Labidesthes sicculus ( Cope 1865 )

Werneke, David C. & Armbruster, Jonathan W., 2015, Silversides of the genus Labidesthes (Atheriniformes: Atherinopsidae), Zootaxa 4032 (5), pp. 535-550 : 538-541

Labidesthes sicculus ( Cope 1865)

Brook Silverside

( Figs. 3–4 )

Chirostoma sicculum Cope, 1865 . Proc. Acad. Nat. Sci. Phila. 17:81.

Material examined. Syntypes: UMMZ 213812, (2), 52–53 mm SL, Grosse Isle, Detroit River, Wayne County, Michigan, by M. Miles.

Nontypes: Arkansas River drainage: NCSM 4544, NCSM 47064, NCSM 47499, TU 12004, UAIC 1013.05 (2), UF 21983 (1), UF 22016 (2), UT 158.43, UT 158.252.

Brazos River drainage: NCSM 36393, TU 91175.

Calcasieu River drainage: TU 44611, TU 64284, TU 121912, TU 124813.

Cumberland River drainage: AUM 28924 (7), NCSM 29291, NCSM 48033, NCSM 48342, UAIC 12354.01 (2 + 2 c&s), UT 158.13, UT 158.26, UT 158.40, UT 158.42, UT 158.105, UT 158.108, UT 158.110, UT 158.111, UT 158.117, UT 158.134, UT 158.139, UT 158.238, UT 158.273, UT 158.274, UT 158.281, UT 158.285, UT 158.324, UT 158.379.

Galveston Bay drainage: TU 61893, TU 61963, TU 62852, TU 66483, TU 67260, UF 29642 (3), UF 29466 (2 c&s).

Great Lakes & St. Lawrence River drainage: TU 19209, UAIC 2985.11 (2), UMMZ 117154 (5 + 2 c&s), UMMZ 132001 (5).

Homochitto River drainage: AUM 50798, AUM 50799, AUM 50803, AUM 50814, AUM 50822, INHS 90112 (2), TU 7439, TU 46524, TU 76761, TU 83817.

Illinois River drainage: AUM 29752 (1), NCSM 47475, UT 158.79.

Meramec River drainage: NCSM 30651, UT 158.109.

Lower Mississippi River drainage: AUM 19060 (1), INHS 76651 (5), NCSM 33682, NCSM 47089, TU 75572, TU 91073, TU 91155, TU 91191, UAIC 6401.07 (1 + 1 c&s), UT 158.83, UT 158.86, UT 158.88, UT 158.118, UT 158.204, UT 158.215, UT 158.216, UT 158.221, UT 158.224, UT 158.233, UT 158.235.

Upper Mississippi River drainage: NCSM 36800, UT 158.261, UT 158.262, UT 158.263.

Missouri River drainage: NCSM 30641, UT 158.179, UT 158.199, UT 158.378.

Neches River drainage: TU 21701, TU 67309, TU 72745, TU 109553, TU 110175, TU 111132, TU 111685, TU 114868, TU 122991.

Ohio River drainage: INHS 42358 (5 + 2 c&s), INHS 43459 (5), NCSM 37765, NCSM 38285, NCSM 38432, NCSM 38652, NCSM 38738, NCSM 38837, NCSM 38853, NCSM 38880, NCSM 39165, NCSM 39376, NCSM 55230, NCSM 55231, NCSM 55232, NCSM 55233, NCSM 55234, NCSM 55235, NCSM 55236, NCSM 55245, NCSM 55246, UAIC 2844.14 (1), UT 158.69, UT 158.70, UT 158.71, UT 158.72, UT 158.73, UT 158.228, UT 158.268.

Pascagoula River drainage: UT 158.291, UT 158.292.

Pearl River drainage: TU 191982, TU 28962, TU 28996, TU 82034, UT 158.87, UT 158.286, UT 158.289, UT 158.290, UAIC 12767.11 (2 + 2 c&s), UAIC 12770.07 (1).

Lake Pontchartrain drainage: TU 45320, TU 76058.

Red River drainage: AUM 13762 (2 c&s), AUM 34112 (5), INHS 44515 (5), NCSM 4493, NCSM 36288, NCSM 36329, NCSM 37363, NCSM 37390, NCSM 37424, NCSM 37482, NCSM 47153, TU 147500, TU 192087, UT 158.23, UT 158.266.

Sabine River drainage: TU 61519, TU 62377, TU 67587, TU 67765, UF 29501 (1).

Tennessee River drainage: AUM 12012 (2 c&s), AUM 29655 (5), NCSM 26857, NCSM 29338, NCSM 29624, UAIC 13312.23 (5), UT 158.2, UT 158.9, UT 158.25, UT 158.29, UT 158.44, UT 158.65, UT 158.66, UT 158.91, UT 158.96, UT 158.97, UT 158.98, UT 158.100, UT 158.104, UT 158.113, UT 158.123, UT 158.126, UT 158.127, UT 158.129, UT 158.137, UT 158.138, UT 158.140, UT 158.160, UT 158.162, UT 158.163, UT 158.171, UT 158.172, UT 158.173, UT 158.180, UT 158.181, UT 158.182, UT 158.183, UT 158.184, UT 158.186, UT 158.187, UT 158.196, UT 158.200, UT 158.201, UT 158.203, UT 158.208, UT 158.209, UT 158.212, UT 158.213, UT 158.214, UT 158.217, UT 158.218, UT 158.227, UT 158.236, UT 158.237, UT 158.241, UT 158.242, UT 158.259, UT 158.267, UT 158.277, UT 158.280, UT 158.294, UT 158.295, UT 158.305, UT 158.309, UT 158.311, UT 158.312, UT 158.313, UT 158.314, UT 158.315, UT 158.316, UT 158.317, UT 158.318, UT 158.319, UT 158.320, UT 158.321, UT 158.322, UT 158.323, UT 158.325, UT 158.326, UT 158.327.

White River drainage: AUM 33957 (5), INHS 81779 (5), NCSM 37452, NCSM 37502, NCSM 37528, NCSM 47128, NCSM 47369, UT 158.30, UT 158.31, UT 158.101, UT 158.112, UT 158.264, UT 158.265, UT 158.377.

Yazoo River drainage: AUM 30226 (2 c&s), AUM 50801, AUM 50802, AUM 50805, AUM 50811, AUM 50813, AUM 50815, AUM 50816, AUM 50817, AUM 50820, AUM 50821, AUM 50826, AUM 50828, AUM 50830, AUM 50831.

Diagnosis. Labidesthes sicculus differs from Labidesthes vanhyningi in having the anterolateral process of the post-temporal longer than width of base (vs. shorter than the base: Fig. 5 ), a midlateral stripe that tapers anterior of the first dorsal fin to a point behind the dorsal insertion of the pectoral fin (vs. maintaining width or expanding anterior of first dorsal fin: Fig. 3 ), and a ratio of thoracic length to abdominal length greater than 2 (vs. less than 2).

Description. Meristics: median lateral scale rows (69–71) 72–91 (92); scales above midline 8–10 (11); scales below midline 8–11; peduncle scales 18–22; predorsal scales 36–48 (49); interdorsal scales (9) 10–15; prepelvic scales (22–23) 24–32; anus-anal-fin scales 3–6 (7); postdorsal scales 14–20; postanal scales 10–16; first dorsal III– V (6); second dorsal I,8–12; pectoral 11–13; pelvic 6; anal-fin I,(19) 20–26 (27); caudal 16–17 ( Table 2 ).

Morphometrics: specimens examined 52.7–82.5 mm; short head, four times into SL; eye large, 2.5 times into maximum body depth. Body compressed and elongate, maximum body depth six to eight times into SL, ratio of thoracic length to abdominal length greater than two.

Premaxillary long, weakly protrusible, curving ventrally midway along length, creating muzzle like snout; terminal mouth, with moderately long, posteriorly curved, pointed, conical teeth. Forked caudal fin; second dorsal and anal fins falcate; anal fin long, extending length from anterior of first dorsal to beyond posterior of second dorsal; pelvic fin extending to anus; first dorsal-fin origin opposite of anal-fin origin; pectoral fin pointed, extending to insertion of pelvic fin. First dorsal spinous, second dorsal with one anterior spine followed by branched rays. Genital papilla short in males, absent in females. Lateral line nearly absent, pored scales, if present, always found posterior to first dorsal usually concentrated on peduncle. Scales cycloid, extending onto caudal fin, absent from other fins; opercle scaled, scales extending to a spot below front of eye; top of head with or without scales, if present may extend to front of eye. Dorsal profile ascending gradually from tip of snout to supraoccipital, profile from supraoccipital to anterior insertion of second dorsal straight, and descending gradually to dorsal procurrent caudal-fin rays. Ventral profile forming gentle arc from snout to ventral procurrent caudal-fin rays.

Color in life. Body translucent, often with yellow or green tint. Midlateral silver band, narrowest on caudal peduncle, broadening and fading anteriorly. Scales above midline and on dorsum outlined with melanophores, forming weak band along center of dorsum. Venter with black stripe originating posterior to anus and terminating at the origin of caudal fin. Distal one-third of first dorsal fin with melanophores on membranes forming a black band in males, not as pronounced in females. Head covered in melanophores, with supraoccipital densely pigmented, chin pigmented, dark spot on lower jaw at rear margin of mouth. Iris silver, dusky dorsally in some individuals, inside of mouth with scattered melanophores along margin and on outside of cheeks. Spines and rays outlined in melanophores, except pelvic fin, which is devoid of pigment. Silver peritoneum visible through body wall.

Color in alcohol. Body pallid, lateral silver stripe along the midline overlaying a dark stripe, fading anteriorly, dark stripe narrowing in advance of first dorsal fin as it approaches pectoral fin. ( Fig. 3 ). Scales above lateral stripe outlined in melanophores, dorsum with black stripe along middle. Scales below lateral stripe faintly pigmented in some individuals. Venter with black stripe originating posterior to anus and terminating at origin of caudal fin. Distal one-third of first dorsal fin with melanophores on membranes forming black band in males, but not as pronounced in females. Head covered in melanophores, with occiput densely pigmented, chin darkly pigmented, dark spot on lower jaw at rear margin of mouth. Iris silver, dusky dorsally in some individuals, inside of mouth with scattered melanophores along margin and on outside of cheeks. Spines and rays outlined in melanophores, except in pelvic fin, which is devoid of pigment.

Range. Labidesthes sicculus occurs in Gulf of Mexico drainages from the Pearl River west to Brazos River (including the Mississippi River drainge), and the Great Lakes (excluding Lake Superior)-St. Lawrence River drainages ( Fig. 1 ).

Etymology. Likely, from the latin sicula meaning small dagger ( Scharpf & Lazara 2014).

Figures

FIGURE 1. Distribution of Labidesthes sicculus (blue dots) and L. vanhyningi (red squares) examined in this study. Stars indicate type localities.

FIGURE 3. Labidesthes sicculus preserved specimen dorsal, lateral, and ventral views. AUM 62249, 71.1 mm SL, Tennessee River drainage, Maury County, TN.

FIGURE 4. Syntypes of Chirostoma sicculum, UMMZ 213812 (A. 53 mm SL, B. 52 mm SL) and C. holotype of Labidesthes vanhyningi USNM 88485 58 mm SL. Scale bars equal 1 cm (shared for A and B). A and B by Ann Barget and the Great Lakes Invasive Species (UMMZ) project and C by Sandra J. Raredon, Smithsonian Institution, National Museum of Natural History.

FIGURE 5. The anterolateral process of the post temporal (indicated by arrows) is longer than its width in Labidesthes sicculus (A.) and shorter than its width in L. vanhyningi (B.).

Tables

TABLE 2. Mode and range of Labidesthes meristics.

	L. sicculus		L. vanhyningi
Meristics	Mode	Range	Mode	Range
1st dorsal spines	4	3–6	5	3–6
2nd dorsal spines	1	1–1	1	1–1
2nd dorsal rays	10	8–12	10	8–12
Pectoral rays	12	11–13	12	11–14
Pelvic rays	6	6–6	6	6–6
Anal spines	1	1–1	1	1–1
Anal rays	23	19–27	22	18–26
Principal Caudal Rays	17	16–17	17	15–18
Midlateral scales	78	69–92	77	65–91
Scales above midline	9	8–11	9	8–11
Sacles below midline	9	8–11	9	7–11
Circumpeduncle scales	20	18–22	20	16–22
Predorsal scales	39	35–49	36	31–46
Interdorsal scales	12	9–15	12	9–17
Prepelvic scales	27	20–32	23	20–30
Anus-anal fin scales	4	3–7	3	2–6
Post dorsal scales	17	14–21	17	12–22
Post anal scales	13	10–16	10	8–14