Some peculiarities of the ultrafine structure of the neurons of the cestode Pelichnibothrium speciosum (Monticelli, 1889) (Cestoda: Tetraphyllidea)]

In the scolex ganglia of the cestode Pelichnibothrium speciosum uni - and multipolar neurons can be found. Their neuroplasm is rich in free ribosomes. The ergastoplasmas membranes are frequently arranged in compact finger print-like structures. The nerve cells processes form tight junctions which cannot be interpreted as synaptic contacts.     

The status of the barbel, Barbus barbus (L.) (Teleostei, Cyprinidae), in the United Kingdom

The barbel was originally a fish with a relatively restricted range in the British Isles. However, despite the general environmental degradation of many British rivers, and in contrast with some native freshwater fishes, the barbel is now more widely distributed than it was a century ago. It may even be more abundant numerically.     

Henneguya tunisiensis n. sp. (Myxosporea: Bivalvulida), a new gill parasite of Symphodus tinca (L.) (Teleostei: Labridae) off Tunisia

Henneguya tunisiensis n. sp., a new myxosporean, is described from the gill-arches of the East Atlantic peacock wrasse Symphodus tinca (L.) collected from off the Kerkennah Islands, Tunisia. It is characterised by the presence of elongate white plasmodia of 1–1.5 × 1.5–2 mm in size. The mature spores are rounded in frontal view and have two identical polar capsules and two caudal appendages which taper considerably at the end. Both light and electron microscopical data show that this species differs in several morphological features from all previously described Henneguya spp. A molecular analysis, based on 18S rDNA sequence data, indicates that H. tunisiensis n. sp. is readily distinguishable from other myxozoan DNA sequences in GenBank. Phylogenetically, the new species is placed in the marine Henneguya clade, which is a sister group of marine Myxobolus spp. from perciform fishes in Tunisian waters.     

Aploparaksis mackoi n. sp. (Cestoda: Hymenolepididae), a parasite of the common snipe Gallinago gallinago (L.) from the Slovak Republic

Aploparaksis mackoi n. sp. is described from a charadriiform bird, Gallinago gallinago (L.), collected from the central Carpathian Region of the Slovak Republic. The new species differs from all previously known species of Aploparaksis Clerc, 1903 by having a very large conical cirrus with a maximum length up to 1.5 times the proglottis width. The species is characterised by 10 aploparaksoid hooks, 19 microm long, with long, thin blades. The position of the vitellarium, with respect to the ovary, varies within the same strobila from median to aporal.     

DNA reassociation kinetics and genome complexity of a fish (Psetta maxima: Teleostei) and its gut parasite (Bothriocephalus gregarius: Cestoda).

1. The genomic structure of a fish (Psetta maxima) and of a Tapeworm (Bothriocephalus), who form a close host-parasite association, was determined by reassociation kinetics experiments. 2. Spectrophotometric readings of single-stranded versus double-stranded DNA separated on hydroxylapatite columns after reassociation at Cot values ranging from 0.0001 to 10(5) allowed the drawing of the reassociation curves of both genomes. 3. Different fractions according to their degree of repetitivity were evidenced, and the relative amounts of repetitive versus single-copy sequences, as well as their complexity, were calculated. 4. It appears that the amount of non-repetitive DNA is lower in the Tapeworm than in its vertebrate host, although the complexity of these single-copy sequences is the same.     

Description of Scalithrium n. gen. (Cestoda,Tetraphyllidea) with Scalithrium minimum (Van Beneden, 1850) n. comb., a parasite of Dasyatis pastinaca (Elasmobranchii,Dasyatidae), as type species

Scalithrium gen. n. (Cestoda, Tetraphyllidea) is proposed with Scalithrium minimum (Van Beneden, 1850) n. comb., parasite of Dasyatis pastinaca (Elasmobranchii, Dasyatidae) as type-species. The new genus Scalithrium (Tetraphyllidea, Phyllobothriidae, Rhinebothriinae) is erected for several species previously included in the genus Rhinebothrium. These species have a scolex with four bothridia, the distal surface of which is divided by transverse septa in a single row of loculi. Scalithrium minimum (Van Beneden, 1850) n. comb. is redescribed from specimens collected from the type-host Dasyatis pastinaca in Tunisia and becomes the type-species of the new genus. After Braun (1900) Echeneibothrium variabile Van Beneden, 1850 is considered as type-species of the genus Echeneibothrium. Species of Rhinebothriinae to be transferred into the genus Scalithrium are discussed and a key is proposed for the eight species.     

Spermatozoon ultrastructure of Aponurus laguncula (Digenea: Lecithasteridae), a parasite of Aluterus monoceros (Pisces: Teleostei)

The mature spermatozoon of Aponurus laguncula, a parasite of the unicorn leatherjacket Aluterus monoceros, was studied by transmission electron microscopy. The spermatozoon possesses 2 axonemes of the 9 + “1” trepaxonematan pattern, attachment zones, a nucleus, a mitochondrion, external ornamentation of the plasma membrane and cortical microtubules. The major features are the presence of: 1) external ornamentation in the anterior part of the spermatozoon not associated with cortical microtubules; 2) one mitochondrion; and 3) cortical microtubules arranged as a single field in the ventral side. The maximum number of microtubules is in the nuclear region. The extremities of the axonemes are characterized by the disappearance of the central core and the presence of microtubule doublets or singlets. This study is the first undertaken with a member of the Lecithasteridae and exemplifies the sperm ultrastructure for the superfamily Hemiuroidea.     

Immune response of turbot, Psetta maxima (L.) (Pisces: Teleostei), to formalin-killed scuticociliates (Ciliophora) and adjuvanted formulations

The increasing frequency of scuticociliatosis in turbot culture has stressed the need of knowledge on the immune responses to these parasites, for further developing of prevention and control strategies. The immune response of turbot to killed parasites, alone (Ag) or in combination with Montanide ISA 763A (MON), was studied in a laboratory-scale experiment. The variations of several innate immune factors and the antibody response were analysed in immunized vs. non-immunized fish at different times after immunization, and also after a challenge with live ciliates. Amongst innate immune factors, serum lysozyme increased progressively in all inoculated groups. Differences in innate immune factors in Ag and Ag-MON fish with respect to controls were mainly evidenced after challenge, especially for serum complement. Serum antibody levels increased in immunized fish after booster and particularly after challenge. In addition, certain protection was obtained for immunized groups compared to controls or to fish receiving MON alone, and the levels of specific antibodies were also the highest in immunized groups. The obtained information could be useful for further design of immunoprophylactic formulations against scuticociliatosis.     

Waveform generation in Rhamphichthys rostratus (L.) (Teleostei,Gymnotiformes)

Rhamphichthys rostratus (L.) emits brief pulses (2 ms) repeated very regularly at 50 Hz. The electric organ shows a heterogeneous distribution of the electrocyte tubes and the occurrence of three electrocyte types (caudally innervated, rostrally innervated and marginallycaudally innervated). In the sub-opercular region the electric organ consists of a pair of tubes containing only caudally innervated electrocytes. At the abdominal region the EO consists of three pairs of tubes. Each pair contains one of the described electrocyte types. The number of electrocyte tubes increases toward the tail to reach nine or ten pairs in the most caudal segments. In the intermediate region most tubes contain doubly innervated electrocytes except the ventral pair that contains caudally innervated electrocytes. The caudal 25% contains exclusively caudally innervated electrocytes. The electric organ discharge consists of five wave components (V1 to V5). Electrophysiological data are consistent with the hypothesis that V1 results from the activity of the rostral faces of rostrally innervated electrocytes. V2 results from the activities of rostral faces of marginally-caudally innervated electrocytes while V3 results from the activities of caudal faces of most electrocytes. Curarization experiments demonstrated that V4 and V5 result from action potential invasion and are not directly elicited by neural activity.Abbreviations AEN1 anterior electromotor nerve 1 - AEN2 anterior electromotor nerve 2 - BMB boraxic methylene blue - CIE caudally innervated electrocytes - EMF electromotive force - EO electric organ - EOD electric organ discharge - I current amplitude - MCIE marginally-caudally innervated electrocytes - MT medial tubes - PEN posterior electromotor nerve - R _n internal impedance - RIE rostrally innervated electrocytes - Rl load resistor - SAT short abdominal tubes - V voltage amplitude     

Pseudanthocotyloides heterocotyle (van Beneden, 1871) Euzet & Prost, 1969 (Monogenea: Polyopisthocotylea: Mazocraeidae), a parasite of herring Clupea harengus L. and sprat Sprattus sprattus L. (Teleostei: Clupeidae)

A total of 690 herring Clupea harengus L. and 88 sprat Sprattus sprattus L. caught off the west coast of Sweden, in the North Sea and off the west and south coasts of the United Kingdom, were examined for gill parasites. The monogenean Pseudanthocotyloides heterocotyle (van Beneden, 1871) Euzet & Prost, 1969 was found in 38 (5.5%) herring and one (1.1%) sprat. The parasite was significantly (P>0.05) more common off the west coast of Sweden than elsewhere and most specimens (62.5%) were found on the pseudobranchs. Only the smaller herring were infected. P. heterocotyle is redescribed and its taxonomy discussed, together with the possibility of host and parasite misidentification in previous reports.     

A western Scottish population of the leopard-spotted goby, Thorogobius ephippiatus (Lowe) (Teleostei: Gobioidea)

A population of the sublittoral leopard-spotted goby, Thorogobius ephippiatus (Lowe, 1839), is recorded from Upper Loch Torridon, Scotland, and the more northerly occurrence of this Mediterranean-Atlantic species along western Scottish coasts confirmed. Modified methods of capture are described. Distinctive systematic features of this population, which tends to have low sensory papilla and pectoral ray values, are examined with reference to other T. ephippiatus and the related T. macrolepis (Kolombatovic, 1891). The time of onset and reasons for this local differentiation are discussed.     

Aploparaksis kornyushini n. sp. (Cestoda: Hymenolepididae), a parasite of the woodcock Scolopax rusticola (L.), and its life-cycle

Aploparaksis kornyushini n. sp. is described from a woodcock Scolopax rusticola L. from Lithuania, Russia (Tver' Region) and the Ukraine. Initially, one specimen of this tapeworm was described and figured by Kornyushin (1975) as A. scolopacis Yamaguti, 1935 together with another specimens belonging to the latter species. A. kornyushini n. sp. and A. scolopacis are morphologically very similar species. They can be distinguished by the slightly different length of the rostellar hooks and by the shape of the cirrus, which lacks basal bulbus in the new species. A. kornyushini can be readily distinguished from the remaining species of Aploparaksis Clerc, 1903 from woodcocks by the structure of its fully-developed embryophore, which has polar thickenings and two large or a few smaller lateral projection; this combination of characters is unknown for embryophores other Aploparaksis spp. (except for A. scolopacis). The life-cycle of A. kornyushini was studied under experimental conditions in Lithuania. The metacestodes were located under the chlorogogenous tissue of the intestine of Dendrobaena octaedra (Lumbricidae). The metacestode exhibits a pattern of postembryonal development typical for the cysticercoid modification termed an 'ovoid diplocyst'.     

Sperm ultrastructure of Helicometra epinepheli (Platyhelminthes, Digenea, Opecoelidae), parasite of Epinephelus fasciatus (Pisces, Teleostei)

This paper describes the ultrastructure of the mature spermatozoon of the digenean Helicometra epinepheli. The ultrastructural elements observed are: two axonemes with a 9+"1" pattern of Trepaxonemata, four attachment zones, a nucleus, two mitochondria, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. A particularity of this spermatozoon is the presence of an apical cone. However, the spermatozoon presents the general pattern of the Opecoelidae and thus differs from Helicometra fasciata (which appears as an exception in this family) by several ultrastructural features: the presence of external ornamentation and spine-like bodies and the arrangement of cortical microtubules around the first mitochondrion in the region of the ornamentation. Each ultrastructural feature is discussed and compared with the literature to highlight characters which could be useful for phylogeny.