Maria Constenla

Parasitisation by Bathycreadium elongatum (Digenea, Opecoelidae) in pyloric caeca of Trachyrincus scabrus (Teleostei, Macrouridae)

A novel process of transmural passive displacement of a digenean parasite was studied in the digestive tract of the roughsnout grenadier Trachyrincus scabrus, which is found in the northwestern Mediterranean Sea. This mechanism seems to facilitate the elimination of a significant portion of intestinal parasites. The digenean parasite Bathycreadium elongatum was found in the intestine, mainly within pyloric caeca, in 74.4% of T. scabrus, with a mean abundance of 44 individuals per fish. Nodule-like lesions were also found in the mesentery of pyloric caeca of infected T. scabrus. Histological sections of the nodules revealed granulomatous inflammatory responses surrounding degraded digeneans. Partial nucleotide sequences of the 28S rRNA gene obtained from intracaecal B. elongatum and from the core of the nodules of the mesentery of pyloric caeca showed 100% mutual identity with an overlap of 971 bp. The greatest abundance of both intracaecal B. elongatum and nodules occurred in spring. During summer, and especially autumn, the abundance of intracaecal B. elongatum decreased. Prevalence and abundance of nodules increased in autumn. In winter intracaecal parasite abundance and prevalence began to increase, but decreased again in nodules. During spring and summer, parasites pass into the visceral cavity, hypothetically owing to the fragility of the wall of pyloric caeca in their apical zone, and become degraded through a granulomatous inflammatory response. This process seems to have a detrimental effect on the B. elongatum cycle since some of parasites are trapped and degrade in the connective tissue in which they are unable to complete their life cycle.

Raphidascaris (Raphidascaris) macrouri n. sp. (Nematoda: Anisakidae) from two deep-sea macrourid fishes in the Western Mediterranean: Morphological and molecular characterisations

A new nematode species, Raphidascaris (Raphidascaris) macrouri n. sp. (Anisakidae), is described from male and female specimens found in the intestine, and occasionally in stomach and pyloric caeca, of two deep-water macrourid fishes (Gadiformes) off Barcelona, Mediterranean Sea: Nezumia aequalis (Günther) (type-host) and Trachyrincus scabrus (Rafinesque). Based on light and scanning electron microscopy examination, the new species shows similar morphological features as the other four valid species of the subgenus Raphidascaris Railliet & Henry, 1915, but it differs from Raphidascaris (Raphidascaris) acus (Bloch, 1779), Raphidascaris (Raphidascaris) lutjani Olsen, 1952 and Raphidascaris (Raphidascaris) mediterraneus Lèbre & Petter, 1983 in the high number of precloacal papillae (23-32) and from Raphidascaris (Raphidascaris) gigi Fujita, 1928 in the length of the spicules. Moreover, Raphidascaris (Raphidascaris) macrouri n. sp. exhibits a high variability on the number and distribution of caudal papillae, which was not recorded in the other four mentioned species. This is the first species of this subgenus reported from the family Macrouridae. Sequences of ITS1-5.8S-ITS2 region are analysed and compared with closely related nematode species. Molecular analysis confirmed the uniformity of the R. (R.) macrouri n. sp. between hosts.

A new species of Hamaticolax (Copepoda: Bomolochidae) from Helicolenus dactylopterus (Delaroche, 1809) (Scorpaeniformes: Sebastidae) in NW Mediterranean deep waters and notes on patterns of host use and host-specificity of the genus

Hamaticolax juanji n. sp. is described from specimens collected from the blackbelly rosefish Helicolenus dactylopterus Delaroche 1809 (Scorpaeniformes: Sebastidae). It is the second Hamaticolax species described and reported from the Mediterranean Sea, after Ha. resupinus Pérez-i-García, Carrassón and Boxshall, 2017. It is distinguished from Ha. resupinus by the presence of only one dorsal naked seta on the third segment of the antennule (vs. four), two unequal short naked setae in distal part of the antenna (vs. four), and the absence of a minute spine on the third endopodal segment of leg 1, among others. It is differentiated from Ha. prolixus Cressey 1969 by a comparatively reduced fourth pedigerous somite, the presence of two naked setae on the third segment of the antennule (vs. three), two naked setae and three curved claws in the distal part of the apical segment of the antenna (vs. three and four), an outer naked seta on the basis of leg 2, and by larger length/width ratio of the third endopodal segment, among others. Hamaticolax juanji n. sp. also has relatively longer inner setae on the first and second endopodal segments of leg 4 than the two former species. Patterns of host-use and host-specificity of the genus Hamaticolax are also discussed. The frequently observed low host-specificity of its members may be better explained by host ecological similarity and host availability phenomena, rather than by host phylogenetic distance.

Description of Arcturinella deltensis sp. nov. (Crustacea, Isopoda, Arcturidae) from the Ebro Delta (Western Mediterranean Sea), with remarks on the status of the genus Arcturinella Poisson & Maury, 1931

This paper includes the complete description of the new species Arcturinella deltensis and the comparison with the other species of the same genus, A. banyulensis. The holotype used by Poisson and Maury (1931) to describe A. banyulensis is currently missing. The unique specimen available was one female from Estepona, Málaga (Strait of Gibraltar area) cited by Rodríguez-Sánchez et al. (2001). The occurrence in the Ebro Delta (Iberian Peninsula) of some females belonging to genus Arcturinella is here reported. A detailed morphological study revealed that the specimens from the Ebro Delta have the same features as the female from Estepona and significant differences compared to A. banyulensis; consequently, A. deltensis sp. nov. is erected. The taxonomical status of A. banyulensis becomes uncertain because it cannot be proved whether its characters are described adequately. However, enough differences are detected among the analyzed specimens and the description and figures from Poisson and Maury (1931) to clearly justify the distinction of a new species. The genus Arcturinella is diagnosed as follows: body flattened dorsoventrally, not geniculate between pereonites 4 and 5; cephalon fused with pereonite 1, incomplete suture at the margins; pereonite 4 hexagonal and widest, with posterior margin not excavated; pleotelson without free segments, with lateral wings; mandibles rounded, pars incisiva and pars molaris absent; pereopods 1–4 reduced; pereopods 1–3 flattened and with articles not fused; pereopod 1 unguis absent; pereopods 2–4 dactyli absent; pereopod 4 vestigial, linear, with circular or angular section, with or without fused articles; brood-pouch of oostegites of pereonites 2–4; pereopods 5–7 with secondary unguis smaller than the primary unguis.