Diplectanids infesting the gills of the barramundi Lates calcarifer (Bloch) (Perciformes: Centropomidae), with the proposal of Laticola n. g. (Monogenoidea: Diplectanidae)

Four species of the Monogenoidea, Laticola lingaoensis n. sp., L. latesi (Tripathi, 1957) n. comb. [previously Pseudorhabdosynochus latesi (Tripathi, 1957) Kritsky & Beverley-Burton, 1986], L. paralatesi (Nagibina, 1976) n. comb. [previously Diplectanum paralatesi Nagibina, 1976] and Diplectanum penangi Liang & Leong, 1991, are reported from the gills of Lates calcarifer (Centropomidae) from the South China Sea (new geographical records for L. latesi and D. penangi). Collections from off Bathurst Island, Northern Territory, Australia, represent a new geographic record for L. paralatesi; Chilka Lake, Orissa, India, is established as the type-locality for L. latesi. Laticola n. g. (Diplectanidae) is proposed for species with a spoon-shaped copulatory organ with two to four concentric incomplete ridges in the base. Laticola lingaoensis, the type-species of Laticola, is described, and L. latesi and L. paralatesi are redescribed based on specimens from the South China Sea. Pseudorhabdosynochus monosquamodiscusi Balasuriya & Leong, 1995 and Pseudorhabdosynochus yangjiangenesis Wu & Li, 2005 are considered junior subjective synonyms of L. latesi and L. paralatesi, respectively.     

The use of sectioned otoliths to age barramundi (Lates calcarifer) (Bloch, 1790) [Centropomidae]

The relationship between the number of rings present in sagittal otoliths and the age of barramundi, Lates calcarifer (Bloch, 1790) [Centropomidae], was investigated by examining cross sectioned otoliths of 37 tagged fish of known age between 1 and 5 years from the Johnstone River, north Queensland. Concentric rings were clearly visible in all otolith sections and were validated as annual marks. The technique was then used to estimate the age and calculate von Bertalanffy growth parameters for 70 barramundi from the Fitzroy River, central Queensland. Growth appeared to be rapid but variable in the first year; the von Bertalanffy growth parameters for length versus age were L =690 mm, K=0.53, t ₀= 0.003 years. October 1 was designated as the birth date. Whole otolith length, width and thickness were also approximated well by the von Bertalanffy equation. We suggest that examination of otoliths is a useful technique for ageing barramundi but note that further validation of the ageing method is still needed for fish older than six years.     

Description of a new blood-fluke,Cruoricola lates n. g., n. sp. (Digenea: Sanguinicolidae), from sea-bass Lates calcarifer (Bloch, 1790) (Centropomidae)

A new blood-fluke, Cruoricola lates n. g., n. sp., is described from sea-bass Lates calcarifer cultured in Malaysia. It is also found in Thailand and Australia. All fish examined over 15 cm in length were infected in the type-locality. This sanguinicolid is differentiated from other genera by: the spherical seminal vesicle; the large, single testis extending beyond the intestinal caeca; the medial, bi-lobed ovary; and the single column of sub-marginal, laterally directed, evenly spaced spines. It has separate genital pores which are close together. Adults are found predominantly in the mesenteric venules of the venous circulation. Juveniles are commonest in the caudal kidney.     

Neotropical Monogenoidea. 43. Diplectanum monticellii n. sp. (Diplectanidae) from the gills of Cynoscion leiarchus (Perciformes: Sciaenidae) in Brazil

Diplectanum monticellii n. sp. is described from the gills of Cynoscion leiarchus, a marine Sciaenidae, from Itacuru?á, Rio de Janeiro (type locality); Baía de Guaratuba, Paraná; and Pontal do Sul, Paraná in Brazil. The new species is characterized by the following features: bell-shaped male copulatory organ with a sleevelike base, accessory piece absent, vas deferens looping left intestinal cecum, vaginal aperture sinistroventral, and ventral anchor with elongate superficial and deep roots.     

Laticola dae n. sp. (Monogenea: Diplectanidae) from Epinephelus maculatus (Perciformes: Serranidae) off New Caledonia

Laticola dae n. sp. is described from specimens collected from the gill-filaments of the highfin grouper Epinephelus maculatus, a coral reef fish caught off Nouméa, New Caledonia, South Pacific. The species is characterised by a spoon-shaped sclerotised male copulatory organ, with four thin walls and 73–m in outer length, and a sclerotised vagina in form of a disc, 16–m in diameter, with a smaller hemisphere on one side. Laticola Yang et al., 2006 was described to accommodate diplectanids from Lates calcarifer (Centropomidae); this is the first Laticola described from a serranid. Other diplectanids, including several species of Pseudorhabdosynochus Yamaguti, 1958, were also found on the same species of fish; specimens of L. dae represented about half of the diplectanids collected; all other species were rare.

---

Résumé Laticola dae n. sp. est décrit à partir de spécimens collectés sur les filaments branchiaux de la loche grisette, Epinephelus maculatus, un poisson de récif corallien pêché au large de Nouméa, Nouvelle-Calédonie, Pacifique Sud. L’espèce est caractérisée par un organe copulateur mâle sclérifié en forme de cuiller, avec quatre parois fines, long de 73–m, et un vagin sclérifié en forme de disque, de diamètre 16–m, avec un hémisphère plus petit d’un côté. Laticola Yang et al., 2006 a été décrit pour rassembler des Diplectanidae de Lates calcarifer (Centropomidae) ; ceci est le premier Laticola décrit d’un Serranidae. D’autres Diplectanidae, y compris plusieurs espèces de Pseudorhabdosynochus, ont aussi été trouvés chez ce poisson ; les spécimens de L. dae représentaient environ la moitié des Diplectanidae récoltés, toutes les autres espèces étaient rares.

     

Neotropical Monogenoidea. 49. Four new species of the Diplectanidae (Dactylogyrinea) from the gills of some pachyurines (Teleostei: Sciaenidae) from the Rio Tocantins and Rio Doce Basins, with the proposal of Anoplectanum n. g. and Spinomatrix n. g.

Four new species of the Diplectanidae from the gills of freshwater sciaenid species (Pachyurinae) in Brazil are described and two new genera, Anoplectanum n. g. and Spinomatrix n. g., are proposed. These are: Diplectanum copiosum n. sp. from Pachyurus junki and Petilipinnis grunniens; Anoplectanum haptorodynatum n. g., n. sp. from Pachyurus junki and Petilipinnis grunniens, and A. microsoma n. g., n. sp. from Petilipinnis grunniens, all in the Tocantins Basin; and Spinomatrix penteormos n. g., n. sp. from Pachyurus adspersus in the Rio Doce Basin. Anoplectanum is proposed to accommodate diplectanids lacking squamodiscs and having a superficial root of the ventral anchor as long or longer than the deep root. Spinomatrix is proposed for species having a haptoral and peduncular armature composed of spines, hooks, anchors, squamodiscs and armed muscular pads.     

Variable growth rates of the tropical estuarine fish barramundi Lates calcarifer (Bloch) under different freshwater flow conditions

Relationships between freshwater flows and growth rates of the opportunistic predatory finfish barramundi Lates calcarifer in a dry tropical estuary were examined using data from a long-term tag-recapture programme. Lagged effects were not investigated. After accounting for length at release, time at liberty and seasonal variation ( e.g. winter, spring, summer and autumn), growth rates were significantly and positively related to fresh water flowing to the estuary. Effects were present at relatively low levels of freshwater flow ( i.e. 2·15 m³ s⁻¹, the 5th percentile of the mean flow rate experienced by fish in the study during time at liberty). The analysis, although correlative, provides quantitative evidence to support the hypothesis that freshwater flows are important in driving the productivity of estuaries and can improve growth of species high in the trophic chain.     

Ontogenetic eye development and related behavioural changes in larvae and juveniles of barramundi Lates calcarifer (Bloch)

Larvae and juveniles of barramundi Lates calcarifer (Bloch) were examined for the development of the retina, occurrence of the retinomotor response and retinal tapetum and change in eye size with age in days. The barramundi hatched with unpigmented non-functional eyes in which retinal cells had not yet differentiated into the various elements. Soon it was followed by rapid changes in the histology of the retina. Two-day-old larvae had a well-pigmented retina with area temporalis which would allow acute vision and prey attack in the nasal direction. At 10 days, rod cells and the retinal tapetum first appeared in the retina and the retinomotor response first occurred; these would allow feeding in dim light. The retinal tapetum moved in unison with the cones and the pigment epithelium during the retinomotor response. At 26 days, the horizontal cells were divided into two layers and the twin cones appeared. These changes in the eyes occurred concurrently or in anticipation of behavioural changes, such as the onset of the first feeding at 2 days, the shift of habitat from coastal waters to swamps at the notochord flexion stage at 7–15 days, the abrupt change in feeding behaviour from roving zooplanktivore to lurking predator at 25–30 days and a later shift of habitat from turbid swamps to open coastal or lake areas at the early juvenile stage.     

Monogeneans from the gills of glassfishes (Teleostei: Perciformes: Ambassidae) in India, with the proposal of Chandacleidus n. g. (Monogenea: Dactylogyridae)

Chandacleidus n. g. (Monogenea, Dactylogyridae) is proposed to include three species collected from the gills of Indian glassfishes (Ambassidae): Chandacleidus recurvatus (Jain, 1961) n. comb. (syn. Urocleidus recurvatus Jain, 1961) from Chanda nama and C. ranga (new host record) is redescribed; and Chandacleidus saiensis n. sp. and C. lucknowensis n. sp., both from Chanda nama and C. baculis, are described. Chandacleidus n. g. is characterised by species possessing: posteriorly united intestinal caeca; overlapping gonads (testis dorsal to ovary); a counterclockwise male copulatory organ; a grooved accessory piece; a dextro-marginal vaginal pore; a haptor with two lateral flaps and armed with dissimilar dorsal and ventral anchor/bar complexes and 14 similar hooks (dissimilar in size); and hook shanks comprised of two subunits.     

Neotropical Monogenoidea: Euryhaliotrema dontykoleos n. sp. (Dactylogyridae) from the gills of the freshwater sciaenid, Pachyurus junki (Perciformes)

Euryhaliotrema dontykoleos n. sp. (Monogenoidea, Polyonchoinea, Dactylogyridae) is described based on specimens collected from the gills of Pachyurus junki (Teleostei, Sciaenidae, Pachyurinae) in the Rio Tocantins and its tributaries, State of Tocantins, Brazil. The new species, the first species of Monogenoidea reported from a pachyurine, is easily differentiated from its congener by the presence of toothlike projections in the border of the vaginal opening and by having a trapezoidal anteromedial projection on the ventral bar. Phylogenetic analysis indicates that the new species is not a member of the clade that includes the Euryhaliotrema spp. from Plagioscion spp., a second lineage of freshwater sciaenids in South America. Euryhaliotrema dontykoleos shares an immediate ancestor with the clade formed by parasites infecting marine Paralonchurus spp., (Sciaenidae), and those of Plagioscion spp.     

Structure and development of free neuromasts in barramundi, Lates calcarifer (Block)

This study was conducted to clarify the development of free neuromasts with growth of the barramundi, Lates calcarifer. A pair of free neuromasts was observed behind the unpigmented eyes in newly hatched eleutheroembryos with a mean total length of 1.93 mm, and two-hour-old eleuthero-embryos could respond to an approaching pipette. At 2 days after hatching, the egg yolk sac was mostly consumed, the eyes were pigmented, and the larvae commenced feeding on rotifers. Free neuromasts increased in number with growth and commenced developing into canal neuromasts in barramundi 15 days old with a mean total length of 8.07 mm. The average length of the major axis of the trunk free neuromasts attained approximately 12.9-15.5 microm, and the number of sensory cells was 15.4-17.5 at 15-20 days old. Developed cupulae of free neuromasts were observed in 1-day-old eleutheroembryos. The direction of maximum sensitivity of free neuromasts, determined from the polarity of the sensory cells, coincided with the minor axis of the lozenge-shaped outline of the apical surface of the free neuromasts. The polarity of trunk neuromasts was usually oriented along the antero-posterior axis of the fish body, but a few had a dorso-ventral direction. On the head, free neuromasts were oriented on lines tangential to concentric circles around the eye.     

The taxonomy of East African Nile Perch, Lates spp. (Perciformes, Centropomidae)

The type specimens of Lates albertianus, L. macrophthalmus, L. niloticus rudolfianus and L. niloticus longispinis are contrasted with each other, with riverine L. niloticus niloticus and with a collection of Nile Perch from Lake Victoria. Contrary to current belief L. niloticus niloticus was found to differ both from L. albertianus and from L. niloticus rudolfianus , but no significant difference was found between L. albertianus and L. niloticus rudolfianus . The Lake Victoria collection was found to differ from all other taxa, suggesting that the characters currently used in the taxonomy of Lates are inappropriate for this purpose. It is recommended that a reappraisal of Nile Perch taxonomy be made using more modern techniques and that studies are initiated to discover how characters change during development under differing environmental conditions.     

The food of barramundi, Lates calcarifer (Bloch), in coastal and inland waters of Van Diemen Gulf and the Gulf of Carpentaria, Australia

Examination of the diet of Lates calcarifer , based on 3684 specimens of 4–1200 mm total length (T.L.), from two localities in north Australia showed it is an opportunistic predator with an ontogenetic progression in its diet from microcrustacea to macrocrustacea to fish. The increasing importance of fish in the diet of L. calcarifer in salt water (up to 87% of food consumed) involved a dietary shift from feeding on bottom-dwelling forms to pelagic forms. There were few differences in the diet of L. calcarifer between the two localities. Cannibalism was rarely encountered in the Gulf of Carpentaria although it was significant (11–4% of the diet of L. calcarifer of 1001–1200 mm T.L.) in Van Diemen Gulf. A significant correlation between predator and prey length was found for Ariidae, Dorosomidae, Engraulidae, L. calcarifer , Mugilidae and Polynemidae. The maximum prey/predator length ratio observed was 0–61 for the dorosomid, Nematolosa erebi.     

Cloning and analysis of antiviral activity of a barramundi (Lates calcarifer) Mx gene

We obtained a full-length cDNA clone for the Mx gene of barramundi (Lates calcarifer), using RACE (rapid amplification of cDNA ends) polymerase chain reaction (PCR) amplification of RNA extracted from a barramundi brain cell line cBB. The Mx cDNA of 2.2kb contains an open reading frame (ORF) of 1875 nucleotides encoding a protein of 624 amino acids. The predicted barramundi Mx protein is 71.4 kDa and contains a tripartite guanosinetriphosphate (GTP)-binding motif at the amino terminal and a leucine zipper at the carboxyl terminal, characteristic of all known Mx proteins. Poly I:C-transfection induced the expression of Mx gene in cBB cells, and the induction level at 28 degrees C was higher than that at 20 degrees C. Moreover, Mx gene expression was also induced by viral infection, including fish nodavirus, birnavirus, and iridovirus. Among these, nodavirus was a stronger inducer than the other two viruses. Using an antiviral activity assay, we revealed that poly I:C-transfected cBB cells had antiviral activity against fish nodavirus and birnavirus, but not iridovirus. Furthermore, the replication of nodavirus and birnavirus could be restored after the expression of Mx gene was down-regulated by siRNA. Therefore, these results indicated that the expression of barramundi Mx gene was able to inhibit the proliferation of fish nodavirus and birnavirus.     

Five new monogenean species from the gills of Mulloidichthys vanicolensis (Perciformes: Mullidae) off New Caledonia, with the proposal of Volsellituba n. g. and Pennulituba n. g. (Monogenea: Dactylogyridae)

Three species of Volsellituba n. g. and two species of Pennulituba n. g. are described from the gills of the yellowfin goatfish Mulloidichthys vanicolensis (Valenciennes) off New Caledonia (South Pacific). Volsellituba and Pennulituba resemble dactylogyrid genera whose species lack eye-spots and possess tandem or slightly overlapping gonads, a single prostatic reservoir, a male copulatory organ without an accessory piece, a dextroventral non-sclerotised vagina, ventral and dorsal anchor/bar complexes, and hooks with shanks comprising a single slender unit. Volsellituba n. g. is characterised by its species having ventral tegumental folds at the level of the vaginal duct, a male copulatory organ with a subterminal basal opening and a two-piece dorsal bar. The following new species of Volsellituba are described: V. orchidea n. sp. (type-species), V. nabla n. sp. and V. elephantina n. sp. Pennulituba n. g. is distinguished by its species possessing a male copulatory organ with a wing-shaped membrane and a dorsal bar with a poorly to non-sclerotised medial part. This genus includes P. piratifalx n. sp. (type-species) and P. cymansis n. sp. A tabular summary of the species of Haliotrema Johnston & Tiegs, 1922 reported from mullids is provided.     

Methodology in the study of seabass (Lates calcarifer Bloch): nutritional requirements in Singapore

This paper describes the effort of the Marine Aquaculture Section of the Primary Production Department in Singapore and the Institut Francais de Recherche pour l'Exploitation de la Mer in developing adequate facilities for fish nutritional requirement studies in Singapore, and in introducing appropriate nutritional methodology so that results are reliable and accurate. One of the first achievements was the demonstration of homogeneous fish (tropical seabass, Lates calcarifer Bloch) growth response in a newly established tank system before any nutritional experiments were initiated. The application of statistical procedures that take into consideration the power of a test and number of replications required has allowed for more accurate interpretation of results. This can be seen in the results of the first nutritional requirement experiment on the optimal dietary protein level of the seabass at constant energy.     

DNA barcoding reveals a likely second species of Asian sea bass (barramundi) (Lates calcarifer)

DNA barcoding – the sequencing of a c. 650 base pair region of the mitochondrial cytochrome c oxidase I gene – strongly suggests that barramundi ( Lates calcarifer ) from Australia and from Myanmar are different species (Kimura 2 parameter distance of c. 9·5%). Cytochrome b sequence data support this conclusion (distance c. 11·3%). Further examination, both genetic and morphological, of L. calcarifer throughout its range is recommended.