Acrossocheilus spinifer, a new species of barred cyprinid fish from south China (Pisces: Teleostei)

Acrossocheilus spinifer sp. nov. is described from the river basins in Fujian Province and the Han Jiang basin in Guangdong Province, south China. It is one of the barred Acrossocheilus species sharing five or six vertical bars on the flanks, with each bar being two scales in width. Acrossocheilus spinifer sp. nov. is morphologically most similar to Acrossocheilus wenchowensis , but distinguished from it by: a colour pattern of all vertical bars extending ventrally to the second scale row below the lateral line, and having the second bar placed posterior to the base of the last simple dorsal‐fin ray, a blunt snout; and a stout, last simple dorsal‐fin ray. Acrossocheilus spinifer sp. nov. resembles Acrossocheilus kreyenbergii and Acrossocheilus stenotaeniatus with which it shares a stout, last simple dorsal‐fin ray with a serrated posterior edge, but is separated from both species by having a narrow median interruption in the lower lip, a lower jaw fully covered by the lower lip when viewed ventrally and the second vertical bar placed posterior to the base of the last simple dorsal‐fin ray. The absence of a longitudinal stripe extending along the lateral line on the flanks in males readily distinguishes A. spinifer sp. nov. from four other species, namely Acrossocheilus fasciatus , Acrossocheilus paradoxus, Acrossocheilus parallens , and Acrossocheilus jishouensis .     

Life styles and patterns of development of gills and muscles in larval cyprinids (Cyprinidae; Teleostei)

A morphometric study of gill structures and of the body musculature during the first weeks after hatching was carried out on larvae of six cyprinid species: Leuciscus cephalus, L. leuciscus, Rutilus rutilus, Alburnus albumus, Chondrostoma nasus and Abramis brama . In all species a unicellular layer of red muscle fibres covers the central muscle mass; this layer is of greatest extent shortly after hatching but diminishes gradually in mass by contracting towards the lateral region of the body until it merges with (or gives rise to) the adult red muscle fibres proper. There is a close relationship between the rate of differentiation of gill structures and the rate at which the larval red muscle layer disappears, the pattern of this relationship reflecting the life style of the species. The longer the larvae delay the start of their free-swimming existence after hatching (which in A. alburnus may be as long as 10 days) the longer does the red layer of muscle fibres serve as the organ of gas exchange and the longer is gill development suppressed. It appears that the metabolism of the swimming muscles is almost entirely aerobic so long as gas exchange takes place across the whole body surface, the glycolytic capacity of the central muscle mass developing only slowly in conjunction with the switch from red layer to gills as the major respiratory organ.     

The eye muscles and their innervation inChaetodon trifasciatus (Pisces,Teleostei, Chaetodontidae)

Synopsis InChaetodon trifasciatus, the large eye has the form of a thick disk rather than that of a globe. A deep cutaneous groove surrounds the eyeball, probably allowing rapid eye movements. The form and innervation of the three pairs of extraocular muscles are described. Each muscle is made of two types of fascicles of fibres, thick and thin. There is neither an anterior nor posterior myodome. The skull attachment of the obliques and of the inferior rectus is made on the thin sagittal ethmoidal membranous septum while that of the other recti occurs on osseous pieces of the skull. The attachment on the eyeball is made on the cartilaginous sclera. The ratio of the lengths of the antagonist muscles, superior vs. inferior oblique, superior vs. inferior rectus and medial vs. lateral rectus, is about 1.43:1. The three oculomotor nerves (III: common oculomotor, IV: trochlear and VI: abducens) as well as the ciliary system are described. For the following reasons, an analogy between the lateral rectus ofChaetodon trifasciatus and the lateral rectus + retractor bulbi of other vertebrates is indicated: (1) the nucleus of nerve III (which innervates four muscles) has four sectors, while that of IV (which innervates only the superior oblique) is made of one sector; (2) nerve VI consists of two roots corresponding to two groups of nerve cells of its motor nucleus and (3) in other vertebrates, nerve VI innervates both the lateral rectus and the retractor bulbi.     

Sinocyclocheilus zhenfengensis,a new cyprinid species (Pisces: Teleostei) from Guizhou Province,Southwest China

Sinocyclocheilus zhenfengensis sp. nov. is a new species from an underground water environment in a karst cave located in Beipanjiang River of the Pearl River Basin in Shuangrufeng (Double Breasts Hill) Scenic, Etian Village, Zhexiang Township, Zhenfeng County, Guizhou Province, Southwest China. The new species has eyes, its body is completely scaled, an anteriorly directed bulge has formed on the back of its head, and a long pectoral fin exceeds the pelvic fin insertion. The body of the new species is apparently similar to that of S. bicornutus, but differs in scale rows above the lateral line, scale rows below the lateral line, snout length, and eye diameter. Phylogenetic reconstruction of the cytochrome b gene using the maximum parsimony (MP) and Bayesian inference (BI) methods indicates that S. zhenfengensis is closely related to S. bicornutus, S. tianeensis, S. jiuxuensis, and S. altishoulderus; however, it differs in terms of eye size, lateral line scales, scale rows above and below the lateral line.     

Arterioles in the swimming muscles of the leatherjacket Parika scaber (Pisces: Balistidae)

Summary The leatherjacket (Parika scaber) is a balistiform fish which swims using its dorsal and anal median fins. The muscles controlling these fins are well vascularised, with control of blood flow effected by arterioles. These arterioles are long with a single layer of smooth muscle surrounding the endothelium, although the amount of contractile material is sparse, probably a consequence of the low blood pressure. The endothelial cells contain microfilaments, probably contractile, running along the length of the arteriole. The function of this material is unknown.     

A gular plate in Pterothrissus (Pisces, Teleostei)

A gular is reported in Pterothrissus belloci Cadenat and P. gissu Hilgendorf (Albuloidei, Pterothrissidae).     

Structural organization of the gills in pipefish (Teleostei,Syngnathidae)

Summary The morphology and structural features of the gills of the two Western Baltic pipefish Nerophis ophidion and Syngnathus rostellatus were investigated using scanning electron microscopy. The general anatomy of the gills complies with the general pattern in fish. Several adaptations though, show the highly specialized nature of pipefish gills. The filaments are extremely short, few in number and carry only a few lamellae due to the limited space in the branchial cavity. The lamellae have a widely projecting form yet still have a small area in comparison to other fish. Gill irrigation is performed by a specialized pumping mechanism which forces respiratory water through the small but densely packed gill sieve. Although both species live in the same habitat and belong to the same family, differences in gill morphology were found and are related to different lifestyles. S. rostellatus is the more active species and therefore has more filaments per gill arch, more lamellae per filament, wider projecting lamellae and a more extreme utilisation of available space in the gill cavity through a very densely packed gill sieve. N. ophidion has a stationary mode of life and therefore has a less extreme gill anatomy.     

A comparative study of ridge-mazes on surface epithelial cell-membranes of fish scales (Pisces,Teleostei)

Summary Scanning EM investigation of posterio-lateral parts of teleostean fish scales showed that the membranes of their surface epithelium are covered by a complicated system of tuberculi and ridges, forming a maze-system over their cells. These ridges, which are 0.4–0.7 m high and 0.2–0.6 m wide, constitute swellings of the cell membrane and form a pattern comparative to the ridge-system found on the skin of higher vertebrates. Epithelial prints of this type were investigated in 43 species of fresh water fish (Cichlidae, Characidae) and marine fish (Serranidae, Apogonidae, Sparidae, Scorpaenidae, Pomacentridae, Girellidae, Gobiidae) of America, Africa, and Asia. The ridge-prints were found to be species-specific, if observed over scales of the same body-site for all individuals. Our investigation, especially on species of the California rockfish (Sebastes), showed that within a given taxonomic group the structure of the ridges is in accordance with the taxonomic as well as ecological relationships of the species involved, usually being more developed in active swimmers and reduced or absent in sessile forms. This research demonstrated that the skin surface microstructures can be used for evolutionary-ecological studies.     

Variability of the behavioral laterality in Teleostei (Pisces)

Factors causing variability of behavioral laterality in Teleostei are reviewed. The laterality has been revealed in many fish species belonging to various families. The best ever demonstrated example of the laterality is the different use of the right and left eyes when a fish responds to different visual objects. Magnitude and sign of the laterality differ in fishes of different species, gender, and age. Also, an observed laterality depends on how familiar a stimulus is to fishes and what it means to them, as well as their motivational level and various behavioral traits. Therefore, comparisons of the laterality among different fish species should be based on experimental methods that also take into account those behavioral differences among them that are not directly linked to the laterality.     

Glycoproteins histochemistry of the gills of Odontesthes bonariensis (Teleostei, Atherinopsidae)

The histochemistry of glycoproteins (GP) in the mucous cells of the gills of the silverside Odontesthes bonariensis was identified with: (1) oxidizable vicinal diols; (2) sialic acid and some of their chain variants, carbon 7 ((7) C), carbon 8 ((8) C) or carbon 9 ((9) C); (3) sialic acid residues without O-acyl substitution and with O-acyl substitution at (7) C, (8) C or (9) C; (4) carboxyl groups and (5) sulphate groups. A battery of seven biotinylated lectins allowed GPs sugar residues to be distinguished. Mucous cells showed the presence of neutral, sulphated and sialylated GPs. Dolichos biflorus agglutinin (DBA) and Glycine max agglutinin (SBA) showed strong positive staining; Arachis hypogaea agglutinin (PNA), Ricinus communis agglutinin-I (RCA-I) and Triticum vulgaris agglutinin (WGA) showed moderate staining, while Ulex europaeus agglutinin-I (UEA-I) was completely negative.     

Profiles of enzyme activity in larvae of two cyprinid species with contrasting life styles (Cyprinidae; Teleostei)

Growth and the development of gills, muscle fibres and 10 enzymes serving different metabolic functions were studied in larvae of Rutilus rutilus (L.) and Chalcalburnus chalcoides (Agassiz, 1832). R. rutilus starts swimming and feeding one to three days after hatching, whereas in C. chalcoides this process is delayed by about 10 days. This difference in behaviour is reflected in the time-course of growth, the differentiation of the red muscle fibres and the activity of the enzymes of aerobic energy metabolism. On the other hand, the activity of the enzymes of anaerobic energy metabolism increases steadily throughout the period of observation (up to 60 days post-hatch), this trend being more pronounced in C. chalcoides than in R. rutilus . A weight-independent and a weight-dependent phase of development can be distinguished in the enzymes of aerobic energy metabolism. It is suggested that, in accord with previous findings, the early phase of locomotor activity of cyprinid larvae is fuelled mainly by aerobic processes, and that the central muscle mass of the larvae is more aerobic than the white muscle fibres of the adults. The delayed development of aerobic enzyme activity in C. chalcoides is compensated by the accelerated development of anaerobic enzyme activity, particularly of creatine kinase and lactate dehydrogenase. This difference between the two species studied suggests differences in the metabolic basis of burst activity.     

Ultrastructure of the testicular gland of Blennius pavo (Pisces,Teleostei)

Summary The testicular gland of Blennius pavo Risso, 1810 is an accessory sex organ situated ventrally, adjacent to the testis. Sperm have to cross it to reach the vas deferens. Changes in the fine structure of the gland were monitored monthly over a period of 1 year. The annual cycle is closely correlated to the reproductive cycle. Maximum synthetic activity and cell size are reached during late prespawning and early spawning. At that time the number of lipid vacuoles increases markedly. Vesicles of smooth endoplasmic reticulum ER, numerous Golgi cisternae and tubulovesicular mitochondria which are characteristics of steroid producing cells can be observed. Secretory vesicles are synthesized in the apical region of the cells and then released into the ducts of the gland. The content of lipids is maintained until the resting period. The supranuclear region of the cells contains accumulations of lamellar bodies that probably derive from lysosomal vacuoles. Fine structural characteristics suggesting the function of the testicular gland are discussed.     

Zur Feinstruktur der Elektrozeptorepidermis der Mormyridae (Teleostei,Pisces)

Zusammenfassung Die schwachelektrischen Mormyridae haben eine dreischichtige Epidermis, deren innere Schicht aus nur etwa 0,22 m dicken sechseckigen Zellen von ca. 60 m Durchmesser besteht. Die etwa 2 m dicken, linsenförmigen Kerne von 7,6 m Durchmesser liegen am Zellrand. Die Zellen sind zu Säulen aufgeschichtet. Ihr Rand ist ausgezackt und dort, wo er die Säulengrenze erreicht, auf etwa 0,34 m verdickt. In der Nähe der Säulengrenzen sind die Zellen über Desmosomen mit den Nachbarn in der eigenen und in der angrenzenden Säule verbunden. Diese Epidermisschicht ist auf die Körperpartien beschränkt, in denen auch Elektrorezeptoren ausgebildet sind.Die beiden anderen Epidermisschichten haben den üblichen Aufbau einer Fischepidermis, abgesehen vom Fehlen der Becherzellen.

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Ultrastructure of the electroceptor epidermis of the Mormyridae (Teleostei, Pisces)

Summary The weakly electric fish of the family Mormyridae have a three layered epidermis, with a medium layer consisting of hexagonal cells of only 0.22 m in thickness and about 60 m in diameter. The lens-shaped nuclei are about 2 m thick and 7.6 m in diameter and are situated near the border of the cells. The cells are piled up to hexagonal columns. Their margin is serrate and where it reaches the boundary of the column, it has a thickness of about 0.34 m. Close to the boundaries of the columns, the cells are linked to their neighbours within the column and of the adjoining column by desmosomes. This layer of the epidermis is confined to those regions of the body surface which also contain electroreceptors.The other layers of the epidermis have a structure as usual in fish, except for the lack of goblet cells.

     

Larval development of the Indo-Pacific perciform fish,Centrogenys vaigiensis (Pisces: Centrogeniidae)

Based on seven larvae from northern Australia, development ofCentrogenys vaigiensis—a species of uncertain phylogenetic affinities—is described for the first time. Identification was established from meristic and osteological characters. Development is characterized by few morphological specializations and is apparently completed at a small size (ca 5 mm standard length). Larvae are deep-bodied and compressed, with very limited head spination (small spines on preopercle, subopercle, opercle and supracleithrum). Fin development takes place at about the time of notochord flexion, and is complete at about 4.3 mm, with the exception of anal spine three, which does not fully transform from a soft ray until after settlement. Fin spines are short, smooth and weak. Larvae are apparently limited to near-shore, shallow marine waters, and based on the size of what are apparently settlement-stage larvae, the pelagic period may be short.     

Reproduction and development of the weakly electric fish,Pollimyrus isidori (Mormyridae,Teleostei) in captivity

Synopsis No clear sexual dimorphism occurs in Pollimyrus isidori. Females usually grew slightly larger than males. The anal-fin reflex, however, makes it easy to discriminate between males and females. Spawning took place during the first six hours of the dark phase, in the territory of the male. During each spawning act 2–4 eggs were laid. The male put the eggs into a well-hidden nest previously constructed from plant material. The eggs, free embryos, and larvae of several spawnings were guarded by the male for several weeks. The females laid on average 120 eggs per fractional spawning. The eggs were 2 mm in diameter, not adhesive and very yolky. There was a relationship between pH and viability (% embryos hatched). Hatching occurred on the third day after spawning. The respiratory network of segmental origin in the median fin fold was well developed in the free embryos. Transition to exogenous feeding occurred on day 14. The larval period ended when the fish were 15 mm long and 40–50 days old. First gonadal recrudescence occurred at a total length of 6 cm (about 200 days old). The environmental factors decreasing conductivity and pH, increasing water level, and imitation of rain led to gonadal recrudescence, but pH did not act as a cue. Recrudescence was triggered by a decrease of conductivity, but absolute values or ionic composition of the water were not important. Maturation was completed after about fifty days. Mature and spawning fish no longer required any variation of these environmental factors to maintain mature gonads. A steady and considerable increase in conductivity led to gonadal regression. The fish did not show postbreeding refractoriness.     

Effects of summer drawdown on cyprinid fish larvae in Lake Biwa, Japan

The effects of artificial water-level manipulations in Lake Biwa, initiated in 1992 to prevent flooding, on cyprinid fish larvae were assessed by measuring and estimating the topographic change in the reed zones. The shallow, litter-accumulated water in those zones was inhabited by larvae of two species, Carassius spp. and Cyprinus carpio. More than 70% (by volume) of these shallow areas in Lake Biwa was estimated to be lost when the water level was artificially lowered by 30cm from June to October 1997. During the low water level period, significantly fewer eggs of these cyprinid fishes were collected in a reed zone than in April and May of the same year, a comparison with a previous study suggesting that spawning of the fishes was inhibited during the period of low water level. The artificial reductions in water level probably resulted in a significant decrease in the volume of shallow water in the lake and may be linked to the drastic decline in these cyprinid fishes.     

Molecular phylogeny of the cyprinid tribe Labeonini (Teleostei: Cypriniformes)

The cyprinid tribe Labeonini (sensuRainboth, 1991) is a large group of freshwater fishes containing around 40 genera and 400 species. They are characterized by an amazing diversity of modifications to their lips and associated structures. In this study, a total of 34 genera and 142 species of putative members of this tribe, which represent most of the generic diversity and more than one third of the species diversity of the group, were sampled and sequenced for four nuclear genes and five mitochondrial genes (totaling 9465bp). Phylogenetic relationships and subdivision of this tribe were investigated and the placement and status of most genera are discussed. Partitioned maximum likelihood analyses were performed based on the nuclear dataset, mitochondrial dataset, combined dataset, and the dataset for each nuclear gene. Inclusion of the genera Paracrossochilus, Barbichthys, Thynnichthys, and Linichthys in the Labeonini was either confirmed or proposed for the first time. None of the genera Labeo, Garra, Bangana, Cirrhinus, and Crossocheilus are monophyletic. Taxonomic revisions of some genera were made: the generic names Gymnostomus Heckel, 1843, Ageneiogarra Garman, 1912 and Gonorhynchus McClelland, 1839 were revalidated; Akrokolioplax Zhang and Kottelat, 2006 becomes a junior synonym of Gonorhynchus; the species Osteochilus nashii was found to be a member of the barbin genus Osteochilichthys. Five historical hypotheses on the classification of the Labeonini were tested and rejected. We proposed to subdivide the tribe, which is strongly supported as monophyletic, into four subtribes: Labeoina, Garraina, Osteochilina, and Semilabeoina. The taxa included in each subtribe were listed and those taxa that need taxonomic revision were discussed.