Trichodinids (Ciliophora: Trichodinidae) on Rocky-tidal Fishes from the Baja California Peninsula, Mexico.

Information regarding trichodinid ectoparasites on marine fishes of North America is relatively scarce. In this study, 5 ciliate species from the family Trichodinidae were found associated with 8 fish hosts from the rocky intertidal zone of the western coast of the Baja California Peninsula (BCP), Mexico. All of the host-parasite relationships recorded here are new. Furthermore, 3 of the trichodinid species found are recorded for the first time for Mexico. Trichodinids taxa do not show a noticeable distributional gradient along the BCP, which suggests a wide-continuous distribution of the species throughout the study area.

A New Species of Ascarophis (Nematoda: Cystidicolidae) Parasitizing Clinocottus analis (Pisces: Cottidae) from Baja California, Mexico.

A new species of nematode, Ascarophis morronei n. sp. (Cystidicolidae), is described from the stomach wall of the woolly sculpin Clinocottus analis (Cottidae) collected in the rocky intertidal from northwestern Baja California, Mexico. Collected nematodes were studied using both light and scanning electron microscopy. Sequence fragments for 18S rDNA molecular markers were obtained from the new nematode species, in order to test its position within the family Cystidicolidae under a phylogenetic context. Main characters distinguishing this new species include the reduced labia and the morphology of the eggs, distances of nerve ring and excretory pore from the anterior end, and left spicule of males. The new species described here is the second for the genus Ascarophis reported as adult in the Southern California Bight, and the first one recorded for the fish genus Clinocottus.

Update on the distribution of the co-invasive Schyzocotyle acheilognathi (= Bothriocephalus acheilognathi), the Asian fish tapeworm, in freshwater fishes of Mexico.

The Asian fish tapeworm, Schyzocotyle acheilognathi (syn. Bothriocephalus acheilognathi) represents a threat to freshwater fish, mainly cyprinids, across the globe. This tapeworm possesses an extraordinary ability to adapt to different environmental conditions and, because of that, from its natural geographical origin in mainland Asia, it has colonized every continent except Antarctica. It is thought that this pathogenic tapeworm was first co-introduced into Mexico in 1965 from China, with the grass carp Ctenopharyngodon idella, although the first formal record of its presence was published in 1981. Over the past 35 years, the Asian fish tapeworm has invaded about 22% of the freshwater fish in Mexico. Because fish communities in Mexico are characterized by high species richness and levels of endemism, S. acheilognathi is considered as a co-introduced and co-invasive species. In this review, we update the geographic distribution and host spectrum of the Asian fish tapeworm in Mexico. Up until December 2016, the tapeworm had been recorded in 110 freshwater fish species (96 native and 14 introduced), included in 51 genera, 11 families and 4 orders; it was also widely distributed in all types of aquatic environments, and has been found in 214 localities. We present novel data from a survey aimed at establishing the distribution pattern of the tapeworm in native freshwater fishes of two rivers in north-central Mexico, and the genetic variation among individuals of this co-invasive species collected from different host species and localities. We discuss briefly the factors that have determined the remarkable invasive success of this parasite in freshwater systems in Mexico.

Record of Urocleidoides vaginoclaustrum Jogunoori, Kritsky and Venkatanarasaiah, 2004 (Monogenea: Dactylogyridae) from a freshwater fish in Mexico.

We describe herein the first occurrence of the monogenean Urocleidoides vaginoclaustrum in the wild. This monogenean was originally described from an aquarium neotropical fish examined in India. Worms were collected from the gills of Xiphophorus hellerii, a species native to tropical Mexico but introduced to the Los Berros Spring in the State of Durango, Northern Mexico. These specimens showed slight morphological differences in the sclerotized structures of the haptor with respect to the specimens described from India. A brief morphological characterization of this species is presented.