Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 (Dactylogyridae) represents one of the most species-rich groups (22 species currently recognized as valid) of all dactylogyrid parasites infecting Neotropical catfishes. Species of Cosmetocleithrum exhibit a remarkable affinity towards catfishes of the Doradidae and the Auchenipteridae. However, phylogenetic relationships between members of this genus have not been yet analysed. This study analysed newly obtained partial sequences of the 28S ribosomal RNA gene of seven species of Cosmetocleithrum, including its type species C. gussevi Kritsky, Thatcher & Boeger, 1986, along with several other dactylogyrids infecting siluriform, gymnotiform, perciform and characiform fishes. Cosmetocleithrum appeared as an evolutionary recent group, composed of two well-defined lineages: lineage 1 includes parasites of doradids – namely, C. bulbocirrus, C. confusum, C. parvum and C. bifurcum – whereas lineage 2 is composed of species from doradids – that is, C. rarum, C. gussevi, C. gigas, C. trachydorasi and C. falsunilatum – together with parasites of auchenipterids – namely, C. laciniatum and C. baculum. The search for synapomorphies to characterize taxonomic groups within Cosmetocleithrum appears challenging, since the morphology of their haptoral elements is quite conservative, and that of the copulatory complex is highly variable between species. The results of the present study support the recent synonymization of Paracosmetocleithrum Acosta, Scholz, Blasco-Costa, Alves & Silva, 2018 with Cosmetocleithrum. Whereas the 28S ribosomal DNA data resolved Cosmetocleithrum as monophyletic, the statistical support for the lineage was low, rendering its phylogenetic position between other Neotropical dactylogyrids yet undefined.

A new genus, Mystocestus, is proposed to accommodate a new species, Mystocestus anindoi n. g., n. sp. from Mystus vittatus (Bloch) (type host) in West Bengal and Mystus cavasius (Hamilton) (Siluriformes: Bagridae) in Maharashtra, India. The new genus is most similar to Lucknowia Gupta, 1961 in the shape of the body, which is elongate, slightly tapering towards the anterior end, and scolex, which is digitiform, but differs in the shape of the ovary, which is H-shaped (vs. inverted A-shaped in Lucknowia), the absence of a seminal receptacle (present in Lucknowia) and exclusively cortical vitelline follicles (vs. some follicles in the medulla in the latter genus). Molecular data support the erection of the new genus and place it close to Bovienia Fuhrmann, 1931, species of which can be easily distinguished by exclusively lateral vitelline follicles (lateral and median in the new genus), the presence of a seminal receptacle (absent in Mystocestus) and scolex shape (digitiform, with blunt or slightly concave anterior edge in the new genus vs. small, unspecialized or spatulate in Bovienia). The convoluted taxonomy of tapeworms placed in Mystoides Mathur, 1992 is critically reviewed to clean up taxonomic chaos in Indo-Malayan caryophyllideans. Mystoides was erected in an unpublished PhD thesis and thus its generic name becomes unavailable and also, its type species is conspecific with Lucknowia fossilisi Gupta, 1961 from the stinging catfish, Heteropneustes fossilis (Bloch). Other species of this genus are also conspecific with L. fossilisi. In addition, specific names of most of these taxa are unavailable because they were described in unpublished theses or conference abstracts. Based on recent revisions of Indo-Malayan caryophyllideans, the following nine genera with 15 species are considered valid (numbers of species of individual genera are provided in parentheses): Bovienia (3), Djombangia (1), Lucknowia (2), Lytocestus (2), Mystocestus (1), Pseudocaryophyllaeus (2) (all family Lytocestidae); Adenoscolex (1), Lobulovarium (2), Paracaryophyllaeus (1) (all family Caryophyllaeidae).

Macrogyrodactylus congolensis (Prudhoe, 1957) is one of six species of Macrogyrodactylus, all of which are endemic to Africa. This monogenean is a host-specific ectoparasite of the African sharptooth catfish, Clarias gariepinus (Burchell, 1822). It attaches to the host with a posterior haptor armed with sclerites. The specific morphology of sclerites is taxonomically significant and usually studied using light microscopy. The aim of the present study was to confirm the identification of macrogyrodactylid parasites using classic morphology (light microscopy of glycerine ammonium picrate mounted specimens) and molecular techniques (18S rDNA, ITS rDNA and cytochrome oxidase subunit 1 (COI) mtDNA). Additionally, the sclerites were accurately described with a technique not previously used for the genus, whereby haptoral sclerites were isolated by removing the encapsulating soft tissue with a digestion buffer and studied with scanning electron microscopy (SEM). Morphology and morphometry of studied specimens corresponded to available data for M. congolensis, confirming the identity of the parasite. All previous descriptions were summarized in a table and discrepancies discussed. Molecular analysis also confirmed the specimens to be M. congolensis, but ITS rDNA and COI mtDNA was more reliable than 18S rDNA in this regard. The isolation of haptoral sclerites and their study using SEM was successful, resolving the morphology of all sclerites. This study provided the first reconstruction of the haptor of a Macrogyrodactylus species following SEM analysis, as well as the first mtDNA for M. congolensis. Further study of isolated haptoral sclerites of other macrogyrodactylids is required to determine the full benefits of studying their isolated sclerites.

Meal frequency is a key parameter in fish larviculture, especially in highlycannibalistic species. Knowledge of the biological bases of cannibalism (growth capacityof cannibals, morphological constraints on cannibalism, prey size preference) can helppredicting the risks of cannibalism for different feeding schedules under cultureconditions. This study relied on the day-by-day analysis of prey size preference andbioenergetics of individual cannibals of the catfish Pseudoplatystoma punctifer(8–65 mm standard length, SL, 0.5–400 mg dry mass,DM) at 28.5 °C under 12L:12D. The results were equated with theontogenetic variations of morphological factors (head and mouth width) and feed efficiencyof larvae feeding on Artemia nauplii, in order to calculate the risks ofcannibalism among fish fed 2–7 daily meals. The predation capacities of P.punctifer were highest at 8 mm SL and decreased in larger fish(largest prey  =  86% and 70% SL in fish of 8 and  >30 mmSL, respectively). Cannibals of increasing size preferred increasinglysmaller prey relative to their own size, but also to their predation capacities. Thesemorphological and behavioural constraints were largely compensated for by bioenergeticsperformance. Cannibals consumed high daily food rations (as high as 171 and 29%DM in fish  <1 and  >300 mg DM,respectively), exhibited high gross conversion efficiencies (0.50–0.55 and about 0.70, infish  <1 and  >30 mg DM, respectively), and grew rapidly(90 and 18% DM day-1 in fish  <1 and  >300 mgDM, respectively). The growth advantage of cannibals over siblings fedArtemia nauplii was decisive, except for high meal frequencies (6–7daily meals). This study supports the view that the risk of cannibalism and adequatefeeding strategies can be largely predicted in a particular fish species if themorphological, behavioural and bioenergetics bases of cannibalism are examined altogetherin an ontogenetic perspective.

The black bullhead, Ameiurus melas of the family Ictaluridae, is a freshwater fish native to North America that was introduced throughout Europe in the late 1800s. Using mitochondrial DNA (mtDNA) as a genetic marker, the present study investigates the genetic structure and historical demography of A. melas in North America. MtDNA-based phylogenetic analyses revealed the existence of two distinct lineages (A and B) of A. melas. While lineage A clustered with the previously reported sequences of A. melas, lineage B emerged as a unique clade like other species of the genus Ameiurus. Individuals belonging to lineage B were mostly from the south central region of the United States, the region that never glaciated during the last Ice Age. Results of a fossil-based molecular clock analysis suggest that lineage A and the paraphyletic lineage B of A. melas diverged from their respective common ancestors approximately 3 (±0.2) and 15.9 (±1.3) million years ago. Lineage B could possibly be a hybrid species, possessing the mtDNA haplotype of its maternal parent, an Ameiurus species that has gone extinct. While lineage A showed evidence of population expansion, lineage B did not show any evidence of population expansion, but rather is comprised of geographically structured populations.

In a manner similar to many other groups of organisms, the tapeworm order Proteocephalidea poses a difficult phylogenetic problem if treated on the basis of single-gene analysis. Since the biogeography and host distribution of proteocephalideans make these tapeworms a potentially interesting model for evolutionary and co-evolutionary studies, we tried to resolve their phylogenetic relationships by applying a multi-gene approach. The ITS2 sequences and V4 hypervariable loop of 18S rRNA were obtained for 43 and 35 proteocephalidean taxa, respectively, and combined with other sequences available in the GenBank. The phylogenetic analysis of the combined DNA set was confronted with characters derived from ITS2 secondary structures. Using this approach, a species-rich Neotropical lineage of proteocephalideans could be reliably resolved. The phylogenetic relationships within this group show a high degree of phylogeny-independent host distribution. The reconstruction of ITS2 secondary structure revealed a universal 4-domain arrangement, which is conserved across a wide range of Neodermata. Several motifs of the secondary structure could be mapped to the phylogenetic tree as possible clade synapomorphies.

The otolith micro-increment technique was applied to assess the growth trajectory of early stages of the neotropical catfish Megalechis thoracata in Kaw Swamp, a coastal swamp in French Guiana, and two contrasting habitats in Suriname: the coastal Lelydorp Swamp with standing water and a rain-forest creek with running water, the Maykaboeka Creek. Daily deposition of increments on the lapilli was validated for the first 35 d after hatching and the innermost increments were deposited from hatching onwards. The natural habitats of M. thoracata in French Guiana and Suriname showed considerable variation in physico-chemical characteristics of the water, density of food organisms and fish fauna. Instantaneous growth rates and size-at-age differed significantly among two vegetation types in Kaw Swamp (3.5% d-1 and 4.1% d-1), Lelydorp Swamp (3.0% d-1) and Maykaboeka Creek (2.5% d-1). Spearman's rank correlation coefficient between instantaneous growth rates and environmental parameters differed significantly from 0 only for water temperature. Hatch date analysis revealed an extended spawning season from January to June in the rain-forest creek.

Within the clariids (air-breathing catfish), a complete range of fusiform to anguilliform species can be observed. This study deals with the cranial morphology of Channallabes apus, an extreme anguilliform (eel-like) species, compared to the anguilliform Gymnallabes typus and the more fusiform Clarias gariepinus. The overall morphology of the head of Channallabes apus shows a hypertrophied adductor mandibulae complex, with the corresponding substantial narrowing of the neurocranium, seen in the frontals, the sphenotics, the pterotics and the posttemporo-supracleithra, as well as the reduction and displacement of the eyes and some canal bones, such as the infraorbitals and the suprapreopercles. The presence of a hypertrophied muscle complex possibly indicates that a more powerful bite may occur. This implies that adaptations can be expected in several parts of the skull. On the lower jaw of C. apus a higher coronoid process is found, and on the suspensorium, two sets of three processes are present on the hyomandibular bone, indicating a stronger connection to the neurocranium. Several of the observed features, such as the elongation of the body, the reduction of the eyes, the increase in vertebrae number, limblessness and the increasing rigidity of the skull, may also be related to a process of miniaturization.

The most distinctive feature of the reproductive biology of Hoplosternum littorale is the building and guarding of an elaborate floating bubble nest. Reproduction starts at the age of one year. Males grow to a larger size than females and, during the breeding season, they develop fat deposits in the pectoral fin and an elongated recurved pectoral spine that often assumes a reddish colour. Analysis of gonadal development and surveys of nesting in swamps show that initiation of reproduction is associated with the onset of the rainy season. Males start building the nest at night, and spawning takes place around noon the day after. Most nests are built in newly flooded swamps, especially in open water in the peripheral area of the swamp. A minimum distance of 10 m between nests is usually observed. The floating bubble nest consists of a dome of plant material supported by oxygen-rich foam produced by the male. Diameter and height of the nest average 30 and 6 cm, respectively. The nest is the centre of a territory that is vigorously defended by the male, using its enlarged pectoral spine, against conspecific and heterospecific intruders. The number of nests that did not acquire spawns (48 %) suggests a bold competition among males for females. There are indications that the female drinks the sperm and that fertilization takes place after the sperm has passed through her digestive tract. Hoplosternum littorale is a multiple spawner. Investment in reproduction is high in females since they can spawn up to 14 times during a 7-month breeding season and each spawn consists of 6 000 to 9 000 eggs. On average, two to four females spawn simultaneously, resulting in an average number of 20 000 eggs per nest. Incubation of the eggs takes two to three days depending on the temperature in the nest. Despite intense predation pressure on eggs and larvae, the guarding behaviour of the male extends for only one or two days after hatching. In the hypoxic water of tropical swamps, the main function of the floating bubble nest appears to be to provide oxygen to the developing eggs by lifting the eggs above the water surface while protecting them from desiccation. Other functions of the nest may be protection of the brood against predators, temperature regulation, identification of the centre of the territory and synchronization of reproductive activities. We suggest that H. littorale may be a useful model for the study of the reproduction of tropical freshwater fish in hypoxic environments.

L'étude du régime alimentaire de C. nigrodigitatus Lacépède (N = 646$) et C. auratus Geoffroy Saint-Hilaire (N = 253) a été réalisée d'après l'analyse des contenus stomacaux de poissons du lac Nokoué et de la lagune de Porto-Novo (Sud-Bénin) en 1990-1991. L'analyse factorielle de correspondance sur l'occurrence de 16 catégories de proies dans 21 catégories de poissons (suivant l'espèce, la taille des poissons, la saison et l'habitat) met en évidence la répartition des ressources alimentaires entre C. auratus et différentes catégories de tailles de C. nigrodigitatus capturés hors acadjas (enclos en branchages). Les indices d'abondance (Iab) et de volume (Iv) des proies et leur régularité (Rab et Rv) dans le régime alimentaire mettent en évidence la tendance benthophage des deux espèces : C. auratus (6-20 cm Ls) est beaucoup plus généraliste (Rv = 0,842) se nourrissant essentiellement de mollusques et de petits crustacés (branchiopodes, copépodes, ostracodes) par fouille du substrat. C. nigrodigitatus, en revanche, se spécialise avec l'âge et la taille (Rv = 0,826 à 0,597 de 6-10 cm à 6-20 cm Ls) vis-à-vis des décapodes (Iv de 13,4 à 49,4 %) et des poissons (œufs et alevins, Iv de 7,8 à 66,9 %). Les différences saisonnières concernent principalement la période des crues, au cours de laquelle les poissons se nourrissent de larves ou de nymphes d'insectes sur des végétaux de la plaine inondée. Dans les acadjas, les deux espèces partagent les mêmes ressources alimentaires. Cette étude de l'écologie trophique des Chrysichthys du complexe lagunaire du Sud-Bénin, mise en parallèle avec leurs potentialités de croissance, suggère que le régime alimentaire généraliste de C. auratus se situe dans un contexte de ségrégation sélective vis-à-vis de C. nigrodigitatus. La valeur adaptative des deux espèces dans un écosystème modifié et exploité par l'homme est brièvement discutée.

In captive Heterobranchus 1ongifilis females, oocytes maturation and ovulation are induced by a single injection of human chorionic gonadotropin (hCG) at a dose of 1.5 I.U./g body weight. In the present study, three experiments were performed in order to specify the timing of ovulation and the effects of varying latency period on the quantity and quality of the collected ova. The ova quality was estimated by hatching percentage and proportion of deformed larvae obtained after artificial fertilization. The results showed that, in an individual female, ovulation of postvitellogenic oocytes is not synchronous and takes 3 to 4 hours to be completed, between 7–8 h and 11 h after hCG injection at 30 °C. The quantity of ova that could be collected by handstripping increased with the latency period, from 18,000 ± 12,000 to 72,000 ± 29,000 ova per female at 8 h and 11 h after injection, respectively. However, the first ova obtained (8 h after injection) were of good quality (94% hatching) and showed no signs of incomplete final maturation. Eleven hours after injection, the percentages of ovulated oocytes within the whole ovarian population of postvitellogenic oocytes were high in all the females, being generally around 90%. After ovulation, aging of ova occurred rapidly: the proportion of deformed larvae increased significantly (from 4 to 20%) 2 h after completion of ovulation and, 4 h post-ovulation, hatching percentage dropped from 92 to 36%. In H. longifilis, the optimal latency period can be defined as the time, from injection to stripping, allowing the best compromise between quantity and quality of ova released. This latency period was found to be 11 h following hCG injection at 30 °C, and corresponds approximately to the completion of ovulation.

The paper summarizes aspects of nutrition and growth in Clarias species. Of the many Clarias species cultured, Clarias gariepinus has been subject to particularly intensive research; the species has been widely introduced for aquaculture outside its natural range. Clarias are omnivorous fish. Their dietary protein requirements are about 40%, their energy requirements range between 13 and 17 kJ.g−1. Controversy exists on their ability to utilize carbohydrates, despite the fact that their natural feed may contain high levels of carbohydrates. Comparison of growth performances as recorded in literature indicate that C. gariepinus seems to perform better in terms of growth rates and feed conversion than other species (C. isheriensis, C. batrachus, C. fuscus). Monosex culture (in C. gariepinus) or triploidy (in C. gariepinus and C. batrachus) do not seem to hold much future for improving growth and feed utilization, in contrast to hybridization. Selection for improved growth could have drawbacks, such as an increased level of agression. To achieve improved growth, selection for lower maintenance requirements or better glucose metabolization seems preferable over selection for high feed utilization efficiencies.

Specimens belonging to 20 species (7 families) of catfishes have been collected in French Guyana. The anatomy and histology of the male reproductive tracts have been studied. In the most primitivespecies (Helogeneidae, Ariidae) no seminal vesicle is present in the males. In the Pimelodidae,Loricariidae and Callichthyidae (and also in an african Bagridae), there is a progressive transition, going from anterior to posterior in the male tract, from testicular tissue towards round germ cell-free tubules and finally to seminal vesicular tissue. All these families produce round-headed spermatozoa and have external fertilization. The Auchenipteridae and Ageneiosidae are characterized by elongated sperm nuclei, internal fertilization with the aid of a gonopodium and sperm storage in the ovaries. In the Auchenipteridae there is a clear-cut distinction between testes and seminal vesicles. In the Ageneiosidae there is no seminal vesicle, but the dilated deferent duct displays a high secretory activity. Depending on the family and species, the seminal vesicles may carry out either one or both of the two main functions: secretion and sperm storage. In addition, in some species, sperm is also stored in one or two accessory pouches until fertilization. The trends that we have observed in the changes in the organization of the reproductive tracts are in agreement with the hypotheses proposed for catfish evolution from comparative anatomical data.