The reproductive cycle ofMothocya epimerica(Isopoda: Cymothoidae) a parasite of the sand smelt,Atherina boyeri(Osteichthyes: Atherinidae), in the Lesina Lagoon, Italy

Parasite and genetic diversity of big-scale sand smelt (Atherina boyeri Risso, 1810) populations in their natural and expansion ranges in Ukraine

The big-scale sand smelt (Atherina boyeri) is an Atlanto-Mediterranean amphidromous fish species found within the Black Sea. Here, we assess differences in the parasite fauna of big-scale sand smelt populations from their natural range in the northwestern Black Sea and from their expansion range in the Lower and Middle River Dnipro. In addition, we undertook a microsatellite analysis to assess the genetic similarity of fish from the different locations. We found that the parasite community of fish in their natural range was wider than that from their expansion range. While the Gulf of Odesa was most distant from all other localities by parasite community composition and the Dnipro Reservoir was characterised by an absence of parasites (newest and most distant expansion locality), only fish from the Danube Delta showed a significant genetic difference. Our results suggest that the parasite community of big-scale sand smelt is primarily influenced by environmental factors, such as habitat type, water salinity and/or prey composition. Both microsatellite analysis and parasite community species composition (e.g. the presence of the marine Telosentis exiguus in the Kakhovka Reservoir and freshwater Raphidascaris sp. in the Gulf of Odesa) confirmed that populations in the River Dnipro reservoirs had, at some time, been connected with native marine populations, thus also confirming the species' amphidromous nature.

Quatrefoil light traps for free-swimming stages of cymothoid parasitic isopods and seasonal variation in their species compositions in the Seto Inland Sea, Japan

Cymothoid parasitic isopods infest a wide range of fish of different taxa living in marine, brackish, and freshwater environments. Most research on the reproductive season of Cymothoidae has been done by collecting or monitoring host fish afflicted with cymothoid parasites. However, collecting ecological data on cymothoid species that infest non-commercial or endangered fishes is complex and challenging. We used a quatrefoil light trap to investigate the seasonal change in species composition of cymothoid free-swimming stages in the Seto Inland Sea, Japan. We also collected preliminary data for efficient light-trap sampling and showed its effectiveness in cymothoid-related research. From October 2020 to December 2021, 613 cymothoid free-swimming stages were sampled monthly. All obtained individuals were identified as Mothocya parvostis (596), Ceratothoa verrucosa (12), and Ceratothoa carinata (5) by DNA barcoding using cytochrome c oxidase subunit I and 16S rRNA gene sequences. Based on the number of M. parvostis mancae collected each month, M. parvostis was anticipated to reproduce from June to December, with two reproduction peaks each year, and C. verrucosa and C. carinata were expected to reproduce in June, July, and September, and September and October, respectively. In addition, free-swimming juveniles were captured, presumably after they had left their optional intermediate hosts. Furthermore, the most effective time to harvest cymothoids with light traps may be during high tide on the night of the new moon. This study serves as a methodological framework for future research on cymothoids using light traps.

Feeding Habits of Predatory Thermophilic Fish Species and Species with Subtropical Affinity from Recently Extended Distributional Range in Northeast Adriatic Sea, Croatia

The study investigates feeding habits of thermophilic species and species with subtropical affinity in the fishing catch in the Bay of Medulin (northeastern Adriatic Sea), and contributes to the knowledge about their presence in recently extended distributional range. In our methodology, the presence of the Seriola dumerili, Sphyraena sphyraena, Lichia amia, Coryphaena hippurus, Caranx crysos, Pomatomus saltatrix, and incidence of Trachinotus ovatus is recorded. A total of 220 specimens are captured during 2017, 2018 and 2019. A dietary assessment is performed, and the index of relative importance IRI was calculated for each prey category. Diet overlap is calculated using Schoener’s index, based on IRI. The principal diet of C. hippurus included Sardina pilchardus and Loligo vulgaris. Pomatomus saltatrix consumed species from the Sparidae family and T. ovatus crustaceans from the Mysidacea family. Different species from genus Atherina are represented important foods for L. amia, S. dumerili and S. sphyraena. Diets of significant importance for L. amia included fishes from the family Sparidae, for S. sphyraena from the Carangidae family, and S. dumerili from the Clupeidae and Muliidae families. Our analysis of diet overlap is based on IRI suggests no diet overlap between analysed fish species from Medulin Bay, and that these species utilise differing trophic niches.

The parasitic isopod Mothocya nana drives dietary shifts and poorer condition of Brazilian silversides Atherinella brasiliensis

Cymothoids are ectoparasites that may attach to various parts of the fish for molting and reproductive purposes, thus increasing the energetic costs of the host. This study investigated the influence of the parasitic isopod Mothocya nana on the physiological condition and diet of adult Brazilian silversides Atherinella brasiliensis at a sandy beach in southeastern Brazil. We collected 268 A. brasiliensis individuals, of which 230 fish were non-parasitized (mean ± SE total weight [TW] = 16.92 ± 0.38 g; total length [TL] = 127 ± 0.88 mm) and 38 were parasitized by up to 2 isopods (TW = 15.89 ± 0.79 g; TL = 126 ± 1.96 mm). Parasitic prevalence (P) and intensity (I) reached highest values in June 2015 (P = 20.88%; I = 1.31) and were slightly higher on males (P = 17.39%; I = 1.33) than on females (P = 13.07%; I = 1.27). Parasitized fish revealed poorer condition than non-parasitized ones, among which male hosts were especially burdened by M. nana's attachment. The condition factor, the eviscerated condition factor and the fullness index each showed a decreasing trend according to the parasite's development and offspring weight (i.e. increase in egg and larval weight). Parasitized and non-parasitized Brazilian silversides fed mainly on microcrustaceans, but the first group showed reduced phytoplankton intake and was associated with fewer trophic categories in comparison to non-parasitized fish. These dietary shifts revealed correlation with the poorer physiological condition reported for infected A. brasiliensis, whose decreased feeding efficiency is likely related to potential impairment of the filter-feeding mechanism and/or altered behaviour due to pressure atrophy and the increased energetic costs imposed by M. nana's development.

High prevalence and infestation of Mothocya renardi (Isopoda, Cymothoidae) in marine fish Strongylura leiura (Bleeker 1850)

Cymothoid isopods are parasites that cause severe damage to the fish species. The present study was focused to carry out the parasitic infestation on the one of the important marine fish Strongylura leiura during the 2 years period between June 2009 and May 2011. 272 fish specimens collected and about 157 (57.72 %) fishes were infested by the cymothoid which were concealed under the gill arches of the host. Infested parasite was identified as Mothocya renardi. The prevalence rate of parasites during different seasons of the range of host specificity of isopods was studied. Variation of infestation rate also depends on the size, length and weight of the host. The sites of infestation by the parasitic crustaceans are highly specific. The infestation had affected the normal growth of the host fish and also probably leads the high levels of secondary infections.

Spatial variation in the parasitic isopod load of the Japanese halfbeak in western Japan

Cymothoid isopods (family Cymothoidae) are commonly found parasitizing diverse fishes, including commercial species. However, the effects of these parasites on host body condition are still poorly known. Here we investigated the spatial variation of the effects of parasite infection on host body condition, using the parasitic load of the cymothoid Mothocya parvostis on the Japanese halfbeak Hyporhamphus sajori at 4 sampling sites in western Japan. M. parvostis prevalence at each site (41.6-74.4%) was higher than that known for other fish host-cymothoid systems (usually less than 30%). The number of isopods in infected hosts, the reproductive status of female isopods (i.e. ovigerous/non-ovigerous), and the body size of female and male isopods relative to the size of their hosts were not significantly different among sites. However, at the site where human activity was most intense, M. parvostis infection had a significantly negative effect on host body condition. These results suggest that the effect of cymothoid infection on host body condition might be benign under natural conditions but becomes detrimental in habitats that are unsuitable for the host, such as highly human-impacted areas.

New record of Norileca indica from the west coast of India

Two hundred and twenty samples of Rastrelliger kanagurta from the Cochin Fisheries Harbour were collected during the month of August 2013. Forty-one specimens (32 females and 9 males) were parasitized by the cymothoid isopod Norileca indica. N. indica is recorded for the first time from the west coast of India.

Host-parasite relationships: Mothocya plagulophora parasitizing Hemiramphus far in the Southeast coast of India

Totally 384 Mothocya plagulophora were collected in the branchial cavities of Hemiramphus far from the Southeast coast of India during the study period (from July to September 2013). 204 parasites were found in the left branchial cavity and 180 in the right one. The maximum prevalence was observed in July 2013 and the minimum in September 2013. The intensity ranged from a minimum value (1.3) in July and August to a maximum (1.4) in September 2013. In most cases, the parasite was located between the second and the third branchial arch, attached either to the vomerine arch or to the internal wall of the branchial operculum.

Some Morphological Characters of Female of Mothocya epimerica Costa, 1851 (Flabellifera: Cymothoidae) from Sea of Marmara

Mothocya epimerica Costa, 1851 (Flabellifera: Cymothoidae) is a cymothoid parasite of fishes belonging to Atherinidae (Atherina hepsetus, Atherina boyeri) from Mediterranean Sea, Black Sea and Atlantic Ocean. Öktener and Sezgin (2000) recorded this parasite for the first time in Turkey. The mentioned authors presented some morphological characters, although, some characters are not explained in the publication. Some morphological characters seen on the mandible, maxilliped, maxilla, maxillue and the spines on pleopods of the female of M. epimerica are shown. The characters presented in our study are based on the drawings made from collected specimens.

A new record of parasitic isopod for the Indian fauna (Mothocya karobran Bruce, 1986) from Strongylura strongylura in the Pazhayar region, Southeast coast of India

Cymothoid isopods are permanent ectoparasites of fish. In the present study Strongylura strongylura captured in gillnets from the inshore waters of Pazhayar from January to March-12. Among the 122 Belonidae fishes examined, 16 specimens were parasitized by isopods belonging to the species Mothocya karobran, a new record of this cymothoid isopod for the first time from India. Lowest prevalence occurred in January (10.5 %) and the highest in February (15.9 %). The infected fishes usually carried one cymothoid per branchial cavity. 12 parasites were found in the left branchial cavity and 4 parasites in the right. The non ovigerous female (18.5-24.7 mm) and female ovigerous (20.8-27.4 mm) in total length.

The helminth community of the sand smelt (Atherina boyeri Risso, 1810) from Lake Iznik, Turkey

Metazoan parasites of the sand smelt Atherina boyeri Risso, 1810 in Lake Iznik were studied. A total of 271 specimens of A. boyeri, 208 female and 63 male, mean ( ± SD) total length 8.4 ± 2.2 cm (range 3.1–12.2 cm) and mean total weight 4.7 ± 3.5 g (range 0.1–11.7 g) were examined between June 2008 and May 2009 at monthly intervals. In 33 fish no parasites were found. In the other fish, four parasite species were recorded: Diplostomum sp. (prevalence 39.13%, mean intensity 3.50 ± 3.03); Tylodelphys clavata (prevalence 74.16%, mean intensity 10.41 ± 14.89); Bothriocephalus cf. acheilognathi (prevalence 40.59%, mean intensity 31.83 ± 57.74); and Eustrongylides excisus (prevalence 6.64%, mean intensity 1.16 ± 0.39). The mean abundance of Diplostomum sp., T. clavata and E. excisus was higher during the winter and early spring months. In contrast, the mean abundance of B. cf. acheilognathi was higher in the summer and autumn months. This distribution of the parasites was related to a change in the environment of A. boyeri from the pelagic zone to deeper water at the end of autumn and a change in food supply.

New records of two parasitic cymothoids from Indian fishes

Two parasitic cymothoidae (Crustacea, Isopoda) are reported parasitizing fishes Hemiramphidae in India. Ceratothoa angulata, found in the buccal cavity of its host, is reported for the first time from India. Mothocya plagulophora, a branchial species, already known from the Southwest coast, is now recorded from the Southeast coast of India. Host-parasite relationships are considered.

Infestation pattern and parasitic castration of the crustacean Riggia paranensis (Crustacea: Cymothoidea) on the fresh water fish Cyphocharax gilbert (Teleostei: Curimatidae)

Cyphocharax gilbert infested by Riggia paranensis shows parasitic castration. The prevalence of parasitism in C. gilbert varied among different environments, being higher in the middle rio Itabapoana. Fish were collected monthly using two cast nets (thrown 30 times during the day) and gillnets kept in the river during 12 hour, from sunset to sunrise, between September 1997 and August 2000. Infestation pattern was investigated on 1358 specimens. Most of them were infested (57.9%), with one or two parasites; the majority (62.9%) was collected during the rainy season (spring-summer). The parasite did not show preference for sex or size of hosts. A total of 91.5% of the 511 examined parasites had a body size that represented 10.1% to 20% of host standard length. The reproductive condition of 311 specimens of R. paranensis was analyzed checking the presence of oocytes in the ovarian and eggs or embryos in the marsupium. Nearly 73% of them were at reproductive phase, and had a body size that represented 5.1% to 20% of host standard length. The size of the immature parasites varied from 0.1% to 5% of the host size. The results suggest that R. paranensis may adopt a fast growth rate strategy and increase the investment in reproduction when they occupy most of the host's pericardial space.