[Ichthyology • 2026] Mesoaphyosemion izyarae • A New killifish Species (Cyprinodontiformes: Nothobranchiidae) from southern Equatorial Guinea

Mesoaphyosemion izyarae Ott, Sonnenberg & Van der Zee,

in Sonnenberg, Ott, Rodriguez, Olias, Martinez et Van der Zee, 2026. 

DOI: doi.org/10.11646/zootaxa.5759.4.5

Abstract

Mesoaphyosemion izyarae sp. nov., is described from a small left-bank tributary of the Mitemele River in southern Equatorial Guinea. The new species is distinguished from all other described Mesoaphyosemion species by a unique combination of male colouration characters: dorsal fin yellow with red streaks between fin rays; anal and pelvic fins yellow with black or dark red margin, basally light blue, caudal fin in centre black with red streaks between fin rays, broad yellow area on dorsal and ventral margin, body metallic light blue with more or regular rows of red dots on side, posteriorly denser and forming a reticulated pattern. The species status is supported by mtDNA analyses, including nine of the eleven described valid Mesoaphyosemion species.

Pisces, phylogeny, colour pattern, taxonomy, mtDNA, Rio Mitemele, Pleistocene rainforest refuge  

Mesoaphyosemion izyarae.
Male (1) and female (2) from the type locality, Rio Mveň basin, near the village of Efulan, Equatorial Guinea (not preserved). 

Mesoaphyosemion izyarae sp. nov., Ott, Sonnenberg & Van der Zee

Diagnosis. Mesoaphyosemion izyarae shares with other species of the genus a combination of the following characteristics in the male: a mostly metallic pale blue, blue or blue-green colouration on the sides; an often variable pattern of red dots on sides, in most species irregularly distributed, in others forming more or less regular stripes or blotches; a latero-ventral red line on the caudal peduncle; unpaired fins without, or with only short, fin extensions, caudal fin nearly straight, slightly rounded or weakly trilobate; no conspicuous markings on ventral side of the head; adults have a yellow snout. Unfortunately, none of these characteristics is diagnostic on its own as they are also known from other nothobranchiid genera or species groups but, in combination, they are significant.

Mesoaphyosemion izyarae is distinguished from all other known Mesoaphyosemion species by a unique combination of colour pattern features in the male: dorsal fin yellow with red streaks between fin rays; anal and pelvic fins yellow with black or dark red margin, basally light blue, caudal fin black in...

RAINER SONNENBERG, HEINZ OTT, ADOLFO GONZALEZ RODRIGUEZ, CARLOS VIZCAINO OLIAS, FRANCISCO PORTAL MARTINEZ and JOUKE R. VAN DER ZEE. 2026.  Description of Mesoaphyosemion izyarae (Cyprinodontiformes: Nothobranchiidae), A New killifish Species from southern Equatorial Guinea. Zootaxa. 5759(4); 453-463. DOI: doi.org/10.11646/zootaxa.5759.4.5 [2026-02-18]

[Ichthyology • 2025] Nothobranchius iridescens, N. marmoreus, ‘Lacustricola’ gemma, ... • Review of Cyprinodontiform Fishes in the Upper Congo Drainage with Descriptions of New Species of Seasonal Nothobranchius (Nothobranchiidae) and ‘Lacustricola’ Lampeye (Procatopodidae) in South-Eastern DR Congo

 

Nothobranchius iridescens, N. katemomandai, N. marmoreus, 
N. dubieensis, ‘Lacustricola’ gemma 

Nagy, 2025 

  

DOI: doi.org/10.70322/ecoldivers.2025.10006 

ABSTRACT

 The cyprinodontiform fish fauna of the Bangweulu–Mweru and Upper Lualaba freshwater ecoregions, situated in the uppermost Congo River drainage, has been reviewed. This study introduces four newly described species of seasonal Nothobranchius killifish and a novel species of lampeye belonging to the genus ‘Lacustricola’. Nothobranchius iridescens, new species, from the Kafila system in the Lufira drainage, is characterized in male colouration by anal fin with irregular red-brown spots and stripes, creating two irregular submedial and medial bands and with broad yellow subdistal band; and a caudal fin with a slender light blue subdistal band, densely marked with irregular red spots, and narrow dark brown distinct distal margin. Nothobranchius katemomandai, new species, from the Kay system in the upper Lualaba drainage, is characterized in male colouration by an anal fin with narrow brown submedial band, followed by a slender yellow band, a slender red-brown band and a slender dark brown distal band; and a caudal fin with brown spots proximally and medially, and with slender white to light blue subdistal band and a narrow dark grey distal band. Nothobranchius marmoreus, new species, from the Lufukwe system in the Lake Mweru basin, is characterized in male colouration by a body with irregular red-brown patches and stripes, forming a marble-like mottled pattern; and anal and caudal fins with slender yellow to amber subdistal band and broad dark brown distal band. Nothobranchius dubieensis, new species, from the Lubule system in the Luvua drainage, is characterized in male colouration by an anal fin with narrow dark brown submedial band, narrow yellow and orange medial bands, narrow white subdistal band, and slender dark brown distal band; and a caudal fin with irregular red-brown spots and stripes proximally and medially, followed by an irregular narrow red-brown subdistal band and slender white distal band, and with interrupted red-brown fin tips. ‘Lacustricola’ gemma, new species, from the Kay system in the upper Lualaba drainage, is characterized by a pattern of iridescent, diamond-shaped, light blue spots in scale centres below mid-longitudinal series on posteroventral portion of flank; median fins yellow to hyaline, with dark grey stripes perpendicular to fin rays; dorsal fin with light blue distinct margin; anal fin with dark grey margin. Analysis of mitochondrial COI gene sequences revealed that the five new species represent phylogenetically distinct lineages. These findings not only underscore their genetic uniqueness but also confirm their placement within the Nothobranchius brieni species group and the genus ‘Lacustricola’. Species of the genus Nothobranchius complete their seasonal life cycle in ephemeral natural habitats within freshwater wetlands, while ‘Lacustricola’ species migrate to breed in flooded areas of shallow, typically seasonal wetland habitats at the onset of the rainy season. These wetlands are highly vulnerable to a variety of human-induced stressors and threats, including agricultural cultivation, water extraction, urban expansion resulting in land-use pressure, and increased pollution, particularly from industrial activities such as mining. Therefore, it is essential to protect the integrity of these unique aquatic habitats throughout all the seasons of the year to maintain healthy wetland ecosystems and safeguard the distinctive seasonal freshwater biodiversity they support.

Keywords: Bangweulu–Mweru freshwater ecoregion; Barcoding; Conservation; Killifish; Upper Lualaba freshwater ecoregion

 Nothobranchius iridescens, New Species

Etymology. The specific epithet iridescens is a Latin participial adjective deriving from the ancient Greek word iris (ἶρις), rainbow, referring to the colourful appearance of the males, containing different colours of the rainbow, such as yellow and red in the fins, reflective blue on the body slightly shifting hue depending on the angle of light.

 Nothobranchius katemomandai, New Species

Etymology. The specific epithet is given in honour of friend Bauchet Katemo Manda, professor at the University of Lubumbashi, the discoverer of this species, for his dedication to the research of the ichthyofauna of the Democratic Republic of Congo. The exciting adventures and numerous challenges faced during joint research expeditions will always remain vivid memories.

 Nothobranchius marmoreus, New Species

Etymology. The specific epithet marmoreus is a Latin adjective deriving from the ancient Greek word marmaros (μάρμαρος) in the meaning of resembling marble, marblelike, and in reference to the irregularly mottled marbled colour pattern on the body of the males.

Nothobranchius dubieensis, New Species

Etymology. The specific name is given in reference to Dubie township in south-eastern DR Congo, near which place this species is found, and the type locality is situated. An adjective derived from the geographical name.

‘Lacustricola’ gemma, New Species

Etymology. The specific epithet gemma is derived from the ancient Greek word γέμω, originally meaning “precious stone” or “gem”. It refers to the pattern of the body scales, which are adorned with numerous iridescent, diamond-shaped markings, evoking the appearance of tiny gems. The name also alludes to the relatively small adult size of the species. It is treated as a noun in the nominative singular, standing in apposition to the generic name.

 

Béla Nagy. 2025. Review of Cyprinodontiform Fishes in the Upper Congo Drainage with Descriptions of Four New Species of Seasonal Nothobranchius (Nothobranchiidae) and a New Species of ‘Lacustricola’ Lampeye (Procatopodidae) in South-Eastern DR Congo. Ecol. Divers. 2(2), 10006. DOI: doi.org/10.70322/ecoldivers.2025.10006 

https://x.com/BaukaManda/status/1940645555790925893

[Ichthyology • 2021] Nothobranchius elucens • A New Species of Seasonal Killifish (Cyprinodontiformes: Nothobranchiidae) from the upper Nile drainage in Uganda

Nothobranchius elucens 

DOI:  10.11646/zootaxa.4915.1.10

Abstract

Nothobranchius elucens, new species, from a seasonal habitat in the Aringa system of the Achwa River in the upper Nile drainage in northern Uganda, is described. It belongs to the N. rubroreticulatus species group, whose members are characterised by male coloration of anal and caudal fins with slender light blue subdistal band and slender dark distal band. Nothobranchius elucens is distinguished from all other members of the genus by the following characters in males: body colouration golden-grey with brown scale margins creating irregular vertical stripes on trunk; anal fin yellow with brown spots proximally, with slender brown median band, followed by a slender light blue subdistal band and a slender black distal band; caudal fin brown proximally and medially, followed by a slender light blue subdistal band and a slender black distal band; dorsal fin golden with irregular brown stripes and narrow light blue subdistal band and with narrow black distal band. Furthermore, it differs from the closest known relative, N. taiti, also by the morphometric characters of having a smaller head length of 29.5–33.1 % SL; smaller prepectoral length of 31.2–33.9 % SL; greater head depth of 81–87 % HL; greater interorbital width of 43–49 % HL; and greater caudal peduncle length of 145–152 in % of its depth.

Keywords: Pisces, Achwa River drainage, Madi Opei area, upper Nile ecoregion

Nothobranchius elucens, new species

Béla Nagy. 2021. Nothobranchius elucens, A New Species of Seasonal Killifish from the upper Nile drainage in Uganda (Cyprinodontiformes: Nothobranchiidae). Zootaxa. 4915(1); 133–147. DOI:  10.11646/zootaxa.4915.1.10

[Ichthyology • 2018] Three New Endemic Aphyosemion Species (Cyprinodontiformes: Nothobranchiidae) from the Massif du Chaillu in the upper Louessé River system, Republic of the Congo; ‘Aphyosemion’ cyanoflavum, ‘A’. mandoroense & ‘A’. cryptum

‘Aphyosemion’ cyanoflavum

 van der Zee, Walsh, Mikembi, Jonker, Alexandre & Sonnenberg, 2018

DOI: 10.11646/zootaxa.4369.1.3  

Abstract

Three new ‘Aphyosemion’ species are described from the upper Louessé River in the Massif du Chaillu, Republic of the Congo, based on a combination of DNA, habitat preference, male colour pattern, and morphological data. ‘Aphyosemion’ cyanoflavum, new species, is a member of the ‘A’. ogoense group. It differs from its congeners by a unique colour pattern and cephalic sensory system which contains a wide supra-orbital groove with large, densely pigmented anterior neuromasts and dark frontal neuromasts housed in one pit with one central anterior lobe. ‘Aphyosemion’ mandoroense, new species, and ‘A’. cryptum, new species, are members of the ‘A’. coeleste group. ‘Aphyosemion’ cryptum, new species, is in appearance very similar to ‘A’. coeleste, but lacks the typical post opercular metallic green blotch and is generally larger in body size. Initial DNA analyses demonstrate that ‘A’. cryptum, new species, is more closely related to ‘A’. mandoroense, new species, than to ‘A’. coeleste, despite similarity in appearance. ‘Aphyosemion’ cryptum, new species, and ‘A’. coeleste occur syntopic in several locations in a sub-catchment of the upper Louessé system, however differ in microhabitat preference. ‘Aphyosemion’ mandoroense, new species, differs by male body and fin colour pattern from all species of the ‘A’. coeleste group except ‘A’. citrineipinnis. From the latter, it can be distinguished by the absence of red pigmentation and a dark grey to black margin in the unpaired fins.

Keywords: Pisces, Cyprinodontiformes, Nothobranchiidae

 

Jouke van der Zee, Gina Walsh, Valdie N. Boukaka Mikembi, Michael N. Jonker, Marco P. Alexandre and Rainer Sonnenberg. 2018. Three New Endemic Aphyosemion Species (Cyprinodontiformes: Nothobranchiidae) from the Massif du Chaillu in the upper Louessé River system, Republic of the Congo. Zootaxa. 4369(1); 63–92. DOI: 10.11646/zootaxa.4369.1.3

[Ichthyology • 2014] Nothobranchius chochamandai • A New Species of Annual Killifish (Cyprinodontiformes: Nothobranchiidae) from the Luapula drainage, Democratic Republic of Congo

Nothobranchius chochamandai Nagy, 2014

Nothobranchius chochamandai, new species, is described from ephemeral swamps of the Kinikabwimba River, tributary of Lufutishi River in the lower Luapula drainage in Katanga province of Democratic Republic of Congo. It is identified as belonging to the N. brieni species-group of which it shows the diagnostic characters in males: proximal portion of caudal and anal fins spotted; dorsal fin lacking dark distal margin; head without dark spots and scales without a black posterior margin. Nothobranchius chochamandai is distinguished from all other species of this species-group by the unique combination of the following characters in males: caudal and anal fins with light blue distal margins and without a submarginal band; dorsal fin without a light blue distal margin; postorbital length 56-60 % HL; snout length 16-19 % HL; head width 65-69 % of its depth, and caudal peduncle length 135-142 % of its depth.

Nothobranchius chochamandai, male (photograph by B. Nagy) 

Béla Nagy. 2014. Nothobranchius chochamandai, A New Species of Annual Killifish from the Luapula drainage, Democratic Republic of Congo (Cyprinodontiformes: Nothobranchiidae). 

 Ichthyol. Explor. Freshwaters. 25(2); 167-183.