Thrissina polynemoides ( Günther, 1868 )

Hata, Harutaka, Mandagi, Ixchel F. & Masengi, Kawilarang W. A., 2023, Resurrection of nominal species previously regarded as junior synonyms of Thrissina baelama (Fabricius, 1775) and their re-descriptions (Teleostei: Clupeiformes: Engraulidae), Raffles Bulletin of Zoology 71, pp. 279-302 : 288-289

Thrissina polynemoides ( Günther, 1868)

[English name: African Baelama Anchovy ] ( Fig. 8 ; Tables 5, 9)

Engraulis polynemoides Günther, 1868 (type locality: Madagascar).

Thrissina baelama (not of Fabricius): Losse, 1966: 177 (Dares-Salaam and Zanzibar, Tanzania; Mombasa and Malindi, Kenya); Losse, 1968: 110, pl. 4a (Dar-es-Salaam and Zanzibar, Tanzania; Mombasa and Malindi, Kenya).

RAFFLES BULLETIN OF ZOOLOGY 2023

Thryssa baelama (not of Fabricius): Whitehead et al., 1988 (in part): 425 (east Africa to Madagascar); Wongratana et al., 1999 (in part): 1743 (east Africa to Madagascar); Fricke et al., 2018: 52 ( Madagascar).

Holotype. BMNH 1979.7 .5.26, 93.3 mm SL, Madagascar.

Other material examined. 8 specimens, 87.1–94.0 mm SL: BMNH 1966.11.16.985–992 , 8 specimens, 87.1–94.0 mm SL, Mombasa, Kenya .

Diagnosis. A species of Thrissina with the following combination of characters: short maxilla, 21.6–22.3% of SL; its posterior tip not reaching to posterior margin of opercle; first supramaxilla elongated, longer than half length of second; lower jaw rather long, 19.7–20.3% of SL; abdomen covered with 5–7 + 9–10 = 14–17 keeled scutes; no scutes anterior to pectoral fin; 1UGR 18–20, 1LGR 23–26, 1TGR 41–46; 2UGR 14–16, 2LGR 22–25, 2TGR 37–40; 3UGR 12–13, 3LGR 14–16, 3TGR 26–29; 4UGR 11–12, 4LGR 12–13, 4TGR 23–25; no distinct black blotches on dorsal fin; caudal peduncle rather narrow [9.9–10.6% (mean 10.2%) of SL] and long (9.1–10.1% of SL); pre-dorsal-fin long, 50.7–51.8% of SL; pre-anal-fin length short, 65.6–66.9% of SL; dorsal-fin base short, 10.4–10.9% of SL; distance between pelvic-fin insertion and anal-fin origin short, 20.5–21.7% of SL; pectoral fin short, 17.1–18.2% of SL; pelvic fin short, 12.4–13.4% of SL; snout short, 4.7–4.9% of SL; body rather elongated, 23.5–25.3% (mean 24.5%) of SL.

Colour of preserved specimens. Body uniformly silver, sometimes pale ivory. Dorsum dark brown. Melanophores densely scattered over entire body and head. Narrow nonpigmented ring-like band surrounding anterior part of snout.

Melanophores scattered along dorsal- and caudal-fin rays. Pectoral, pelvic, and anal fins without melanophores. No distinct black blotches on dorsal fin.

Distribution. The species is currently known from Madagascar and Kenya ( Fig. 4 ).

Comparisons. Thrissina polynemoides has the highest gill raker counts among the five species redescribed in this study [41–46 (modally 43) in T. polynemoides vs. 40 or fewer in T. baelama , T. evermanni , and T. samam , 40–44 (modally 42) in T. tuberculosa ; Fig. 6 ]. Thrissina polynemoides further differs from T. baelama in having greater pre-dorsal-fin (50.7–51.8% of SL in T. polynemoides vs. 48.0–50.4% in T. baelama ) and snout lengths [4.7–4.9% in SL vs. 3.9–4.8% (shorter than 4.6% in specimens> 80 mm SL)] ( Fig. 7 ). Moreover, T. polynemoides differs from T. tuberculosa by lacking a black spot anteriorly on the dorsal fin (vs. black spots present in T. tuberculosa ), and having a deeper body (23.5–25.3% of SL in T. polynemoides vs. 20.6–23.4% in T. tuberculosa ), and shorter head and body proportions, including preanal length (65.4–66.9% of SL vs. 66.7–69.6%), dorsal-fin base (10.4–10.9% of SL vs. 11.2–11.6%), pelvic-fin insertion to anal-fin origin (20.5–21.7% of SL vs. 22.7–25.3%), pectoral fin (17.1–18.2% of SL vs. 18.4–19.4%), pelvic fin (12.4–13.4 of SL vs. 13.6–14.8%), maxilla (21.6–22.3% of SL vs. 22.5–23.7%), and lower jaw [19.7–20.3% (mean 20.1%) of SL vs. 20.1–21.4% (20.8%)].

Remarks. Although this nominal species has long been regarded as a junior synonym of T. baelama (e.g., Whitehead et al., 1988; Kottelat, 2013), the present study found both species to be valid.

Figures

Fig. 8. A, Holotype of Engraulis polynemoides (BMNH 1979.7.5.26, 93.3 mm SL, Madagascar), and B, non-type specimen of T. polynemoides (BMNH 1966.11.16.985–992, 94.0 mm SL, Mombasa, Kenya).

Fig. 4. Distributional records of Thrissina baelama (triangles), T. evermanni (squares), T. polynemoides (diamonds), T. samam (circles), and T. tuberculosa (star), based on specimens examined in this study.

Fig. 6. Relationships of total gill-raker numbers (TGR) on A, first gill arch (1GA), B, second gill arch (2GA), C, third gill arch (3GA), and D, fourth gill arch (4GA) to standard length in Thrissina baelama (blue triangles ▲), T. evermanni (yellow squares ■), T. polynemoides (green diamonds ◆), T. samam (red circles ●), and T. tuberculosa (pink stars).

Fig. 7. Morphometrics of Thrissina baelama (blue triangles ▲), T. evermanni (yellow squares ■), T. polynemoides (green diamonds ◆), T. samam (red circles ●), and T. tuberculosa (pink stars) (all vs. standard length; SL). A, Ratio of caudal-peduncle depth to SL; B, pre-dorsal-fin length to SL; C, snout length to SL, D, body depth to SL; E, pre-anal-fin length to SL; F, dorsal-fin base length to SL; G, distance from pelvic-fin insertion to anal-fin origin to SL; H, pectoral-fin length to SL; I, pelvic-fin length to SL; J, maxilla length to SL; K, lower-jaw length to SL; L, caudal-peduncle length to SL.