Expression variations in ectodysplasin-A gene (eda) may contribute to morphological divergence of scales in haplochromine cichlids

Background Elasmoid scales are one of the most common dermal appendages and can be found in almost all species of bony fish differing greatly in their shape. Whilst the genetic underpinnings behind elasmoid scale development have been investigated, not much is known about the mechanisms involved in moulding of scales. To investigate the links between gene expression differences and morphological divergence, we inferred shape variation of scales from two different areas of the body (anterior and posterior) stemming from ten haplochromine cichlid species from different origins (Lake Tanganyika, Lake Malawi, Lake Victoria and riverine). Additionally, we investigated transcriptional differences of a set of genes known to be involved in scale development and morphogenesis in fish. Results We found that scales from the anterior and posterior part of the body strongly differ in their overall shape, and a separate look on scales from each body part revealed similar trajectories of shape differences considering the lake origin of single investigated species. Above all, nine as well as 11 out of 16 target genes showed expression differences between the lakes for the anterior and posterior dataset, respectively. Whereas in posterior scales four genes (dlx5, eda, rankl and shh) revealed significant correlations between expression and morphological differentiation, in anterior scales only one gene (eda) showed such a correlation. Furthermore, eda displayed the most significant expression difference between species of Lake Tanganyika and species of the other two younger lakes. Finally, we found genetic differences in downstream regions of eda gene (e.g., in the eda-tnfsf13b inter-genic region) that are associated with observed expression differences. This is reminiscent of a genetic difference in the eda-tnfsf13b inter-genic region which leads to gain or loss of armour plates in stickleback. Conclusion These findings provide evidence for cross-species transcriptional differences of an important morphogenetic factor, eda, which is involved in formation of ectodermal appendages. These expression differences appeared to be associated with morphological differences observed in the scales of haplochromine cichlids indicating potential role of eda mediated signal in divergent scale morphogenesis in fish.Peer reviewe

Transcriptomics unravels molecular players shaping dorsal lip hypertrophy in the vacuum cleaner cichlid, Gnathochromis permaxillaris

BackgroundTeleosts display a spectacular diversity of craniofacial adaptations that often mediates ecological specializations. A considerable amount of research has revealed molecular players underlying skeletal craniofacial morphologies, but less is known about soft craniofacial phenotypes. Here we focus on an example of lip hypertrophy in the benthivorous Lake Tangnayika cichlid, Gnathochromis permaxillaris, considered to be a morphological adaptation to extract invertebrates out of the uppermost layer of mud bottom. We investigate the molecular and regulatory basis of lip hypertrophy in G. permaxillaris using a comparative transcriptomic approach.ResultsWe identified a gene regulatory network involved in tissue overgrowth and cellular hypertrophy, potentially associated with the formation of a locally restricted hypertrophic lip in a teleost fish species. Of particular interest were the increased expression level of apoda and fhl2, as well as reduced expression of cyp1a, gimap8, lama5 and rasal3, in the hypertrophic lip region which have been implicated in lip formation in other vertebrates. Among the predicted upstream transcription factors, we found reduced expression of foxp1 in the hypertrophic lip region, which is known to act as repressor of cell growth and proliferation, and its function has been associated with hypertrophy of upper lip in human.ConclusionOur results provide a genetic foundation for future studies of molecular players shaping soft and exaggerated, but locally restricted, craniofacial morphological changes in fish and perhaps across vertebrates. In the future, we advocate integrating gene regulatory networks of various craniofacial phenotypes to understand how they collectively govern trophic and behavioural adaptations.Peer reviewe

Invasionserfolg der Regenbogenforelle (Oncorhynchus mykiss) in Österreich : Modellierung der Ursachen, die diesen beeinflussen

Die aus Nordamerika stammende Regenbogenforelle (Oncorhynchus mykiss) ist der am weitesten verbreitete Lachsfisch und wurde weltweit in mindestens 97 Staaten eingeführt, so auch in Europa Ende des 19ten Jahrhunderts. Heute ist sie ein wesentlicher Bestandteil der Fischgemeinschaft in der alpinen Region. Ihr Reproduktionserfolg und ihre invasive Ausbreitung in Österreich fand jedoch international kaum Beachtung. In dieser Arbeit werden die Ergebnisse von 940 Befischungen, mit zumindest einer von 3 untersuchten Salmonidenarten, aus den Jahren 1991-2010 zusammengefasst. Insgesamt wurden dabei 86.437 Bachforellen (Salmo trutta), 12.132 Äschen (Thymallus thymallus) und 14.021 Regenbogenforellen gefangen. Bei 803 (85%) Befischungen wurden 36.597 juvenile Bachforellen, bei 203 (22%) Befischungen 3.387 juv. Äschen und bei 317 (34%) Befischungen 4.667 juv. Regenbogenforellen gefangen. Etablierte Populationen (zumindest 3 gleichzeitig vorhandene Jahrgänge) konnten von Bachforellen an 736 (78%), von Äschen an 135 (14%) und von Regenbogenforellen an 231 (25%) Stellen gefunden werden. Logistische Modelle testen verschiedene hydrologische, abiotische und biotische Variablen auf ihre Vorhersagekraft hinsichtlich des Invasionserfolges der Regenbogenforelle in Österreich. Hydrologische Variablen welche mit dem zeitlichen Auftreten, der Dauer und der Variabilität von Hochwasserereignissen zusammenhängen, können den Invasionserfolg mit einer Wahrscheinlichkeit von bis zu 75% vorhersagen. Anhand weiterer Variablen wie der Wassertemperatur, der Seehöhe und der Anwesenheit anderer Salmoniden erreicht die Vorhersagekraft der Modelle 92%. Adulte Äschen haben sich aufgrund überlappender Lebensraumansprüche als Indikator für geeignete Regenbogenforellenhabitate herausgestellt. Diese sind vor allem von Kalkgestein dominierte geologische Regionen zwischen 300 und 600m Seehöhe, welche mittlere Wassertemperaturen von 3,5C im Jänner, 12,5C im Juli und 7,9C über das Jahr gesehen aufweisen.The rainbow trout Oncorhynchus mykiss has been introduced in at least 97 countries and thus is the most broadly distributed salmonid fish in the world. Native to North America, it was introduced to Europe at the end of the 19th century. Today, the rainbow trout is a significant component of many fish communities in the alpine region. Nonetheless, their reproductive success and invasive spread has gained little international attention. Here, I summarize quantitative fishing data from 940 sites, each of which had at least one of three salmonid fishes present. Between 1991 and 2010 a total of 86,437 brown trout Salmo trutta, 12,132 grayling Thymallus thymallus and 14,021 rainbow trout were caught. A total of 803 (85%) sites contained juvenile brown trout (N = 36,597), 203 (22%) sites juvenile grayling (N = 3,387) and 317 (34%) sites juvenile rainbow trout. Based on the presence of at least three year classes, brown trout were established in 736 (78%) sites, grayling in 135 (14%) sites and rainbow trout in 231 (25%) sites. A series of logistic regression models tested the predictive power of various hydrological, landscape and biotic variables in predicting the successful invasion of rainbow trout in Austrian rivers. Hydrological variables involving flood frequency, timing, duration and overall variability predicted the invasive success of the rainbow trout correctly with a probability of up to 75%. By including further variables like water temperature, altitude and the presence of other salmonids, the predictive power of the models reached 92%. The presence of adult grayling proved to be a good indicator of suitable habitat for rainbow trout, reflecting the very similar habitat requirements of these two species. Particular geological regions, mostly dominated by limestone deposits, between 300 and 600 meters above sea level with mean water temperatures of 3.5C in January, 12.5C in July and 7.9C annually represented suitable habitat for rainbow trout.vorgelegt von Wolfgang GesslZsfassung in dt. und engl. SpracheGraz, Univ., Masterarb., 2012(VLID)22516

Appetite regulating genes may contribute to herbivory versus carnivory trophic divergence in haplochromine cichlids

Feeding is a complex behaviour comprised of satiety control, foraging, ingestion and subsequent digestion. Cichlids from the East African Great Lakes are renowned for their diverse trophic specializations, largely predicated on highly variable jaw morphologies. Thus, most research has focused on dissecting the genetic, morphological and regulatory basis of jaw and teeth development in these species. Here for the first time we explore another aspect of feeding, the regulation of appetite related genes that are expressed in the brain and control satiety in cichlid fishes. Using qPCR analysis, we first validate stably expressed reference genes in the brain of six haplochromine cichlid species at the end of larval development prior to foraging. We next evaluate the expression of 16 appetite related genes in herbivorous and carnivorous species from the parallel radiations of Lake Tanganyika, Malawi and Victoria. Interestingly, we find increased expression of two appetite-regulating genes (anorodgenic genes), cart and npy2r, in the brain of carnivorous species in all the three lakes. This supports the notion that appetite gene regulation might play a part in determining trophic niche specialization in divergent cichlid species, already prior to exposure to different diets. Our study contributes to the limited body of knowledge on the neurological circuitry that controls feeding transitions and adaptations in cichlids and other teleosts.Peer reviewe

Divergence in larval jaw gene expression reflects differential trophic adaptation in haplochromine cichlids prior to foraging

Peer reviewe

Maternal mRNA input of growth and stress-response-related genes in cichlids in relation to egg size and trophic specialization

Background: Egg size represents an important form of maternal effect determined by a complex interplay of long-term adaptation and short-term plasticity balancing egg size with brood size. Haplochromine cichlids are maternal mouthbrooders showing differential parental investment in different species, manifested in great variation in egg size, brood size and duration of maternal care. Little is known about maternally determined molecular characters of eggs in fishes and their relation to egg size and trophic specialization. Here we investigate maternal mRNA inputs of selected growth- and stress-related genes in eggs of mouthbrooding cichlid fishes adapted to different trophic niches from Lake Tanganyika, Lake Malawi, Lake Victoria and compare them to their riverine allies. Results: We first identified two reference genes, atf7ip and mid1ip1, to be suitable for cross-species quantification of mRNA abundance via qRT-PCR in the cichlid eggs. Using these reference genes, we found substantial variation in maternal mRNA input for a set of candidate genes related to growth and stress response across species and lakes. We observed negative correlation of mRNA abundance between two of growth hormone receptor paralogs (ghr1 and ghr2) across all haplochromine cichlid species which also differentiate the species in the two younger lakes, Malawi and Lake Victoria, from those in Lake Tanganyika and ancestral riverine species. Furthermore, we found correlations between egg size and maternal mRNA abundance of two growth-related genes igf2 and ghr2 across the haplochromine cichlids as well as distinct clustering of the species based on their trophic specialization using maternal mRNA abundance of five genes (ghr1, ghr2, igf2, gr and sgk1). Conclusions: These findings indicate that variations in egg size in closely related cichlid species can be linked to differences in maternal RNA deposition of key growth-related genes. In addition, the cichlid species with contrasting trophic specialization deposit different levels of maternal mRNAs in their eggs for particular growth-related genes; however, it is unclear whether such differences contribute to differential morphogenesis at later stages of development. Our results provide first insights into this aspect of gene activation, as a basis for future studies targeting their role during ecomorphological specialization and adaptive radiation

New data on Garra makiensis (Cyprinidae, Labeoinae) from the Awash River (Ethiopia) with remarks on its relationships to congeners on the Arabian Peninsula

On the African continent, the genus Garra consists of several species often insufficiently separated from each other by diagnostic characters. Herein, a detailed morphological redescription of Garra makiensis from the Awash River drainage is presented, together with additional data on the type specimens of G. makiensis and G. rothschildi. Mitochondrial CO1 sequence data are also provided, including the historic paralectotype of G. makiensis, with a comparison to Garra species from Africa and the Middle East. Based on these sequences, G. makiensis clusters outside the group of African congeners and is a sister lineage to species from the south-east of the Arabian Peninsula. Although morphologically variable, G. makiensis is characterised by having a single unbranched pectoral-fin ray, a short distance between vent and anal-fin origin (7.3–19.7 % of pelvic – anal distance), chest and belly covered with scales, and a prominent axillary scale at base of pelvic fin (18.8–35.5 % of pelvic-fin length)

Conserved Molecular Players Involved in Human Nose Morphogenesis Underlie Evolution of the Exaggerated Snout Phenotype in Cichlids

Instances of repeated evolution of novel phenotypes can shed light on the conserved molecular mechanisms underlying morphological diversity. A rare example of an exaggerated soft tissue phenotype is the formation of a snout flap in fishes. This tissue flap develops from the upper lip and has evolved in one cichlid genus from Lake Malawi and one genus from Lake Tanganyika. To investigate the molecular basis of snout flap convergence, we used mRNA sequencing to compare two species with snout flap to their close relatives without snout flaps from each lake. Our analysis identified 201 genes that were repeatedly differentially expressed between species with and without snout flap in both lakes, suggesting shared pathways, even though the flaps serve different functions. Shared expressed genes are involved in proline and hydroxyproline metabolism, which have been linked to human skin and facial deformities. Additionally, we found enrichment for transcription factor binding sites at upstream regulatory sequences of differentially expressed genes. Among the enriched transcription factors were members of the FOX transcription factor family, especially foxf1 and foxa2, which showed an increased expression in the flapped snout. Both of these factors are linked to nose morphogenesis in mammals. We also found ap4 (tfap4), a transcription factor showing reduced expression in the flapped snout with an unknown role in craniofacial soft tissue development. As genes involved in cichlid snout flap development are associated with human midline facial dysmorphologies, our findings hint at the conservation of genes involved in midline patterning across distant evolutionary lineages of vertebrates, although further functional studies are required to confirm this.Peer reviewe

Radiofrequenzablation von Schilddrüsenknoten : Good Clinical Practice Empfehlungen

(VLID)359991