Synodontis

Richter, Helga, 2024, A New Species of Synodontis (Mochokidae) from the Congo River Basin with Notes on Its Ecological Adaptations, FishTaxa 34, pp. 12-22 : 16-19

publication ID

https://doi.org/10.5281/zenodo.16975742

DOI

https://doi.org/10.5281/zenodo.17228263

persistent identifier

https://treatment.plazi.org/id/03C8879A-FC66-1F77-FFF1-FB12B134FF3D

treatment provided by

Felipe

scientific name

Synodontis
status

 

Ecological View in CoL Adaptations

The newly discovered species of Synodontis from the Congo River Basin provides specific examples of an impressive number of ecological preadaptation’s that allow this fish to exist in conditions that are clearly anomalous for it in the Congo River Basin. The Coco that is among the most productive and geologically varied international River is energetic with giant rapids, and huge channels, and varying turbidity degree ( Figure 1 View Figure 1 ). Such conditions have led to specialization in many aspects of the aquatic lives giving rise to this new Synodontis species. Morphological, behavioural and physiological adaptations need to be described, and all these changes are strongly related to the hydrological and ecological constraints of the river habitat. Morphologically the new Synodontis species, has characters which would enable it to survive in water currents that have high velocity. It has a thin shaped body that enables it to reduce drag and maneuver in position within areas of highwater currents. Also, pectoral and pelvic fins are altered to be useful for the purpose of substrate fixation coupled with a firm spine support while into rocky stream beds, movements are most vigorous due to high currents. It has been found that these adaptations minimize energy use in locomotion and allow the fish occupy territories that remain unreachable for less adaptive other species. The species also has fairly developed sensory organs, for instance extensively developed barbels which are paramount in searching for food in water where illumination is low. These are adaptations that help the species acquire its prey and compromise fluid movement in the various areas even in difficult weather. The feeding behaviour of the species also points towards its ecological adaptations. Gut contents combined with behavioural observations suggest that they indeed feed mainly on bottom-dwelling invertebrates and detritus that are easily found at the river bottom. Its teeth and jaws designed to differentiate it from other fish allows it to scrape algae and biofilm off surfaces or crush mollusacking its beak like hard-shell prey. Such feeding versatility is useful in that resources are known to go through change in availability within a specific area. It thereby guarantees that the species feeds on as many resources as possible making it very flexible to any changes on the environment. Physiologically, the species has characteristics that may help them live in the oxygen fluctuating waters that characterize the fast-flowing rivers. These requirements, for example, enlarged gill surface area as well as appropriate mechanism for oxygen uptake maintenance are essential for meeting metabolism demand in water environments with low DO levels variation. Also, the fact that most of the fish possess swim bladders to control their buoyancy is an adaptation and a key to occupy different micro habitats including the deeper channels, sometimes the shallower rapids too. Some of the other unique physical changes which have been proved to be very useful to this Synodontis species are the behavioral adaptations. Inferences given about it indicate that it is a nocturnal species and movement during the day has few competitors and predators. These behavioural characteristics compounded with camouflaging colouration increases its foraging efficiency and predation avoidance. It’s body colour is also suitable for a mottled pattern designed to hide well just like rocks on the bottom of the sea and this makes it survive well in its environment that is dominated by predators. All these ecological adaptations point at effects of the changes that came with evolution due to the abiotic factors present in the Congo River. They especially emphasize interactions of species with their surroundings, pointing at the influence of the outside world on the species’ variety. The analysis of these adaptations also helps to expand the knowledge of Synodontis species and at the same time stresses the need to preserve the extraordinary habitats of the Congo River Basin moving peacefully into the future. The environment in the Congo River presents a number of unique and difficult challenges thus specific adaptations are seen in S. congolensis and thus it is clearly an ecologically successful species. These drawbacks are: a dorsoventrally flattened head and body enables it to deal with opposes currents with ease. The long bristles called barbels act like feelers to definitely locate its pray especially when water is murky hence common in rivers. The feeding ecology studies show that S. congolensis is a generalized, or perhaps an opportunistic omnivore. Gut content analysis revealed that experiential diet included invertebrates, detritus, algae and small fish. Because of this, the species is capable of utilizing a variety of foods in the ecosystem which minimizese competition with the other related species in the same environment. According to Mang_SAMPLES9, the strong saw like margins in the dorsal and pectoral fins are thought to discourage predators, in addition the loose lobe like or forked caudal fin facilitates rapid manoeuvring through crevices in rocks typical of their habitat.

Discovery and Habitat

The new species was discovered in a fast-flowing part of the Congo River where the water is both deep and rocky bottomed. The area has remained relatively unstudied because access is limited and the physical environment features fluctuating water levels, irregular flow, and a range of micro-sites. Such conditions explain the intensity of endemism in aquatic fauna populations, which has initially been mentioned. The new species described here inhabits a range of substrata, including large coarse gravel and rocky areas with some sandy and muddy patches. Submerged roots and overhanging vegetation along the riverbanks supply more cover than aquatic plants, which are absent of the area. The physico-chemical characteristics and water quality at the collection sites were as follows; pH 6.5-7.2, DO> 6mg /L and temperature 22-27 o C. These conditions are characteristic of a relatively young and whether, oxygen-containing environment.

Morphological Description

The newly identified species, which is provisionally known as Synodontis congolensis, is dorso-ventrally compressed, reflecting a life style on fast water currents. Its standard length is between 80 and 120 mm and the head are more broad than its scape and slightly dorsoventrately compressed. The colouration is also propitious; dorsum is dark brown or black and there are irregular lighter spots which join up at the lateral side. The ventral side is paler, which has the desired balance of illumination against potential opponents. Diagnostic features of S. congolensis include three pairs of barbels: One set of maxillary barbels and two set of mandibular barbels are developed in the larvae of this species. The maxillary barbels are long and surpass in length the pectoral fins; these are glandular and are not bifid as seen the related species. Both the pectoral and the dorsal fins have a strong, sharp spine which is fully developed and a general trait of Synodontis genus concerning its predator's repellent part. The fork-like caudal fin is useful for operation in choppy waters to produce quick and delicate movements. Another characteristic shard with dentition in S. congolensis where premaxillary toothpads are comparatively wider and more rounded than most of its related species as per the nutritional habits of the specific species.

Genetic Distinctiveness

COI sequences further endorse the genetic isolation of S. congolensis ( Figure 2 View Figure 2 ). The species has about 8.5 % genetic difference from its nearest neighbour, Synodontis schoutedeni – a distance that puts this population over a standard genetic threshold of 2% that defines species boundaries among fish. The phylogram generated through maximum likelihood and Bayesian inference supports the idea of S. congolensis as a new species and it is positioned at a sister relationship with S. schoutedeni.

Behavioural Observations

The field observations show that S. congolensis has more nocturnal activity; the animals that inhabits rocky piles forage at dusk and during night on the river bed. During the day, the animals are usually seen in houses or behind crevices or any underwater structure that will keep them out of the reach of any natural enemies. Juveniles of the species show schooling behaviour, which may mean that the species is protective when in groups. Adolescents, on the other hand, are more independent, perhaps because they are territorial or feed differently.

Comparisons with Related Species

The two corresponding forms, S. schoutedeni and S. nigrita, are nearer to S. congolensis, but they present some character differences ( Figure 3 View Figure 3 ). In terms of morphology, the head of the S. schoutedeni is more rounded and the animal lacks the kind of spotting that is distinguishably seen with S. congolensis. From the discussed earlier genetic assessments show that there is a clear and very substantial sequence variation between the species as well. Morphologically, S. nigrita resides in waters with slower currents and muddy bottoms, while S. congolensis is associated with fast water currents and rocky substrates. Such differences called attention to the specialization of the new species in terms of its geographical location and the partitioning of resources it obtained within the genus. Recent described Synodontis from the Congo River Basin portrays certain morphological features different from other Syno-dontis species within the family Mochokidae . The Genus Synodontis or squeaker or upside-down catfish is rich and diverse, with several species spread across various freshwater ecologies in Africa. However, the complex and sectional habitat of the Congo River Basin has led to adaptation of different structural, functional and physiological characteristics in the species. Specifically, comparisons with other species suggest important clues as to what selective forces may have been operating on this new species and how best to characterize it. Of these features, the most blatant is probably the alterations of the body structures of the new species. Contrary to its congeners, the species that are distinguished by merger, the fin ray counts, especially the dorsal and caudal, as well as, the body size and proportion. The features of body and particularly the organization of pectoral fin spines suitable for holding on fast water are different from species inhabiting slow or still water. These spines are, however, stronger and have an inclined design for ability to maneuver through the high power rapids of Congo River. Thus, while synodontis, typically habitat in quiet waters, have relatively less developed fins because of the lower forces at work. Coloration and patterning of the new species also differ from that of its congenerics and have adaptive functions. Due to its irregular skin patterning, the sexual selection of L. Lombardi has a cryptic element that enables the snake to camouflage with rocks and, therefore, escape from predators. This is in contrast to fishes such as Synodontis decorus which displays conspicuous spots and bars and which may be well adapted for murkier and vegetation filled water bodies where such body expressions may serve to break up the visual silhouette of the fish. In terms of ecology, the new species is unusual in respect to feeding characteristics and diet events relative to congeners. While many Synodontis species are opportunisitic omnivores that can utilize a broad assemblage of prey items, this species is adapted to feed on benthos. Its jaw skeleton and teeth are adapted for the scraping of biofilm algae and small invertebrates from surfaces, which is a needed foraging strategy that is less apparent in individuals in sedimentbased and vegetation-supported environments. For example, Synodontis eupterus with broader geographical distribution as a species has more generalized morphology of the feeding apparatus and feeds not only on benthos but also detritus and plankton. This is further made clear by the behavioural differences that help to define the new species. Makach was confident that it is indeed a nocturnal creature, and that suggests its preference for the deeper and faster water channels. On the other hand, there are forms which include Synodontis multipunctatus from lake and slow-moving water species that are active during the day, differing in social and reproduction behaviors. It also differs from related species, which it identified with rowing eggs or buried larval substrate spawning. Molecular data support the recognition of the species: 12S/16S rRNA gene sequences indicate that the species is highly divergent from closely related Synodontis spp. Such differences reflect the large time of isolation and the specific adaptation of this species to the conditions of the Congo River Basin. Therefore, related species’ analysis shows the distinct morphological, ecological, and behavioural features of the new Synodontis species. These differences illustrate how the rapidly changing environment of the Congo River has presented evolutionary challenges and signifying the value of protecting this as a centre of endemism to ensure the conservation of these species’ particular adaptations and evolution.

Conservation Implications

While the habitat of S. congolensis seems pretty natural though largely wooded, the Congo River Basin continues to undergo immense pressure from human activities such as: deforestation, mining, and construction of hydro-power dams. Such activities may result to deterioration of habitat structure, changes in water flow, water pollution which may cause some impacts on the riverine apo fauna. Due to the narrowly defined habitat preference for S. congolensis and dependence on specific features, it may be quite sensitive to environmental changes. Further , lack of exhaustive population data calls for further evaluation of fish populations and protection of habitats and land utilization that are ecologically sustainable to support the survival of this and other species in the basin. People's involvement shall also be made necessary since their lives depend on the river and therefore, they shall be closely involved in the conservation processes. The identification of a new Synodontis species in the Congo River Basin teaches us a valuable lesson of the need to protect this diverse and valuable area. The Congo River Basin of central Africa is second only in size to the Amazon in South America , and like most large river systems, sustains an incredibly rich and diverse fish fauna, the majority of which are endemic, which means that they are not known to occur elsewhere. This water basin is characterized by the constantly changing currents, deep water zones, and annually inundated floodplains, producing high levels of species richness. Yet , habitat destruction, pollution, overfishing, climate change among others are harsh realities and they lean heavily on the ecological health of the seas and oceans. The newly discovered Synodontis species provides an opportunity to understand the susceptible nature of specialized organisms in relation to altered environment. Those physical characteristics that include the use of fast currents, special type of feeding, and other features related with its habitat render it as one of the most sensitive species to disturbance. Things like building dams and changing the channel of rivers hinder the natural form and take away habitats where these species for example, can be found. They split populations of organisms, restrict access to spawn sites and decrease water availability and quality – all of which results in loss of habitats. This means that species although have the ability to undergo developmental changes that are gradual but may affect the species a lot and lead to endangerment or even extinction of species that are ecologically sensitive species. Habu also notes that pollution is a major threat to Congo River Basin in Africa. Water pollution resulting from industrial waste, agricultural drainage or raw sewage increases the risk of aquatic life health. Due to feeding on bottom debris, the new Synodontis species is vulnerable to risks that may be associated with bioaccumulation of toxins in the benthic region. Furthermore, overfishing that is sustained by the locals, as well as by the international market, threatens fish populations. Target-specific and incidental fishing of species like Synodontis , which are food-security fish in most African countries, may lead to declines in stock abundance and disruption of the ecosystem. These threats are further aggravated by climate change, particularly increased temperatures and changes in the timing, amount and intensity of rainfall that affects the rivers. Alterations in water temperature and dissolved oxygen concentration are able to alter the physiology and geographical location of water living organisms. They undergo changes in floodplain management, fluctuating water levels and seasons affecting their breeding and feeding patterns, forcing species to their limits. Conservation measures for the Congo River Basin have to focus on acting toward the protection of habitats, including controlling the pollution of natural resources and the rational use of natural resources. Creation of protected areas and impose restriction measures against habitat degradation is the initial approach necessary for its achievement. Multilateral approach is appropriate crucial because the basin cuts across a number of countries, and therefore there is need to have a harmonized approach to conservation and management. It is also crucial to imply inhabitants into the process because people remain reliant on the river as an essential source of their income. Non-governmental conservation strategies can involve education campaigns and participants in sustainable fishing and pollution fights along with financial and initiative motivators for restoring damaged ecosystems. The two principal processes that are crucial in the conservation of the Bio diversity are research and monitoring. This new Synodontis species proves the existence of the basin and is a clear indication that more research and documentation is needed among this basin. Speciesspecific and distribution databases offer considerable information that can inform conservation efforts. Besides, stimulating tourism and other forms of sustainable development might help to secure funding and permanent action towards the aims of protection.

Kingdom

Animalia

Phylum

Chordata

Order

Siluriformes

Family

Mochokidae

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