Characterisation of Myxobolus stellatus n. sp. (Cnidaria: Myxobolidae) infecting the cranial nerves and ganglia of the spotfin hatchetfish Thoracocharax stellatus (Kner) (Characiformes: Gasteropelecidae) from Colombia

Systematic Parasitology - A previously undescribed Myxobolus sp. was isolated from the cranial nerves and ganglia of the spotfin hatchetfish Thoracocharax stellatus (Kner) that exhibited neurologic...     

A new species of Philometra Costa, 1845 (Nematoda: Philometridae) from the freshwater fish (red piranha) Pygocentrus nattereri Kner (Characidae) in Amazonia, Brazil

A new nematode species, Philometra nattereri n. sp. (Philometridae), is described from female specimens found in the oculo-orbits and nasal cavity of the red piranha Pygocentrus nattereri Kner (Characiformes: Characidae) from five lakes in Central Amazonia, Brazil, collected in 2008 and 2009 (overall prevalence 12%, intensity 1?C3 nematodes per fish). Based on light and scanning electron microscopical examination, the new species differs from most other congeners parasitising freshwater fishes in that its oesophageal gland extends anteriorly far anterior to the level of the nerve-ring, in the presence of 14 small cephalic papillae arranged in two circles and in having two minute caudal projections. This is the first species of Philometra Costa, 1845 reported from fishes of the family Characidae and the second valid species of this genus parasitic in freshwater fishes of Brazil and South America.     

Genetic differentiation in red‐bellied piranha populations (Pygocentrus nattereri,Kner, 1858) from the Solimões‐Amazonas River

Red‐bellied piranhas (Pygocentrus nattereri) are widely caught with different intensities throughout the region of Solimões‐Amazonas River by local fishermen. Thus, the management of this resource is performed in the absence of any information on its genetic stock. P. nattereri is a voracious predator and widely distributed in the Neotropical region, and it is found in other regions of American continent. However, information about genetic variability and structure of wild populations of red‐bellied piranha is unavailable. Here, we describe the levels of genetic diversity and genetic structure of red‐bellied piranha populations collected at different locations of Solimões‐Amazonas River system. We collected 234 red‐bellied piranhas and analyzed throughout eight microsatellite markers. We identified high genetic diversity within populations, although the populations of lakes ANA, ARA, and MAR have shown some decrease in their genetic variability, indicating overfishing at these communities. Was identified the existence of two biological populations when the analysis was taken altogether at the lakes of Solimões‐Amazonas River system, with significant genetic differentiation between them. The red‐bellied piranha populations presented limited gene flow between two groups of populations, which were explained by geographical distance between these lakes. However, high level of gene flow was observed between the lakes within of the biological populations. We have identified high divergence between the Catalão subpopulation and all other subpopulations. We suggest the creation of sustainable reserve for lakes near the city of Manaus to better manage and protect this species, whose populations suffer from both extractive and sport fishing.     

Allometry and developmental integration of body growth in a piranha,Pygocentrus nattereri (Teleostei: Ostariophysi)

Piranhas, like many teleosts, change their diets on both ontogenetic and phylogenetic time scales. Prior studies have suggested that pervasive morphological changes in body form on a phylogenetic time scale may be related to changes in diet, but previous reports have found little shape change in piranhas on an ontogenetic time scale. We re-examine the post-transformational allometry of body form in one piranha, Pygocentrus nattereri (Kner), using the method of thin-plate splines decomposed by their partial warps. We find substantial evidence of allometry, primarily elongation of the mid-body relative to the more anterior and posterior regions, elongation of the postorbital and nape regions relative to the more anterior head and posterior body, and deepening of the head relative to the body. In addition to these pervasive changes throughout the body, there are some that are more localized, especially elongation of the postorbital region relative to eye diameter and snout, and an even more localized elongation of the snout relative to eye diameter. Initial dietary transitions are associated with changes in head and jaw proportions, but rates of shape change decelerate through growth, so that the final transition to a diet increasingly dominated by small whole fish appears associated with change largely in overall body size. © 1995 Wiley-Liss, Inc.     

Henneguya schizodon n. sp. (Myxozoa, Myxobolidae), a parasite of the Amazonian teleost fish Schizodon fasciatus (Characiformes, Anostomidae)

A new histozoic species of myxosporean (Henneguya schizodon n. sp.) is described from the Amazon River teleost fish Schizodon fasciatus Spix & Agassiz, 1892 (Characiformes, Anostomidae). The plasmodia, which showed asynchronous development, were located in the kidney of the host. The spore body was ellipsoidal and was 13.1 (12-14) micron long by 3.3 (3-4) micron wide. The total length of the spore was 28.9 (27-30) micron, and each value had a caudal process measuring 16.3 (15-17) micron. The polar capsules were 5.4 (5-6) micron long by 1.3 (1-1.5) micron wide, and each had a polar filament with 8-10 coils. The characteristics of the species were compared with nearly all the species described so far, including all the species reported from South American fishes. This comparison allows to consider the materials as a new species, and the name Henneguya schizodon n. sp. is proposed.     

Myxobolus goensis n. sp. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the gills of Mugil cephalus (Osteichthyes, Mugilidae) from Goa, India

Two species of Myxobolus are reported from the gills of Mugil cephalus collected at Goa, India: M. goensis n. sp. and M. parvus Shulman, 1962. Myxobolus goensis n. sp. forms digitiform or rounded plasmodia between the gill rakers. Their spores are oval in frontal view, with tapered anterior extremity, and lemon-shaped in lateral view, measuring 9.7 (9.5-10.5) microm in length, 6.6 (6-7.5) microm in width, and 5.2 (5-6) microm in thickness. The polar capsules are pyriform and unequal in size. The larger ones are 5.3 (4.5-6) microm long and 2.4 (2-3) microm wide; the smaller ones are 2.4 (2-3) microm long and 1.8 (1.5-2) microm wide. The polar filament forms five turns aligned perpendicularly to the longitudinal axis of the larger polar capsules. Within the smaller polar capsules the polar filament is difficult to observe and, apparently, forms three coils. The spores are distinctly different from other Myxobolus species infecting M. cephalus and other Mugil spp. Furthermore, the present material is also different from 204 Myxobolus species presenting differently sized polar capsules, representing nearly all the known species with this characteristic. The fact that only the M. cephalus specimens were infected among a sample of 206 fish specimens, comprising 27 different species, strongly suggests that this parasite is specific to M. cephalus.     

Population ecology of Red-bellied Piranha Pygocentrus nattereri Kner, 1858 (Characidae: Serrasalminae) in the Negro River, Pantanal, Brazil

This study defined some population parameters for growth of the Red-bellied Piranha (Pygocentrus nattereri) in the Pantanal, based on the bimonthly length-frequency distribution of individuals in samples taken from October 2005 through August 2008 in the Negro River. The samples were taken by means of gill nets and cast nets, with meshes of 1.5?C8?cm between adjacent knots. The standard length of the fish ranged from 10.2 to 30.2?cm with a mean of 20.51?±?3.39. The gonadosomatic index (GSI) varied significantly among months (F?=?5.45; p?<?0.01), it was significantly higher from October to February, and was positively correlated and synchronized with day length (rs?=?0.92; p?<?0.01) and rainfall (rs?=?0.70; p?<?0.01). It was desynchronized from and not correlated with river level (rs?=?0.12; p?=?0.69). The GSI reached the highest values and ripe individuals were more frequent in December, prior to the months of highest river levels from February to April. The estimated growth parameters were L???=?31.8; k?=?0.45; Rn?=?0.204. In the Pantanal, P. nattereri has a life expectancy (6.9?years) compatible with the 7 cohorts indicated by the growth curve. Sexual maturation occurred at around 15.4?cm, after 1.6?years.     

Early ontogeny of the commercially valuable fish red-bellied pacu Piaractus brachypomus (Characiformes,Serrasalmidae) from the Amazon,Brazil

The initial development of the red-bellied pacu Piaractus brachypomus is described using morphological, meristic and morphometric characteristics. A total of 127 individuals were analysed (47 in the yolk-sac, 35 in pre-flexion, five in flexion, 20 in post-flexion and 20 in juvenile) with standard length varying between 2.92 and 48.61 mm. The larvae are born poorly developed and have a discoidal yolk at ~6.33 mm standard length. During early ontogeny, the mouth passes from terminal to subterminal and the anal opening reaches the vertical line over the midline region of the body. There are changes in body shape from long and moderate to deep, head length from small to large, and eye diameter from moderate to large. Dendritic chromatophores were present in the ventral, dorsal and upper part of the swim bladder in the early larval stages. Rounded spots are evident all over the body in juveniles. The total number of myomeres ranges from 39 to 41 (20–23 pre-anal, 17–20 post-anal). Through the morphometric relationships, it was evidenced that the greatest changes during the initial ontogeny of P. brachypomus occur in the transition from the post-flexion stage to the juvenile period, indicating changes in behaviour, foraging and physiology.     

Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the Amazonian teleost fish Semaprochilodus insignis (Osteichthyes, Prochilodontidae)

A new myxosporean species is described from the fish Semaprochilodus insignis captured from the Amazon River, near Manaus. Myxobolus insignis sp. n. was located in the gills of the host forming plasmodia inside the secondary gill lamellae. The spores had a thick wall (1.5-2 microm) all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, and oval in lateral view. They were 14.5 (14-15) microm long by 11.3 (11-12) microm wide and 7.8 (7-8) microm thick. Some spores showed the presence of a triangular thickening of the internal face of the wall near the posterior end of the polar capsules. This thickening could occur in one of the sides of the spore or in both sides. The polar capsules were large and equal in size surpassing the midlength of the spore. They were oval with the posterior extremity rounded, and converging anteriorly with tapered ends. They were 7.6 (7-8) microm long by 4.2 (3-5) microm wide, and the polar filament formed 6 coils slightly obliquely to the axis of the polar capsule. An intercapsular appendix was present. There was no mucous envelope or distinct iodinophilous vacuole.     

Myxobolus shuifuensis sp. n. (Myxozoa: Myxobolidae) infecting the exotic mrigal Cirrhinus mrigala feral in China

Myxobolus species represents a group of cosmopolitan metazoan parasites commonly harbored in the farmed and wild fish populations. Here, a species of Myxobolus is found in the kidney of an exotic mrigal Cirrhinus mrigala feral in the Yangtze River and utilized for an integrative characterization. Ellipsoidal myxospores are measured at 15.68 ± 0.8 (13.93–17.11) × 11.42 ± 0.54 (10.34–12.3) × 7.94 ± 0.35 (7.58–8.5) μm in dimension. The polar capsules are pyriform, and unequal in size. The morphological and morphometric characteristics of the present isolates are distinct from those of other congeners. Molecularly, the pairwise comparison based on the SSU rDNA sequence indicates that the present amplicon does not match any sequences available in the GenBank database and shares the highest similarity of 92.12% to Myxobolus pavlovskii (MG520369). Accordingly, we propose a name Myxobolus shuifuensis sp. n. for the present isolates. Phylogenetical trees indicate an apparent host-associated phylogenetic pattern. M. shuifuensis sp. n. groups loosely with other Myxobolus species isolated from Cirrhinus fish. Insead, it forms a sister clade to some myxosporeans belonging to the Thelohanellus genus. This result underpins the species identification and provides evidence for challenging the taxonomic separation among both morphologically comparable genera.     

Myxobolus myleus n. sp. infecting the bile of the Amazonian freshwater fish Myleus rubripinnis (Teleostei: Serrasalmidae): morphology and pathology

Myxobolus myleus n. sp. is described from the gall-bladder of the freshwater fish Myleus rubripinnis collected near the city of Oriximiná in the Amazon System, Brazil. The spores obtained from the bile contained two equal symmetrical and smooth valves, each forming the spore wall. The spores were large, with a cone-like form, a semi spherical basal contour and measured (in μm) 19.3 ± 0.5 (n = 25) × 8.3 ± 0.5 (n = 25) × 4.0 ± 0.3 (n = 15). The apical end of the spores contained two elongate, equal and pointed conical polar capsules measuring 13.2 ± 0.4 μm (n = 25) in length and 3.0 ± 0.3 μm (n = 15) in width, each having a slightly tapering polar filament with 19 to 21 turns. The polar capsules were extended below at about 4/5 of the total length of the spores. The sporoplasm was binucleate and contained some sporoplasmosomes. All infected fish presented hypertrophy of the gall-bladder due to presence of the brownish parasite floating in the bile. In this paper we describe this new species of myxosporean based on light and ultrastructural observations, together with its associated pathology.     

Auriculostoma astyanace n. gen., n. sp. (Digenea: Allocreadiidae), from the banded astyanax, Astyanax fasciatus (Characiformes: Characidae), from Nicaragua, with a reevaluation of neotropical Crepidostomum spp

Auriculostoma n. gen. (Trematoda: Allocreadiidae) is proposed for Auriculostoma astyanace n. sp. from the intestine of the characid fish Astyanax fasciatus in the Atlantic coastal drainages of Nicaragua. The new genus differs from all papillose allocreadiid genera, except Bunoderella, in possessing 2 pairs of muscular oral papillae (instead of 1 or 3), of which the ventrolateral pair is moderately developed and the dorsolateral papillae are long and auricular. Auriculostoma differs from Bunoderella Schell, 1964, in having lateral vitelline follicles, completely separated or confluent only in the posttesticular region, a uterus limited to the pretesticular region or with a few eggs at the level of the testes, and a long cirrus sac that overlaps the acetabulum or usually reaches posteriorly to the ovarian level. Three other allocreadiid species, all from South American freshwater fishes and each of which had previously been placed in Crepidostomum, are transferred to Auriculostoma based on the presence of the diagnostic muscular oral papillae. These include Crepidostomum platense Szidat, 1954, C. macrorchis Szidat, 1954, and C. stenopteri Ma?é-Garzón and Gascón, 1973. Diagnostic features for Auriculostoma also include mainly pretesticular uterus, lateral vitellaria with variation in posttesticular confluence, and tandem testes. The genus appears to be typically associated with neotropical siluriforms (catfishes) and characiforms (tetras).     

Lernaeopoda tenuis n. sp. andPseudolernaeopoda caudocapta n. g., n. sp. (Copepoda,Lernaeopodidae) parasitic onTriakis maculata (Kner & Steindachner) from the Chilean coast,South Pacific

Summary One new genus and two new species of the Lernaeopodidae (Copepoda: Siphonostomatoida), parasitic onTriakis maculata off the coast of Chile, are described and illustrated. The new genus,Pseudolernaeopoda, parasitizes the cloaca of its host. Its type-species,P. caudocapta, can be distinguished fromLernaeopoda by the absence of modified uropods. A new species ofLernaeopoda, L. tenuis, was found on the gills of the same host. In absence of the male, the generic affinities of this species must be considered only tentative. ac]19850409     

Morphological,ultrastructural, and molecular analysis of a new species of Myxobolus (Cnidaria,Myxosporea) parasitizing Apareiodon piracicabae (Characiformes,Parodontidae) from Brazil

About forty-two species of Myxobolus have been previously described to parasitize characiform fishes in South America. Here, we described a new myxozoan species, Myxobolus parodontidis n. sp., in the gills of Apareiodon piracicabae (Characiformes, Parodontidae) from the streams of the Middle Paranapanema River basin, Brazil. The proposed new species is supported by a combination of morphological, ultrastructural, and molecular characterization (small subunit ribosomal DNA). Thirteen specimens of A. piracicabae were analyzed and 30.8% was infected by Myxobolus parodontidis n. sp. The myxospores was classified as intralamellar asymmetric type. A few aberrant myxospores with three polar capsules were observed: the spore length and width were the same of normal myxospores, but the polar capsules had smaller sizes. Ultrastructural analysis showed that the plasmodial membrane of Myxobolus parodontidis n. sp. was in direct contact with the host tissue and a connective capsule surrounding the plasmodium was not observed. The phylogenetic analysis showed that the main influence in the clustering of species of myxobolids seems to be related to the phylogenetic relationships established among fish hosts, mainly at the level of family and order. This is the first record of a myxozoan species parasitizing parodontid fish, contributing to the knowledge of the biodiversity of myxozoans from Brazil.     

Ultrastructural and Cytochemical Observations on Sporogenesis of Myxobolus sp. (Myxosporida: Myxobolidae) from the Common Shiner Notropis cornutus*

SYNOPSIS. The structure and cytochemistry of spores of Myxobolus sp. from plasmodia which occur in the gill filaments of the common shiner Notropis cornutus were studied by light microscopy and by scanning and transmission electron microscopy. The thin-walled valves of the pyriform spores are thickened in the lateral sutural and apical regions. Mucous material is associated predominantly with the posterior end of many spores. The plasmodium is surrounded by a syncytial wall bounded by 2 membranes. Pinocytotic channels are formed by the inner membrane and numerous dense vesicles are pinched off at the distal ends of the channels. Sporogenesis is initiated by the envelopment of one vegetative cell by another. The larger, enveloped cell divides to form a disporous pansporoblast, which contains 2 pairs of capsulogenic and valvogenic cells and 2 binucleate sporoplasm cells. Each capsular primordium and connecting external tubule gives rise to a polar capsule which houses a helically coiled polar tubule. The apical end of each polar capsule is plugged by a stopper. The valvogenic cells surround the capsulogenic and posteriorly situated sporoplasm cells to form the spore valves. Iodinophilic (glycogen) inclusions were not seen in spores stained with iodine or Best's carmine. A darkly stained band was observed around the posterior region of most spores stained with Best's carmine. In the electron microscope large aggregates of β glycogen particles were seen in the cytoplasm of sporoplasm cells in mature spores.     

Myxobolus absonus sp. n. (Myxozoa: Myxosporea) parasitizing pimelodus maculatus (siluriformes: Pimelodidae), a South American freshwater fish

A new myxoporean species is described from a freshwater fish in Brazil. Myxobolus absonus sp. n. was found infecting Pimelodus maculatus captured in the river Piracicaba, State of S?o Paulo, Brazil. Cysts were found free in the opercular cavity. The spores are large (length--15.7 +/- 1.5 microns, width--10.2 +/- 0.7 microns; mean +/- S.D.) and oval in shape, with the anterior end slightly pointed. The spore valves are relatively thin, smooth, and asymmetrical in a frontal view. The polar capsules are pyriform in shape, and unequal in size; the largest are 6.4 +/- 0.7 microns long and 3.6 +/- 0.5 microns wide, while the smallest are 4.2 +/- 0.6 microns long and 2.5 +/- 0.5 microns wide.