THE NOTHOBRANCHIUS SITE

MRAC A7-02-P-33, 1 male, 52.9 SL; Tanzania: Mafia Island, approximately 3 km south of Kirongwe, 07°49.58’ S, 39°48.87’ E, about 15 m asl; B. Watters, B. Cooper & O. Schmidt, 31 May 2002 [field code: Mafia Island TAN 02-5].

MRAC A7-02-P-34 (1), MRAC A702-P-38-44 (7)

Nothobranchius insularis is distinguished from all species of the N. melanospilus group, except N. lucius, in possessing snout pointed in lateral view, jaws moderately long (vs. snout blunt to weakly pointed, jaws short); caudal fin, in males, with broad dark grey to black band on the posterior margin (vs. narrow); presence, in females, of dark dots over the whole flank (dark dots when present restricted to the posterior portion of the flank). The new species differs from N. lucius by having inner premaxillary teeth smaller than teeth of the outer premaxillary tooth row (vs. larger); caudal fin subtruncate in males (vs. rounded); in females, flank dark dots are vertically elongated and often arranged in oblique rows (vs. dots rounded, arranged in horizontal rows); unpaired fins, in females, with dark grey dots when present restricted to their basal portion (extending over most fin); as well as morhometric characters and neuromast pattern (from Costa, 2017).

Subgenus: Adiniops

Species group: N. melanospilus group

​At the discovery in 2002, populations of this species found in Mafia Island were referred to N. aff. melanospilus, based on some general similarities with that species but also some important differences. Morphometric and molecular analyses confirmed the distinction from N. melanospilus and the populations from Mafia Island, together with other populations from coastal mainland Tanzania, were described as N. lucius by Wildekamp et al. in 2009. Nothobranchius insularis itself was established as a species by Costa in 2017, the name applied to the island populations occurring in Mafia Island, by separating them from the mainland populations of N. lucius.

Tanzania: Mafia Island, approximately 3 km south of Kirongwe, 07°49.58’ S, 39°48.87’ E.

This species is endemic to freshwater habitats in coastal Tanzania. It is known from two sites in close proximity to each other in the northern part of Mafia Island, eastern Tanzania.

Coastal East Africa (564)

14–15 m

Personal observation at collecting site:

Water temperature: 33.3 °C

pH: 7.59

TDS:  411 ppm

Conductivity: 822 µS

N. korthausae - 33%

This species has a semi-annual life cycle.

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

Maximum size reported: 55.2 mm SL; MRAC A702-P-38-44 (paratype)

Not known

The specific name is formed from insularis (in Latin for pertaining to an island), and referring to the occurrence of the new species on Mafia Island.

Endangered B1ab(iii)+2ab(iii) (Nagy & Watters, 2019)

    Wildekamp, R. H., K. M. Shidlovskiy & B. R. Watters. 2009. Systematics of the Nothobranchius melanospilus species group (Cyprinodontiformes: Nothobranchiidae) with description of two new species from Tanzania and Mozambique. Ichthyological Exploration of Freshwaters, 20 (3): 237–254. [taxonomy as Nothobranchius lucius]   

    Nagy, B. 2008. Mafia Island - Notes on the distribution of Nothobranchius and my recent collections. Journal of the American Killifish Association, 41 (5): 129–144. [collecting, ecology]

    Costa, W. J. E. M. 2017. Redescription of Nothobranchius lucius and description of a new species from Mafia Island, eastern Tanzania (Cyprinodontiformes, Aplocheilidae). Zoosystematics and Evolution, 93 (1): 35–44. [taxonomy as Nothobranchius insularis]

    Nagy, B. & B. R. Watters. 2019. Nothobranchius insularis. The IUCN Red List of Threatened Species: e.T131470835A131470840. [conservation]

    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, IEF-1149, pp. 1–28. [phylogeny]