Secutor mazavasaoka, Baldwin, Zachary H. & Sparks, John S., 2011

Baldwin, Zachary H. & Sparks, John S., 2011, A new species of Secutor (Teleostei: Leiognathidae) from the Western Indian Ocean, Zootaxa 2998, pp. 39-47 : 41-46

Secutor mazavasaoka , new species

Figures 3 , 4A , & 5 ; Table 1

Secutor sp. “ Madagascar ” — Sparks et al. (2005): phylogeny.

Secutor n. sp. “ Madagascar ” — Sparks (2006); Chakrabarty et al. (2011): phylogeny. Secutor insidiator — James (1984): description, line drawing; Mochizuki and Hayashi (1989) in part description, black and white photograph.

Holotype. AMNH 251200, 77.4 mm SL, Maroansetra Market (15° 26’S, 49° 45’E), Antongil Bay, Madagascar, coll. J.S. Sparks, W.L Smith, K. Tang, et al., 29 November 2003.

Paratypes. AMNH 231398, 1 ex., 80 mm SL, mouth of Lanefitra River, Madagascar, coll. P. Doukakis & local fishermen, 16 September 2000. AMNH 236061, 1 ex., 97 mm SL, Faritany de Toamasina (18° 56’S, 48° 28’E), Antongil Bay, Madagascar, coll. P. Doukakis & local fishermen, 0 1 October 2005. AMNH 244283, 43 ex., 70–88 mm SL, Maroansetra Market (15° 26’S, 49° 45’E), Antongil Bay, Madagascar, coll. J.S. Sparks et al., 23 November 2003. AMNH 244293, 12 ex., 77–86 mm SL, Maroansetra Market (15° 26’S, 49° 45’E), Antongil Bay, Madagascar, coll. J.S. Sparks et al., 29 November 2003. AMNH 244306, 1 ex., 84 mm SL, Maroansetra Market (15° 26’S, 49° 45’E), Antongil Bay, Madagascar, coll. J.S. Sparks et al., 24 November 2003. AMNH 245638, 10 ex., 56–77 mm SL, Tulear Market (23° 21’ 13”S, 43° 40’ 05”E), Toliara Province, Madagascar, coll. P. Chakrabarty & P.W. Willink, 10 June 2008. AMNH 253842, 1 ex., 102 mm SL, Antsiranana Market (12° 16'S, 49° 17'E), Madagascar, coll. Z.H. Baldwin, 7 June 2011. AMNH 253843, 5 ex., 60–71 mm SL, Maromandia Market (13° 13'S, 48° 05'E), Madagascar, coll. Z.H. Baldwin, 31 May 2011. ANSP 53115, 1 ex., 91 mm SL, Maputo Bay (25° 57’S, 32° 32’E), Mozambique, coll. H.W. Bell-Marley, July 1923. ANSP 54891, 5 ex., 67–103 mm SL, Durban, KwaZulu-Natal province, South Africa, 1932. ANSP 64215, 1 ex., 77 mm SL, KwaZulu-Natal province, South Africa, coll. H.W. Bell-Marley, 1925. ANSP 88786, 102 mm SL, KwaZulu-Natal province, South Africa, coll. H.W. Bell-Marley, 1925. USNM 373273, 7 ex., 78–103 mm SL, Anton Bruun, Cr. 8, Stat. 403A, Mozambique, 9 October 1964. USNM 373279, 7 ex., 82–86 mm SL, Mozambique Channel, E. of Besalampy, Madagascar, Anton Bruun, Cr. 8, Stat. 408B, coll. L. Knapp, 15 October 1964. USNM 373282, 17 ex., 83–107 mm SL, near Durban Harbor Inlet, Durban, South Africa, coll. F. Schwartz, 31 January 1969.

Diagnosis. Together, the new species, S. indicius , and S. insidiator are readily distinguished from all congeners except S. hanedai by a more elongate (depth 40.5–57.7% SL) and essentially oval-shaped body (vs. deep and diskshaped in S. ruconius and S. interruptus [depth 53.4–65.5% SL], and S. megalolepis [depth 58.6–62.6% SL]). The new species is distinguished from S. hanedai by the presence of scales on the chest (vs. chest asquamate), and from S. indicius by an overall deeper (depth 47.3–57.7% SL), hatchet-shaped body (vs. body oval, depth 40.5–48.3% SL in S. indicius ), and by pigmentation pattern on the dorsal flank comprising eight to eleven well-defined columns of irregular small spots and blotches (vs. 14 to 17 thin columns of spots or vertical lines in S. indicius ; Fig. 4 D). The new species is distinguished from S. insidiator by an overall more hatchet-shaped body (vs. body oval and evenly rounded ventrally in S. insidiator ), dorsal pigmentation pattern as described above (vs. larger, irregular blotches in poorly defined columns in S. insidiator ; Fig. 4 B, C), a strongly upturned mouth and compressed pug-like snout, and dorsal-fin insertion well posterior of vertical through pectoral-fin base (vs. about level of pectoral-fin base in S. insidiator ).

Description. Selected proportional measurements and meristic data presented in Table 1 . A comparatively large, moderately shallow bodied and laterally compressed species of Secutor . Dorsal profile markedly less convex than ventral, particularly anteriorly. Body more or less hatchet-shaped, with greatest depth at vertical from dorsalfin origin to just anterior of anal-fin origin. Snout strongly oblique and mouth oriented dorsally. Concavity present dorsal to orbit, at anterior margin of divergent left and right supraorbital ridges. Exposed rising dorsal aspect of supraoccipital crest (= nuchal spine) easily visible in lateral view.

Dorsal-fin origin slightly posterior to vertical through pelvic-fin origin. Anal-fin origin near vertical through midpoint of body, just anterior to vertical between last dorsal-fin spine and first dorsal-fin ray. Caudal peduncle slender and shallow. Mouth small, projecting anterodorsally when extended. Posterior margin of maxilla exposed and reaching vertical through anterior orbital margin. Eye large and circular. Sensory pores around eye weakly to moderately developed. Nasal pores closely apposed and separated by only small bridge of tissue. Both nasal pores ranging from oval to slit-shaped; anterior pore roughly half size of posterior pore. Preopercular margin weakly to moderately serrated along ventral and ventrocaudal margins. First ceratobranchial with 23 or 24 elongate, triangular, and moderately denticulate gill rakers. Vertebral count 23 (10 precaudal + 13 caudal). Single supraneural present. Supraneural moderate in size as observed through radiographs. Dorsal aspect of supraneural spine short, about equal in length to radius of eye lens, whereas vertical (elongate) aspect about equal to diameter of orbit.

Dorsal fin with VIII spines and 16 branched rays. First dorsal-fin spine greatly reduced in length and weak. Second through fourth dorsal-fin spines elongate and robust; second spine longest. Third and fourth dorsal-fin spines serrate along anterior margin, and “lock” into groove on posterior margin of preceding spine when erect. Dorsal-fin spines five through eight feeble, shorter than second through fourth spines. Anal fin with III spines and 14 branched rays. First anal-fin spine very short. Second and third spines robust; second spine longest, but not appreciably longer than third. Third anal-fin spine serrate on anterior, proximal margin, and “locks” into groove on posterior margin of second spine when erect. Spinous dorsal and anal fins with asquamate basal sheath. Pelvic fins short, over one pelvic fin length from first anal-fin spine when adducted; with I spine and 5 branched rays. Eight upper and lower branched caudal-fin rays. Sixteen or 17 total pectoral-fin rays.

A single row of closely set elongate and recurved conical teeth of uniform size in both upper and lower jaws. Lips not fleshy and teeth exposed.

Flank covered with small, regularly imbricate scales, with scales extending onto and fully covering chest. Fins, suborbital series, and supraorbital region asquamate. Scales present in nuchal region (except dorsally). Otherwise, dorsal flank fully scaled. Lateral line complete, extending from opercle to posterior margin of caudal peduncle, and comprised of about 60 scales. Frequently, however, posterior third of lateral line missing due to highly deciduous nature of ponyfish scales in preservation. Lateral line slightly arched and pores well developed.

Character N Holotype Range Mean SD Light organ system and sexual dimorphism. Among members of Gazzini, comprising Gazza and Secutor , the structure, orientation, and degree of sexual dimorphism of the circumesophageal light organ is similar, and characterized by a pronounced lateral expansion of the ventral light organ lobes ( Fig. 2 ). Lateral expansion of the ventrolateral light organ lobes is appreciably more pronounced in Gazza than in Secutor , which is most likely correlated with placement of the translucent opercular patches just lateral to the ventrolateral lobes in Gazza .

Although male members of the tribe Gazzini possess markedly enlarged ventrolateral light organ lobes compared to conspecific females of similar size, rostrolaterally oriented “windows” (= light emitting regions of the light organ) are present in both sexes on these contralateral lobes, in addition to the “window” at the ventrorostral margin of the gas bladder that is common to all ponyfishes ( Fig. 2 : bright yellowish regions studded with chromatophores in diagram). The rostrolateral light organ “windows” are oriented into a silvery, guanine-lined, reflective chamber ( Sparks et al., 2005; Fig. 2 : sc). Uniquely within Leiognathidae , both male and female members of Gazzini possess an external translucent opercular margin ( Gazza ) or gular ( Secutor ) patch studded with chromatophores ( Fig. 2 ), which are not associated with light reflection and transmission via the gas bladder. Members of Gazzini are, however, sexually dimorphic with regard to light organ volume and size of the translucent opercular or gular patches; both of these features are enlarged in males compared to similarly sized conspecific females.

Secutor is unique within Leiognathidae in possessing internal silvery, guanine-lined “light tubes” to facilitate the transmission of bacterially-generated light from the light organ “windows” on the contralateral ventral lightorgan lobes to the distally situated translucent gular patches ( Sparks et al., 2005; Fig. 2 : sc). In all other sexuallydimorphic ponyfish genera, the translucent external patch(es) are located proximate to the light organ itself, with the possible exception of Nuchequula (see Chakrabarty and Sparks, 2007).

Coloration in life. Overall body color iridescent silvery-blue on flank above lateral midline, and uniform silvery on head and body ventral to lateral midline. Iridescent gold present on dorsal half of orbit, in interorbital space, temporal region, and along lateral line. Pigmentation pattern above lateral midline consisting of eight to eleven darkly pigmented columns of irregular spots, interspersed with thin, vertical lines. Strong oblique black line present along margin of lower jaw and suspensorium. Black pigmentation present along inner portion of base of pectoral fin. Dorsal fin silvery with distal black patch. Other fins hyaline with a yellowish hue.

Pigmentation in preservation. Body generally light brown with some silvery-blue highlights above midline. Ventral half of body, from slightly above midline, covered in silvery guanine, except for variable guanine-free region ventral to pectoral-fin base that is common to all species of Secutor . Operculum, suborbital/cheek region, and lower jaw silvery and reflective. Distinct oblique black line at margin of lower jaw and suspensorium; black pigmentation extends onto membrane of protracted jaws. Region immediately anterior and dorsal to orbit lacks silvery guanine. Lateral pigmentation pattern dorsal to midline comprising numerous columns of irregular small roundish dark brown to blackish blotches and short vertical lines arrayed in our horizontal rows ( Figs. 3 , 4A , & 5 ). Uppermost one or two horizontal series more or less short vertical lines, whereas third and fourth series comprised of oval or round blotches. Continuous dark line present along entire base of dorsal fin and extending caudally along dorsal margin of caudal peduncle. Thin black line present on snout at anterior margin. Pectoral fin with broad black bar along internal portion of base. Dorsal fin with distinct black patch distally. All other fins light olive or hyaline, except caudal, which is edged distally in charcoal/black. Diverging left and right supraoccipital ridges edged in charcoal/black. Narrow black vertical bar present at base of caudal fin.

Distribution. Known range of the new species extends from eastern coast of Africa (from east coast of South Africa and northward to coastal waters of Mozambique), throughout coastal Madagascar, and to the Mascarene islands.

Etymology. Named in reference to translucent gular (=chin) patch characteristic of genus and particularly well pronounced in new species (from the Malagasy mazava = lighted or illuminated, and saoka = chin). Specific epithet, mazavasaoka , to be treated as a noun in apposition.

Remarks and comparisons. Despite several morphological differences, the new species has been consistently misidentified as S. insidiator in the literature (e.g. James, 1984; Mochizuki and Hayashi, 1989). In the family-level phylogenetic analysis of ponyfishes of Sparks et al. (2005), based on the simultaneous analysis of nucleotide sequence data and morphological evidence, the new species was recovered as the sister taxon to a clade comprising S. insidiator and S. indicius . A recent and more comprehensive phylogenetic analysis of ponyfishes by Chakrabarty et al. (2011), which included several putative populations of S. insidiator spanning a broad geographic range (from Madagascar to Taiwan), recovered the new species as the sister taxon to S. insidiator . Interestingly, in addition to the apomorphic morphological features observed in the new species in the course of this investigation, these family-level molecular phylogenetic studies corroborate our anatomical findings by demonstrating that the new species is also quite distinct from its sister taxon at the level of DNA sequence data.

Examination of the two syntypes of S. insidiator (ZMB 1676) along with Bloch’s (1787) original illustration shows that the species bears 8 to 10 loosely-defined columns of irregularly-shaped blotches above the lateral midline (see Fig. 4 B, C). Secutor mazavasaoka differs from S. insidiator by possessing uniformly arranged columns of spots, and by the presence of thin vertical lines interspersed between each column of spots (see Figs. 3 , 4A , & 5 ). It is useful to note that based on our observations, S. insidiator appears to be much more narrowly distributed than previously thought. In addition to the syntypes collected in the Gulf of Khambhat in India, and a single lot of specimens collected recently in Thailand, we have not encountered any other specimens of this species in the collections we have examined. Most museum holdings of Secutor either remain unsorted, are not identified to species, or are misidentified. This is clearly due to the difficulty in identifying members of the genus to species, and suggests that a more exhaustive search of collections is therefore necessary to bolster comparative material for S. insidiator , and to gain a better understanding of the extent of its geographic range. Given the relatively high level of morphological conservatism within Secutor , coupling molecular and morphological data is critical to understanding intrageneric diversity. Recent ( Chakrabarty et al., 2011) and ongoing molecular work indicates that Secutor is considerably more diverse than previously thought, and that a revision of the genus is warranted.

Figures

FIGURE 2. Schematic of light-organ system (LOS) in representative male member of Secutor dissected to show internal anatomy. Tranlucent gular patch highlighted in light blue, and light organ windows in bright yellow. Stippling on gular patch and light organ windows indicates presence of chromatophores on these structures. Abbreviations: aw = anterior light organ window; es = esophagus; g = gut; gb = gas bladder; lo = circumesophageal light organ; sc = silvery, guanine-lined, light chamber or tube.

FIGURE 3. Secutor mazavasaoka, new species, holotype, AMNH 251200, 77.4 mm SL, Madagascar.

FIGURE 5. Image of freshly collected specimen of Secutor mazavasaoka, new species (paratype), Maroansetra, Madagascar.

FIGURE 4. A. Secutor mazavasaoka, new species, paratype, USNM 373279, 99.8 mm SL, Mozambique. B. S. insidiator, ZMB 1676, syntype, 68.5 mm SL, India. C. S. insidiator, AMNH 240594, 65.9 mm SL, Thailand. D. S. indicius, AMNH 242615, 83.6 mm SL, Taiwan.

Tables

TABLE 1. Morphometric and meristic data for Secutor mazavasaoka, new species.

Standard length (mm)	69	77.4	56.2–109.4	85.1	12.45
Percentage of SL
Head width (max.)	68	13.0	10.1–14.6	12.4	0.89
Head length	63	28.4	23.2–29.3	26.4	1.29
Body depth	63	53.9	47.3–57.7	51.9	2.16
Caudal peduncle length	67	9.9	40.1–11.6	7.5	2.25
Caudal peduncle width	69	2.6	1.4–3.5	2.5	0.51
Caudal peduncle depth	69	5.7	3.3–5.9	5.0	0.43
Pectoral-fin length	67	20.1	16.6–23.5	20.9	1.34
Pelvic-fin length	65	10.3	7.0–11.8	8.8	0.95
Pre-dorsal length	64	40.1	34.4–44.7	39.1	2.34
Pre-anal length	67	58.7	52.0–63.6	57.8	2.73
Pre-pelvic length	66	45.9	39.9–51.7	45.2	2.97
Percentage of HL
Snout length	63	33.6	25.2–38.4	31.3	3.34
Orbit diameter	66	36.8	28.0–40.0	34.8	3.31
Upper jaw length	54	46.4	39.3–55.0	46.6	4.46
Lower jaw length	53	50.9	32.0–63.1	55.0	5.39
Interorbital width	63	22.7	24.9–37.7	31.9	3.04
Caudal peduncle length/width	66	3.9	1.3–5.7	3.0	1.19
Caudal peduncle length/depth	67	1.8	0.7–2.5	1.5	0.47
Vertebrae (precaudal + caudal)	38	10 + 13 = 23	10 + 13 = 23
Dorsal fin	50	VIII 16	VIII 16
Anal fin	50	III 14	III 14