THE NOTHOBRANCHIUS SITE

ZFMK 13927, holotype, male, 50.0 mm SL; Tanzania: swamp between Mtanza and the north entrance of the Selous Game Reserve, (approx. 07°51' S, 38°25' E), G. Eggers, C. Kasselmann & L. Seegers, 31 Dec 1980. [but not received, as per Herder et al., 2010, pers. comm., 2019]

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Neotype. MRAC A0-071-P-0019, male, 92.5 mm SL; Tanzania: Rufiji drainage: pool on immediate north side of road, 53 km east of Selous Game Reserve east gate (Mtemere) on road to Kibiti, 2.7 km west of Kikongono village centre and 19 km west of road junction (to Kibiti) at Mkongo village, 07°52.3' S, 38°36.0' E; B. Watters, R. Wildekamp & I. Sainthouse, 10 Jun 1995, [field code: Kikongono TAN 95-9] (Watters et al., 2020).

MRAC A0-071-P-0020-0021 (2), MRAC A0-071-P-0412-0415 and 0001-0003 (7), MRAC 2019.016.P.0004-5 (2), MRAC 2019.016.P.0006 (1), MRAC 2019.016.P.0011-0013 (3), MRAC 2019.016.P.0007-0010 (4)

Paranothobranchius ocellatus is most closely related to N. microlepis. There are similarities in the high number of small scales and the coloration. Differences in coloration includes that N. microlepis shows a vertical black stripe through the eye, which P. ocellatus lack, and also that the latter has the eye spots in the caudal fin base, which in turn N. microlepis lack. However, this species is much more compressed and higher in body shape and almost bull-shaped whereas P. ocellatus is almost pike-shaped (translated from Seegers, 1985).

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Nothobranchius ocellatus is distinguished from all other congeners, except Nothobranchius matanduensis, by a sagittiform shape, including relatively long head with depressed and pointed snout, and lower jaw markedly extended; male colouration pale blue to blue-grey on the sides, with moderately dense irregular pattern of dark red-brown and relatively sparse black spots on the head and anterior part of the body; grey caudal fin with white to light blue subdistal band and black distal margin; scales irregularly arranged on flank; scales extending on proximal and medial zones of caudal-fin in males; anal fin with brick-red or red-brown, with light magenta hue, proximal and medial parts grading distally to grey; pelvic-fin bases separated by interspace; presence of an ocellus or multiple ocelli on middle part of basal portion of caudal fin in adult females and in juveniles of both sexes.

 Males of N. ocellatus differ from those of N. matanduensis by moderately dense, irregular pattern of dark red-brown (vs. very dark grey to black) spots on head, operculum and branchiostegal membrane; head blue-green to grey (vs. light blue-green or bronze to grey); red-brown scale margins on trunk and head (vs. grey to grey-brown); dorsal fin blue green with irregular red-brown spots (vs. light grey to weak blue-green with irregular black and grey spots); greater head width (56-64 vs. 55, respectively); and smaller number of scales in mid-longitudinal series (39-41 vs. 42, respectively); and differences in the cephalic sensory system (Watters et al., 2020).

Subgenus: Paranothobranchius

This species was established as Paranothobranchius ocellatus by Seegers in 1985, belonging to that monotypic genus. Wildekamp and Haas (1992) assigned Paranothobranchius as a subgenus in Nothobranchius, including also N. bojiensis, N. fasciatus and N. microlepis, which latter three species were thought to form a monophyletic sister group within the subgenus. Costa (2018) confirmed N. ocellatus as belonging to the subgenus Paranothobranchius and separated from the other three species, which in turn were assigned to a newly created subgenus Cynobranchius. Molecular study further confirms the subgenus status of Paranothobranchius within the genus Nothobranchius (Watters et al. 2020).

The original description by Seegers (1985) was based on a preserved immature male specimen designated as the holotype that formed the primary basis for the description, and on a photograph of a non-preserved female specimen. However, the museum holdings and records of the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK) in Bonn indicate that the holotype specimen was in fact never received by the museum (Herder et al. 2010) and the holotype is considered as lost. The species was redescribed in detail by Watters et al. (2020), and a neotype was designated from a site near the original type locality.

Further, combined morphometric and molecular analyses from disjunct populations in the Matandu River system, previously regarded as belonging to N. ocellatus, belong to a distinct species described as N. matanduensis by Watters, Nagy & Bellstedt in Watters et al. (2020).

"Sumpf zwischen Mtanza und dem Nordeingang des Selous Game Reserve, nördlich des Rufiji, Ost-Tanzania, Ostafrika."

[Tanzania: swamp between Mtanza and the north entrance of the Selous Game Reserve, (approx. 07°51' S, 38°25' E).]

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Tanzania: Rufiji drainage: pool on immediate north side of road, 53 km east of Selous Game Reserve east gate (Mtemere) on road to Kibiti, 2.7 km west of Kikongono village centre and 19 km west of road junction (to Kibiti) at Mkongo village, 07°52.3' S, 38°36.0' E.

This species is endemic to seasonal freshwater habitats in coastal Tanzania. It is known from seasonal pools and swamps on floodplains in the lower Rufiji and Ruvu river drainage systems in eastern Tanzania (Watters et al. 2020).

Coastal East Africa (564)

1–49 m

Habitat water parameters at 14 sites across the full range of distribution, were as follows (mean values, with range in parentheses): pH of 7.5 (7.0–7.9); total dissolved solids of 132 ppm (30–320 ppm); conductivity of 264 μS (60–640); water temperature of 28 °C (25–31 °C). Water in the habitats is typically highly turbid (Watters 2015, Watters et al. 2020).

Based on our site data the syntopic occurrence of other species of the genus with N. ocellatus is: N. melanospilus (100 %), N. janpapi (~71 %), N. annectens (~34 %), N. eggersi (~32 %), N. foerschi (~3 %) and N. flammicomantis (~3 %). It should also be noted that N. ocellatus has been found at numerous sites together with as many as four other Nothobranchius species (Watters et al., 2020).

This species has a semi-annual life cycle.

Embryonic development under captive conditions in peat moss is about three to four months at room temperature.

Maximum size reported: 105.7 mm SL; MRAC A0-071-P-0412-0415, 
2019.016.P.0001-0003 (7).

​Karyotype structure unique in the genus (Krysanov, pers. comm.).

The specific name is given in reference to the eye-spot on the caudal peduncle of juveniles of both sexes and adult females.

Near Threatened B1b(iii)+2b(iii) (Nagy & Watters, 2021);

Previous assessment: Near Threatened B1ab(iii) (Nagy & Watters, 2019); Data Deficient (IUCN Red List, 2006).

​    Seegers, L. 1985. Beschreibung von Paranothobranchius ocellatus nov. gen. nov. spec. aus dem Rufiji-Einzug, Tanzania, Ostafrika. Pp 47–48, in: Seegers, L. 1985. Prachtgrundkärpflinge, die Gattung Nothobranchius: Systematik, Vorkommen, Pflege und Zucht. Deutsche Killifisch Gemeinschaft Journal, Supplement Nr. 1: 48pp. [taxonomy as Paranothobranchius ocellatus]

    Wildekamp, R. H. & Haas, R. 1992. Redescription of Nothobranchius microlepis, description of two new species from northern Kenya and southern Somalia, and note on the status of Paranothobranchius (Cyprinodontiformes: Aplocheilidae). Ichthyological Exploration of Freshwaters, 3 (1): 1–16. [systematics in Nothobranchius]

    Herder, F., J. Huylebrouck & K. Busse. 2010. Catalogue of type specimens of fishes in the Zoologisches Forschungsmuseum Alexander Koenig, Bonn. Bonn zoological Bulletin, 59: 109-136.

    Watters, B. R., B. Nagy, P. D. W. van der Merwe, F. P. D. Cotterill & D. U. Bellstedt. 2020. Redescription of the seasonal killifish species Nothobranchius ocellatus and description of a related new species Nothobranchius matanduensis, from eastern Tanzania (Teleostei: Nothobranchiidae). Ichthyological Exploration of Freshwaters, 30 (2): 151–178. [systematics, phylogeny, distribution, ecology]

    Nagy, B. & B. R. Watters. 2021. Nothobranchius ocellatus. The IUCN Red List of Threatened Species: e.T182279465A182279513. [conservation]

    Nagy, B. & B. R. Watters. 2022. Observations on growth rate and allometry in the seasonal predatory killifish Nothobranchius ocellatus (Teleostei: Cyprinodontiformes). Zootaxa 5175 (5): 501–520.

https://doi.org/10.11646/zootaxa.5175.5.1