Thrissina tuberculosa ( Lacepède, 1803 )

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 : 293-300

Thrissina tuberculosa ( Lacepède, 1803)

[English name: Mauritian Baelama Anchovy ] ( Fig. 10 ; Tables 7, 11)

Clupea tuberculosa Lacepède, 1803: 425 (original type locality: Mauritius, Mascarenes ; type locality: Black River District, Mauritius, based on neotype designated herein).

Engraulis nesogallicus Bennet, 1832: 168 (original type locality: Mauritius, Mascarenes ; type locality: Black River District, Mauritius, based on neotype designated herein).

Thrissocles baelama (not of Fabricius): Fowler, 1941 (in part): 683 ( Mauritius).

Thryssa baelama (not of Fabricius): Whitehead et al., 1988 (in part): 425 ( Mauritius); Wongratana et al., 1999 (in part): 1743 ( Mauritius).

Neotype. BPBM 41797 , also neotype of Engraulis nesogallicus , 90.9 mm SL, Black River District, Mauritius, 0–1.5 m depth.

Other materials examined. 11 specimens, 79.3–94.6 mm SL: BPBM 20277 , 11 specimens, 79.3–94.6 mm SL, collected with the neotype.

Diagnosis. A species of Thrissina with the following combination of characters: short maxilla, 22.5–23.7% 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, 20.1–21.4% of SL; abdomen covered with 5–7 + 9–11 = 14–16 keeled scutes; no scutes anterior to pectoral fin; 1UGR 17–20, 1LGR 23–24, 1TGR 40–44; 2UGR 14–17, 2LGR 22–25, 2TGR 36–42; 3UGR 12–15, 3LGR 13–17, 3TGR 26–32; 4UGR 9–12, 4LGR 12–14, 4TGR 21–26; distinct black blotches on dorsal fin; pre-anal fin rather long, 66.7–69.6% of SL; dorsal-fin base long, 11.1–11.6% of SL; distance between pelvic-fin insertion and anal-fin origin rather long, 22.7–25.3% of SL; pectoral fin rather long, 18.4–19.4% of SL; pelvic fin rather long, 13.6–14.8% of SL; body elongate, 20.6–23.4% (mean 21.6%) of SL.

Colour of fresh specimens. Body uniformly silver. Dorsum and upper lateral surface of body green, with small densely scattered orange spots (also on upper lateral surface of head). Lateral surface of mid-part of snout transparent. Narrow non-pigmented ring-like band surrounding anterior part of snout. Branches of cephalic lateralis sensory canal on upper part of gill opening distinctly orange, forming an orange blotch. Fin rays of dorsal and caudal fins greenishbrown. Dorsal and caudal fins, centrally reddish-orange, posteriorly margined black. Pectoral, pelvic, and anal fins whitish, semi-transparent. Iris and pupil bluish-black and silver, respectively.

Colour of preserved specimens. Body uniformly light brown. Dorsum dark brown. Melanophores densely scattered over entire body and head. Narrow non-pigmented ringlike band surrounding anterior part of snout. Melanophores scattered along dorsal- and caudal-fin rays. Pectoral, pelvic, and anal fins without melanophores. Distinct black blotches anteriorly on dorsal fin.

Distribution. Thrissina tuberculosa is distributed only in waters off Mauritius ( Fig. 4 ), so far as is known, and is considered a Mauritian endemic.

Comparisons. Among the five species redescribed in this study, T. tuberculosa is uniquely characterised by black spots anteriorly on the dorsal fin ( Fig. 11 ).

Remarks. The original description of Clupea tuberculosa was based on a specimen collected from Mauritius by Lacepède (1803). Although Fricke (1999) suggested that the nominal species was a synonym of Stolephorus commersonnii Lacepède, 1803 , supposing both names to have been based on the same manuscript description of S. commersonnii, Hata et al. (2021a) indicated that the two nominal species were clearly based on different descriptions (descriptions of S. commersonnii and C. tuberculosa having been given on pp. 381 and 382–383, and pp. 425 and 460, respectively). Therefore, the two names are not objective synonyms. Although the original description of C. tuberculosa was brief, fin-ray counts of the dorsal (14), anal (30), pelvic (7), and pectoral (14) fins generally matched those of specimens of T. tuberculosa examined in this study (except slightly higher numbers of pectoral-fin rays (11–13 in this study) and anal-fin rays (31–34 in this study). Nine species of Engraulidae occur off the African east coast to Mauritius, [viz. Encrasicholina intermedia Hata & Motomura, 2016 , Encrasicholina pseudoheteroloba ( Hardenberg, 1933) , Engraulis capensis Gilchrist, 1913 , Stolephorus belaerius Hata, Lavoué & Motomura, 2021 , Stolephorus holodon ( Boulenger, 1900) , Stolephorus commersonnii Lacepède, 1803 , T. polynemoides , T. tuberculosa , and Thrissina vitrirostris ( Gilchrist & Thompson, 1908) ]. Anal-fin ray counts shown by Lacepède (1803) approximated those of T. polynemoides or T. tuberculosa determined in the present study [31–35 in T. polynemoides and 31–34 in T. tuberculosa vs. fewer than 23 in species of Encrasicholina , Engraulis , and Stolephorus ; 39–42 in T. vitrirostris ( Whitehead et al., 1988; Hata & Motomura, 2016a, b, 2019; Hata et al., 2021a; this study)]. Finally, Lacepède’s (1803) C. tuberculosa had a red spot above pectoral fin, a colour feature found in T. tuberculosa specimens recognised herein. However, since no specimens of T. polynemoides have been confirmed from Mauritius to date, T. tuberculosa is considered to be a valid Mauritian species, and not conspecific with the other eight engraulid species (above).

Abbreviations: D–P1 (distance between dorsal-fin origin and pectoral-fin insertion); D–P2 (distance between dorsal-fin origin and pelvicfin insertion); D–A (distance between origins of dorsal and anal fins); P1–P2 (distance between insertions of pectoral and pelvic fins); P2–A (distance between pelvic-fin insertion and anal-fin origin); TB ( Thrissina baelama ); TP ( Thrissina polynemoides ); TS ( Thrissina samam ); TT ( Thrissina tuberculosa ).

Abbreviations: D–P1 (distance between dorsal-fin origin and pectoral-fin insertion); D–P2 (distance between dorsal-fin origin and pelvic-fin insertion); D–A (distance between origins of dorsal and anal fins); P1–P2 (distance between insertions of pectoral and pelvic fins); P2–A (distance between pelvic-fin insertion and anal-fin origin); TB ( Thrissina baelama ); TE ( Thrissina evermanni ); TS ( Thrissina samam ); TT ( Thrissina tuberculosa ).

Abbreviations: D–P1 (distance between dorsal-fin origin and pectoral-fin insertion); D–P2 (distance between dorsal-fin origin and pelvicfin insertion); D–A (distance between origins of dorsal and anal fins); P1–P2 (distance between insertions of pectoral and pelvic fins); P2–A (distance between pelvic-fin insertion and anal-fin origin); TB ( Thrissina baelama ), TE ( Thrissina evermanni ); TP ( Thrissina polynemoides ); TT ( Thrissina tuberculosa ).

Abbreviations: D–P1 (distance between dorsal-fin origin and pectoral-fin insertion); D–P2 (distance between dorsal-fin origin and pelvicfin insertion); D–A (distance between origins of dorsal and anal fins); P1–P2 (distance between insertions of pectoral and pelvic fins); P2–A (distance between pelvic-fin insertion and anal-fin origin); TB ( Thrissina baelama ), TE ( Thrissina evermanni ); TP ( Thrissina polynemoides ); TS ( Thrissina samam ).

Although no type specimens exist for Engraulis nesogallicus (originally E. Neso-Gallicus) ( Kottelat, 2013; Fricke et al., 2022; this study), the original description by Bennett (1832) noted dorsal-, anal-, pelvic-, and pectoral-fin ray numbers as 14, 32, 7, and 14, respectively, which generally matched those of specimens of T. tuberculosa examined here, and supported the former being considered conspecific with T. tuberculosa (in addition to their coincident type localities). In the absence of type specimens of either species ( Whitehead, 1967a; Kottelat, 2013; Fricke et al., 2022; this study), BPBM 41797, 90.9 mm SL ( Fig. 10 ), collected from Black River District, Mauritius is herein designated as the neotype of Clupea tuberculosa Lacepède, 1803 and Engraulis nesogallicus Bennett, 1832 , the collection locality becoming the type locality for both nominal species under Article 76.3 ( ICZN, 1999). Therefore, E. nesogallicus becomes a junior objective synonym.

Comparative material: Encrasicholina macrocephala, RUSI 11270, 2 specimens, 46.7–53.8 mm SL, Red Sea. Thrissina encrasicholoides , NSMT-P 50306 , 69.8 mm SL, Philippines .

Figures

Fig.10. Neotype ofClupea tuberculosa, BPBM 41797, 90.9 mm SL, Black River District, Mauritius (also neotype of Engraulis nesogallicus): A, fresh condition (courtesy of Bishop Museum); B, preserved condition.

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. 11. Dorsal fins of A, Thrissina tuberculosa (BPBM 20277, 86.6 mm SL, Mauritius; triangles indicate several distinct dark spots scattered on anterior part), B, T. baelama (BMNH 1963.12.9.1–19, 102.4 mm SL, Djibouti), C, T. evermanni [BPBM 41796, 87.3 mm SL, Tonga (left-right inverted)], D, T. polynemoides (BMNH 1966.11.16.985–992, 89.5 mm SL, Mombasa, Kenya), and E, T. samam (BMNH 1971.2.8.50–58, 75.3 mm SL, New Britain, Papua New Guinea).