Gnathia termitoides Leach, 1814 (= Cancer maxillaris Montagu, 1804); by monotypy (Cohen and Poore 1994); type locality: south coast of Devon, Cornwall Peninsula, south west England.

Anterior part of body (cephalosome and pereonites 1–4) not densely covered by tubercles; frontal margin with serrated triangular mediofrontal process and two superior frontolateral processes; paraocular ornamentation not developed; pereonite 1 not reaching lateral margins of cephalon; pereonites 4–6 with two lateral lobes; epimera of pleonites 1–5 not prominent; pleotelson 0.8 × shorter than its anterior width; lateral side of pleotelson sinuate; maximum width of peduncle article of antenna 3.2 × maximum width of flagellar article; article 1 of pylopod with two areolae; appendix masculina of pleopod 2 0.8 × as long as endopod; endopod of uropodal rami extend beyond apex of pleotelson; exopod of uropodal rami almost apex of pleotelson.

Holotype. Australia • 1♂ (2.4 mm TL, 1.9 mm BL, dissected); sandy substrata of seagrass Amphibolis griffithii (J.M. Black) Hartog, 1970 patch bed surrounded by the seagrass Posidonia sinuosa Cambridge & Kuo, 1979 bed, 5 m depth, Thomson Bay, Rottnest Island, Western Australia (32°00'S, 115°32.5'E), 18 January 1996, Hiroshi Mukai leg. (WAM C-79675).

Thomson Bay, Rottnest Island, Western Australia (32°00'S, 115°32.5'E).

Body (Figs 1, 2A) 2.7 × as long as greatest width, widest at pereonite 2; dorsal surfaces smooth, sparsely setose. Cephalosome (Fig. 1A–C) rectangular, 0.7 × as long as wide, lateral margins parallel, posterior margin concave; dorsal surface tubercles around eyes; dorsal sulcus wide, shallow, short; translucent region present, elliptical; paraocular ornamentation not developed, posterior median tubercle absent. Frontolateral processes present. Frontal margin (Fig. 1B) straight, median point with process. External scissura present, wide, shallow. Mediofrontal process present, strong, serrate triangular, without ventral notch and fine setae. Superior frontolateral process present, single, strong, conical, with three pairs of long simple setae. Inferior frontolateral process absent. Supraocular lobe not pronounced; accessory supraocular lobe not pronounced. Eyes present, round, 0.3 × as long as cephalosome length, contiguous with head surface, ommatidia arranged in rows, eye colour faded.

Figure 1. 

Photograph of fixed Gnathia antennacrassa sp. nov. (holotype, WAM C-79675). Scale bar: 1 mm.

Figure 2. 

Gnathia antennacrassa sp. nov. (holotype, WAM C-79675) A whole body (dorsal view) B cephalosome and mandible (dorsal view) C pereonite 1, cephalosome, and mandible (left lateral view) D pleotelson (dorsal view) E left antennula F left antenna.

Pereon (Figs 1, 2A) lateral margins narrowing posteriorly, with few setae; anteriorly smooth. Pereonite 1 not fused dorsally with cephalosome. Pereonite 2 wider than pereonite 1. Pereonite 4 with anterior constriction, median groove present. Areae laterales present on pereonite 4 and pereonite 5, with two lateral lobes, dorsal sulcus wide. Pereonite 6 with strongly developed lobi laterales, lobuii weak, conical. Pereonite 7 short, narrow, and overlapping pleonite 1. Pleon epimera not dorsally visible on pleonites. Pleonites (Figs 1, 2A) lateral margins with one pair of simple setae, with two pairs of simple setae medially. Pleotelson (Fig. 2D) 0.8 × as long as anterior width, not covered in pectinate scales; lateral margins smooth, anterolateral margins concave, without submarginal seta; posterolateral margin concave, with one pair of submarginal setae, mid-dorsal surface with a pair of sub-median setae, apex with two setae.

Antennula (Fig. 2E) composed of four peduncular and three flagellar articles, 0.8 × as long as antenna; peduncle article 2 0.6 × as long as article 1; article 3 2.1 × as long as article 2, 2.9 × as long as wide; flagellum as long article 3; article 3 with one aesthetasc and one simple seta; article 4 terminating with one aesthetasc and four simple setae. Antenna (Fig. 2F) composed of four peduncular and seven flagellar articles; maximum width of peduncle article 3.2 × the maximum width of flagellar articles; peduncle article 3 1.7 × as long as wide, 0.7 × as long as article 2, with one penicillate seta, and nine simple setae; article 4 as long as article 3, 1.5 × as long as wide, and with 20 simple setae; flagellum 1.2 × as long as article 4, with seven articles, terminating with two simple setae.

Mandible (Figs 1, 2A–C) 0.7 × as long as cephalosome; triangular, weakly mesially curved; apex 20% total length; mandibular seta present. Carina present, smooth along proximal half. Incisor elevated, standing clear of surface. Blade present, dentate, weakly convex, straight, dentate along 58% of margin. Pseudoblade, internal lobe, and dorsal lobe absent; basal neck short; erisma present; lamina dentata not visible in dorsal view.

Maxilliped (Fig. 3A). Article 1 lateral margin with continuous marginal scale-setae; article 2 lateral margin with three plumose setae; article 3 lateral margin with eight plumose setae; article 4 lateral margin with five plumose setae; 5 lateral margin with six plumose setae, and three simple setae; endite extending to distal margin of article 2.

Figure 3. 

Gnathia antennacrassa sp. nov. (holotype, WAM C-79675) A left maxilliped (ventral view) B left pylopod (ventral view) C left pereopod 2 (lateral view) D penes (ventral view) E left pleopod 2.

Pylopod (Fig. 3B). Article 1 2.0 × as long as wide; with two distinct areolae; without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 24 plumose setae; mesial margin with continuous fringe setae; distal margin with five simple setae; article 2 1.2 × as long as wide, with five simple setae; article 3 semicircular with two short setae.

Pereopod 2 (Fig. 3C) sparsely covered with short simple setae on basis and ischium, inferior margins with prominent tubercles on basis to carpus; basis 1.3 × as long as greatest width, superior margin with three simple setae, inferior margin with two simple setae; ischium as long as basis, 2.2 × as long as wide, superior margin with five simple setae; merus 0.4 × as long as ischium, 1.1 × as long as wide, superior margin with four simple setae, and bulbous protrusion, inferior margin with three simple setae; carpus 1.1 × as long as ischium, 0.9 × as long as wide, superior margin with three setae, inferior margin with five setae; propodus 1.6 × as long as ischium, 2.6 × as long as wide, superior margin with two simple setae and one penicillate seta, inferior margin with three pectinate scales, and two robust setae; dactylus 0.4 × as long as propodus. Pereopods 3 and 5 similar proportions of each article as pereopod 2. Pereopod 4 longer than pereopod 2, basis, ischium, and merus slightly longer than those of pereopod 2; propodus somewhat rounded. Pereopod 6 slightly shorter than pereopod 2, basis shorter than that of pereopod 2, distal margin of merus rounded.

Penes (Fig. 3D) with two small papillae, 0.5 × as long as basal width.

Pleopod 2 (Fig. 3E). Exopod 2.2 × as long as wide, distally broadly rounded, with nine plumose setae; endopod 1.8 × as long as wide, distally narrowly rounded, with seven plumose setae; appendix masculina present, with parallel margins, 0.8 × as long as endopod, distally narrowly rounded; peduncle 0.5 × as wide as long, mesial margin with two coupling setae, lateral margin with one simple seta. All pleopods similar in shape; exopods each with eight or nine plumose setae; endopods each with 7–9 plumose setae.

Uropod (Fig. 1D). Peduncle without dorsal setae. Uropodal endopod 1.6 × as long as greatest width, apex broadly rounded, extending beyond apex of the pleotelson, dorsally with five penicillate setae; lateral and proximomesial margin with seven plumose and three simple setae. Uropodal exopod not extending to end of endopod, 3.8 × as long as greatest width, apex broadly rounded, reaching almost apex of pleotelson; lateral and proximomesial margin with four plumose and seven simple setae.

Known only from the type locality.

Sandy substrata of seagrass; 5 m depth.

Unknown.

The specific name, antennacrassa, is derived from Latin, meaning “stout antenna”.

Among the other Gnathia species worldwide, G. illepida Monod, 1923 is similar to G. antennacrassa sp. nov., but differs in that the tubercles densely cover the anterior part of the body (cephalosome and pereonites 1–4), the paraocular ornamentation is developed with several distinct tubercles and setae, and the maximum width of peduncle articles of the antenna is 2.4 × of that of the flagellar articles (Monod 1926).

Gnathia vellosa Müller, 1988 is also similar, but differ in that tubercles and long setae densely cover the anterior part of the cephalosome and pereonites 2, 3, and anterior part of pereonite 4; the maximum width of peduncle articles of antenna is 2.4 × that of flagellar articles; and three areolae are present on article 1 of the pylopod (Müller 1988).

Gnathia luxata Kensley, Schotte & Poore, 2009 differs from our new species as it has three processes on the frontal border but the mesial lobe is present on the mandible and, similarly to G. vellosa, it has three areolae present on article 1 of the pylopod (Kensley et al. 2009).

The gnathiid fauna of Western Australia, in contrast to the eastern Australian coast (see Cohen and Poore 1994; Coetzee et al. 2008, 2009; Ferreira et al. 2009, 2010; Farquharson et al. 2012; Svavarsson and Bruce 2012, 2019) remains almost undocumented. Cohen and Poore (1994) mention that G. mulieraria Hale, 1924 occurred from Victoria and south Australia to Western Australia. However, the original description mentioned G. mulieraria only from South Australia and there is no evidence or reference to its distribution as referred to in Cohen and Poore (1994). Therefore, G. antennacrassa represents the first recorded species of Gnathiidae from Western Australia.

Large body length more than 8.0 mm; long setae covering most part of dorsal body (cephalosome, pereonites 1–7, and mid-dorsal and lateral parts of pleonites 1–5); frontal margin with rounded mediofrontal process and two superior frontolateral processes; paraocular ornamentation composed of several tubercles and setae; pereonite 1 reaching lateral margins of cephalon, epimera of pleonites 1–5 not prominent; pleotelson 1.3 × longer than its anterior width, eight or nine long setae present on lateral side of pleotelson; mandible almost vertically elongated; article 1 of pylopod with one areolae; appendix masculina of pleopod 2 extending half-length of the endopod; endopod of uropodal rami extends beyond apex of pleotelson; exopod of uropodal rami not extends apex of pleotelson.

Holotype. Australia • 1♂ (9.6 mm TL, 8.2 mm BL, dissected); reared from a juvenile collected from a species of Rhynchobatus (TL 129 cm, female), Heron Island, Great Barrier Reef (23°26'32.9"S, 151°54' 53.8"E), 7 October 1998. Ian D. Whittington leg. (QM W29819). Paratype. 1♂ (9.4 mm TL, 8.2 mm BL); same data as holotype (QM W29820).

Heron Island, Great Barrier Reef, Australia (23°26'32.9"S, 151°54'53.8"E).

Body (Figs 4, 5A) 2.6 × as long as greatest width, widest at pereonite 5; dorsal surfaces with tubercules or granules, densely setose. Cephalosome (Figs 4, 5A–C) rectangular, 0.7 × as long as wide, lateral margins sub-parallel, posterior margin concave; dorsal surface conspicuous granules anteriorly; dorsal sulcus narrow, shallow, short; translucent region absent; paraocular ornamentation weakly developed and with several tubercles and setae; posterior median tubercle present; lateral tubercles with several long setae. Frontolateral processes present. Frontal margin (Fig. 5B) straight and medially concave, median point with process. External scissura present, wide, shallow. Mediofrontal process present, weak, rounded, without ventral notch, without setae. Superior frontolateral process present, single, strong, rounded, with four or five long simple setae. Inferior frontolateral process absent. Supraocular lobe not pronounced; accessory supraocular lobe not pronounced. Eyes present, round, 0.2 × as long as cephalosome length, contiguous with head surface, ommatidia not arranged in rows, eye colour dark brown.

Figure 4. 

Photograph of fixed Gnathia taurus sp. nov. (paratype, QM W29820). Scale bar: 1 mm.

Figure 5. 

Gnathia taurus sp. nov. (holotype QM W29819) A whole body (dorsal view) B cephalosome and mandible (dorsal view) C pereonite 1, cephalosome, and mandible (right lateral view) D pleotelson (dorsal view) E right antennula F right antenna.

Pereon (Figs 4, 5A) lateral margins ovate, with many setae; with sparse fine granules on anterior parts of pereonites 2–4. Pereonite 1 not fused dorsally with cephalosome; dorsolateral margins not obscured by cephalosome. Pereonite 2 wider than pereonite 1. Pereonite 4 with anterior constriction, median groove absent. Areae laterales present on pereonite 5, dorsal sulcus wide. Pereonite 6 with strongly developed lobi laterales, lobuii absent. Pereonite 7 short, narrow, and overlapping pleonite 1. Pleon epimera not dorsally visible on all pleonites. Pleonites (Figs 4, 5A) lateral margins with 5–7 pairs of simple setae, with 6–9 simple setae medially. Pleotelson (Fig. 5D) 0.8 × as long as anterior width, covered in pectinate scales; lateral margins smooth, anterolateral margins strongly concave, with 1–3 submarginal setae; posterolateral margin weakly convex, with eight or nine pairs of submarginal setae; mid-dorsal surface with one pair of sub-median setae, apex with two setae.

Antennula (Fig. 5E) composed of four peduncular and four flagellar articles, 0.6 × shorter than antenna; peduncle article 2 1.1 × as long as article 1; article 3 2.2 × as long as article 2, 4.4 × as long as wide; flagellar article 3 with one aesthetasc seta, and one simple seta; article 4 with one aesthetasc seta; article 5 with one penicillate seta, terminating with one aesthetasc seta and three simple setae. Antenna (Fig. 5F) composed of four peduncular and seven flagellar articles; peduncle article 3 2.8 × as long as wide, 2.5 × as long as article 2, with two penicillate setae, and seven simple setae; article 4 1.3 × as long as article 3, 4.3 × as long as wide, with five penicillate setae, and 18 simple setae; flagellum 0.8 × as long as article 4, terminating with four simple setae.

Mandible (Fig. 5B, C) 0.4 × the head length; strongly curved dorsally; apex positions before dentate blade (but it positions after dentate blade in paratype of Fig. 4), 23% of total length; mandibular seta present. Carina absent. Incisor dentate, distal denticulation absent. Blade present, dentate, straight, proximally convex, dentate for 28% of margin. Pseudoblade, internal lobe and dorsal lobe absent; basal neck long; erisma present; lamina dentata absent.

Maxilliped (Fig. 6A). Article 1 lateral margin with continuous marginal scale-setae; article 2 lateral margin with six plumose setae; article 3 lateral margin with seven plumose setae; article 4 lateral margin with six plumose setae; article 5 with nine plumose setae, and six simple setae; endite extending to distal margin of article 2.

Figure 6. 

Gnathia taurus sp. nov. (holotype QM W29819) A right maxilliped (ventral view) B right pylopod (ventral view) C right pereopod 2 (lateral view) D penes (ventral view) E. right pleopod 2.

Pylopod (Fig. 6B). Article 1 1.9 × as long as wide; with one areola; without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 59 plumose setae; mesial margin with continuous fringe setae; distal margin with five simple setae; article 2 1.3 × as long as wide, with 11 simple setae; article 3 minute and semicircular without setae.

Pereopod 2 (Fig. 6C) covered in pectinate scales on inferior margins of ischium, merus carpus, and propodus; basis 2.2 × as long as greatest width, superior margin with 19 simple setae, inferior margin with 21 simple setae; ischium 4.5 × as long as basis, 4.5 × as long as wide, superior margin with 21 simple setae, inferior margin with 11 simple setae; merus 0.3 × as long as ischium, 1.1 × as long as wide, superior margin with eight simple setae and bulbous protrusion, inferior margin with eight simple setae; carpus 1.1 × as long as ischium, 1.9 × as long as wide, superior margin with eight simple setae, inferior margin with four simple setae; propodus 1.1 × as long as ischium, 2.5 × as long as wide, superior margin with three simple setae, superior margin with one penicillate seta, inferior margin with four simple setae, and two denticulate compound spines; dactylus 0.5 × as long as propodus. Pereopods 3, 5, and 6 almost same proportion of each article as pereopod 2; basis of pereopod 4 slightly shorter than that of pereopod 2.

Penes (Fig. 6D) produced, penial process 0.4 × as long as basal width.

Pleopod 2 (Fig. 6E) exopod 1.8 × as long as wide, distally broadly rounded, with nine plumose setae; endopod 2 × as long as wide, distally broadly rounded, with seven plumose setae; appendix masculina present, with parallel margins, 0.5 × as long as endopod, distally bluntly rounded; peduncle 1.4 × as wide as long, mesial margin with two coupling setae, lateral margin with one simple seta. All pleopods similar in shape; exopods each with 7–11 plumose or simple setae; endopods each with seven or eight plumose or simple setae in total.

Uropod (Fig. 5D). Peduncle with two dorsal setae. Uropodal endopod 2.9 × as long as greatest width, apex narrowly rounded, extending beyond apex of pleotelson, dorsally with three penicillate setae; lateral margin weakly convex, lateral margin with nine simple setae; proximomesial margin sinuate, with seven long plumose setae. Uropodal exopod not extending to end of endopod, apex narrowly rounded, not extending beyond apex of pleotelson, 3.6 × as long as greatest width; lateral margin weakly convex, with 24 simple setae; proximomesial margin weakly convex and sinuate, with five plumose setae.

Heron Island, Great Barrier Reef, Australia.

Unknown.

A species of Rhynchobatus. The original data label identified the host as Rhynchobatus djiddensis, but the distribution range of this species is the western Indian Ocean; therefore, the host is most probably Rhynchobatus australiae Whitley, 1939 or R. palpebratus Compagno & Last, 2008, two species that do occur on the GBR (Last et al. 2016).

The specific name taurus, the second sign of the zodiac, is derived from taûros, Latin for bull, and refers to the gnathiid’s dorsally elongated mandible which resemble the horns of a bull.

Among Gnathia species worldwide, Gnathia grandilaris Coetzee, Smit, Grutter & Davies, 2008 is most similar to Gnathia taurus sp. nov., but differs in that its mediofrontal process is acute, the mandible is not vertically elongated, and two areolae are present on article 1 of the pylopod (Coetzee et al. 2008).

Gnathia nubila Ota & Hirose, 2009 is also similar but the apex of the mediofrontal process is bifid and dentate, the epimera is prominent on pleonites 3–5, and two areolae are present on article 1 of the pylopod (Ota and Hirose 2009b).

Nakagusku Bay (26°N, 127°E), Okinawajima Island, Japan.

Australia • 1♂ (5.0 mm TL, 4.5 mm BL, SEM); reared from a juvenile collected from a cowtail stingray Pastinachus sephen (Forsskål, 1775) (TL and sex, unknown), Lizard Island, GBR (14°40'08"S, 145°27'34"E), 19 June 1998, Ian D. Whittington leg. (QM W29821). 1♂ (5.5 mm TL, 4.9 mm BL, dissected); reared from a juvenile collected from a species of Rhynchobatus (TL 126.5 cm, female), Shark Bay, Heron Island, GBR (23°26'37.03"S, 151°55'5.64"E), 7 Oct. 1998, Ian D. Whittington leg. (QM W29822).

The male morphologies of these GBR specimens show the deep and narrow dorsal sulcus on the cephalosome, the narrow body (Fig. 7A, B), and the almost semicircular pylopod article 1 with three areolae (Fig. 7C). These characters can be identified as Gnathia maculosa Ota & Hirose, 2009. However, this species was originally described from the Ryukyu Islands, southwestern Japan (Ota and Hirose 2009a) and our records are a great distance from this island group. The apices of the frontolateral processes on anterior margin of heads of the present specimens are smooth, while those of original description are serrate (Ota and Hirose 2009a). The number of setae on the pleotelson of the present species is two pairs (Fig. 7D), while that of the original description is three pairs (Ota and Hirose 2009a). Thus, these GBR specimens are identified as G. aff. maculosa.

Figure 7. 

Gnathia aff. maculosa Ota and Hirose, 2009 (A–D; QM W29822) and G. trimaculata Coetzee, Smit, Grutter & Davies, 2009 (E; QM W29825) A whole body (dorsal view) B pereonite 1, cephalosome, and mandible (dorsal view) C pleotelson (dorsal view) D right pylopod (ventral view) E frontal border of G. trimaculata (dorsal view).

The GBR specimens of G. aff. maculosa have a bundle of several long setae on the ventral frontal border (Fig. 8). Ota and Hirose (2009a) did not show the ventral frontal border but the Japanese specimens G. maculosa also have a bundle of several long setae (YO pers. obs.).

Figure 8. 

Scanning electron micrograph of the ventral view of the frontal border of Gnathia aff. maculosa Ota & Hirose, 2009 (QM W29821) showing bundles of several long setae (two arrows). Scale bar: 500 µm.

Gnathia aff. maculosa: Lizard Island and Heron Island, Great Barrier Reef, Australia; Gnathia maculosa: Okinawa-jima Island, Kume-jima Island, Ishigaki-jima Island, Japan.

Unknown.

Two elasmobranch species from GBR: Pastinachus sephen (Forsskål, 1775), Rhynchobatus sp.

Ota and Hirose (2009a) recorded the two host elasmobranchs of G. maculosa and Ota (2015: table 2) summarised gnathiids ectoparasitising on elasmobranchs in the Ryukyu Islands and documented G. maculosa obtained from 11 elasmobranch species including two host species previously recorded by Ota and Hirose (2009a): Rhynchobatus djiddensis (Forsskål, 1775), Neotrygon orientalis Last, White & Séret, 2016 [Neotrygon kuhlii Müller & Henle, 1841 in Ota 2015], Taeniura meyeni Müller & Henle, 1841, Himantura undulata (Bleeker, 1852), Himantura sp., Aetomylaeus vespertilio (Bleeker, 1852), Aetobatus ocellatus (Kuhl, 1823) [Aetobatus narinari (Euphrasen, 1790) in Ota 2015], Rhinoptera javanica Müller & Henle, 1841, Nebrius ferrugineus (Lesson, 1831), Triaenodon obesus (Rüppell, 1837), and Negaprion acutidens (Rüppell, 1837).

Gill chambers, interbranchial septa, gill filaments, and the floor of oral cavities. Rarely nostrils, body surface near the gill slits, or claspers.

Off Lizard Island (14°40'54.68"S, 145°26'53.72"E), Australia.

Australia • 1♂ (6.4 mm TL, 5.2 BL); reared from a juvenile collected from a cowtail stingray Pastinachus sephen (Forsskål, 1775) (TL and sex, unknown), Lizard Island, GBR (14°40'54.68"S, 145°26'53.72"E), 19 June 1998, Ian D. Whittington leg. (QM W29823). 2♂ (5.8 mm TL and 4.6 mm BL, 5.7 mm TL and 4.6 mm BL); reared from a juvenile, infested on P. sephen (TL and sex, unknown), Heron Island, GBR (23°26'32.9"S, 151°54'53.8"E), 9 July 1998, Ian D. Whittington leg. (QM W29824). 1♂ (4.2 mm TL, 3.6 mm BL, drawings); reared from a juvenile, infested on epaulette shark, Hemiscyllium ocellatum (Bonnaterre, 1788), Heron Island, GBR (23°26'32.9"S, 151°54'53.8"E), 7 November 1998, Ian D. Whittington leg. (QM W29825).

This species can be identified as Gnathia trimaculata Coetzee, Smit, Grutter, & Davies, 2009 by a frontal border with a mediofrontal process divided into two lobes which almost touch anteriorly and form a distinct key-hole shape, four or five pairs of long pappose setae present ventrally on both lobes, a mandible with seven or eight processes on the dentate blade, a cluster of setae between all processes, and an armed carina (Coetzee et al. 2009).

Ota and Hirose (2009a) reported G. trimaculata from the Ryukyu Islands, demonstrating a greater number of setae on peduncle 4 of antenna than that of the GBR specimens. In the present material, we observed that the mediofrontal process of our specimens does not almost touch and has a smooth margin (Fig. 7E). Therefore, it appears to be two frontolateral processes instead of one mediofrontal process.

This shape of mediofrontal process looks like that of G. aff. maculosa. Gnathia aff. maculosa of GBR also has a bundle of several long setae on the ventral frontal border. Thus, these two species cannot be distinguished by the morphology of the frontal border alone. However, G. trimaculata can be distinguished from G. maculosa by pectinate scales covering the pleotelson, four pairs of long setae on the lateral margin of pleotelson, and a long pear-shaped pylopod with one areola.

This record of G. trimaculata establishes two new hosts for this widely distributed species. Ota et al. (2012) recorded G. trimaculata from several areas in the Ryukyu Islands and southern Pacific coast of Japan. They demonstrated the first and second stages of the juveniles ectoparasitised four teleost species, while the third stage ectoparasitised 25 elasmobranch species including two unidentified elasmobranch species (see Ota et al. 2012: table 3). Ota (2015: table 2) also showed G. trimaculata collected from 18 elasmobranch species including two unidentified elasmobranch species but all of them except for one were already reported by Ota et al. (2012). These host species are listed below; in GBR, our host records of Pastinachus sephen and Hemiscyllium ocellatum were not included the previous studies and these are new host records.

Off Lizard Island and Heron Island, Great Barrier Reef, Australia. The Ryukyu Islands and southern Pacific coast of Japan.

Unknown.

Four elasmobranch species from GBR: Carcharinus melanopterus (Quoy & Gaimard, 1824), Carcharinus amblyrhynchos (Bleeker, 1856), Pastinachus sephen (Forsskål, 1775), and epaulette shark Hemiscyllium ocellatum (Bonnaterre, 1788). Three teleost species from Japan: Enneapterygius etheostomus (Jordan & Snyder, 1902), Enneapterygius miyakensis Fricke, 1987, Springerichthys bapturus (Jordan & Snyder, 1902), 24 elasmobranch species and two unidentified species from Japan: Urolophus aurantiacus Müller & Henle, 1841, Gymnura japonica (Temminck & Schlegel, 1850), Rhynchobatus djiddensis (Forsskål, 1775), Neotrygon orientalis Last, White & Séret, 2016 [Neotrygon kuhlii Müller & Henle, 1841 in Ota et al. 2012 and Ota 2015], Taeniura meyeni Müller & Henle, 1841, Dasyatis izuensis Nishida & Nakaya, 1988, Hemitrygon akajei (Müller & Henle, 1841) [Dasyatis akajei (Müller & Henle, 1841) in Ota et al. 2012 and Ota 2015], Himantura undulata (Bleeker, 1852), Himantura spp., Aetomylaeus vespertilio (Bleeker, 1852), Aetobatus ocellatus (Kuhl, 1823) [Aetobatus narinari (Euphrasen, 1790) in Ota et al 2012 and Ota 2015], Aetobatus flagellum (Bloch & Schneider, 1801), Rhinoptera javanica Müller & Henle, 1841, Mobula mobular (Bonnaterre, 1788) [Mobula japanica (Müller & Henle, 1841) in Ota et al. 2012 and Ota 2015], Mobula thurstoni (Lloyd, 1908) [Mobula diabolus (Shaw, 1804) in Ota et al. 2012 and Ota 2015], Mobula tarapacana (Philippi, 1892), Nebrius ferrugineus (Lesson, 1831), Rhincodon typus Smith, 1828, Stegostoma fasciatum (Hermann, 1783), Sphyrna lewini (Griffith & Smith, 1834), Triaenodon obesus (Rüppell, 1837), Negaprion acutidens (Rüppell, 1837), Galeocerdo cuvier (Péron & Lesueur, 1822), Carcharhinus albimarginatus (Rüppell, 1837), Carcharhinus limbatus (Müller & Henle, 1839), and Carcharhinus spp.

Gill chambers, interbranchial septa, gill filaments, and the floor of oral cavities. Rarely nostrils, body surface near the gill slits, or claspers of elasmobranchs. Fins and skin of teleosts.

Off Lizard Island (14°40'S, 145°27'E), Australia.

Australia •1♂ (7.1 mm TL, 6.6 mm BL); reared from a juvenile collected from P. sephen (TL and sex, unknown), Heron Island, GBR (23°26'32.9"S, 151°54'53.8"E), 9 July 1998, Ian D. Whittington leg. (QM W29826).

The original description of G. grandilaris was based on males reared from larvae found infesting a white tip reef shark, Triaenodon obesus (Rüppell, 1837), and grey reef sharks, C. amblyrhynchos, collected off Lizard Island, GBR (Coetzee et al. 2008) and subsequently reported from the Ryukyu Islands (Ota and Hirose 2009b; Ota 2015). The specimen from Heron Island corresponded well with the original description. This record constitutes a new host and a new locality record for G. grandilaris.

Lizard Island and Heron Island, Great Barrier Reef, Australia. Okinawa-jima Island, Kume-jima Island, Ishigaki-jima Island, the Ryukyu Islands, Japan.

Unknown.

Three elasmobranch species from GBR: Triaenodon obesus (Rüppell, 1837), Carcharhinus amblyrhynchos (Bleeker, 1856), and Pastinachus sephen (Forsskål, 1775). Seven elasmobranch species from Japan: Himantura sp., Himantura fai Jordan & Seale, 1906, Neotrygon orientalis Last, White & Séret, 2016 [Neotrygon kuhlii Müller & Henle, 1841 in Ota and Hirose 2009b and Ota 2015], Taeniura meyeni Müller & Henle, 1841, Mobula japanica (Müller & Henle, 1841), Nebrius ferrugineus (Lesson, 1831), Triaenodon obesus (Rüppell, 1837), and Negaprion acutidens (Rüppell, 1837).

Gill chambers, interbranchial septa, gill filaments, and the floor of oral cavities. Rarely nostrils, body surface near the gill slits, or claspers.