Trachypterus cristatus, (Bonelli 1820)

Martin, Jennifer M. & Hilton, Eric J., 2021, A taxonomic review of the family Trachipteridae (Acanthomorpha: Lampridiformes), with an emphasis on taxa distributed in the western Pacific Ocean, Zootaxa 5039 (3), pp. 301-351 : 334-335

Zu cristatus ( Bonelli 1820)

Figures 2B , 3B , 18 , 22

Type species. Trachypterus cristatus Bonelli 1820

Holotype. MZUT 1190. 590 mm SL. Purchased from a fisherman at the Port of Genoa, taken from the Gulf of Spezia.

Material Examined. Trachypterus ijimae (= Zu cristatus ) NSMT P 590 (holotype, 137 mm SL, Pacific, Japan, Tokyo Bay); AMS I.17877-022 (304 mm SL, Pacific , Australia, New South Wales, Sydney ); AMS I.27499-001 (211mm SL, Pacific , Australia, Queensland, Hamilton Island ); AMS I.36042-001 (6 mm TL, Pacific , Australia, Queensland, Osprey Atoll ); AMS I.36044-001 (5 mm TL, Pacific , Australia, Queensland, Osprey Atoll ); AMS I.38598-003 (310 mm SL, Pacific , Australia, New South Wales, Sydney ); AMS I.39622-001 (330 mm SL, Pacific , Australia, New South Wales, Angourie Point ); AMS I.42086-005 (35 mm SL, Pacific , Australia, Queensland, Coral Sea ); AMS I.42452-018 (30 mm SL, Pacific , Australia, Queensland, Coral Sea ) ; BMNH 1887.12 .7.21 (32 mm SL, Pacific, Philippines) ; HUMZ 3045 (197 mm SL, Pacific, Taiwan) ; HUMZ unregistered (872 mm SL, unknown); KPM-NI0023199 (12 mm SL, Pacific, Japan, Ogasawara Islands ) ; MCZ 59320 (49 mm SL, Atlantic, Caribbean) ; MCZ 157795 (21 mm SL, NW Atlantic) ; VIMS 40937 (271 mm SL, Gulf of Mexico ); NPM K l/d2998 Atlantic, Mediterranean, Adriatic, Dalmatia ).

Diagnosis: Dorsal-fin rays 120–151 total (135–145 most common), six most anterior in juveniles more robust and elongate than others; pectoral-fin rays 10–12, first element short and stout; pelvic-fin rays 6–7, first short and stout, elongate in juveniles, reduced to only bony base in adults; caudal-fin rays 10–12, dorsal lobe with 8–9 rays, ventral lobe with 2–3 rays, ventral lobe greatly reduced in adults. Gill rakers 2–3 + 8–9. Lateral-line plates 96–106. Vertebrae: 63–69 total, 22–24 precaudal, 32–33 preanal. SVL 40.6–50.1% SL (43.1–54.9 % in specimens from 137–248 mm); body depth 19.7 –21 % SL (decreasing with increasing SL); eye diameter 5.1–7.2 % SV, eye diameter 1.5–2.0 in length of lower jaw. Premaxilla with 9–21 teeth, 10 on dentary; vomer with 1–4 teeth in adult; palatine teeth present (up to 3 on each) or absent.

Remarks. In juveniles, the three fleshy lobes present on the ventral midline (i.e., the scalloped ventral margin) between the pelvic-fin base and the anus are smooth ( Fig. 18 ). The post-anal ventral constriction is abrupt in juveniles and the orientation of the lateral line runs straight from its origin to the point of ventral constriction just posterior to the anus, at which point it joins the ventral midline.

The presence of deciduous cycloid scales was reported by Bolin (1933), Tortonese (1958), Walters & Fitch (1960), Palmer (1961), and Fitch (1964). Rosenblatt & Butler (1977) indicated that there were no scales present on their eight specimens of Zu. Heemstra & Kannemeyer (1984) suggested squamation over the entire body and reported the presence of only scale pockets on adults, except near the tail. On all adult specimens examined here there are thin delicate scales present in the caudal region that can appear as shiny patches and scale pockets are present across trunk. One adult specimen (HUMZ unregistered, 872 mm SL) was covered in delicate, imbricated cycloid scales throughout the body, but scales were absent in the head region. Each scale on the trunk overlapped multiple skin tubercles. In juveniles, scales typically persist along the lateral line and onto the caudal fin.

Distribution: Worldwide in tropical and temperate waters.

Habitat: It appears there is an ontogenetic shift in habitat. There is a trend of increasing collection depth and distance from shore with increasing length.Adult specimens are rarely collected in bottom trawls or long-lines ranging in depth from roughly 150–1200m (to 400m in the Mediterranean and to 1200 m in the Tasman Sea). Juvenile specimens are found in more nearshore, midwater habitats. Although rare, early juveniles have been photographed on coral reefs in all oceans ( Figs. 20 , 21 ). Eggs and larvae are planktonic and not uncommon in long-term ichthyoplankton surveys (e.g., Great Barrier Reef, Gulf of Mexico, Eastern Pacific).

Geographic variability. While revising the Trachipteridae of the Mediterranean and Northeast Atlantic, Palm- er (1961) reported that the first five dorsal-fin rays of Z. cristatus are elongate. However, this is in contrast to all other reported values from all oceans, including the Mediterranean and Northeast Atlantic. In all specimens examined here, the first six dorsal rays are elongate in larvae and juveniles, and persist as the nuchal pennant which is separated from the remaining dorsal-fin rays in adults. There does not appear to be any geographic variation in this character. However, specimens from the Eastern Pacific Ocean tend to have slightly fewer total dorsal-fin rays (6 + 132–138) than those from the Western Pacific Ocean (6 + 137–145).

Figures

FIGURE 2. Illustrations of representatives of the three genera of Trachipteridae. A, Trachipterus fukuzakii (large juvenile). B, Zu cristatus (large juvenile). C, Desmodema polystictum (juvenile). Illustrations © Val Kells, used with permission.

FIGURE 3. Photographs of adult representatives of the three genera of Trachipteridae. A, Trachipterus ishikawae Jordan & Snyder, 1901; KPM-NI 48485; © Hiroshi Senou; obtained from http://fishpix.kahaku.go.jp. B, Zu cristatus (Bonelli, 1820); CSIRO H-6325-01; 1142 mm SL. C, Desmodema lorum Rosenblatt & Butler 1977. Holotype; USNM 216726; 1098 mm SL.

FIGURE 18. Zu cristatus (Bonelli 1820). AMS I.39622-001; 330 mm SL.

FIGURE 22. Zu cristatus (Bonelli 1820). CSIRO H-6325-01; 1142 mm SL. A, Whole specimen, prior to fixation. B, Ventral view of pelvic “slits” (white arrows).

FIGURE20.Zusp.Live specimen(notcollected)photographedinMallorca,Spain.©MichaelMakowiecki,used withpermission.

FIGURE21.Zusp.Livespecimen(notcollected)photographedinNusaPenida,Indonesia.©HelenMitchell,usedwithpermission.