THE NOTHOBRANCHIUS SITE

MRAC 2019.016.P.0014, holotype, male, 94.8 mm SL; Tanzania: Matandu drainage: floodplain between Liwale and Makubwa tributary systems: small pool on the north side of the road at a culvert, 45 km northeast of Liwale in the direction of Kilwa, 09°32.7' S, 38°10.4' E; B. Watters, R. Wildekamp & B. Cooper, 7 Jun 1997, [field code: TAN 97-29].

MRAC 2019.016.P.0015-0016 (2)

Nothobranchius matanduensis is distinguished from all other congeners, except N. ocellatus, 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 dense irregular pattern of very dark grey to black spots on the head and anterior part of the body; grey caudal fin with white to light blue subdistal band and black or dark grey distal margin; scales irregularly arranged on flank; scales extending on proximal and medial zones of caudal-fin in males; 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.

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Males of Nothobranchius matanduensis differ from those of N. ocellatus by: moderately dense, irregular pattern of very dark grey to black (vs. dark red-brown to very minor small black) spots on head, operculum and branchiostegal membrane; head light blue-green or bronze to grey (vs. blue-green to grey); grey to grey-brown scale margins on trunk and head (vs. red-brown); dorsal fin light grey to weak blue-green with irregular black and grey spots (vs. blue green with irregular red-brown spots); lesser head width (55 vs. 56-64, respectively); and greater number of scales midlongitudinal series (42 vs. 39-41, respectively). Further, Nothobranchius matanduensis differs from N. ocellatus by a cephalic sensory system at supraorbital level fragmented in two discontinuous shallow grooves with two and four or five exposed neuromasts (vs. undivided in a long continuous shallow groove with eight exposed neuromasts); at supratemporal level with four or five exposed neuromasts in a strongly curved deep groove (vs. six exposed neuromasts); and a postorbital canal in deep groove with one exposed neuromast (vs. two to three exposed neuromasts).

Subgenus: Paranothobranchius

Populations of this species from the Matandu drainage were regarded as belonging to Nothobranchius ocellatus, a species that was described by Seegers (1985) as Paranothobranchius ocellatus. Combined morphometric and molecular analyses from populations across the entire range of N. ocellatus in Tanzania, including representative material from the lower Ruvu and lower Rufiji drainages, shows that the populations from the Matandu drainage belong to a distinct species described as N. matanduensis by Watters, Nagy & Bellstedt in Watters et al. (2020).

Tanzania: Matandu drainage: floodplain between Liwale and Makubwa tributary systems: small pool on the north side of the road at a culvert, 45 km northeast of Liwale in the direction of Kilwa, 09°32.7' S, 38°10.4' E.

This species is endemic to seasonal freshwater habitats in coastal Tanzania. It is known from south-eastern Tanzania in seasonal pools on the south bank floodplain of the middle reaches of the Matandu River system.

Coastal East Africa (564)

350–362 m

Habitat water parameters for Nothobranchius matanduensis, as determined by Watters at the type locality on June 7, 1997 at 10:38, were as follows: pH of 7.7; total dissolved solids of 70 ppm; conductivity of 140 μS; water temperature of 22 °C. Water in the habitat was highly turbid (Watters et al. 2020).

N. cf. melanospilus - 100%

N. cardinalis - 63%

This species has an annual life cycle.

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

Maximum size reported: 94.8 mm SL (MRAC 2019.016.P.0014, holotype, male)

Diploid chromosome number 2n = 30, NF = 40, karyotype structure 2m+8sm+20st/a [referred to as N. ocellatus] (Krysanov & Demidova, 2018).

Diploid chromosome number and karyotype structure unique in the genus.

The specific name, matanduensis, is in reference to the Matandu River, in which drainage system this species is found. An adjective derived from the geographical name.

Vulnerable B1ab(iii)+2ab(iii) (Nagy & Watters, 2021)

    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. [taxonomy as Nothobranchius matanduensis, phylogeny, distribution, ecology]

    Nagy, B. & B. R. Watters. 2021. Nothobranchius matanduensis. The IUCN Red List of Threatened Species: e.T182279674A182279678. [conservation]