Morphological features of the testis of freshwater blood flukes of the genus Sanguinicola Plehn, 1905, with consideration of the testicular patterns in the Aporocotylidae

This is the first detailed study assessing the morphological features of the testis and testicular sperm of members of the freshwater blood flukes Sanguinicola sp. from Leuciscus idus (Cyprinidae) and for S. volgensis from Pelecus cultratus (Cyprinidae), and the marine blood fluke Aporocotyle simplex from Hippoglossoides platessoides (Pleuronectidae). The present study reports a unique feature in the distribution of germinal cellular components in freshwater Sanguinicola sp., showing the presence of the individual spermatocytes or their clusters in the testicular lobes, and the gathering of spermatid rosettes and spermatozoa within middle testicular lumen, which extends along the entire length of the testis. In contrast, each testis of marine A. simplex contains the usual mixed distribution of germ cells at various stages of development. The first TEM data on spermatozoon character of studied species has shown, unusual for digenean sperm structure, the absence of cortical microtubules in sperm principal region. Moreover, a variation in axoneme patterns is revealed in the studied aporocotylids, belonging to the different aporocotylid lineages a 9 + 0 axonemal type observed for freshwater teleost-infective species, Sanguinicola sp. and S. volgensis, and a 9 + ‘1’ axonemal type revealed in spermatozoa of marine teleost-infective species A. simplex. The results discussed with the published data on the digenean sperm structure and the testicular patterns in the Aporocotylidae likely represent additional characteristics supporting the divergent evolutionary lineages of freshwater and marine aporocotylids. We anticipate future morphological studies of the sperm structure in aporocotylids of three lineages for an understanding of their phylogenetic relationships

Gyrodactylus triglopsi n. sp. (Monogenea: Gyrodactylidae) from the Gills of Triglops nybelini Jensen, 1944 (Teleostei: Cottidae) in the Barents Sea

Introduction Monogeneans of the genus Gyrodactylus were found on the gills of specimens of the bigeye sculpin Triglops nybelini Jensen, 1944 caught by trawl in the Barents Sea in January–February 2016. Methods Morphological preparations of the parasites were examined and photographed under a microscope at magnifications of × 100–1000 and morphometric analyses were carried out on 22 specimens using ImageJ2 software. Eight of the specimens used for the morphological comparisons were also subjected to molecular analyses by sequencing a region of the ribosomal DNA spanning partial 18S, the internal transcribed spacers 1 and 2 (ITS1 and 2), 5.8S and partial 28S and comparing this with other species through a BlastN-search in GenBank and through phylogenetic analyses. Results The morphology of the species from T. nybelini was markedly different to that of any of other species of Gyrodactylus. It is characterized by having relatively long hamulus roots, a character that it shares with two other species described from marine sculpins (Cottidae); G. armatus and G. maculosi. It also has a narrow rectangular ventral bar membrane with a posterior notch which it shares with G. maculosi only. Compared with all the seven species from marine Cottidae described so far, it has the smallest opisthaptoral hard parts. A comparison of the internal transcribed spacer (ITS) rDNA sequence with available sequences in GenBank and a phylogenetic analyses also showed it to be highly divergent from other sequences. Therefore, a new species is proposed, Gyrodactylus triglopsi n. sp. Conclusion Both the morphological and molecular analyses support the status of G. triglopsi as a new species. This is to our knowledge the first species of Gyrodactylus described from Triglops nybelini and the description extends the list of Gyrodactylus species found on fish in the Barents Sea to 17.publishedVersio

Comparative analysis of the cytoarchitecture of the excretory bladder of adult Digenea (Platyhelminthes) with consideration of the presence of mineralized excretory corpuscles in marine and freshwater adult worms

The ultrastructural differences are shown between the cytoarchitecture of the excretory bladder and excretory inclusions in four digenean species, two azygiids, the marine Otodistomum cestoides and the freshwater Azygia lucii, the marine derogenid Derogenes varicus and the freshwater allocreadiid Acrolichanus auriculatus. The unusual cytoarchitecture of the bladder epithelium of the azygiid digeneans, consisting along its entire length of two alternating, morphologically different zones, tegumental and cellular excretory epithelial zones, connected by septate junctions, has recorded for the first time for the Digenea and, in general, for the Neodermata. It, possible, suggests the participation of the tegumental distal cytoplasmic layer in the formation of their excretory bladder epithelium. Like most digeneans, the excretory bladder of A. auriculatus and D. varicus has a syncytial epithelial lining. Based on available literature and our own results, we can confirm the presence of the excretory corpuscles in adult marine digeneans and their absence from freshwater species, regardless of the digenean localization in their host. The present study shown that in marine digeneans, the excretory corpuscles are associated with specialized excretory cells or excretory syncytial epithelium. Ultrastructural data were obtained on the possible growth of the excretory bladder epithelium due to the migration of undifferentiated cells into the epithelial lining in studied marine species. We may assume that the bladder epithelium of marine adult digeneans specializes, in addition to the excretory function, in osmoregulatory function

Failure of two consecutive annual treatments with ivermectin to eradicate the reindeer parasites (Hypoderma tarandi, Cephenemyia trompe and Linguatula arctica) from an island in northern Norway.

The highly efficient endectocide ivermectin is used to reduce the burden of parasites in many semidomestic reindeer herds in northern Fennoscandia. In the autumn of 1995 and 1996 all reindeer on the island of Silda (42 km2) were treated with ivermectin in an attempt to eradicate the warble fly (Hypoderma (=Oedemagena) tarandi (L.)), the nose bot fly (Cephenemyia trompe (Modeer)) (Diptera: Oestridae) and the sinus worm (Linguatula arctica Riley, Haugerud and Nilssen) (Pentastomida: Linguatulidae). Silda is situated 2-3 km off the mainland of Finnmark, northern Norway, and supports about 475 reindeer in summer. A year after the first treatment, the mean abundance of H. tarandi was reduced from 3.5 to 0.6, but a year after the second treatment the mean abundance unexpectedly had increased to 4.5. After one year without treatment, the mean abundance and prevalence of the three target parasites were at the same level, or higher, than pre-treatment levels. The main hypothesis for the failure to eliminate the parasites is that gravid H. tarandi and C. trompe females originating from untreated reindeer in adjacent mainland areas dispersed to the island during the warm summer of 1997 (possibly also in 1998). As these oestrids are strong flyers, it may not be too difficult for them to cross >2-3 km of oceanic waters. There are no good explanations for the failure to eradicate L. arctica, but the results indicate that there may be elements in its life cycle that are unknown. The conclusion of the study is that it may be difficult or impossible to eradicate these parasites permanently, even locally such as on islands unless adjacent areas on the mainland are also cleared

Pseudalataspora vanderlingeni n. sp. (Myxosporea: Bivalvulida) from gall bladders of the Cape hakes Merluccius capensis Castelnau, and M. paradoxus Franca (Teleostei: Merlucciidae)

Reed, Cecile, Kalavati, Chaganti, Mackenzie, Ken, Collins, Catherine, Hemmingsen, Willy (2018): Pseudalataspora vanderlingeni n. sp. (Myxosporea: Bivalvulida) from gall bladders of the Cape hakes Merluccius capensis Castelnau, and M. paradoxus Franca (Teleostei: Merlucciidae). Zootaxa 4497 (3): 422-428, DOI: https://doi.org/10.11646/zootaxa.4497.3.

Two new species of myxosporean parasites (Myxosporea: Bivalvulida) from gall bladders of Macruronus magellanicus Lönnberg, 1907 (Teleostei: Merlucciidae)

Kalavati, Chaganti, Mackenzie, Ken, Collins, Catherine, Hemmingsen, Willy, Brickle, Paul (2013): Two new species of myxosporean parasites (Myxosporea: Bivalvulida) from gall bladders of Macruronus magellanicus Lönnberg, 1907 (Teleostei: Merlucciidae). Zootaxa 3647 (4): 541-554, DOI: 10.11646/zootaxa.3647.4.

Ultrastructural evidence for the participation of muscle cells in the formation of extracellular matrices in aporocotylid blood flukes (Digenea)

The muscle cells and extracellular matrices (ECMs) of two teleost-infecting blood flukes belonging to distinct evolutionary lineages of the Aporocotylidae (Digenea) were examined using Transmission Electron Microscopy. Four morphotypes of muscle cells were found in the freshwater species Sanguinicola sp., but were considered to be various developmental stages of a single cisternic type. In the marine species Aporocotyle simplex, three types of muscle cells were apparent, one of which is cisternic. The first ultrastructural evidence is presented for the exocytosis of the moderately dense contents of dilated cisternae of cisternic muscle cells into the extracellular space in both Sanguinicola sp. and A. simplex. The basal matrices of aporocotylids support various types of epithelia. In Sanguinicola sp., beneath the distal tegumental cytoplasm, there is a thin lamina densa, whereas the intestinal epithelium is supported by a lamina reticularis. In A. simplex, both a thin lamina densa and a thick lamina reticularis underlie the distal cytoplasm of the tegument and are present at the periphery of the ovary, but beneath the epithelial lining of the caeca and both genital and excretory ducts there is only a lamina reticularis. Significant variation in the development and amount of the ECM in marine and freshwater aporocotylids is described, since A. simplex has a much better developed ECM than occurs in Sanguinicola sp. Moreover, thin myofilaments of muscle fibres participate in the ECM formation in A. simplex and represent its dominant component. The presence of two mechanisms for ECM formation in A. simplex, as opposed to a single mechanism in Sanguinicola sp., may represent further evidence for the affiliation of these two taxa to divergent evolutionary lineages. The data presented are discussed in relation to available information on these structures in other neodermatan groups

FIGURE 11 in Two new species of myxosporean parasites (Myxosporea: Bivalvulida) from gall bladders of Macruronus magellanicus Lönnberg, 1907 (Teleostei: Merlucciidae)

FIGURE 11. Myxidium baueri. Fresh spore under Nomarski interference-contrast illumination. Scale bar: 10μm

Treatment of reindeer with ivermectin. Effect on dung insect fauna.

Ivermectin is an antiparasitic drug widely used in reindeer (Rangifer tarandus (L.)) in Fennoscandia and North America. Most of the ivermectin injected in the animal is excreted unchanged in the faeces. Several reports show that ivermectin in cattle dung disrupts colonisation and survival of beneficial dung breeding insects. The present study investigated the effect of ivermectin on the reindeer dung fauna. Four reindeer calves (males, 6 months of age) were injected subcutaneously with standard doses of ivermectin (0.2 mg/kg body weight) in early December. The daily produced faeces was collected until day 30 after treatment, and the concentration of ivermectin was determined by high pressure liquid chromatography (HPLC) with fluorescence detection. The highest concentration measured (mean 1632 ng/g faeces (dry weight), range 907 to 2261 ng/g among the animals) was on day 4 after treatment. The concentration decreased gradually to 28 ng/g (range 6 to 58 ng/g) on day 30. Faeces portions from day 4 and from untreated reindeer were placed in the field on 2-4 July and recollected on 13-22 September in order to detect possible differences in decomposition fauna between the samples. The most important coprophilous beetles (Apbodius spp.) and flies (Scatbophaga spp.) were not detected in this winter dung whether it contained ivermectin or not, probably because of the dry consistency and small size of the pellets. On the other hand, these insects (larvae and imagines) were common in summer dung, which had been deposited naturally in the field and later placed together with the ivermectin-containing winter dung for comparison. The summer dung has a more soft and lumpy consistency. Treatment in autumn or early winter implies that the bulk of the ivermectin from the animal will be present in faeces with winter consistency, since this bulk portion is excreted during the first 30 days after treatment. This dry and pelleted faeces is not utilized by the important coprophilous insecr species, and the current practice of treatment of reindeer with ivermectin in autumn or early winter is therefore the regime representing the least danger of harmful influence on the coprophilous fauna and their contribution to the dung decomposition process

Caligus elongatus and other sea lice of the genus Caligus as parasites of farmed salmonids: A review

Accepted manuscript version, licensed CC BY-NC-ND 4.0. This review was prompted by reports of unusually large numbers of sea lice tentatively identified as Caligus elongatus infesting farmed salmon in northern Norway. Following a brief introduction to the sea lice problem in salmonid aquaculture, the review is divided into a further eight sections. The first is a review of existing information on the life cycle and behaviour of Caligus spp. The second is a description of the morphology of different stages in the life cycle of C. elongatus. The third describes the effects of caligid infestations on salmonid hosts. The fourth reviews information on the geographical distributions and host preferences of the six species of Caligus reported from farmed salmonids in different parts of the world: C. elongatus, C. curtus, C. clemensi, C. rogercresseyi, C. teres and C. orientalis. The fifth section describes interactions between farmed and wild fish and the sixth presents information on the genetics of C. elongatus. A section reviewing the different methods used to control sea lice infestations follows. The eighth section discusses the predicted effects of climate change and invasive host species on the distribution and occurrence of caligid copepods, and the ninth gives conclusions and recommendations on how to further investigate the infestation that prompted this review. These include the confirmation of the identity of the caligid causing the problem, confirmation of the genotype involved and a study of the vertical distribution in the water column of the infective stages