Nothobranchius melanospilus ( Pfeffer, 1896 )

Costa, Wilson J. E. M., 2017, Taxonomic revision of the seasonal killifish genus Nothobranchius from Zanzibar, East Africa (Cyprinodontoidei: Aplocheilidae), Journal of Natural History 51 (27 - 28), pp. 1609-1624 : 1616-1621

Nothobranchius melanospilus ( Pfeffer, 1896)

( Figures 3 (b), 5, 6)

Fundulus melanospilus Pfeffer, 1896, p. 48 , fig. 19a (type locality: Longo-Bay and Seychelles [correctly Zanzibar]; lectotype: BMNH 2016.12 .2.1, female, 35.2 mm SL, here designated, formerly part of BMNH 1865.3 .18.98 – 99, collected in Zanzibar) .

Nothobranchius emini: Ahl, 1935, p. 125 (type locality: Kongoran Botto [correctly Ikongoro], German East Africa [now Tanzania]; holotype: ZMB 21392).

Nothobranchius seychellensis: Ahl, 1935, p. 126 (type locality: Seychelles [correctly Zanzibar as discussed in Costa 2012]; syntypes: BMNH 1865.3 .18.98 – 99 (4) and BMNH 2016.12.2.1).

Material examined

All from eastern Tanzania. Zanzibar Island . BMNH 2016.12 . 2.1, lectotype; BMNH 1865.3 . 18.98 – 99, 4 paralectotypes; Zanzibar; Playfair . – MRAC 81 – 59 -P-12 – 16, 5; MRAC 81 – 59 P-17 – 19, 3; about 1.5 km south of Kinyasini , 5.9921° S, 39.3188° E, about 45 m asl; L . Seegers et al., Dec. 1980. – MRAC A0-017-P-0391 – 0399, 9; MRAC A0-071-P-128, 1; 5 km south of Kinyasini , 6.0112° S, 39.3245° E, about 50 m asl; R . Wildekamp, 29 May 1997. – MRAC A0-017-P-0129 – 0130, 2; fast flowing stream with nearly still pools, 2 km south of Mahonda , 6.0055° S, 39.2505° E, about 40 m asl; R . Wildekamp, 29 May 1997. – UFRJ 6874 , 1 ; temporary channel about 500 m south of Kinyasini , 5.9870° S, 39.3163° E, about 45 m asl; W . J. E. M. Costa & C. P. Bove, 29 December 2011 . Ruvu River basin and adjacent areas . – ZMB 21392, holotype of Fundulus emini Ahl, 1935 ; Kongoran Botto; F . Stuhlmann. – MRAC 75 – 72 -P-1 – 2, 2; road A7, Ruvu River floodplains; Jan Pap , 1975 . – MRAC 76 – 49 -P-101 – 113, 13; road A7, about 40 km west of Dar es Salaam; R . Wildekamp, 12 June 1976. – MRAC 87 – 38 -P-38 – 39, 2; small pool near the Ruvu river at Nguhi ; J . Lourens, 13 June 1976. – MRAC A0-071-P-0410 – 0411, 2; pools on the floodplain of the Ruvu River, a few kilometres from ferry terminal west of Bagamoyo ; R . Wildekamp et al., 10 June 1997. – MRAC 76 – 49 -P-83 – 84, 2; road A7, about 750 m from the bridge over Ruvu River , 6.6955° S, 38.6995° E, about 25 m asl; R . H. Wildekamp, 12 June 1976. – MRAC 96 – 045 -P-28, 1; a few kilometres from ferry terminal west of Bagamoyo, roadside pools and flooded grassy areas on the Ruvu River floodplain; R . Wildekamp, 12 June 1995. – UFRJ 6515 , 13 ; UFRJ 6591 , 4 (C&S); Ruvu river floodplains near Bagamoyo , 6.4758° S, 38.8430° E, about 25 m asl; W . J. E. M. Costa et al., 13 June 2007. – UFRJ 6757 , 9 ; UFRJ 6753 , 2 ; idem; W . J. E. M. Costa et al., 9 Jan. 2009. – UFRJ 6651 , 11 ; UFRJ 6652 , 3 (C&S); Ruvu river floodplains near Mlandizi , 6.6980° S, 38.7042° E, about 30 m asl; W . J. E. M. Costa et al., 13 Jan. 2009. Mbezi River basin . MRAC A0-071-P-124 – 127, 4; MRAC A0-071-P- 131 – 139, 10; road B2, Mbezi River floodplains, 7.1862° S, 39.1697° E, about 65 m asl; R . Wildekamp et al., 31 May 1997. UFRJ 6758 , 13 ; UFRJ 6759 , 4 C&S); UFRJ 6765 , 2 ; Mbezi River floodplains, near Kitonga , road B2, 7.1872° S, 39.1717° E, about 80 m asl; W . J. E. M. Costa et al., 10 Jan. 2009. – UFRJ 6760 , 5 ; Mbezi river floodplains, between Mkuranga and Binga, 7.1622° S, 39.2317° E, about 65 m asl; W . J. E. M. Costa et al., 10 Jan. 2009. Rufiji river basin . MRAC 81 – 39 -P-6 – 7, 2; left bank of Ruhoi River next to the bridge on the road Kibiti-Ndundu , road B2, 7.8517° S, 38.9620° E, about 30 m asl; L . Seegers et al., 29 December 1980. – MRAC 81-59 -P-08 – 11, 4; Mtanza, close to the northern entrance of the Selous Game Reserve , 7.7737° S, 38.2370° E, about 60 m asl; L . Seegers et al., 31 December 1980. – MRAC 98 – 008 -P-0001 – 0002, 2; pools 1 km north of Ndundu, ferry terminal on Rufuji River , road B2, 7.9997° S, 38.9658° E, about 25 m asl; R . Wildekamp et al., 11 June 1995. – MRAC 98 – 008 -P-0003 – 0006, 4; 21 km south of Kibiti, 21 km north of Ndundu, on main road to Dar es Salaam, pools adjacent to Ruhoi River , southwest of the bridge; 7.8592° S, 38.9617° E, about 35 m asl; R . Wildekamp et al., 11 June 1995. – MRAC A0-071-P-140 – 148, 9; MRAC A0-071-P-149 – 151, 3; pool 2 km south of Kitonga ferry terminal on south bank of Rufiji river , 8.0522° S, 39.0089° E, about 20 m asl; R . Wildekamp, 31 May 1997. – UFRJ 6761 , 29 ; UFRJ 6762 , 4 (C&S); floodplains of left bank of Rufiji River , 7.9838° S, 38.9755° E, about 20 m asl; W . J. E. M. Costa et al., 14 Jan. 2009.

Diagnosis

Distinguished from all congeners by the combination of the following character states: caudal fin red with black posterior margin in males; posterior portion of flank and unpaired fins with black spots in females; pre-dorsal length in males 62.4 – 65.1% SL; 3 + 12 – 14; 5 + 15 – 16 gill-rakers on first branchial arch; 29 – 31 scales in longitudinal series; 16 – 18 series of scales around caudal peduncle; two longitudinal rows of scales between anterior supraorbital series of neuromasts; anterior supraorbital series of neuromasts arranged continuously, with four well-developed neuromasts; four neuromasts in posterior supraorbital series; 29 – 31 caudal-fin rays; 30 – 31 vertebrae; second proximal radial of dorsal fin between neural spines of 13th and 15th vertebrae.

Description

Morphometric data appear in Table 2. Dorsal and ventral profiles slightly convex from snout to posterior end of dorsal and anal-fin bases, approximately straight on caudal peduncle. Body moderately deep, compressed. Greatest body depth at vertical just in front of pelvic-fin base. Jaws short, snout slightly pointed in lateral view; mouth superior, lower jaw slightly anterior to upper jaw. Jaw teeth canine, numerous, irregularly arranged; outer teeth greater than internal teeth. Vomerine teeth 8 – 12. Branchiostegal rays 6. Gill-rakers of first branchial arch 5 + 15 – 16. Basihyal sub-triangular, greatest width about 85% of length; basihyal cartilage about 80% of total length of basihyal.

Dorsal and anal fins broad in males, extremity rounded, with short filamentous rays along distal margin; in females, dorsal fin rounded, anal fin sub-triangular and slightly longer than dorsal fin. Caudal fin subtruncate to rounded. Pectoral fin sub-elliptical, posterior extremity between pelvic-fin base and anus. Pelvic fin small, tip reaching between urogenital papilla and anal-fin origin; pelvic-fin bases medially in contact. In males, minute papillate contact organs on first and second pectoral-fin rays and distal portion of middle dorsal-fin rays, and rows of well-developed papillate contact organs along two-thirds of most rays of anal fin. Dorsal-fin origin on vertical between base of second and fourth anal-fin rays. Dorsal-fin rays 15 – 17; anal-fin rays 16 – 19; caudal-fin rays 29 – 31; pectoral-fin rays 18 – 21; pelvic-fin rays 6. Total vertebrae 30 – 32. Second proximal radial of dorsal fin between neural spines of 13th and 15th vertebrae; first proximal radial of anal fin between pleural ribs of 12th and 15th vertebrae. Ventral process of post-temporal well-developed. Hypurals completely fused, forming single hypural plate without vestige of median gap.

Scales small, cycloid; body and head entirely scaled, except ventral surface of head. Minute filamentous contact organs along posterior margin of scales on middle portion of flank and latero-ventral portion of head in males. Body squamation extending over anterior 30% of caudal-fin base; no scales on dorsal and anal-fin bases. Frontal squamation irregularly arranged in two longitudinal rows between anterior supraorbital neuromast series ( Figure 3 (b)). Longitudinal series of scales 29 – 31; transverse series of scales 9 – 11; scale rows around caudal peduncle 16 – 18.

Anterior supraorbital series of neuromasts arranged in single section placed in nearly continuous depression, with five neuromasts ( Figure 3 (b)). Posterior supraorbital series with four neuromasts placed in shallow depression. Infraorbital series with 18 – 25 neuromasts, pre-opercular series 15 – 18, mandibular 17 – 21. One neuromast per scale of lateral line. Two neuromasts on caudal-fin base.

Colouration in life. Males: flank light green to light greenish blue; posterior margin of scales red, forming red reticulate pattern, often with narrow chevron-shaped red bars overlapping red reticulum on posterior half of flank. Dorsum pale brown, venter yellowish white. Side of head light greenish blue; jaws, dorsal and ventral parts of head pale yellow; red pigmentation forming reticulate pattern on post-orbital region, often forming three oblique, short red bars. Iris light blue. Dorsal fin pale yellow, with dark red transverse oblique bars with irregular sinuous margins, broader on basal and posterior portions of fin; distal filaments white. Anal fin pale yellow, basal portion with red bars irregularly arranged; filaments light grey with white tips. Caudal fin red, with dorsal and ventral posterior corners of fin black, sometimes black pigmentation extending along whole posterior border, forming narrow black posterior margin. Pectoral fin yellowish hyaline, with bluish white distal margin, wider dorsally. Pelvic fin pale yellow with small red spots; margins white; often black pigmentation concentrated on subdistal portion of fin. In some males collected in the middle Ruvu River basin and Lower Rufiji River basin, red pigmentation was absent, making exemplars predominantly pale blue.

Females: flank pale brown, often with horizontal rows of pale greenish blue spots on anterior portion; black dots on posterior portion of flank, and few dark grey on anterior portion. Dorsum pale brown, venter white. Head pale brown, opercular region pale greenish yellow. Iris pale yellow. Fins hyaline, with grey dots on basal portion of unpaired fins.

Distribution

Nothobranchius melanospilus occurs in a vast area of eastern Tanzania, comprising Unguja Island, Zanzibar archipelago, and adjacent mainland coastal rivers, eastern Tanzania ( Figure 4 ).

Remarks

As described in the introduction above, the type series of Fundulus melanospilus comprises syntypes from Zanzibar and Longa Bay (possibly present Ilonga). One syntype from the former locality is here designated as lectotype (BMNH 2016.12.2.1), which was previously illustrated by Playfair & Günther (1866: plate XVII, fig. 3) in a book on fishes from Zanzibar, by Pfeffer (1896, p. 47, fig. 19) in the original description of N. melanospilus , and by Boulenger (1915, p. 34, fig. 25) in a subsequent revision (see Introduction above). This lectotype choice is primarily based on recommendation 74B of the ICZN referring to lectotype selection, which recommends giving preference to a ‘ syntype of which an illustration has been published ’ (ICZN, 1999). When examining the five syntypes from Zanzibar (see online supplemental material), it is possible to unequivocally identify that specimen previously illustrated by the following features: general shape after fixation keeping body nearly straight in lateral view, with a dorsal curve at nape level; mouth closed, clearly showing a pointed snout in lateral view; and dorsal and anal fins slightly posteriorly directed. In addition, syntypes from Zanzibar are in better conditions of preservation and the collecting site is clearly recorded in the original book collection ( Costa 2012).

Figures

Figure 3. Diagrammatic representation of the latero-sensory system and frontal squamation on the dorsal surface of the head in: (a) Nothobranchius melanospilus, UFRJ 6874, male, 39.8 mm SL; (b) Nothobranchius guentheri, UFRJ 8416, male, 34.1 mm SL; asss: anterior section of the anterior supraorbital series; anss: posterior rostral neuromast; psss: posterior section of the anterior supraorbital series; poss: posterior supraorbital series; prn: posterior rostral neuromast. Scale bar: 2 mm.

Figure 4. Geographical distribution of Nothobranchius guentheri (Pfeffer 1893), circles, and Nothobranchius melanospilus (Pfeffer 1896), squares.