A new nematode species, Comephoronema multipapillatum sp. n. (Cystidicolidae), is described from the anterior intestine and caecum of the squirrelfish Holocentrus adscensionis (Osbeck) (Beryciformes: Holocentridae) collected in Angra dos Reis, State of Rio de Janeiro, offshore Brazil. The new species was placed in Comephoronema Layman, 1933 by having an oval oral aperture, four submedian labia, four bilobed submedian sublabia, two narrow lateral pseudolabia and four single cephalic papillae, but mainly by numerous precloacal papillae in males (more than six pairs), in which it differs from species of the otherwise morphologically similar genus Ascarophis van Beneden, 1871. Comephoronema multipapillatum sp. n. can be easily distinguished from other congeners based on the high number of precloacal papillae in males (18 pairs + one unpaired) and also by the bidentate plate structure on the inner margin of pseudolabia, mature eggs with two long filaments on a single pole, body length of male (9.4-11.5 mm) and female (10.2-19.9 mm), left spicule size (222-278 µm) and length ratio of spicules (1 : 2.2-2.8). This is the fifth nominal species of Comephoronema, the first nematode registered parasitizing H. adscensionis and the first species of the genus in the Neotropical part of the Atlantic Ocean.
Breizacanthus aznari sp. n. is described from the banded cusk-eel Raneya brasiliensis (Kaup) (Ophidiiformes: Ophidiidae) from the Patagonian coast in Argentina. Breizacanthus Golvan, 1969 is currently composed of five species (including the new species) and is characterised by the absence of trunk spines, a short cylindrical proboscis with two types of hooks and lemnisci longer than the proboscis receptacle. Breizacanthus aznari is clearly distinguished from B. chabaudi Golvan, 1969 by having 12 longitudinal rows of hooks on the proboscis, instead of 16-18. The new species resembles B. golvani Gaevskaya et Shukhgalter, 1984, B. irenae Golvan, 1969, and B. ligur Paggi, Orecchia et Della Seta, 1975, all possessing 12 longitudinal rows of hooks. However, B. aznari differs from B. golvani in having 4-5 large hooks per row (vs. 8-9) and larger eggs. The new species can be distinguished from B. irenae by the shorter body size of females, the different range of numbers of large hooks of males (4-5 and 5-6, respectively), the smaller maximum number of small hooks of females (3 and 4, respectively), and the shorter lemnisci. Breizacanthus aznari differs from B. ligur by the smaller body length of females, the smaller maximum body length of males, the different range of numbers of large hooks of males (4-5 and 5-6, respectively), and smaller lemnisci. This is the first record of a species of Breizacanthus from fishes of the order Ophidiiformes and from the Southern Hemisphere. Comparative data on species of Euzetacanthus Golvan et Houlin, 1964 and Breizacanthus are also provided.
A new species of parasitic copepod, Chondracanthus hoi sp. n. (Copepoda: Chondracanthidae), is described based on specimens of both sexes collected from the buccal cavity and gill arches of the silvery john dory, Zenopsis conchifer (Lowe) (Zeiformes: Zeidae), from waters off northern Argentina (35-36°S, 53-54°W). Female of C. hoi differs from its congeners by the following combination of characters: presence of five pairs of trunk processes, antennule with four knobs tipped with small setae and absence of denticles on the terminal process of maxilla. Chondracanthids and zeiform fishes have been proposed as an example of co-speciation; this assumption is derived from a series of analyses based on incomplete records of both geographical distribution and host range of some parasite species, as well as misidentification of fish hosts. These inconsistences observed during our bibliographical analyses are also discussed.