Podocerus chelonophilus ( Chevreux & de Guerne, 1888 )

Kilgallen, Niamh M., 2009, Podoceridae *, Zootaxa 2260 (1), pp. 841-860 : 848-850

Podocerus chelonophilus ( Chevreux & de Guerne, 1888)

( Fig. 5 )

Cyrtophium chelonophilum Chevreux & de Guerne, 1888: 625 .

Platophium cheloniae Stebbing, 1888: 1190 , pl. 30.

Platophium chelonophilum . — Chevreux, 1900: 115, pl. 13, fig. 2; pl. 14, fig. 7.

Podocerus cheloniae . — Stebbing, 1906: 701.

Podocerus chelonophilus . — Stebbing, 1906: 703. — Chevreux, 1911: 272. — Chevreux & Fage, 1925: 375, fig. 383. — Chevreux, 1935: 130. —Mateus & Alfonso, 1974: 36, figs 27, 28. — Thomas & Barnard, 1992: 110, figs 1, 2. — Ruffo, 1993: 675, fig. 462. — Moore, 1995: 253. — Baldinger, 2001: 441, figs 1–6.

? Podocerus umigame Yamato, 1992: 281 , figs 1–3. — Ren, 1994: 265, fig. 13.

Material examined. 5 males, 5 females, QM W7398 ; 5 males, 5 females, QM W7394 ; 5 males, 5 females, QM W7397 (each taken from a vial of several hundred specimens) , Mon Repos near Bundaberg , Queensland, on loggerhead turtle Caretta caretta ( Linnaeus, 1758) , C. Limpus, 1975-1976 (CL 1) .

Type locality. Carapace of a loggerhead sea turtle, Caretta caretta , which landed on the beach in front of the Aquarium of the Seto Marine Biological Laboratory, Wakayama, Japan (3341' N 13520 'E) .

Description. Based on male, 7.5 mm, QM W7398.

Head. Eyes large, protruding. Antenna 1 between 0.3–0.5 body length; peduncle article 2 slightly longer than article 3; accessory flagellum present, 1-articulate; primary flagellum 0.3–0.5 peduncle length, with 5 articles. Antenna 2 distinctly longer than antenna 1; flagellum with 3 articles. Mandible right incisor with 5 teeth; lacinia mobilis with 2 teeth; setal row with 3 setae; molar well developed; left incisor with 5 teeth; lacinia mobilis with 4 teeth; setal row with 3 setae. Maxilla 1 outer plate with 9 setal teeth. Maxilliped inner plate smaller than outer plate, quadrilateral; outer plate well developed, 1.5 – 2 x length of inner plate, inner margin with row of robust setae, and few fine setae; palp article 2 setose on inner margin; article 3 with moderately dense distal setae; article 4 reduced, blunt.

Pereon. Pereonites not fused, not posterodorsal produced, without dorsal setae; pereonites 2 to 6 with gills. Gnathopod 1 distinctly smaller than gnathopod 2; propodus triangular to subtriangular, with 5–6 rows of submarginal setae near anterior margin; palm straight beginning about one-third along posterior margin of propodus; dactylus curved, distinctly shorter than palm and with 3 – 4 accessory teeth. Gnathopod 2 coxa reduced; basis with rounded anterodistal lobe; merus forming short, blunt distal projection; propodus massive, subovate, length about 1.25 x width; palm margin irregular, with distinct proximal projection defining palm, and large midpalmar projection separated from broad, well developed distal projection by deep, wide sinus; distal projection bearing 6 – 8 small, rounded lobes. Pereopods 3 and 4 basis largely expanded posteriorly into rounded lobe. Pereopod 5 basis with rounded posterodistal lobe, longer than merus; carpus loner than merus; propodus longer than carpus; dactylus short, about one-third propodus length. Pereopod 6 basis about subequal in length to merus; carpus longer than merus; propodus longer than carpus; dactylus about one-third propodus length. Pereopod 7 similar to pereopod 6.

Pleon. Pleonites not fused, not posterodorsal produced, without dorsal setae. Uropod 1 well developed; peduncle lacking distoventral spine; biramous with inner ramus subequal in length to peduncle, inner margin with dense marginal row of robust setae. Uropod 2 well developed, peduncle lacking distoventral spine; biramous with rami much longer than peduncle, inner ramus inner margin with dense marginal row of robust setae. Uropod 3 uni-articulate, with 2 small apical robust setae. Telson subquadrate, posterodorsally produced into subacute knob with 4–8 apical setae.

Female (sexually dimorphic characters). Based on female, 6 mm, QM W7398. Gnathopod 1 dactylus fitting palm. Gnathopod 2 basis without anterodistal projection; propodus large, subovate, with convex palm lacking any projections, defined by 3 robust setae; dactylus with accessory tooth.

Habitat. Epibiontic on the loggerhead turtle ( Caretta caretta ( Linnaeus, 1758)) and the hawksbill turtle ( Eretmochelys imbricata (Linnaeus, 1766)) .

Remarks. To date, three Podocerus species have been recorded as epibionts of sea turtles — P. chelonophilus ( Chevreux & de Guerne, 1888) , P. cheloniae ( Stebbing, 1888) and P. umigame Yamato, 1992 . Confusion exists as to the validity of the latter two. Most authors agree that P. cheloniae is likely a junior synonym of P. chelonophilus and, though some morphological variation exists between the two, this is accounted for by the fact that Stebbing (1888) based his original description of P. cheloniae on an immature specimen.

Podocerus umigame was described from the carapace of a loggerhead turtle ( Caretta caretta ) from Wakayama, Japan. In his remarks, Yamato distinguishes P. umigame from P. chelonophilus by the differing numbers of setae on the telson, and the morphology of the gnathopod 2 palm. According to him, P. chelonophilus has only 2 setae on the telson and a bi-lobed projection near the dactylus hinge on the gnathopod 2 palm. Podocerus umigame has 5 long setae on the telson and has a 5-lobed tooth on the gnathopod 2 palm. However, Baldinger (2001) examined a number of specimens from different regions and reported variation in both these characters within both species. For example, he noted a range of 0–9 setae on the telson of P. chelonophilus , and 5–7 on P. umigame . Likewise, a high degree of variation is reported in the form of the proximal projection on the gnathopod 2 palm. This degree of intra-specific variation led Baldinger (2001) to suggest that these species are not distinct, but rather P. umigame is a morphological variant of, and therefore, a junior synonym of P. chelonophilus .

Examination of the present specimens, collected from loggerhead turtles, Caretta caretta , on Heron Island and Mon Repos Beach, Queensland, supports this opinion. They also exhibit variation in the number of telsonic setae and the form of the gnathopod 2 palm, which usually displays a small proximal projection, but occasionally this projection takes the form of two small, rounded lobes.

Distribution. Atlantic Ocean. Azores ( Chevreux, 1900); Madeira ( Moore 1995); Florida and South Carolina, USA ( Thomas & Barnard 1992). Mediterranean. Algeria ( Chevreux & de Guerne 1888). Pacific Ocean. Heron Island and Mon Repos Beach, Queensland, Australia (current study); Ecuador ( Baldinger 2001);? Wakayama, Japan ( Yamato 1992).? South China Sea: Hong Kong ( Ren 1994).

Figures

FIGURE 5. Podocerus chelonophilus (Chevreux & de Guerne, 1888), male, 7.5 mm, female, 6 mm, QM W7398, Mon Repos Beach, near Bundaberg, Queensland.