Cichlid Fish Species Research Articles

Histopathology of Ichthyophthirim multifiliis infections in fishes

Histopathological changes involved in Ichthyophthirius multifiliis infections are described from a wide range of host fishes—carp, crucian carp hydrids, Carassius carassius×C. auralus, goldfish, eels, African catfish, Glorias lazera, several species of cichlid fishes and rainbow trout. Fish were obtained from diverse geographical regions: Israel, South Africa, Portugal and Venezuela, as well as from laboratory experimental infections. Observed histopathological changes could not demonstrate any interspecific differences, but individual fish or different groups of fish of the same species demonstrated wide variability in susceptibility to infection and consequently in the nature and severity of the histopathological response. Low to moderate primary infection and secondary reinfestations did not induce significant histopathological changes in the integument. The proliferative response of the integumentary epithelium appeared only following subsequent infections. Repeated heavy reinfections induced massive cellular necrosis and in very heavy infections extensive lysis of the epithelial tissue. Host‐parasite interactions in the light of the histological findings are discussed.

The development of the retinopetal nucleus olfacto-retinalis of two cichlid fish as revealed by horseradish peroxidase

Adult patterns and the development of the nucleus of origin of centrifugal innervation of the retina, the nucleus olfacto-retinalis (NOR), were studied with horseradish peroxidase in 2 cichlid fish species. In the adults large and small cells within the nuclear boundaries can be distinguished by their cytoarchitecture and their HRP-labelling. The NOR is already formed at hatching (5.5 days post-spawning) but cannot be filled by HRP injections into one eye until 2 days later. The number of labelled neurons increases steadily until adult cell density is reached. Later larval stages show that the NOR neurons also increase in size. The two cell types found in the adult can first be distinguished at around 30 days post-spawning. Early unilateral enucleation reduces the density of the small cells in the contralateral NOR. In spite of different environmental constraints on the growth of the larvae, the NOR develops in a similar way in both species but always somewhat later in the substrate-spawner than in the mouth-brooder. The centrifugal innervation of bird (isthmo-optic nucleus, ION) and fish (NOR) retinae starts at comparable developmental stages of the retina, but no cell death as found in the developing ION in birds occurs in the developing NOR in fish. It is suggested that this is due to the constant adjustment of the NOR to the ever increasing cell numbers in the fish retina. The NOR is thus the only known centrifugally projecting nucleus in vertebrates which lacks extensive degenerating patterns during early development. The known LH-RH immunoreactivity, the two cell types, the early development, and the projection to the retina of the NOR in cichlid fish resemble closely characteristics of the ganglion of the terminalis nerve of other piscine species.

Punctuated equilibria, morphological stasis and the palaeontological documentation of speciation: a biological appraisal of a case history in an African lake

The present-day faunas of the great African lakes present some of the world's best examples of ‘explosive speciation’. Lakes Victoria and Malawi each probably have several hundred endemic species of cichlid fishes. Much can be inferred about the evolution of these fishes from morphology, behaviour and intra-lacustrine distribution and from the fact that they include taxa ranging from local races, through sibling species, to forms that display extensive differentiation. The time taken to acquire specific distinctness can sometimes be accurately defined, but fossil lineages are unknown. A recent study of a fossil sequence of molluscs in the Turkana basin throws new light on the history of African lake faunas. It also claims to have resolved events during speciation. While critical analysis based on our knowledge of living molluscs in this area fails to substantiate this claim, the fossil molluscs complement information provided by the biology of extant fishes and invertebrates and emphasize the importance of these lakes in the study of evolution in living and extinct populations.

Influences of Motivation On Display Divergences in Three Cichlid Fish Species (Haplochromis)

AbstractDifferences between three cichlid fish species in responsiveness to a restrained territorial intruder have been investigated while an experimenter, considered a disturbing stimulus, was sitting 2 meters in front of the tank in view of the fish. The purpose of the analyses was to determine which motivational factors control responses to intruders and disturbances between Haplochromis elegans, H. squamipinnis, and H. angustifrons. This could be done on the basis of a model for the causal organization of these responses that was developed in an earlier paper (CARLSTEAD, 1982). It was found that H. angustifrons responds significantly less to the intruder than the other two species, and this is because it responds more to the experimenter. H. squampinnis hides from the experimenter in longer bouts than the other two. It was concluded that angustifrons has a basically higher activation level of system D (refer to model, Fig. 3), a system determining the responsiveness to stimuli indicative of potential danger and controlling motor patterns for hiding responses. Elegans has a relatively higher activation level of system T for responding to territorial intruders. Squamipinnis was found to have a higher level of a general factor for reactivity to all unexpected, thus novel stimuli. Species differences in courtship display were also investigated. These displays differ little between species, but each shows one particular display more often than expected in temporal association with spawning. This display proved in each species to be the display performed more often than expected to a restrained male territorial intruder in the behavior sequence after a conflict to approach it or withdraw from it had occurred (Turning-Around). Using the model, the motivational differences between the three species described above could account for the latter differences. If only one particular motivational configuration can be assumed to be required for a display to occur in any situation, then a approach/withdrawal conflict to a male intruder and a female showing willingness to spawn must elicit the same motivational configuration. It was concluded that species divergences in the activation level of certain motivational factors are reflected in this particular momentary motivational configuration. Characteristics of each species' ecological niche in Lake George, to which they are all endemic, have been discussed with respect to the factors selecting for these motivational divergences, It was concluded that the hypothesis is supported that adaptations for features of a species' habitat may cause divergences in display behavior that are not directly selected for their signal value. This occurs through selection for optimal activation levels of motivational factors that in the behavioral organization control both responsiveness to types of environmental stimuli and motor patterns of display.

A new species of cichlid fish from the Malagarasi Swamps and River (Tanzania, east Africa)

A new species of cichlid fish from the Malagarasi Swamps and River (Tanzania, east Africa)

Evidence for rapid speciation in African cichlid fishes

Extremely rapid divergence among 7 species of African cichlid fishes is suggested by high estimates of allozymic similarity. Significant differences in gene frequencies among sympatric populations support reproductive isolation of these taxa.

A Quantitative Study of Long-Term Courtship: II. a Comparative Study of the Dynamics of Courtship in Two New World Cichlid Fishes

i. The courtship behavior of two sympatric species of New World cichlid fish was quantitatively studied. The two species were Cichlasoma citrinellum (Gunther) and C. zaliosum Barlow. The species are closely related. 2. Data recording was based on heterosexual, homospecific dyads. Ten event categories, representing cichlid courtship behaviors, were recorded for each sex. 3. Both species showed long-term courtship behavior, the minimum time to spawning after first contact being 52 hrs. Data were recorded three times a day for each pair throughout the courtship period. 4. Four measures based on information theory were used to describe overall changes in behavior with the pair. These were H1, the first order diversity; D1, the first order redundancy (repetition); H2, the second order diversity; and D2, the second order redundancy (divergence from independence). 5. Courtship in these species has three distinct phases that can be characterized quantitatively by their patterns of behavioral diversity. There is an early phase of high activity, high first order diversity, and low first order redundancy. This appears to be the time of pair formation. The second, intermediate phase, is a period of relatively low activity and intermediate behavioral diversity and redundancy. This is the interval after pair formation, but prior to attachment to a spawning site. The third phase is characterized by high activity, primarily by the female, with low diversity and high redundancy. This phase is primarily one of spawning-site preparation and synchronization for the release of gametes. 6. The changes in the overall organization of behavior within the pair were primarily the result of frequency of occurrence (first order). There were no apparent overall changes in the level of dependency between events during courtship (second order). 7. Similar analysis of a species showing short-term courtship should reveal greater importance of second order effects due to reliance on releasers and chaining of events between the sexes. 8. The two species differ primarily in the frequency with which they performed various courtship behaviors. C. zaliosum did more agonistic behaviors such as Bite, Lateral, Frontal and Yield; C. citrinellum performed more behaviors typical of later stages of courtship, such as Quiver and Nip Off. 9. The frequencies with which the behaviors followed each other differed in the two species. 10. The species were least similar in their courtship behavior during the earliest stages of courtship, and showed the greatest resemblance during the parental period. II. Heterospecific pairs resembled C. citrinellum more in their overall behavior than they did C. zaliosum, but this may have been an artifact of the abnormal size ratios within those pairs. 12. The differences in behavior seem due mainly to a lower threshold of aggression in C. zaliosum, while C. citrinellum has a lower threshold for sexual behavior. 13. The differences in courtship are sufficient to explain the reproductive isolation of the two species, but the mechanism is effective only when a choice of mates from both species is available.

Visual pigments of cichlid fishes from Malawi

Visual pigments were studied from 23 species of cichlid fishes from Lake Malawi, four species from the Lower Shire River, and one from Lake Chilwa. The water in Lake Malawi is very clear, and the fishes occupying it have visual pigments that vary with the depth at which they live, with the maximal absorption ranging from just above 500 nm for surface living forms to about 492 nm for species living at 50–90 fathoms. The visual pigment of the species from Lake Chilwa, which is highly turbid, absorbs maximally at approx 530 nm, while the visual pigments of the Lower Shire species are intermediate. The results are also compared to previous data for Amazonian cichlids. The visual pigments of the Amazonian species show much greater variation, both within and between species, than do those of Lake Malawi cichlids. It is suggested that the variation between the visual pigments of different fishes occupying a given habitat may be related to the variability of the light conditions in their environment.

Trophic radiation through polymorphism in cichlid fishes

Several morphologically defined species of cichlid fishes (Cichlasoma) endemic to the Cuatro Cienegas basin of Mexico and differing in tooth structure, body shape, and diet are allelically identical at 27 gene loci. The presence of only one Mendelian population in each of three drainage systems studied and the occurrence of two of the morphotypes in the same broods indicate that the supposed species are morphs. That trophic radiation in the Cuatro Cienegas cichlids has been achieved through ecological polymorphism rather than speciation raises questions regarding the genetic basis for the extensive intralacustrine radiation of cichlids in Africa and elsewhere.

Vergleich des Agonistischen Verhaltens von Zwei Gruppen Jungfischen (Haplochromis Burtoni) Gleichen Alters

When a batch of young of the mouthbreeding cichlid Haplochromis burtoni is divided into two groups of equal size, they show different behaviour. The ones that are caught first are less aggressive than the second, more shy ones. If agonistic behaviour has a positive selection value, it can be an important factor for the rapid speciation in cichlid fishes. In order to investigate this assumption experimentally, one has to bear in mind that early experience, group size and group density can influence the agonistic behaviour.

Parental behavior and some histological features of scales in Cichlasoma citrinellum (Pisces, Cichlidae)

Young Cichlasoma citrinellum contact parents preferentially, depending on sex and color of the parents. The number of epidermal mucus cells on adults' scales is positively correlated with the amount of contacting by the young. The epidermal thickness of these scales is negatively correlated with the amount of contacting. These correlations are discussed as possible cause–effect relationships with the contacting preferences of the young, and are compared to similar behavior in other cichlid fish species.

Random processes describing the occurrence of behavioural patterns in a cichlid fish

Territorial males of the cichlid fish species Haplochromis burtoni were observed over periods of approximately 3 hr and seven different behaviours were recorded. A statistical analysis of the data led to the following results: The short-term sequential organization in the occurrence of the seven recorded behaviours can be described in terms of renewal processes (Figs 1,2 and 3). In order to cope with long-term fluctuations in the rate of occurrence of some behaviours one has to assume that some parameters characterizing the renewal processes involved may slowly fluctuate in time. Long-term fluctuations in the rate of occurrence show particular correlations among the seven behaviours investigated (Figs 4 and 5). The correlation pattern found (Fig. 5) suggests that the seven behaviours share at least four slow ‘basic’ processes, ν 1, …, ν 4, which to different extents contribute to long-term fluctuations in the rate of different behaviours. A linear model representing slow fluctuations in the rate of a particular behaviour as a linear combination of four basic processes yields a reasonable approximation to the long-term correlation pattern observed (Figs 6 and 8).

Natural hybrids of the African cichlid fishes Tilapia spilurus nigra and T. leucosticta: a case of hybrid introgression

Hybridization is documented between two species of African cichlid fishes, Tilapia spilurus nigra and T. leucosticta. First discovered in a rice padi at Tebere in eastern Kenya (ostensibly stocked only with T. s. nigra), similar hybrids were later found in Lake Naivasha, Kenya (stocked inter alia with T. s. nigra and T. leucosticta). Hybrid characters are examined individually and by summation as a hybrid index. Pond and laboratory crosses indicate that hybridization occurs readily and produces at least partially fertile hybrids. Hybrid introgression appears to be occurring in the Tilapia populations of Lake Naivasha. Ecological features of the natural populations of both parental species and of the hybrids are examined with particular reference to habitat preferences and sex ratios.

Immunological determination of injected mammalian prolactin in cichlid fishes

In the present paper an attempt is made to determine, by quantitative radial immunodiffusion, the level of intramuscularly-injected mammalian prolactin (LtH) in serum and organs of two species of cichlid fishes ( Aequidens pulcher and Tilapia mariae) at different times after application. With injections of 0.05 or 0.02 mg/gm bodyweight, the maximum LtH concentration in serum is reached after 1–3 hours. Within 3–25 hours prolactin rapidly disappears, and 28–30 hours after application, it is eliminated totally from circulation. In the kidney the maximum level appears at 2–7 hours after injection, but in this organ LtH concentration decreases somewhat slower than in serum, so that total elimination occurs 7–10 hours later. The hormone could not be identified on other organs (skin, musculature, thyroid-containing tissue, brain, and intestine), except in the liver and spleen of Aequidens, in which minute amounts of prolactin were detectable. There is discussed the correlation of these findings with the control mechanism of some behavioral and histotropic effects which are inducible by mammalian prolactin in cichlid fishes.

Radioactive Fallout

<h3>Abstract</h3> A new species of cichlid fish, <i>Lethrinops atrilabris</i> is described from specimens collected by trawling at a depth of around 90m off Monkey Bay, southern Lake Malawi. It is assigned to the genus <i>Lethrinops</i> on the basis of its vertical flank barring, lack of enlarged cephalic lateral line canal pores and the form of the lower jaw dental arcade. It can be distinguished from congeneric species by its male breeding dress of contrasting flank barring and dark ventral surface, most strikingly on the lips, throat and chest, its relatively small known maximum size (&lt;75mm SL), large eyes (38-41% head length), laterally compressed body (depth 2.5-2.7 times max head width) and lower gillraker count (13-14).

LVII.—On two species of Cichlid fishes from the Malagarazi River (Tanganyika), with notes on the pharyngeal apophysis in species of theHaplochromisgroup

LVII.—On two species of Cichlid fishes from the Malagarazi River (Tanganyika), with notes on the pharyngeal apophysis in species of the<i>Haplochromis</i>group

Speciation in Cichlid Fishes of East African Lakes

Prof. C. Kosswig has suggested1 that factors which may contribute to the high evolutionary response of Cichlid fishes to the environments of the Great African Lakes are selective mating and specialized breeding habits, including monogamy at least until one brood becomes independent. A beginning has been made in the study of a group of closely related species in Lake Nyasa, the Tilapia of the T. squamipinnis group2,3. Before 1939 these had been considered as a single species. Slight differences in pharyngeal dentition had been observed in the larger fishes among a score of specimens in the British Museum (Natural History); but these, and slight variations in proportions of head and mouth, had not been thought sufficient for the recognition of more than one species. Field-work during the fishery survey of 1939 revealed that there are in Nyasa probably four closely related species, for some of which it is still convenient to use local names, Chambo, Saka, Lidole and T. karongae (the local name of which I do not know). These seem to be the Nyasa representatives of the T. galilae group of the genus, but all resemble each other much more closely than any species outside the Lake. Females and non-breeding males of all are silver-grey with nearly vertical black bars. In Chambo the male becomes pale blue as the testes ripen; in the other three, ripe males are black. The four species (if they are species) cannot yet be recognized at all stages, but Lidole and Chambo can be distinguished from each other at a total length of 26 cm. and more, and it is to these two that the following remarks apply.

Selective Mating as a Factor for Speciation in Cichlid Fish of East African Lakes

IN most of the modern texts on evolution1, one of the outstanding proofs of speciation, that is, development of forms separated from one another under normal conditions by their immiscibility, without geographical isolation, is the very high number of species and genera of the Cichlidae in almost every one of the great lakes in East Africa. This remarkable phenomenon (Woltereck's “schizotypische Artaufspaltung”) is characteristic only for the Cichlidae of the East African lakes; other genera of freshwater fish can be represented in the same area also by more than one species, but in no other family is the diversity of types—some of them being specialized to a certain mode of life and nutrition—so well developed as in the Cichlidae.

XXIV.—Tilapia Esculenta, a new species of cichlid fish from the Victoria Nyanza, with notes on the habits of this species and the nearly-related Tilapia variabilis, Blgr.

(1928). XXIV.—Tilapia Esculenta, a new species of cichlid fish from the Victoria Nyanza, with notes on the habits of this species and the nearly-related Tilapia variabilis, Blgr.. Annals and Magazine of Natural History: Vol. 2, No. 8, pp. 209-213.