The effect of body coloration and group size on social partner preferences in female fighting fish (Betta splendens)

Females of the fighting fish Betta splendens have been shown to associate with other B. splendens females in a manner reminiscent of shoaling behavior. Since body coloration varies dramatically in this species, and since body coloration has been shown to affect shoalmate choice in other species of fish, we examined the influence of body coloration on association preferences in female B. splendens. In dichotomous choice tests, B. splendens females spent more time swimming near groups of females (regardless of coloration) than swimming near an empty chamber, and chose to swim near fish of similar coloration to their own when choosing between two distinctly colored groups of females. When examining the interplay between body coloration and group size, focal fish spent more time swimming near larger groups (N = 5) of similarly colored fish than swimming near an individual female of similar coloration. However, focal fish showed no preference when presented with an individual female of similar coloration and a larger group of females of dissimilar coloration. These results suggest that association choices in B. splendens females are strongly affected by both body coloration and by group size.     

Hypoxic cardiorespiratory reflexes in the facultative air-breathing fish jeju (Hoplerythrinus unitaeniatus): role of branchial O2 chemoreceptors

In one series of experiments, heart frequency (f _H), blood pressure (P _a), gill ventilation frequency (f _R ), ventilation amplitude (V _AMP) and total gill ventilation (V _TOT) were measured in intact jeju (Hoplerythrinus unitaeniatus) and jeju with progressive denervation of the branchial branches of cranial nerves IX (glossopharyngeal) and X (vagus) without access to air. When these fish were submitted to graded hypoxia (water PO₂ ~140, normoxia to 17 mmHg, severe hypoxia), they increased f _R , V _AMP, V _TOT and P _a and decreased f _H. In a second series of experiments, air-breathing frequency (f _RA), measured in fish with access to the surface, increased with graded hypoxia. In both series, bilateral denervation of all gill arches eliminated the responses to graded hypoxia. Based on the effects of internal (caudal vein, 150 μg NaCN in 0.2 mL saline) and external (buccal) injections of NaCN (500 μg NaCN in 1.0 mL water) on f _R , V _AMP, V _TOT, P _a and f _H we conclude that the O₂ receptors involved in eliciting changes in gill ventilation and associated cardiovascular responses are present on all gill arches and monitor the O₂ levels of both inspired water and blood perfusing the gills. We also conclude that air breathing arises solely from stimulation of branchial chemoreceptors and support the hypothesis that internal hypoxaemia is the primary drive to air breathing.     

Development of the cranium and paired fins in Betta splendens (Teleostei: Percomorpha): Intraspecific variation and interspecific comparisons

The development of the chondrocranium and the relative timing of ossification of the osteocranium is described in the teleost fish Betta splendens from a large series of cleared and differentially stained specimens. General trends in ossification patterns are examined from developmental, phylogenetic, and functional contexts. As in many other vertebrates, dermal bones form before cartilage bones. Ossification sequence conforms to functional need in a very general way, but there are many inconsistencies in the details of order. For example, some bones that are directly involved in feeding ossify no earlier than bones more indirectly involved. Comparisons of ossification sequence within specific cranial regions are made among Betta splendens, Oryzias latipes (Atherinomorpha), and Barbus barbus (Ostariophysi) within a phylogenetic framework. Many evolutionary changes in relative sequence of ossification are evident within regions among these taxa, yet many other sequences are conserved. The logistic difficulty of comparing entire cranial ossification sequences (vs. regional sequences) makes evident the need for new methods for identifying and quantifying sequence changes. Intraspecific variation in order of ossification is described for the first time in teleost fishes. To the extent that ossification sequence varies intraspecifically, conclusions drawn from previous interspecific comparisons are compromised. Understanding the importance of changes in ossification order within and among taxa will require experimental, functional, and evolutionary work. © 1996 Wiley-Liss, Inc.     

Visual perception of texture in aggressive behavior of Betta splendens

Summary In order to elucidate the role of texture in fish vision, the agonistic behavior of male Siamese fighting fish (Betta splendens) was tested in a response to models composed by means of image processing techniques. Using the models with the contour shape of a side view of Betta splendens in an aggressive state, the responses were vigorous when there was a fine distribution of brightness and naturalistic color, producing textures like a scale pattern. Reactions became weaker as the brightness and color distribution reverted to more homogeneous levels and the scale pattern disappeared. When the artificial models with the circular contour shape were used, models with the scale pattern evoked more aggressive behaviors than those without it, while the existence of spherical gradation affected the behavior slightly. These results suggest that texture plays an important role in fish visual perception.     

Large‐scale,multidirectional larval connectivity among coral reef fish populations in the Great Barrier Reef Marine Park

Larval dispersal is the key process by which populations of most marine fishes and invertebrates are connected and replenished. Advances in larval tagging and genetics have enhanced our capacity to track larval dispersal, assess scales of population connectivity, and quantify larval exchange among no‐take marine reserves and fished areas. Recent studies have found that reserves can be a significant source of recruits for populations up to 40 km away, but the scale and direction of larval connectivity across larger seascapes remain unknown. Here, we apply genetic parentage analysis to investigate larval dispersal patterns for two exploited coral reef groupers (Plectropomus maculatus and Plectropomus leopardus) within and among three clusters of reefs separated by 60–220 km within the Great Barrier Reef Marine Park, Australia. A total of 69 juvenile P. maculatus and 17 juvenile P. leopardus (representing 6% and 9% of the total juveniles sampled, respectively) were genetically assigned to parent individuals on reefs within the study area. We identified both short‐distance larval dispersal within regions (200 m to 50 km) and long‐distance, multidirectional dispersal of up to ~250 km among regions. Dispersal strength declined significantly with distance, with best‐fit dispersal kernels estimating median dispersal distances of ~110 km for P. maculatus and ~190 km for P. leopardus. Larval exchange among reefs demonstrates that established reserves form a highly connected network and contribute larvae for the replenishment of fished reefs at multiple spatial scales. Our findings highlight the potential for long‐distance dispersal in an important group of reef fishes, and provide further evidence that effectively protected reserves can yield recruitment and sustainability benefits for exploited fish populations.     

Fine structure of diffused pseudobranchial neurosecretory cells associated with carotid labyrinth in an air‐breathing catfish Clarias batrachus

Fish are known to have branchial chemoreceptors and even extrabranchial chemoreceptors to meet the challenges of aquatic environment. The pseudobranchial neurosecretory system associated with carotid labyrinth (CL) is one such example. CL – a chemosensory organ is well known in amphibians. The homologous structure also exists in fish. Clusters of neurosecretory cells, close to the CL and the first two efferent branchial arteries occur in catfish and a few other groups of teleosts. These cells belong to the pseudobranchial neurosecretory system (PNS). To reveal the ultrastructure of CL and the pseudobranchial neurosecretory cells (PNSCs), environmental scanning electron microscope (ESEM) and transmission electron microscope (TEM) investigations were made in an Asian air‐breathing catfish Clarias batrachus. Under ESEM, the PNS appeared as a mass of cells innervated by nerves and supplied by blood capillaries. The CL appeared to have a network of blood capillaries. The transmission electron microscopic investigations showed pear shaped PNSCs having different sizes of dense cored vesicles (DCVs), numerous mitochondria, nerve varicosities, indicating a secretory function of the cells. The CL shows a close association with PNSCs and smooth muscles. Although the exact function of the CL and associated PNSCs in the biology of fish is far from clear, their morphology suggests they are involved in a stress response such as to hypoxia.     

Social partner preferences of male and female fighting fish (Betta splendens)

While the social interactions of Betta splendens have been studied in the contexts of dominance hierarchies, mate choice and communication networks, the social partner preferences of Betta have been largely overlooked. In this study, we presented male and female Betta with a single male, a single female, and a group of three females in dichotomous choice tests in order to better understand basic social interactions in this largely nonsocial species. The highly territorial Betta preferred associating with conspecifics in nearly every configuration we tested, with exceptions noted when single females were given the choice between a lone male and an empty chamber, and when males were presented with a single female and an empty chamber. Also, in most tests, the fish chose to spend more time with the larger group of females. The motivation for this preference certainly varied from reproductive to anti-predator. While such behavior might not suggest true shoaling behavior, it does demonstrate a subtle degree of sociality.     

A survey of coccidian infections of freshwater fishes of Peninsular Malaysia,with descriptions of three species of Goussia Labbé, 1896 (Apicomplexa: Eimeriidae)

Ninety-five specimens of 14 freshwater fish species from small streams in the Kuala Terengganu district and the Lake Kenyir Reservoir, Malaysia, were surveyed for coccidian infections. Six fish species proved to be infected with apicomplexans belonging to the genus Goussia. In all of these fishes Goussia species were found in unsporulated and semisporulated stages. Oöcysts of four species inhabiting the intestinal epithelium became sporulated in tap-water within 24 hours. In two fish species sporulation failed and only unsporulated oöcysts were recorded in the intestine. Three of the intestinal species finishing sporulation proved to be new to science and were described as Goussia malayensis n. sp., G. bettae n. sp. and G. pogonognathi n. sp. from Apocheilus panchax, Betta splendens and Hemirhamphodon pogonognatus, respectively. The fourth species, found in Trichogaster pectoralis, was identified as G. trichogasteri Székely &; Molnár, 1992, a species known from aquarium-cultured T. trichopterus.     

Occurrence of a novel acetylated amino acid,Nα-acetylhistidine,in skeletal muscle of freshwater fish and other ectothermic vertebrates

The occurrence of N^α-acetylhistidine (NAH) in skeletal muscle of 91 species of freshwater fish and 9 species of other ectothermic vertebrates was investigated, with consideration of phylogenetic relationships. Of the 91 freshwater fish species examined, 13 species (7 cichlids, 5 anabantids, and 1 catfish) contained considerable amounts (> 1 µmol/g) of NAH in their skeletal muscles. The highest level (10.37 µmol/g) of NAH was found in the tissue of Betta splendens (Siamese fighting fish). Moreover, the NAH contents in the tissues of Trichogaster trichopterus (three spot gourami), Kryptopterus bicirrhis (glass catfish), Oreochromis niloticus (Nile tilapia), Mikrogeophagus ramirezi (ram cichlid) and Parachromis managuensis (Guapote tigre) were 3.17–6.16 µmol/g. The skeletal muscle of amphibians (5 species) and reptiles (4 species) had a low level (< 0.25 µmol/g) of NAH. The present findings clearly demonstrate NAH as the fifth imidazole-related compound, in addition to histidine, carnosine, anserine and ophidine (balenine), recognized as a major non-protein nitrogenous constituent in the skeletal muscle of vertebrate animals.     

Effect of a Dummy Audience on Male–Male Interactions in Siamese Fighting Fish, Betta splendens

Recent research on Siamese fighting fish, Betta splendens, and other taxa has demonstrated that an audience can cause males to alter their behavior in aggressive interactions. One factor not taken into account in these studies is how exactly the audience influences these interactions. It is possible that a live audience may interact with the subjects, creating an active communication network rather than a signaler–receiver dyad with a passive audience. Here, we used a dummy audience to control for information exchange between the audience and the interactants that might cause them to modify their behavior. Audience treatments included dummies of male and female B. splendens, a dummy cichlid, and a control condition with no audience present. The presence of a dummy audience did not influence male–male interactions. However, males spent the most time near the audience tank when the audience was a dummy of a B. splendens. This suggests that some factor other than the physical presence of the audience is responsible for the modification of behavior found in previous audience effect studies in Siamese fighting fish. However, we cannot rule out definitively that our dummy audience is viewed as unimportant by the opponents and, thus, ignored. Further research is necessary to determine which component of the audience is important for producing audience effects.     

Gross and fine anatomy of the respiratory vasculature of the mudskipper,Periophthalmodon schlosseri (Gobiidae: Oxudercinae)

To illustrate vascular modification accompanying transition from aquatic to amphibious life in gobies, we investigated the respiratory vasculatures of the gills and the bucco‐opercular cavities in one of the most terrestrially‐adapted mudskippers, Periophthalmodon schlosseri, using the corrosion casting technique. The vascular system of Pn. schlosseri retains the typical fish configuration with a serial connection of the gills and the systemic circuits, suggesting a lack of separation of O₂‐poor systemic venous blood and O₂‐rich effluent blood from the air‐breathing surfaces. The gills appear to play a limited role in gas exchange, as evidenced from the sparsely‐spaced short filaments and the modification of secondary lamellar vasculature into five to eight parallel channels that are larger than red blood cell size, unlike the extensive sinusoidal system seen in purely water‐breathing fishes. In contrast, the epithelia of the bucco‐opercular chamber, branchial arches, and leading edge of the filaments are extensively laden with capillaries having a short (<10 μm) diffusion distance, which strongly demonstrate the principal respiratory function of these surfaces. These capillaries form spiral coils of three to five turns as they approach the epithelial surface. The respiratory capillaries of the bucco‐opercular chamber are supplied by efferent blood from the gills and drained by the systemic venous pathway. We also compared the degree of capillarization in the bucco‐opercular epithelia of Pn. schlosseri with that of the three related intertidal‐burrowing gobies (aquatic, non‐air‐breathing Acanthogobius hasta; aquatic, facultative air‐breathing Odontamblyopus lacepedii; amphibious air‐breathing Periophthalmus modestus) through histological analysis. The comparison revealed a clear trend of wider distribution of denser capillary networks in these epithelia with increasing reliance on air breathing, consistent with the highest aerial respiratory capacity of Pn. schlosseri among the four species. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Instrumental conditioning of choice behavior in male Siamese fighting fish (Betta splendens)

Despite the differences in the response of male Betta splendens toward various stimuli, no research has attempted to determine the preference for a live conspecific versus a mirror presentation. A submerged T-maze was used to present both stimuli to healthy male B. splendens (N=16). The results indicated that subjects' start box and swimway latencies decreased significantly over the 30 trials. Moreover, the analysis of choices demonstrated a modest, but statistically significant, preference for the live conspecific over the mirror presentation. The results are discussed in terms of the stimuli qualities that elicit an aggressive response in B. splendens and the implications for common experimental procedures.     

Interval timing in Siamese fighting fish (Betta splendens)

The present study evaluated the temporal performance of Siamese fighting fish (Betta splendens) given short-term exposure to four fixed interval (FI) schedules of reinforcement, FI 30, 60, 120, and 240 s, during which a reinforcer (mirror image) was given for the first response (swimming through a hoop) after the interval requirement had elapsed. Response levels were generally low early in an interval and increased as the interval elapsed; wait times and break points in an interval increased with increases in the FI requirement. The results were similar to that obtained with other species and different types of responses and reinforcers, and demonstrate that the procedure is a feasible method for studying interval timing in fish.     

Alarm reaction and alert state inGambusia Affinis (Pisces,Poeciliidae) in response to chemical stimuli from injured conspecifics

We studied the behavior of the Poeciliid fishGambusia affinis after the introduction of 3 substances into their tank: a homogenization ofGambusia affinis, a homogenization of the Anabantid fishBetta splendens, and a blank made of distilled water. The response of the fish was measured as a change in their spatial distribution in the tank after the introduction of the substance. Two sizes of fish were used, and theGambusia homogenization produced clear alarm reactions in both, the fish fleeing to the bottom of the tank. This is one of a few examples available of recognition of alarm substances in non-ostariophysian fish. In addition, we found that the small fishes that had recently been exposed to the alarm substance stayed in an ‘alert state’, in which they had an increased sensitivity to mechanical and visual fright stimuli.     

Observations on the reproductive and larval biology ofBlennius pavo (Pisces: Teleostei)

Social behaviour and spawning of adultBlennius pavo kept in the laboratory are described. Eggs are deposited in batches on the walls of artificial spawning places (PVC pipes). One male guards and tends the eggs of different females in one spawning place. Larval hatching occurs in groups according to oviposition. Minimum incubation temperature is around 14–15°C. Larval survival in 1-1 rearing jars is not related to larval total length but to density of larval stock. An experimental population of laboratory reared juvenile and adolescentB. pavo displays a male to female ratio of 1:1.4. Factors possibly influencing the sex ratio of this littoral fish are discussed in view of the situation in its natural environment.     

The role of air breathing in the resistance of bimodally respiring fish to waterborne toxins

The bimodally respiring catfish Clarias macrocephalus Günther responded to a toxic extract of Croton tiglium (Euphorbiaceae) seeds by increased air breathing under both normoxic (8.1 ± 0.4 mgO₂ l⁻¹) and hypoxic (0.7 ± 0.1 mgO₂l⁻¹) conditions. Fish in hypoxia survived longer than those in normoxia when surface access was provided. When air breathing was prevented, survival time in toxin was greatly reduced at both levels of dissolved oxygen, and fish in normoxia survived longer than those in hypoxia. Non-toxin controls without surface access survived in normoxia but in hypoxia died at the same time as the fish in toxin. These results suggest that air breathing increases the resistance offish to toxins by permitting a decrease in the rate of gill ventilation and hence the rate at which toxins are absorbed.     

Observations on feed size and capture success in the larval butterfly splitfin (Ameca splendens Miller & Fitzsimons, 1971, Pisces: Goodeidae) reared on zooplankton

In this study, we quantified the feeding behaviour (encounter, attack, capture. and ingestion) of larval A. splendens on micro‐crustacean prey [cladocerans: Alona rectangula, Simocephalus vetulus (separately neonates and adults), Ceriodaphnia dubia, Daphnia pulex (juveniles), Moina macrocopa and ostracods: Heterocypris incongruens]. Although we initially (first 4 weeks) offered rotifers (Brachionus calyciflorus and B. patulus), they were not consumed by the larvae and hence observations with these prey were discontinued. Feeding behaviour was observed during the first 10 weeks. Fifteen observations were made with each prey species (seven diets × four replicates). Experiments were conducted in 50 ml transparent containers with 20 ml fish‐conditioned water into which one fry was introduced. Before introducing the fish, 20 individuals of a given cladoceran prey species or 50 individuals of a rotifer prey species were introduced. Until the fourth week, we used 20 ml of medium and thereafter 30 ml, but the prey density used remained constant (1 ind. ml⁻¹). Observations (10 min per fry per cladoceran replicate) were taken under a stereomicroscope (20×) for the first 2 weeks and later with a lamp and a magnifying lens. The number of encounters (E), attacks (A), captures (C) and ingestions (I) were recorded. During the study period, there was a 60% increase in gape size but only a 30% increase in body length. The number of encounters of larval A. splendens was highest (192) on M. macrocopa and lowest (29) on ostracods and adult S. vetulus (59). The inverse relationship between capture success and prey size was more pronounced during the latter half of the study period. Compared with all the other prey types offered, A. splendens fed maximally on M. macrocopa, which therefore could be a suitable diet for the larval rearing of this fish species.     

Veligers of the invasive bivalve Limnoperna fortunei in the diet of indigenous fish larvae in a eutrophic subtropical reservoir

Larval fish development depends largely on their ability to capture and ingest food items, and on food availability. In this context, invasive species, eutrophication and river impoundments have complex impacts on fish larvae. Using samples collected in 2005–2009 in the Salto Grande reservoir (Argentina–Uruguay), periodically affected by cyanobacterial blooms, we studied the impact of the larvae of the exotic bivalve Limnoperna fortunei (Dunker, 1857) (Bivalvia) on larval fish diets. Compared with other nearby waterbodies, the abundance of fish larvae was scarcer in the reservoir, especially during algal bloom periods. Only 20% of the larval fish with gut contents fed on L. fortunei veligers. Seven fish taxa (of a total of 12) consumed veligers of L. fortunei, but only two showed a preference for this prey. Taxonomic changes in the larval fish assemblages due to the river's impoundment, and temporal uncoupling between veliger densities (affected by the toxigenic effects of Microcystis spp.) and ichthyoplankton could account for the comparatively low trophic importance of the invasive bivalve's veligers. These results reflect the complexity of interactions brought about when the same invasive species invades different environments, underscoring that the impacts involved depend as much on the invader, as on the regional and ecological settings of the area invaded.     

Comparison of inshore and offshore fish larval assemblages within the wider Yangtze River estuary (China)

It is hypothesized that fish larvae undertake vertical movements in estuarine waters. To test this hypothesis, a sampling period was selected during times when many spring‐spawning fish reach maximum abundance in coastal waters so that spring and summer variations in larval fish assemblages could be determined in the Yangtze River estuary. Six oceanographic surveys were conducted across the salinity gradient of an inshore (freshwater) and offshore area (brackish intersection) during spring (May) and summer (August) between 2010 and 2012. The fish larval community was dominated by species of Engraulidae, Gobiidae, Champsodontidae and Mugilidae. The pre‐flexion and flexion larval stages of euryhaline marine species, which are dependent on estuaries as nursery areas, were common. The brackish and marine larval assemblage was the most abundant with taxa such as Coilia mystus and Engraulis japonicus accounting for more than 57.3% of the total catch. Spatial differences in the taxonomic composition of larval fish assemblages were evident between the inshore and offshore areas. Additionally, the Yangtze River runoff regulatory functions as affected by the Three Gorges Reservoir operational mode (hydrological alternating operations) showed weak influences on fish and habitat environments. Low salinities from high freshwater inflow limited bay anchovy production in the inshore area.     

Bubble nest habitat characteristics of wild Siamese fighting fish

Siamese fighting fish Betta splendens in Thailand inhabit shallow water amongst dense emergent vegetation near the margin of rice paddy fields. Nesting water was low in dissolved oxygen, pH, salinity but high in free carbon dioxide and temperature. This fish aggregated with a mean population density of 1·7 fish m^-2 and an equal adult sex ratio. Males were heavier, longer and wider than females. The size of their bubble nest is in proportion to their weight and length.