Parequula melbournensis Castelnau 1872
Creators: name: Iwatsuki, Yukio
name: Pogonoski, John J.
name: Last, Peter
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Perciformes
Gerreidae
Parequula
Parequula melbournensis

description: Parequula melbournensis (Castelnau 1872)
English name: Silverbelly
(Figures 1 B, 2A–B; Table 1)
Gerres melbournensis Castelnau 1872: 158 (type locality: Melbourne, Victoria, Australia); Castelnau 1873: 37 (Melbourne, Australia).
Parequula bicornis Steindachner, 1879a: 30 (Hobsons Bay, Vic., ca. 37°51'S, 144°56'E and Murray River, South Australia); Steindachner, 1879b: 8 (proposed for this new genus); Fricke 1995: 13 (Hobsons Bay, Vic.); Fricke 2005: 39 (Hobsons Bay, Vic.).
Chthamalopteyx melbournensis; Ogilby 1888: 616, unnumbered figure (proposed as a new genus); McCulloch 1911: 63 (Flinders Island, Tas., off Murray River mouth, off Kingston, off Flinders I and Spencer Gulf, South Australia).
Parequula melbournensis; Waite 1921: 106, fig. 163 (southeastern Australia); McCulloch 1930: 216 (southern Australia); Fowler 1933: 257 (listed as above localities); Whitley 1964: 45 (southern Australia); Scott 1964: 95 (Tasmania); Scott and Glover 1974: 223, unnumbered figure (Hobsons Bay); Coleman 1980: 158, unnumbered figure (Vic., Tas., SA, WA); Last et al. 1983: 367 (Tasmania); Hutchins and Thompson 1983: 38, fig. 168 (southern half of Australia to Rottnest Island, WA); Hutchins and Swainson 1986: 62, fig. 313 (Merimbula, NSW to Vic., Tas., SA and WA [Rottnest Island]); Bauchot and Desoutter 1989: 27 (Melbourne, Victoria, Australia); Kuiter 1993: 194 (southern Australia); Fricke 1995: 39 (Hobsons Bay, Australia); Kuiter 1996: 166 (southern Australia); Edgar 1997: 451 (southern Australia); Hutchins 2001: 34 (WA checklist, listed); Fricke 2005: 39 (Hobsons Bay, Vic.); Hoese and Bray 2006: 1217 (NSW [36˚53’ S] to Rottnest Island, WA [32˚S] and throughout Tasmania); Gomon et al. 2008: 587 (southern Australia).
Lectotype. MNHN A–0968, 94 mm SL (MX), Melbourne, Victoria, Australia (ca. 37°49’S, 144°58’E) (herein designated).
Other specimens. 36−159 mm SL, n =31, all from Australia. AMS I. 12146, 133 mm SL, off Port Albert, Victoria, Australia (38°00’S, 146°00’E), 27 m; AMS I. 21305−006, 139 mm SL, Great Oyster Bay, Tasmania, Australia (42°13’S, 148°13’E), 16 m; CSIRO A 1447, 62 mm SL (MX), no accurate locality data, but probably southern Western Australia, 4 m; CSIRO A 1513 (MX), 77 mm SL, Exmouth (locality data questionable), Western Australia (ca. 22°S, 114°10’E); CSIRO A 1521 (MX), 70 mm SL, Warnbro Sound, Western Australia (32°20’S, 115°43’E); CSIRO C 1941, 121 mm SL (MX), Limestone Head, King George Sound, Western Australia (ca. 35°05’S, 118°00’E); CSIRO C 2001, 116 mm SL (MX), Two Peoples Bay, Western Australia (ca. 34°57’S, 118°10’E); CSIRO C 2004, 88 mm SL (MX), Lakes Entrance, Victoria (ca. 37°53’S, 148°00’E); CSIRO C 2692, 104 mm SL (MX), Cockburn Sound, Western Australia (ca. 32°12’S, 115°44’E); CSIRO CA 52, 157 mm SL (MX), Great Oyster Bay, Tasmania (42°15’S, 142°09’E), 12 – 17 m; CSIRO CA 170, 116 mm SL (MX), CA 171, 102 mm SL (MX), CA 172, 110 mm SL (MX), CA 173, 87 mm SL (MX), off Waterhouse I., Ringarooma Bay, Tasmania (40°45’S, 147°45’E), 34 m; CSIRO CA 3405, 127 mm SL (MX), CA 3406, 124 mm SL (MX), off Point Culver, Great Australian Bight, Western Australia (33°20’S, 124°46’E), 48 m; CSIRO H 2923–01, 50 mm SL (MX), CSIRO H 3536–06, 159 mm SL, off Disaster Bay, NSW (37°24’S, 149°58’E), 42–43 m; CSIRO H 6346– 17, 110 mm SL (MX), CSIRO H 6346–27, 2 specimens, 86–98 mm SL (MX); off Rottnest, Western Australia (31°55’S, 115°36’E), 28–29 m; CSIRO H 6942–05, 108 mm SL (MX), Investigator Strait, South Australia (35°24’S, 137°55’E), 37 m; CSIRO T 1675, 70 mm SL (X), Settlement Point, Flinders I., Bass Strait, Tasmania (ca. 40°01’S, 147°51’E); CSIRO T 1711–09, 65 mm SL (MX), norterneast coast of Flinders I., Tasmania (ca. 40°S, 148°E); MUFS 32940, 93 mm SL (MX), off Rottnest, Western Australia (31°55’S, 115°36’E), 28–29 m; MUFS 32941–32943, 3 specimens, 47–54 mm SL (M), off King Island, Bass Strait, Tasmania (39°53’S, 144°21’E), 33–35 m; NMW 90675 (1 of 2 syntypes of Parequula bicornis), 125 mm SL, Murray River, Victoria; SAMA F 12112, 36 mm SL (MX), Great Australian Bight, South Australia (32°15’S, 132°39’E), 61 m; SMNS 2236 (1 of 2 syntypes of Parequula bicornis), 127 mm SL, Hobsons Bay, Victoria (37°51'S, 144°56'E).
Diagnosis. Distinguished from congeners in having the following combination of characters: a deeper body 2.0–2.7, mean 2.3 in standard length; semi-translucent to bluish with a narrow, parallel, yellowish vertical line on each fin membrane and a yellowish fin margin; soft anal-fin rays 16–18, mode 17; pored lateral-line scales 37–40, mode 38.
Description. Counts and proportional measurements of the lectotype and 29 other specimens of P. melbournensis are shown in Table 1. Data for the lectotype are presented first, followed by those of other specimens in parentheses if different.
Body ovate, compressed; rostro-occipital (dorsal) profile of head weakly convex; weakly to strongly concave in lateral view above eye, interorbital space slightly convex (slightly convex or flat, sometimes grooved when skin tightly connected with skull in preserved specimens); a pair of slight protuberances (nasal bones) projecting from anterior of snout, observed as naked nasal bones, more obvious when jaws protracted (Fig. 3 C); predorsal length shorter than body depth; orbit diameter 2.9 (2.1–3.0) in head, almost equal to bony interorbital width (subequal to or slightly greater than interorbital width); snout flattened in dorsal view (flat or with very shallow groove on snout and anterior orbit for process of intermaxillary bones, especially in specimens less than 100 mm SL), its length slightly less than orbit diameter; maxilla not reaching to vertical at anterior margin of eye, its posterior edge concave (usually concave); mandibular profile weakly concave; anterior premaxillary bone with a pair of blunt bony protuberances (weak to prominent) anteriorly, most visible in dorsal view; no scales on preopercular flange, rounded angle slightly less than 90º; mouth protractile; teeth minute, weakly curved, in a broad band on both jaws, those on outer row somewhat enlarged.
Dorsal fin not usually notched; length of soft portion exceeding that of spinous (slightly exceeding in paratypes), length of spinous dorsal-fin base subequal to three quarters length of soft anal-fin base; dorsal-fin spines moderately strong and gradually increasing in height to penultimate spines, last three spines subequal, the last ca. 0.4 in head length (closer to one third head length in many specimens); anterior soft rays subequal in height to posterior spines; anal fin commencing beneath anterior dorsal-fin ray, length of its base about one quarter more than length of head; spines slightly stronger than dorsal-fin spines; third spine longest, more than a third of head length; pelvic-fin origin beneath posterior angle of base of pectoral fin; pelvic fin not quite extending to vent, length about 60% of head length, its spine length about 80% of length of adjacent ray; pectoral fin elongate, slightly shorter than head length, fourth and fifth rays longest, extending posteriorly to level of third anal-fin spine; caudal fin moderately forked to slightly lunate.
Gill rakers short: rakers of upper limb shorter than uppermost rakers on lower limb, and rakers on lower limb gradually becoming shorter anteroventrally; body scales oval and cycloid; interorbital space, snout, and preorbital naked; head and body punctuated with numerous, small, round pores, usually visible without magnification on specimens larger than ca. 100 mm SL (Fig. 3 C–D); most pronounced on snout and interorbital region, but also evident on dorsal and anal fin bases when deciduous scales are lost; scattered small round pores, often observed together with a probable neuromast cell at each pores’ center (Fig. 3 D); posterior nostril twice size of anterior nostril, placed very close to eye, a small skin flap between anterior and posterior nostril; scales of cheek smaller than those of body, extending on to mandible; branchiostegals 6; pseudobranchiae present; 3 supraneural bones, usually 0/0/0+2/, but variably 0/0+0/2/ (on CSIRO A 1521, CSIRO C 2004, CSIRO CA 52, CSIRO CA 170 and CSIRO H 3536–06; see Remarks section below); upper caudal fin rays (dorsal) 17–20, lower caudal fin rays (ventral) 15–17, total caudal fin rays 32–37, upper procurrent rays (dorsal) 8–11, lower procurrent rays (ventral) 7–9, total procurrent rays 15–20; vertebrae 10+15.
Coloration. Fresh coloration is based on color photographs of CSIRO H 6346–17 (110 mm SL), CSIRO H 6942–05 (108 mm SL), fig. p 587 of Gomon et al. 2008 (presumably ca. 15 cm SL), and an underwater photograph (http://australianmuseum.net.au/image/Silverbelly-Parequula-melbournensis): head and body whitish, yellowish or silvery bronze, with alternating, narrow, broken bluish bars; darker with bluish shine above; pectoral, pelvic and anal-fin membranes translucent to pinkish; dorsal fin semi-translucent bluish with narrow, parallel, yellowish vertical line on each fin membrane; margin of dorsal fin yellowish; (see a photograph on the above internet site); upper and lower rays of caudal fin brighter yellow than central part; cheeks and opercles washed with same color as body; iris whitish or golden, often with a dark vertical bar. In preservative (based on all examined specimens, except those listed below) head and body yellowish to brownish, abdominal part paler, upper-most and lower-most caudal fin membranes usually darker than adjacent rays. CSIRO H 2923–01, CSIRO H 6346–27 and MUFS 32941–32943 have white posterior opercle and whitish ventral body coloration.
Distribution. Currently known from Merimbula, New South Wales (36˚53’S) to near Rottnest Island, Western Australia (ca. 32˚S), and throughout Bass Strait and off Tasmania (Hutchins and Swainston 1986). One specimen (CSIRO A 1513) from Exmouth Gulf, Western Australia (ca. 22˚S) has questionable locality data as this locality is 10˚ latitude further north of its confirmed distribution in WA.
Ecological notes. Gomon et al. (2008) noted “over sand or mud bottom, often associated with seagrass, from intertidal zone to more than 100 m; forms schools, sometimes in large numbers” but can also be solitary (Last et al. 1983). The frequency of records in the literature suggest it is a reasonably common non-commercial component of bycatch in shallow trawl fisheries. Maximum depth data for over 200 lots of P. melbournensis in Australian fish collections (AMS, CSIRO, NMV, SAMA, WAM) was 84 m, but very few records were from deeper than 50 m. Both Parequula species were collected in the same trawl survey off southwestern Australia by Last et al 2006, but not in the same trawl stations, suggesting depth-related and/or habitat partitioning.
Recently, Platell et al. (1997) studied the body size and mouth morphology of P. melbournensis. Bruce et al. (2009) reported that P. melbournensis co-occurs in different seasons and locations with the carangid Pseudocaranx wrighti. Parequula melbournensis mainly fed on polychaetes (45%), molluscs, crustaceans (29%) and echinoderms. In addition, a recent dietary study of Australian fur seals (Arctocephalus pusillus doriferus), using pyrosequencing prey DNA techniques from faeces collected at three breeding colonies from Victoria, southeastern Australia (Deagle et al. 2009), found that P. melbournensis was a small dietary component, together with primary pelagic prey species, Emmelichthys nitidus (Emmelichthyidae) and Trachurus declivis (Carangidae). The body shape and images of live specimens swimming or hovering above the substrate suggests that it leads a benthopelagic lifestyle.
Remarks. Gerres melbournensis Castelnau 1872 was described from two syntypes (Eschmeyer & Fricke, 2011). Syntype MNHN A–0968 (94 mm SL) has been designated as the lectotype. The other syntype, a skin (AMS A 7138, unknown size, collected near Melbourne, Victoria, ca. 37°49’S, 144°58’E), appears to have been lost (not found in a search in January 2011 according to M. McGrouther, personal communication). The two syntypes (NMW 90675, 125 mm SL and SMNS 2236, 127 mm SL) of Parequula bicornis Steindachner 1879, conforms to Parequula melbournensis (Table 1), and it is considered to be a junior synonym.
Formula of supraneural bones in P. melbournensis was basically “0/0/0+2/”, which is typical of most gerreid species (Iwatsuki et al. 1999a), but five specimens of P. melbournensis noted in description above showed “0/0+0/ 2/”, which is characteristic of the Gerres erythrourus complex (i.e. G. erythrourus and G. phaiya with deep bodies; Iwatsuki et al. 1998; Iwatsuki & Heemstra 2001, see fig. 2A–B). The same formula (“0/0+0/2/”) was also observed in P. elongata n. sp. only for MUFS 32938. Therefore, Parequula species might exhibit variability in the formula of their supraneural bones although variation in the formula of supraneural bones of each gerreid complex, group or species have not been reported in Iwatsuki’s serial reports cited earlier.
description: Published as part of Iwatsuki, Yukio, Pogonoski, John J. & Last, Peter, 2012, Revision of the genus Parequula (Pisces: Gerreidae) with a new species from southwestern Australia, pp. 42-54 in Zootaxa 3425 on pages 48-51, DOI: 10.5281/zenodo.282006