Sagittalarva Victor

Victor, Benjamin C., Alfaro, Michael E. & Sorenson, Laurie, 2013, Rediscovery of Sagittalarva inornata n. gen., n. comb. (Gilbert, 1890) (Perciformes: Labridae), a long-lost deepwater fish from the eastern Pacific Ocean: a case study of a forensic approach to taxonomy using DNA barcoding, Zootaxa 3669 (4), pp. 551-570 : 557-560

Sagittalarva Victor , n. gen.

Type species: Sagittalarva inornata (Gilbert, 1890) , Baja California, Mexico; here designated.

Diagnosis. Dorsal rays IX,12; anal rays III,12; pectoral rays 13 (12 plus uppermost rudimentary ray); lateral-line continuous, inclined sharply downward below soft portion of dorsal fin, the pored scales 27, canals on scales with a single pore; head naked except for a set of small scales on each side of nape forward of the dorsal-fin origin; scales on thorax much smaller than body scales; jaws with a single pair of enlarged canine teeth at the front of the upper jaw (one tooth per side) and a single pair at the front of the lower jaw (one tooth per side) which fit between the upper pair when the mouth is closed; teeth behind enlarged canines in a regular row of caniniform to conical teeth; no posterior canine at the corner of the mouth; posterior half of upper lip with a dorsal fleshy flap, variably developed; 10+6 gill rakers, larger ones serrated and branched; snout long and pointed, snout length 3.3–3.4 in HL for fish over 70 mm SL (3.36 in holotype); body slender, depth of body 4.6–4.7 in SL for fish over 70 mm SL (4.57 in holotype, “depth 5 2/ 3 in length” in Gilbert (1890) must refer to TL); body very compressed, body width 9.0- 10.5% SL; dorsal-fin spines pungent, first spine shortest, subsequent spines and rays progressively longer; caudal fin only slightly rounded.

Mid to late-stage larvae (7–14 mm SL) slender, flattened, and dart-shaped with marked horizontal symmetry (symmetrical above and below the lateral midline); forehead low and straight; mouth small, terminal, and at the level of the lateral midline; snout long and sharply pointed; melanophore pigment limited to the tip of the upper and lower jaws and a few small melanophores along the edge of the caudal-fin and posterior dorsal and anal-fin membranes.

Etymology. The name Sagittalarva derives from the combination of sagitta, arrow or dart in Latin, and larva, originally ghost or mask in Latin and first applied to immature forms by Linnaeus, referring to the unusual dartshaped larva of the Cape Wrasse; both nouns and the combination are feminine.

Remarks. A single pair of enlarged canines at the tip of each of the upper and lower jaws with no canine at the corner of the jaw and rows of caniniform to conical teeth along the jaws ( Fig. 1 ) separates Sagittalarva from all other New World julidines as well as from Pseudojuloides . All western Atlantic Halichoeres differ in having a prominent canine at the corner of the jaw and all but two have two pairs of enlarged canines in the lower jaw ( H. maculipinna and its Brazilian sibling have only a single pair of enlarged canines at the lower jaw). Most eastern Pacific Halichoeres also have the canine at the corner of the jaw and the exceptions have two pairs of enlarged canines at the tip of the lower jaw ( H. notospilus (Günther) , H. adustus (Gilbert, 1890) , and H. insularis Allen & Robertson, 1992 ) or more than a single enlarged pair at both the upper and lower jaw tips ( H. melanotis , H. salmofasciatus , and H. malpelo Allen & Robertson, 1992 ; as well as Oxyjulis californica ). Species of Thalassoma do not have a particularly enlarged pair of canines, while Pseudojuloides have flattened chisel-like incisiform teeth behind a pair of canines ( Fig. 2 ).

There is some ambiguity in the literature for the pectoral fin-ray counts for eastern Pacific Halichoeres species, with counts of 12 or 13 inconsistently cited in descriptions and guides. All of the species were examined but H. malpelo and they all have 13 total rays (12 plus one upper rudimentary). The species description for H. malpelo also reports 13 pectoral rays (Allen & Robertson 1992; 1994). In all species, the uppermost pectoral ray is a short unbranched ray, more obvious on smaller individuals and sometimes not grossly visible in adults. The next ray is typically the largest ray of the pectoral-fin series and should be counted as the second ray from the top (Randall & Allen 2010).

The larvae of New World Halichoeres and Thalassoma species differ markedly in morphology from larval Sagittalarva inornata . They have relatively stout bodies that are not horizontally symmetrical, relatively short snouts, and different patterns of melanophores (Watson et al. 1996; Beltrán-Leon & Herrera 2000; Jones et al. 2006; Victor 2012 and unpublished data) ( Fig. 3 ). None have melanophores on the head and the basic complement is melanophores on the membranes between adjacent fin rays in discrete patches spaced out along the length of the dorsal and anal fins. On most larval Halichoeres there are three patches on the dorsal fin (front, mid, and rear) and two on the anal fin (front and rear). Halichoeres maculipinna larvae have only the rear patch on the dorsal and anal fins. Larval Thalassoma generally have very few melanophores: T. bifasciatum (Bloch) larvae have a patch on the membranes of the first few dorsal spines and isolated small edge melanophores along the rim of the dorsal, caudal, and anal fin membranes (these are similar to the melanophores on larval S. inornata ). Larvae of other Thalassoma in the literature are typically shown with no melanophores, although the small fin-edge melanophores are present on well-preserved larvae of the eastern Pacific species and some western Pacific species as well (Victor 2012). It is likely that they occur on all Thalassoma larvae.

The larvae of Pseudojuloides cerasinus (Snyder) have been identified by DNA-barcode matching (collected from Hawaii by David Carlon, pers. comm. and in BOLD project FLHI) as well as by morphology (Miller et al. 1979, as Labrid L3, 7.2 mm SL). They differ markedly from Sagittalarva inornata larvae, having a short upturned snout and some very different markings from other labrid larvae, in particular distinctive internal melanophores along myomere edges within the musculature of the rear body, in addition to patches of melanophores on the membranes between the last few dorsal and anal-fin rays ( Fig. 4 ). Bruce Mundy (pers.comm.) identified larval P. cerasinus in his Hawaiian collections and found both the internal and fin-membrane melanophores as well as additional melanophores over the cranium and a complex pattern of erythrophores (usually lost in preservation) on fresh late-stage P. cerasinus larvae.

Figures

FIGURE 1. Radiograph of the head of the holotype of Sagittalarva inornata (USNM 44273) showing a single pair of enlarged canines at the front of the upper and lower jaws followed by rows of caniniform to coniform teeth, courtesy Sandra Raredon, USNM.

FIGURE 2. Upper jaw of Pseudojuloides severnsi showing spatulate incisiform teeth behind canine.

FIGURE 3. Larval labrids of the eastern Pacific Ocean: from top, Sagittalarva inornata 11.6 mm SL & 8.3 mm SL, Halichoeres 13.1 mm SL, Thalassoma 10.2 mm SL (identified by DNA-barcode matching).

FIGURE 4. Larva of Pseudojuloides cerasinus from Hawaii, identified by DNA-barcode matching, courtesy David Carlon.