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At least 19 recordsLinked to original sources
PubMed1975

The role of chemical and visual stimuli in the preferential discrimination of young by the cichlid fish cicblasoma nigrofasciatum (günther).

During the parental period, females of the cichlid fish Cichlasoma nigrofasciatum have demonstrated a keen ability to locate and preferentially discriminate their own wiggling young from those of other species on the basis of chemoreception. Males also apparently perceive chemical substances emitted by their young, but their response is weak in comparison to that of the female. There was no apparent perception of chemical substances emanating from eggs until 10 to 15 hours prior to hatching at which time, females began responding to them. No clear nor consistent preference by visual means, alone was shown by pairs of C. nigrofasciatum toward wiggling young of either their own species or those of Hemichromis; however, rapid preferential discrimination, by such means, was shown when a pair's own wiggling young were tested with free-swimming young of a foreign species. Vision apparently serves primarily for orienting the parents to young during their wiggling stage of development, while chemoreception serves primarily a discriminative function, at least, when both chemical and visual stimuli are present in a given situation. Once the free-swimming stage of development has been reached, parental vision not only continues to mediate orientation to the young, but also assumes an increasing role in discriminating among different types of young. When combining the chemical stimuli of wiggling young of their own species with the visual stimuli of either these same young or wiggling young of another species, females of C. nigrofasciatum apparently can learn, within 15 to 19 hours, sufficient visual characteristics to show preferential discrimination, at least, for a period of 5 to 7 hours after removal of the chemical stimuli. This result was in sharp contrast to that seen when visual stimuli, alone were tested for the same or longer periods. The interaction of chemical and visual stimuli in young recognition by parental cichlids and the relevance of the present findings to previous studies, dealing with similar mechanisms, are discussed.

Animals↗
PubMed2026

Same Sex Chromosomes With Independent Origins in Haplochromine Cichlids.

Elucidating theories of sex chromosome evolution requires approaches that allow fine scale delimitations of sex-determining regions within a phylogenetic context. This can address whether shared sex chromosomes across related species are due to shared ancestry, or whether genetic sex-determining regions have repeatedly evolved. Haplochromine cichlids, as one of the most successful fish lineages on Earth, have been a focal study system of sex chromosome research, both because of their rapid rate of sex chromosome turnover and the repeated emergence of certain sex chromosomes across the lineage. Here, we newly describe sex chromosomes in members of the earliest branch of the modern haplochromines, the Tropheini, based on whole-genome sequencing data, using a combination of SNP- and kmers-based methods. We show that despite the repeated co-options of ancestral chromosomes LG5 and LG7 in these species, the origins of these sex chromosomes are independent. Investigation of gene functions, allele differences, and sex-biased gene expression within the discovered sex-linked regions provides no evidence that sexual antagonism has driven the repeated evolution of a region on LG5 that overlaps between four of these species. By comparing the sex-determining regions on LG5 and LG7 across haplochromines, we show that a common origin is unlikely, and that while sex chromosomes themselves may be shared between several Haplochromini, the sex-determining genes or mechanism likely differ. This study paves the way to explore newly emerging theories of sex chromosome evolution, such as the role of chromosomal fusion or recombination patterns across the genome.

Animals↗
PubMed2025

Rapid Divergence of Visual Systems and Signaling Traits to Contrasting Light Regimes During Early Speciation of African Crater Lake Cichlid Fish.

Sensory adaptation is widely hypothesized to drive ecological speciation, yet empirical evidence from natural populations undergoing early stage divergence remains limited. In Lake Masoko, a young crater lake in East Africa, the haplochromine cichlid Astatotilapia calliptera is undergoing early stage sympatric speciation into shallow-water littoral and deep-water benthic ecotypes that experience contrasting light environments. Here, we integrate retinal transcriptomics, phenotypic analyses, and visual modeling to uncover rapid sensory divergence associated with this ecological transition. We find striking shifts in cone opsin expression, with the benthic ecotype exhibiting a switch from short-wavelength sensitive SWS2B to SWS2A and an overall narrowing of cone sensitivity toward the center of the light spectrum, consistent with changes in deep-water light environment. In contrast, coding sequence variation in opsin genes was limited and no significant differences in allele frequencies were detected across nine polymorphic sites, pointing to expression regulation as the primary axis of early divergence in visual systems. In parallel, we observed divergence in male signaling traits, with benthic males displaying deeper red egg-spots, aligning with predictions from visual modeling of signal efficiency in different light environments. These results demonstrate rapid transcriptomic and phenotypic divergence in associated signaling traits-within ∼1,000 years-supporting a potential role for regulatory evolution in sensory adaptation during early ecological speciation.

Animals↗
PubMed1975

Induced parental care in male convict cichlid fish.

Three parameters of parental care were recorded for pairs of cichlid fish (Cichlasoma nigrofasciatum) caring for their own young to determine the normal parental role of the male. Nonreproductive adult males were induced to exhibit parental behavior (e.g. herding, fin-digging, and defense of young) by daily presentation of free-swimming conspecific young. This process of sensitization to young appears to be species-specific in that males did not exhibit parental care toward alien (Hemichromis bimaculatus) young. Parental behavior in reproductive and nonreproductive males, as well as the implications and function of sensitization in these fish, is discussed.

Aggression↗
PubMed1979

A duration-dependent negative potential in the cichlid electroretinogram.

A negative potential can be evoked in the local electroretinogram of the cichlid fish Cichlasoma octofasciatum by light stimuli of duration longer than 70 msec. This response superficially resembles the proximal negative response, but differs in some waveform components and dependence upon stimulus configuration and duration.

Animals↗
PubMed1979

Gill lesions in Cichlid fishes after intoxication with the insecticide Fenthion.

The toxic effects of Fenthion on the gills of Cichlid fishes were investigated. In Herotilapia multispinosa hyperplasia and separation of the respiratory epithelium, lamellar telangiectasis and thrombosis occurred. The lamellar epithelium of surviving fish regenerated in all cases. In Tilapia leucosticta no telangiectasis was found, but all the secondary lamellae were fused due to the severe hyperplasia of the gill epithelium.

Animals↗
PubMedDate not supplied

Alcohol, habituation and the patterning of aggressive responses in a cichlid fish.

Territorial cichlids were presented for 30 min with a conspecific male intruder (contained in a clear glass tube). Eight hr prior, 2 groups were administered alcohol (0.15 or 0.30 percent in the aquaria water). A third group served as a control. Three responses were recorded to allow analysis of topographic changes in behavior as well as changes in absolute levels. During the habituation phase, the normal group showed a sequence of long displays, followed by shorter ones as the frequency of attacks increased. The occurrence of threat which gradually gives way to attack is characteristic of the agonistic behavior of this species. In contrast to the controls, the 0.15 percent group was hyperaggressive, while the 0.30 percent group was hypoaggressive. Furthermore, the patterning of responses were abnormal. The 0.15 percent group gave abbreviated threats and more attacks (interpreted as a tendency to attack without warning); whereas, the 0.30 percent group gave many long threat displays, but few attacks. A stimulus specificity test provided strong evidence that the waning found during the initial phase was habituation.

Aggression↗
PubMed1979

Motivational variables and the sensitization and habituation of aggression in the convict cichlid (Cichlasoma nigrofasciatum).

Four experiments using territorial Convict Cichlids investigated motivational factors involved in the incremental and decremental processes associated with aggression resulting from exposure to conspecifics intruded into the territory. The first three experiments varied some single aspect of the experimental situation (temperature, distance from the nest or size of the intruder). The fourth experiment combined those factors which resulted in faster habituation (small intruder, far from the nest, in cool water) and compared the response to factors which resulted in slower habituation or an increase in response rate (large intruder, close to the nest in warm water). While a combination of higher intensity stimuli did result in slower habituation than the combination of lower intensity stimuli, response rate was not a simple algebraic summation of the factors. Results are discussed in relation to multi-factor theory of habituation and the nature of "drive".

Aggression↗
PubMed1976

The effect of testosterone on the behavior and coloration of adult male cichlid fish (Haplochromis burtoni, Günther).

The African cichlid fish Haplochromis burtoni shows specific behavioral responses to the intramuscular injection of testosterone. Approaching and attacking were significantly increased by injections, while six other observed behaviors remained unchanged. The results suggest that the injected testosterone affected the control of both sexual and agonistic behaviors.

Animals↗
PubMed2026

Body tactile stimulation intensifies appeasement behavior in a cichlid fish.

Social touch, provided by body tactile stimulation (TS), is known to trigger appeasement behavior and social stability in mammals. Recent studies have shown that TS also plays a role in regulating social interactions in fish by reducing aggression between individuals. While this effect may stem from decreased aggression in dominants, the potential contribution of increased appeasement behavior in subordinates has been overlooked. Here, we investigated whether TS facilitates the onset of appeasement behavior in the cichlid fish Geophagus iporangensis, a species that exhibits clear dominance-subordination relationships. Isolated individuals were assigned to one of two treatments, either with TS (provided by plastic sticks lined with silicone bristles) or without it for 21 days. Then, each fish was paired with a socially experienced dominant individual to enable rapid hierarchy resolution. Initial appeasement scores did not differ between treatments. However, individuals who experienced TS exhibited significantly higher appeasement scores during the final 5 min of the contest than the control group. Additionally, fish under TS showed an increase in the appeasement score after 10 min of agonistic interaction, while it did not change in the treatment without TS. Overall, this study provides the first evidence that TS can mitigate aggressive interactions by intensifying subordinates' appeasement behavior, thereby affecting social dynamics similarly to mammals.

aggression↗
PubMed1978

Photoreceptors and visual pigments in a cichlid fish, Nannacara anomala.

Correlation of visual pigment content and photoreceptor cell structure is studied in the cichlid fish Nannacara anomala the retina of which is characterized by simple organization of the outer plexiform layer. The visual cell types consist of long and bulky rods and only two types of cones: equal double cones and short single cones. Both types of cones differ form other known teleost cones in that their outer segments are very slender yet twice as long as the inner segments. The double cones form a square mosaic with four doubles along the sides an a single cone in the center. Four rods usually surround the single cone and a few others lie in the corners of the square. The population densities of photoreceptor cells in the central part of the retina is 45,600 cones and 52,600 rods per mm2. The cone to rod ratio is 1:1.15; the double cone to single cone ratio is 4.07:1. The outer segments of photoreceptors contain four spectroscopic types of pigment: one type in rods with lambda max = 498 +/- 5 nm, one type in single cones with lambda max = 460 +/- 5nm, and one in each member of the double cones with lambda max of 555 +/- 5 and 600 +/- 10 nm. Single cones are found to contain only the blue-absorbing pigment. The double cones, whenever both members are successfully recorded from, appear to use two spectrally different pigments. Based on spectral bandwidth determination, the four pigments are probably of the prophyropsin class, although some admixture (10--20%) of rhodopsin-class pigments is also indicated, especially in double cones.

Animals↗
PubMed1975

Morphology of lymphoid organs in a cichlid teleost, Tilapia mossambica (Peters).

In Tilapia mossambica organized lymphoid tissues are present in the thymus, head-kidney and spleen, whereas they are lacking in pericardial tissue, liver, mesonephros, intestine and rectum. No lymphoid tissue was observed in the chondrocranium and cartilaginous viscerocranium of young adults. The thymus in Tilapia is encapsulated by thin strands of collagen fibers and consists of outer, middle and inner zones. While middle and inner zones are comparable to the thymic cortex and medulla of higher vertebrates, the homology of the outer zone is not clear. At the anterior end of the thymus, a loose aggregation of lymphocytes without a definite boundary has been observed. The head-kidney is characterized by the presence of lymphoid follicles, a subcapsular sinus, a hilus-like area and lymphatic vessels. The spleen is grossly divisible into white pulp and red pulp; the white pulp contains only a reticular area without definite lymphoid centers and the latter contains predominantly erythrocytes. Morphological changes in the lymphoid organs associated with immune response have been discussed.

Animals↗
PubMed1975

The inheritance of aggressiveness in the convict cichlid fish, Cichlasoma nigrofasciatum (Pisces: Cichlidae).

Intraspecific comparisons in aggression were made between X-irradiated (2 times 500 R) ancestors and untreated control animals. Bites delivered to sub-adult conspecifics were counted to measure aggressiveness. When compared with corresponding controls, a significant reduction in male aggressiveness was found in the post-irradiation F1 generation. A greater variation in bites delivered occurred among the F2 post-irradiation generations than among the control equivalents. Three distinct back-cross generations were obtained as follows. a single F1 female from the irradiated line was mated to (a) her high aggressive (I-A) and (b) her low aggressive (I-NA) F2 son; a F1 control female was mated to her low aggressive F2 son. In the back-cross generations, both I-A and C-NA males were more aggressive than I-NA males. No differences were found between I-A and C-NA back-cross males. The findings are discussed in terms of a two-factor model based on Mendelian laws.

Aggression↗