Native Cichlid Research Articles

Invasive Cichlids Display Higher Aggression During Nest Defence Compared to the Native Mexican Mojarra

ABSTRACTNest defence is one component of parental investment by which individuals can increase the survival of their offspring. Aggressive behaviours and the time spent protecting nests are determining factors in the reproductive success of cichlid species. The Mexican mojarra is the only cichlid native to the Balsas River Basin in Mexico. At least four invasive cichlids have been introduced, including the convict cichlid and the spotcheek cichlid. These three species establish their nests in the River and defend them aggressively. We quantified the number of nests, aggressive behaviours and time spent in the nest by parents of the native species and these two invasive species. We expected that the invasive parents would be more aggressive during defence, spent more time protecting the eggs, and would have a higher density of nests. We also explored differences in nest defence between the sexes within each species. We found that invasive cichlids had a greater number of nests than the Mexican mojarra. In the two invasive species, there was no difference between males and females in the time spent in the nest or the number of aggressive behaviours. In contrast, male Mexican mojarras spent less time in the nest and performed fewer aggressive behaviours than their mates. The smaller number of nests and nest defence behaviour of this native species could compromise its reproductive success and population size. This differential nest defence between the Mexican mojarra and the invasive cichlids could have negative implications for the physiology, reproduction, and health of this native cichlid.

First report of infectious spleen and kidney necrosis virus (ISKNV) in two native cichlids cultured in Brazil

Peacock bass (syn.: tucunaré, Cichla ocellaris) and the pearl cichlids (syn.: acará, Geophagus brasiliensis) are South American cichlids that are highly valued in both the ornamental and sport fish industries. Since 2017, a number of outbreaks of infectious spleen and kidney necrosis virus (ISKNV) have been reported on Brazilian food and ornamental fish farms. In this study, we detected ISKNV in farmed peacock bass and pearl cichlid by PCR and sequence analysis of the partial major capsid protein (MCP) gene. Moribund peacock bass (n=10) and pearl cichlids (2) from a farm experiencing elevated mortality among juveniles and adults of these species, were submitted for bacteriological and molecular diagnostics. Spleen, liver, brain, and kidney tissues were cultured on 5% sheep blood agar and cystine heart agar with 1% glucose and bovine haemoglobin. No bacteria were isolated from the 12 fish. Additionally, DNA extracts from the liver and spleen of all animals were tested for ISKNV using two conventional polymerase chain reaction (cPCR) assays and two nested PCR (nPCR) assays. ISKNV DNA was amplified in all 12 fish DNA extracts tested, in two or more of the PCR assays. Selected ISKNV amplicons were confirmed by Sanger sequencing. The nucleotide sequences derived from these animals were identical to ISKNV strains previously detected in food (e.g., tilapia and carp) and ornamental species, including strains previously detected in fish from Brazil. To the authors’ knowledge, this is the first report of ISKNV in these native Brazilian cichlids.

Invasive cichlids (Teleostei: Cichliformes) in the Amacuzac River, Mexico: Implications for the behavioral ecology of the native Mexican mojarra Amphilophus istlanus

The introduction of species is a leading cause of biodiversity loss and habitat alteration. Several species have invaded Mexican freshwater ecosystems, adversely affecting native fishes. Specifically, in the Amacuzac River of the Balsas Basin (Central Mexico), at least four non-native cichlids have been recorded: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These species co-occur with the Mexican mojarra Amphilophus istlanus, the only native cichlid in the Basin. Invasive cichlids compete for resources such as shelter and food, and prey on offspring of the Mexican mojarra. In the presence of invasive cichlids, the costs and risks of foraging and finding available shelter increase for the native cichlid. Predation pressure from invasive cichlid fishes on the Mexican mojarra increases the time invested by parents in caring for offspring and their stress levels, potentially contributing to Mexican mojarra population declines. Here, we gathered the best evidence available to discuss some mechanisms and consequences of such co-occurrences in relation to reproductive behaviors, parental care, competition for resources, and dominance hierarchy, and how the four invasive cichlids have negatively affected the Mexican mojarra.

Invasive black mussel (Mytella strigata) biofouling in brackish water cage fish farms

ABSTRACT The American brackish water mussel invaded Kerala’s backwaters in 2019, and a complete eradication may not be possible at this point. Management protocols and strategies need to be developed to overcome the issue. Biological management against biofouling is a new possible approach, although it needs to be sustainable in aquaculture, where the sustainability of the method is important. The present study reports the success of a biological management strategy against biofouling of Mytella strigata by employing a native cichlid Etroplus suratensis (pearlspot), as they feed on bivalves. The study was conducted in the brackish water cage farm of a 1 ha area located at Veerampuzha backwaters, Ernakulam, in the southwest of Kerala. Pearlspot fishes were stocked inside and also in the gap between inner and outer nets of the test cages as the anti-biofouling agent. Pearlspot grew considerably by feeding on the mussel spat settled on the nets and removing a considerable amount of the fouling on the nets (287%), the increases in the average growth of seabass, in the survival rate, and in overall production of the cages.

TESTING THE ENEMY RELEASE HYPOTHESIS IN THE INVASIVE FISH <i>AMATITLANIA NIGROFASCIATA</i> (PERCIFORMES: CICHLIDAE) IN MEXICO

The enemy release hypothesis (ERH) posits that invasive species are released from their natural enemies in their introduced range, which promotes their successful invasion. In this study, we tested the ERH in a population of the convict cichlid Amatitlania nigrofasciata , an invasive species in Mexico. The ERH predicts that the convict cichlid: a) is not infected by specialist helminth parasites in the introduced range; b) has lower infection parameter values, as measured through richness, prevalence, abundance and diversity of helminths, than a native species-the redside cichlid Cichlasoma istlanum ; and c) is not affected in its condition factor by the abundance of helminths it carries. The convict cichlid was infected by two (33%) specialist helminths relative to the six specialist helminths that infect the cichlid in its native range. The convict cichlid had lower helminth richness and diversity than the redside cichlid. However, the prevalence and abundance of the parasite species varied between the host fish. While the prevalence and abundance of the nematode Rhabdochona kidderi was higher in the redside cichlid, the prevalence and abundance of the trematode Uvulifer sp. was higher in the convict cichlid. The condition factor in both host fish was not correlated with helminth abundance. Our results do not agree with the prediction that the convict cichlid is completely released from specialist parasites, nor with the prediction that this invasive species has lower infection parameter values than the native redside cichlid. However, our results agree with the prediction that the abundance of parasite helminths do not affect the cichlid’s condition factor. More studies are necessary to determine the advantages that the convict cichlid could have in the introduced range when it is infected with a low richness and diversity of helminths.

Steroid Profiles of Wild Terror Green (Andinoacara rivulatus) Associated with Gonadal Histology in the Baba River, Ecuador

Native cichlids in Ecuador are represented by Andionoacara rivulatus and Cichlasoma festae mainly. These aquatic species are a fundamental part of the food chain of rural communities in the western subtropical region of Ecuador. For the first time, a detailed study on the gonadal development in A. rivulatus males and females was carried out, and the characterization of sex hormones present in their blood plasma from May 2019 to January 2020. Fish samples were captured in the multipurpose Baba River dam upstream of the Guayas River, Ecuador. Gonad and blood samples were collected for histological analysis and assaying of steroidal hormones such as 17β-estradiol and 11-ketotestosterone. The sex steroids were quantified by enzyme immunoassay (ELISA). As a result, the fish samples have asynchronous characteristics and show all development stages in testes and ovaries. The serological fluctuations show statistical differences (p <0.05) between the development stages, with low concentrations of estradiol and 11-KT. These results are somewhat related to the hydrological period of capture, where the temperature, luminosity, and rainfall play a fundamental role in the oogenesis and spermatogenesis in the captured fishes. The highest concentration of E2 is detected in female vitellogenesis stages and the highest concentration of 11-KT in the male spermatogenesis stage. These results confirm the fundamental role of these hormones in the key periods of gonadal development. In future studies, it is important to monitor the maturational hormone 17α, 20β-DHP, and the vitellogenin concentrations and thus understand the reproductive physiology of A. rivulatus.

The impact of turbidity on foraging and risk taking in the invasive Nile tilapia (Oreochromis niloticus) and a threatened native cichlid (Oreochromis amphimelas)

Anthropogenic activity can increase water turbidity, changing fish behaviour by reducing visibility. The spread of invasive species is also facilitated by human activity, further increasing the pressure on native species. In two experiments, we measured the foraging efficiency, risk perception and inter-individual consistency of risk-taking (personality variation in boldness) of an invasive species, the Nile tilapia (Oreochromis niloticus), and a threatened tilapia, the Manyara tilapia (Oreochromis amphimelas), in clear and turbid water. In experiment one, O. niloticus was faster to initiate feeding, encountered more food items and consumed more than O. amphimelas. The latency to start foraging by O. niloticus decreased in turbid water. Turbidity did not affect the latency to start foraging in O. amphimelas but the number of food items they encountered was highest at the intermediate turbidity. There was however no significant effect of turbidity in either species on the total food consumed. In contrast to this foraging context, in experiment two with a refuge and no food available, risk taking behaviour was similar in both species and they both responded with similarly reduced risk taking in turbid water. Evidence of personality variation was weak, being observed only in O. amphimelas when first leaving the shelter in turbid water. Overall, species differences were greater in the foraging context but turbidity was more important in the risk-taking context. O. amphimelas is more sensitive to turbidity during foraging, and O. niloticus is likely to have a competitive advantage in foraging situations, especially in degraded turbid habitats.Significance statementUnder human-induced environmental change, native species are often exposed to multiple stressors. Here, we tested the responses of two cichlid fish to increasing turbidity, the Nile tilapia (Oreochromis niloticus), which is invasive throughout the tropics, and the Manyara tilapia (Oreochromis amphimelas), a threatened species, indigenous to Tanzania. We found that turbidity was beneficial to the foraging of O. niloticus, which in both clear and turbid water consumed and encountered more food than O. amphimelas. In contrast, without food present, both species displayed similar responses of increased risk perception in turbid water with little evidence of personality variation between individuals in either species. Our results suggest that invasive species tolerant of degraded habitats may outcompete less well-adapted native species for food.

Comparative characterization of digestive proteases in redhead cichlid (Vieja melanurus) and twoband cichlid (Vieja bifasciata) (Percoidei: Cichlidae)

ABSTRACT In the Southeast of Mexico, there are many native cichlids with commercial interest such as redhead cichlid (Vieja melanurus) and twoband cichlid (V. bifasciata), which have a great local demand and excellent meat quality. However, it is necessary to implement their culture based on nutrition studies and digestive biochemistry. This study’s objective was to characterize these two cichlids’ digestive proteases (pH, temperature, and inhibitors) through biochemistry techniques. Results showed that V. melanurus and V. bifasciata have a digestive capacity analogous to other omnivore fishes, where the optimal pH values of stomach proteases (4 and 2, respectively) and intestinal proteases (6 and 12, respectively), the optimal temperature of acid (35°C and 55°C, respectively) and alkaline proteases (45°C and 55°C, respectively) are quite similar. Both species presented high thermal and pH stabilities. Inhibition showed that V. melanurus is more sensitive to specific inhibitors for alkaline proteases than V. bifasciata. In conclusion, V. bisfasciata and V. melanurus have different digestive protease patterns. Both species can hydrolyze different protein ingredients to formulate a specific diet. Nevertheless, V. bifasciata is more resistant to the presence of inhibitors, which allow it to include vegetable proteins in its diet.

Trophic interactions between native and exotic cichlids in a shallow tropical estuary (Lake Vembanad, India)

Feeding ecology and seasonal diet variation between a non-native (Oreochromis mossambicus) and two native cichlids (Etroplus suratensis and Pseudetroplus maculatus) in a tropical estuary was studied. E. suratensis and O. mossambicus fed predominately on blue green algae, whereas P. maculatus preferred aquatic insects. Trophic niche breadth analysis showed that P. maculatus had a broader diet spectrum than did E. suratensis and O. mossambicus. Feeding strategy analysis through dominant prey items showed that E. suratensis and O. mossambicus preferred blue green algae, whereas P. maculatus relied mostly on animal diet (mainly insects), highlighting food segregation shown by this species compared with the other two large-growing cichlids. The highest diet overlap index value was recorded between E. suratensis and O. mossambicus (0.83), compared with P. maculatus and O. mossambicus (0.69), and E. suratensis and P. maculatus (0.64). Intensity of trophic interdependence among the three cichlids showed that the two, large growing species share available food resources, whereas the smaller species considerably alters its food preference.

Rapid morphological change in multiple cichlid ecotypes following the damming of a major clearwater river in Brazil.

While anthropogenic disturbances can have damaging effects on biodiversity, they also offer an opportunity to understand how species adapt to new environments and may even provide insights into the earliest stages of evolutionary diversification. With these topics in mind, we explored the morphological changes that have occurred across several cichlid species following the damming of the Tocantins River, Brazil. The Tocantins was once a large (2,450 km), contiguous river system; however, upon closure of the Tucuruí Hydroelectric Dam in 1984, a large (~2,850 km2), permanent reservoir was established. We used geometric morphometrics to evaluate changes in native cichlids, comparing historical museum specimens collected from the Tocantins to contemporary specimens collected from the Tucuruí reservoir. Six species across five genera were included to represent distinct ecomorphs, from large piscivores to relatively small opportunistic omnivores. Notably, statistically significant changes in shape and morphological disparity were observed in all species. Moreover, the documented changes tended to be associated with functionally relevant aspects of anatomy, including head, fin, and body shape. Our data offer insights into the ways cichlids have responded, morphologically, to a novel lake environment and provide a robust foundation for exploring the mechanisms through which these changes have occurred.

Evaluation of hematological parameters, oxidative stress and DNA damage in the cichlid Australoheros facetus exposed to the fungicide azoxystrobin

Azoxystrobin (AZX) is a broad-spectrum systemic fungicide massively used worldwide. Its mode of action consists in the inhibition of mitochondrial respiration decreasing the synthesis of ATP and leading to oxidative stress in the target fungus. However, whether this effect occurs in non target organisms has been scarcely studied. The objectives of this work were (1) to evaluate biomarkers of oxidative stress, hematological, physiological and of genotoxicity in the native cichlid fish Australoheros facetus exposed to environmentally relevant concentrations of AZX and (2) to compare these biomarkers in different developmental stages using juvenile and adult fish (n = 6) exposed during 48 h. The exposure concentrations were 0 (negative control, C (−)), 0.05, 0.5, 5 and 50 μg/L AZX of the commercial formulation AMISTAR®. Blood was drawn to evaluate hematology, and DNA damage through the comet assay (CA) and micronucleus test (MN). Genotoxicity was observed by mean of both biomarkers in juvenile and adult fish at 50 μg/L AZX. Samples of liver and gills were used to determine antioxidant enzymes activity, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. In juvenile fish inhibition of superoxide dismutase (SOD) was observed in liver at 0.05, 5 and 50 μg/L AZX and in gills at 5 and 50 μg/L AZX. Glutathione- S- transferases (GST) activity increased in gills at all AZX concentrations tested. In adult fish, increase of hepatic catalase (CAT) activity at 0.5 and 50 μg/L AZX and MDA content at 50 μg/L AZX were observed. In gills only H2O2 content showed changes at 50 μg/L AZX. The sensitivity showed by gills constitutes the first report about AZX toxicity in this organ. All these negative effects were observed in the range of realistic AZX concentrations, which warns of the possible consequences that it may have on the health of aquatic biota. Differences between juvenile and adult fish demonstrate the relevance of considering the developmental stage on the evaluation of biomarkers.

From Africa to Brazil: detection of African Oreochromis niloticus parasites in Brazilian fish farms

Abstract Aim To evaluate the introduction of Oreochromis niloticus gill parasites in the Paranapanema River basin, northern Paraná, southern Brazil, as well as to inventory its occurrences in Brazilian fish farms and discuss the risks of transmission to native fauna. Methods The gills of 632 fish specimens from four fish farms in the Paranapanema Basin were analyzed. The parasites were collected, processed and identified according to specific procedure. Literature review was carried out to compile records of occurrence of gill parasites species in other Brazilian river basins. Results A total of seven (7) species of parasites were recorded, five (5) of the genus Cichlidogyrus, one (1) of Scutogyrus (Ancyrocephalidae, Monogenoidea) and one (1) of Lamproglena, Lamproglena monodi (Copepoda, Lernaeidae). All native from Africa. Some of these species have been reported in fish farms located in five other Brazilian watersheds. However, in this study a greater number of African gill parasite species was recorded in fish farms in northern Paraná (seven species), in the Paranapanema Basin, with Cichlidogyrus rognoni reported only for this basin. Conclusions The results confirm the introduction of these African parasites along with their host, O. niloticus, and the establishment of these species in Brazilian waters, since many specimens belonging to the species identified herein presented breeding activity for at least one period of the year. Although, only L. monodi has been recorded parasitizing Brazilian native species, data reported for other countries demonstrates the imminent risk of transmission of these O. niloticus parasites to native cichlids.

Fighting behaviour in native fish: the Mexican mojarra (Cichlasoma istlanum) wins when confronted with the non-native convict cichlid fish (Amatitlania nigrofasciata)

The convict cichlid fish Amatitlania nigrofasciata, an aggressive fish species, was introduced in 1987 into the Balsas River basin in central Mexico, which is home to the native cichlid Mexican mojarra, Cichlasoma istlanum. Local populations of the Mexican mojarra have been hypothesized to be negatively affected by the introduction of the non-native convict cichlid fish, and the two species have been observed engaging in aggressive behaviours over resources such as food and shelter along this basin. Thus, we evaluated agonistic interactions between the native Mexican mojarra and the non-native convict cichlid fish. In experimental contests between the species, chases, bites, refuge use and defence, and food consumed were recorded and analysed. Contrary to expectation, the Mexican mojarra engaged in a greater number of chases and bites than the convict cichlid fish and was more successful in obtaining the resource under dispute (a refuge and food).

Reconciliation ecology in Neotropical reservoirs: can fishing help to mitigate the impacts of invasive fishes on native populations?

Despite the increased use as tool for conservation of native fish, the creation of non-fishing reserves is more recent in Neotropical impoundments and its effectiveness rather variable. Although not intentionally created for conservation purposes, areas located near dams could function as fish reserves, since fishing activity is often forbidden in these sites for security reasons. We investigated the effects of a fishing-restricted area in Lajes Reservoir, a Neotropical reservoir dominated by invasive species, notably the yellow peacock bass Cichla kelberi, subject to intensive local fisheries. Cichlid populations associated with rocky banks of similar size and complexity were compared between fishing and non-fishing sites, after accounting for spatial autocorrelation. Native cichlids were significantly less abundant in the non-fishing area, in contrast to invasive cichlids. Accordingly, there were smaller individuals of the two native species in the fishing-allowed sites, where the mean size of peacock bass was also smaller. Our results suggest that angling can sometimes provide demographical control of large invasive piscivores and hence predation refuges for native fish in highly modified ecosystems such as reservoirs, thus resulting in reconciliation ecology. Fishing prohibition can sometimes be counterproductive for the conservation of native populations, illustrating the importance of context-specific management strategies.

Quantity and species of fish consumed shape breast-milk fatty acid concentrations around Lake Victoria, Kenya.

Long-chain PUFA (LCPUFA) found in breast milk are derived from dietary sources and critical for optimal infant development. We examined associations between fish consumption and concentrations of LCPUFA and essential n-3 and n-6 fatty acids in breast milk among mothers living around Lake Victoria. We used cross-sectional analyses of associations between recent fish consumption and breast-milk fatty acid concentrations. The study was conducted around Lake Victoria on Mfangano Island, Kenya, where multiple fish species are key dietary components and also are widely exported. Breast-feeding mothers (n 60) provided breast-milk samples, anthropometric measurements and questionnaire responses. In the previous 3 d, 97 % of women consumed a mean of 178 (sd 111) g fish (~2 servings/3 d). Mean breast-milk concentrations included DHA (0·75 % of total fatty acids), EPA (0·16 %), α-linolenic acid (ALA; 0·54 %), arachidonic acid (AA; 0·44 %) and linoleic acid (LA; 12·7 %). Breast-milk DHA concentrations exceeded the global average of 0·32 % in fifty-nine of sixty samples. We found native cichlids (Cichlidae) and dagaa (Rastrineobola argentea) contributed high levels of DHA, EPA and AA to local diets. We also found evidence for associations between fish species consumed and breast-milk LCPUFA concentrations when controlling for intake of other fish species, maternal body mass, maternal age, child age and exclusive breast-feeding. The fatty acid composition of breast milk was influenced by the fish species consumed. Ensuring access to diverse fish and particularly inexpensive, locally available species, may be important for diet quality as well as infant growth and development.

Inundated shore vegetation as habitat for cichlids breeding in a lake subjected to extreme water level fluctuations

Climate change and human overexploitation of freshwaters jointly lead to extreme fluctuations in lake water levels. The latter induces changes in the structure and availability of littoral habitats, thereby affecting fish that reproduce in the littoral zone. Recent increased water level fluctuations in Lake Kinneret, Israel, provided an opportunity to evaluate the impacts of those fluctuations on reproduction of fishes that spawn in the littoral zone. We assessed the use of inundated shore vegetation for reproduction by the common native cichlids, Sarotherodon galilaeus and Oreochromis aureus, in a series of field surveys of reproduction activity in littoral areas with and without inundated vegetation. The cichlids spawned in spring and early summer, when water levels are at their annual maximum and part of the shore vegetation is inundated. Spawning was always in water <2 m depth. Lagoon habitats constituted nesting “hotspots,” with nest densities 3-fold higher than open-shore sites. At open-shore sites, significantly higher nest densities were found in areas with inundated vegetation than in plant-free areas. Juvenile cichlids were significantly more abundant in littoral zone habitats with inundated vegetation. These findings highlight the important role of inundated vegetation, particularly at low lake levels when lagoon habitats are dry. We recommend maintaining water levels that support the existence of lagoons and vegetated littoral habitats. When development of lakeshore vegetation is massive, we recommend selectively removing part of the vegetation to form narrow vegetation-free corridors. In addition, wherever possible the vegetation should be removed to form lagoon-type habitats. Our insights and recommendations are probably applicable to similar situations of seasonal destabilization of lake water levels elsewhere.

Genetic diversity of Geophagus brasiliensis from the South American Atlantic Rainforest

The Atlantic Rainforest is one of the global conservation hotspots, representing a seriously threatened area with high levels of endemism and species richness. The fishes from the Atlantic Rainforest are one of the most exploited vertebrate groups by the international aquarium commerce, with an annual trade volume of about U$15-25 billions, now aggravated by the Internet e-Commerce and playing a crucial role on the sales and distribution of these species. The Cichlidae is one of the most exploited groups with several species being commonly sold in several online sites and aquarium stores all around the world. In this sense, our aim is to study the genetic diversity of the native cichlid Geophagus brasiliensis from the South American Atlantic Rainforest in Brazil. We constructed a database including 75 sequences from Geophagus brasiliensis from the Ubatiba river with 540bp of the mtDNA D-loop region using primers H16498 and L15774M and conducted molecular analyses with Geneious v4.82, DnaSP v5, Arlequin v3.5 and PopART. Our results point show that although G. brasiliensis is considered as a territorialist species, which exhibits parental care and small movement rates, population genetic structure could not be observed along the sample area, suggesting the existence of considerable gene flow at least among the sampled populations.

First trial of production of a native cichlid Herichthys cyanoguttatus comparison with the tilapia Oreochromis niloticus in aquaculture

Native species, in comparison to exotic species in aquaculture, such as tilapias, are an alternative with a lower risk to regional biodiversity, due to competition for resources caused by introduced species. Productivity, length-weight relationship and relative condition factor of a native cichlid Herichthys cyanoguttatus were investigated in comparison to tilapia Oreochromis niloticus . Fish with a wet weight of 0.54 ± 0.07 g were placed in 100 L tanks inside a polyethylene greenhouse during 84 days. Wet weight (g) was obtained each week and standard length once per month. Both species had a high survival rate with a relative condition factor close to 1, showing a length-weight relationship with an isometric growth, meaning that they were in good condition. A significant difference was found in growth (P < 0.05) from the second week, with a specific growth rate of 2.28 ± 0.07% day -1 for tilapia and 1.35 ± 0.02% day -1 for the native cichlid, tilapia reached twice the total weight gain than the native cichlid (31.26 ± 0.95 g; 83.70 ± 4.54 g). Food conversion rate was higher in tilapia than in H. cyanoguttatus . The survival rate of H. cyanoguttatus , as well as the relationship of isometric growth and condition factor of both species, suggests that H. cyanoguttatus has the ability to grow in aquaculture systems. Normal 0 false false false ES-MX JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:10.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-ansi-language:ES-MX; mso-fareast-language:JA;}

In vitro digestibility and proteases inhibitory effect of several feedstuffs for Parachromis dovii juveniles and P. dovii hybrid larvae.

Parachromis dovii, a native cichlid from Costa Rica, is highly appreciated for its size and flesh quality. Further, P. dovii easily accept inert feed from the beginning of exogenous feeding; however, its growth is low compared to live food. For this reason, evaluation of several feedstuffs using two in vitro techniques was done. The quantification of the in vitro inhibitory effect of seven plant ingredients on the alkaline protease activity was done using enzymatic extracts from larvae samples of 6, 15, 22 and 30days after hatching (DAH). The in vitro alkaline digestibility assays were run for six protein sources (from animal and plant origin) using the enzymatic extract from larvae 30 DAH. Independent of fish age, all plant feedstuffs reduced alkaline digestive proteases activity; however, the wheat flour (14.1% at 6 DAH, 33.4% at 15 DAH) and broken rice meal (51.6% at 22 DAH) showed the lowest inhibition percentage of alkaline digestive activity, whereas the highest inhibition percentage was found with soybean and palm kernel meals (92.5% at 30 DAH and 87.4%, respectively) (P<0.05). The alkaline proteases inhibition percentage of feedstuffs varied during larvae ontogeny. From six protein dietary sources tested, tankage and fish meal presented the highest in vitro digestibility values, 113.9 and 74.9%, respectively. Contrary, the lowest digestibility was found for blood and soybean meals (38.07 and 19.82%, respectively).

Contribution to the knowledge of the feeding and growth biology of the Iranian cichlid,Iranocichla hormuzensis

AbstractGrowth parameters and feeding indices, such as condition factor (CF), of the Iranian cichlid, Iranocichla hormuzensis, the only native cichlid of Iran, were investigated during the period between August 2008 and August 2009. The estimated b value (the slope in length–weight equation) for males and females was 2.94, which is not significantly different from 3 that is indicative of isometric growth (p > 0.05). There was a significant difference (p < 0.05) between mean CFs of males and females. Males in the length group of 56–85 mm showed a higher CF than those in smallest (46–55 mm) and largest (86–100 mm) length groups. A total of 432 guts (217 of males and 195 of females) were investigated during the thirteen-month study period. The mean gut length, gut weight, relative gut length (RGL) and relative gut mass were significantly higher for males than females (p < 0.05). The RGL of males ranged between 1.12 and 8.24 (5.31 ± 1.26) and that of females between 0.58 and 10.43 (4.55 ± 1.53). Although I. h...