Himantura uarnak, 4 Rhinoptera javanica, 14 Aetobatus flagellum, and 39 Pastinachus sephen) were sampled and studied. Results showed that most species had positive allometric or isometric growth but that more studies were needed for final decisions on growth patterns. Both the disk length‐body weight (DL/BW) and disk width‐body weight (DW/BW) relationships also showed a good fit, reinforcing the credibility of the data in relation to the LWRs. This study is the first report of LWRs for these elasmobranchs in the northern Oman Sea.     

The visual system of the guitar fish (Rhinobatos productus)

Summary The retinal projections in adult and juvenile guitar fish (Rhinobatos productus) were determined with the aid of the Nauta-Fink-Heimer techniques. The visual system was found to be more extensive and more differentiated than in any other elasmobranch studied to date. Massive projections exist to the dorsal and ventral thalamus, tectum and pretectum, in addition to the usual weak contributions to the hypothalamus and the ventral mesencephalic tegmentum. The projection to the lateral tectum is significantly less distinct than that to the medial part of this structure, suggesting that the ventral visual field has a smaller input, perhaps due to the fact that this visual field is normally aimed at the body of this flat fish.