Cymothoa eremita (Brünnich, 1783), Brunnich, 1783

Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2013, Review of the fish-parasitic genus Cymothoa Fabricius, 1793 (Isopoda, Cymothoidae, Crustacea) from the southwestern Indian Ocean, including a new species from South Africa, Zootaxa 3640 (2), pp. 152-176 : 158-163

Cymothoa eremita (Brünnich, 1783)

( Figs 3–5 )

Oniscus oestrum .—Spengler 1775: 312–315, pl. 7 (figs. i–k) [not C. oestrum Leach, 1756 ].

Oniscus eremita Brünnich, 1783: 319 –325.

Cymothoa Leschenaultii Leach, 1818: 352 ; Desmaret, 1825: 309.

Cymothoa Mathoei Leach, 1818: 353 ; Desmarest, 1825: 309.

Cymothoa mathoei .—Milne Edwards, 1840: 270–271; Hilgendorf, 1869: 114; Gerstaecker, 1901: 182, 258.

Cymothoa leschenaultii .—White, 1847: 109; Miers, 1880: 461; Ellis, 1981: 124.

Cymothoa matthaei [sic].—White, 1847: 110; Bleeker, 1857: 22.

Cymothoa mathaei .—Lucas, 1850: 248; Kossmann, 1880: 117–118, pl. 10 (figs. 1–3).

Cymothoa edwardsii Bleeker, 1857: 21 , 33–35, tab. II, fig. 12; Miers, 1880: 461; Gerstaecker, 1901: 261.

Cymothoa stromatei Bleeker, 1857: 21 , 33, 35–36, tab II, fig. 13; Miers, 1880: 461; Gerstaecker, 1901: 181, 261; Lanchester, 1902: 377; Richardson, 1910: 22–23; Hale, 1926: 214–215, fig. 9h; Brian & Dartevelle, 1949: 184; Sachlan, 1952: 41, 50q photo 28; Pillai, 1954: 15.

Cymothoa eremita .—Schioedte & Meinert, 1884: 259–266, tab. VII (Cym. XXV), figs. 3–13; Stebbing, 1893: 354–355; 1910: 102–103; Gerstaecker, 1901: 182; Thielemann, 1910: 39–41, figs. 37–38, tab. 4; Nierstrasz, 1915: 90–91; 1931: 135, pl. 10, fig. 9; Monod, 1924c: 100; 1933: 195; 1976: 859–860, figs. 23–25; Boone, 1935: 215–217, pl. 63; Shiino, 1951: 81, 85, figs. 2 (b–c); Avdeev, 1978: 30; 1982: 69–77; Trilles, 1975: 987–989, pl. II (12–13); 1979: 261–262; 1986: 627, tab. 1; 1994: 139–141; 2008: 23; Bowman & Tareen, 1983: 25–28, fig. 20; Radhakrishnan & Nair, 1983: 96, 105, 107; Saito, Itani & Nunomura, 2000: 65; Shireen, 2000: 21–32, figs. 1–3; Kensley, 2001: 232; Yu & Li, 2003a: 228, fig. 4; 2003b: 267; Williams & Bunkley-Williams, 2009: 557–561; Trilles, Ravichandran & Rameshkumar, 2011: 446–459; Rameshkumar, Ravichandran & Trilles, 2012: 191–193.

Cymothoa edwardsi .—Nierstrasz, 1931: 135.

Cymothoa sp. (an. eremita Brünnich, 1783 ) [sic].—Monod, 1934: 13–14, pl. 27 (a–b), pl. 30 (b).

Cymothoa erimitae (typographical error?).—Sachlan, 1955: 31, 33.

Cymothoa cinerea Bal & Joshi, 1959: 567 –569, pl. 2, figs. 1–5; Kensley, 2001: 232.

Cymothoa cinerius .—Joshi & Bal, 1960: 446.

Cymothoa mathieui .—Ellis, 1981: 124.

Cymothoa leaschenaultii [sic].—Kensley, 2001: 232.

Uncertain identification:

? Cymothoa limbata Schioedte & Meinert, 1884: 248 –250, tab. VII (Cym. XXV), figs. 1–2; Hale, 1926: 214; Nierstrasz, 1931: 136.

Material examined. Holotype ( Fig. 3 ). Young Ƥ (26 mm TL; 11 mm W) (Fig. 6.15 A–B), found still inside the host fish, Parastromateus niger (previously Coryphaena apus ) (Brünnich, 1783) (ZMUC-CRU-10078).

Syntypes for Cymothoa mathoei ( Fig. 4 ) Leach, 1818. Two Ƥ (27, 31 mm TL; 12, 14 mm W), collected from Mauritius (“ Ile-de-France ”), White’s MS Cat no. 221 (a, b) (BMNH 1979.407.2). Also noted: the small female (27 mm TL) had oostegites and pleopods missing, as well as pereopod 4. The other female (31 mm) was squashed but drawn for comparison purposes. Ƥ (28 mm TL; 13 mm W), presented by J. Banks, labelled as “ Cymothoa nathieui ” (BMNH 1979.408.1).

Holotype for Cymothoa leschenaultii ( Fig. 5 ) Leach, 1818. Ƥ (36 mm TL; 20 mm W), collected from Pondicherry, India, presented by Leschenault (BMNH 1979.406.1). Also noted: there is a small hole in pereonite 5 (probably a pin hole from dry mount), and a damaged pleotelson.

Description (based on the female holotype). Female, length 26 mm, width 11 mm.

Body elongate, 1.9 times as long as greatest width, dorsal surfaces smooth and polished in appearance, widest at pereonite 5, most narrow at pereonite 1, lateral margins slightly convex. Cephalon 0.6 times longer than wide, visible from dorsal view, trapezoid shaped. Frontal margin thickened, ventrally folded and medially indented. Eyes not visible. Pereonite 1 smooth, anterior border straight, anterolateral angle rounded and with small distinct produced point, posterior margin of pereonite smooth and slightly curved laterally. Coxae 2–3 with posteroventral angles acute, posteriorly produced; 4–7 rounded. Pereonites 1–5 increasing in length and width; 6–7 decreasing in length and width; 6 and 7 narrower and becoming more progressively rounded posteriorly. Pleon with pleonite 1 same width as other pleonites, visible in dorsal view; pleonites posterior margin smooth, mostly concave; posterolateral angles of pleonite 2 rounded, not posteriorly produced. Pleonites 3–5 similar in form to pleonite 2. Pleonite 5 with posterolateral angles free, not overlapped by lateral margins of pleonite 4, posterior margin straight. Pleotelson 0.6 times as long as anterior width, dorsal surface with 2 sub-medial depressions, lateral margins convex, posterior margin sub-truncate, without median point.

Antennule more stout than antenna, comprised of 7 articles; peduncle articles 1 and 2 distinct and articulated; article 2 0.9 times as long as article 1; article 3 0.5 times as long as combined lengths of articles 1 and 2, 1.1 times as long as wide; flagellum with 4 articles, extending to middle of pereonite 1. Antenna comprised of 8 articles; peduncle article 3 1 times as long as article 2, 1.2 times as long as wide; article 4 1 times as long as wide, 0.7 times as long as article 3; article 5 0.8 times as long as article 4, 0.8 times as long as wide. Antenna flagellum with 3 articles, last article terminating without setae, extending to middle of pereonite 1. Labrum lateral margins converging to anterior, anterior margin with median indentation, without small median point.

Pereopod 1 basis 1.7 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 1.7 times as long as wide; dactylus slender, 1.1 as long as propodus, 2.6 times as long as basal width. Pereopods gradually increasing in size towards posterior and all without robust or simple setae. Pereopod 7 basis 1.8 times as long as greatest width; ischium 0.7 as long as basis, with a large proximal bulbous protrusion; merus proximal margin without bulbous protrusion, merus 0.7 as long as ischium, 0.5 times as long as wide; carpus 1.3 as long as ischium, without bulbous protrusion, 1.1 times as long as wide; propodus 1.1 as long as ischium, 1.3 times as long as wide; dactylus slender, 1.4 as long as propodus, 2.2 times as long as basal width. Uropod more than half the length of pleotelson, peduncle 0.6 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, marginal setae absent, apices broadly rounded.

Distribution. Recorded from the Indian Ocean and Indo-Pacific regions: from the Western Indian Ocean to the Western Pacific ( Philippines to New Caledonia); for a detailed listing of these localities see Trilles (1994). Recent records are from India (Rameshkumar et al. 2012; Trilles et al. 2011); Japan (Saito et al. 2000); and Arabian Gulf (Shireen 2000); South China Sea (Yu & Li 2003b); and Philippines (Trilles 2008).

Hosts. Recorded from Parastromateus niger (Bloch, 1795) (as Stromateus niger ) (see Brünnich 1783; Bleeker 1857; Schioedte & Meinert 1884; Gerstaecker 1901; Nierstrasz 1915; Sachlan 1952; Pillai 1954; Radhakrishnan & Nair 1983; Shireen 2000; Rameshkumar et al. 2012); Psettodes erumei (Bloch & Schneider, 1801) (see Schioedte & Meinert 1884; Nierstrasz 1915; Monod 1934; Trilles 1979); Liza vaigiensis (Quoy & Gaimard, 1825) (as Mugil waigiensis ) and Peprilus paru (Linnaeus, 1758) (as Stomateus paru ) (see Kossmann 1880; Gerstaecker 1901); “Mouthparts of fish, chiefly of Ikan dalam” (see Lanchester 1902); in a barracuda-like fish and an Iniistius fish (see Richardson 1910); Psuedanthias evansi (Smith, 1954) (see Nierstrasz 1915); Arothron leopardus (Day, 1878) (as Tetrodon leopardus ) (see Monod 1924); “ Tetrodon sp.” (see Nierstrasz 1931); Hime formosana (Lee & Chao, 1994) (as Aulopus japonicus ) (see Shiino 1951); Parastromateus sp. and Psettodes sp. (see Sachlan 1955); Pampus argenteus (Euphrasen, 1788) (as Stromateus cinereus ) (see Bal & Joshi 1959; Bowman & Tareen 1983); Siganus canaliculatus (Park, 1797) (as S. oramin ) (see Monod 1976); Plectorhinchus nigrus (Cuvier, 1830) (as Pseudopristipoma nigrum ) (see Trilles 1979); Sphyraena obtusata Cuvier, 1829 (see Bowman & Tareen 1983).

Remarks. Cymothoa eremita has anterolateral projections which extend to half the length of the cephalon; truncate anterior margin of the cephalon; pleon as wide as pereon; uropods which do not reach the posterior margin of the pleotelson; ischium on pereopod 7 with a bulbous protrusion; and small lateral projections on the posterolateral margins of pereonite 1 (seen in larger specimens such as the C. leschenaultii syntype in Fig. 5 A).

The identity of the type host has been subject to some confusion as no species of Cymothoa had ever been reported from ‘dolphin fish’ (assumed to be Coryphaena apus , Coryphaenidae ). Recently, Williams and Bunkley- Williams (2009) clarified this situation and identified the “barbugede Pampelfisk, Coryphaena apus ”, mentioned by Brünnich (1783) as the host of Cymothoa eremita , as the Black Pomfret, Parastromateus niger , the misconception arising from an error in translation.

Schioedte and Meinert (1884) mentioned that the type specimens for C. eremita were placed in ZMUC and MCZ. They examined Brünnich’s (1783) specimen which was still attached to the tongue of the host “ Coryphaena apus ” and stored in ZMUC. Stebbing (1893) also noted that the specimen from ZMUC was still attached to the tongue of the host fish from which it was originally taken. When looking for this specimen at ZMUC, no “ type ” specimen for C. eremita could be found in ZMUC. After further investigations (on site at ZMUC, as part of this study), a fish ( Parastromateus niger ) with the isopod still inside the mouth was discovered and after closer examination was determined to be Brünnich’s (1783) holotype material.

Miers (1880) examined a large number of Bleeker’s (1857) collection of isopods and noticed a large variation in the anterolateral lobes of the first pereonite and on the basis of the last pereopod. Miers (1880) furthered explained how no difference could be seen between Leach’s (1818) C. leschenaultii (single specimen from Ponducherry) and Bleeker’s (1857) C. stromatei and C. edwardsii , synonymising all three species. Kossmann (1880) later synonymised C. mathoei with C. eremita and Schioedte and Meinert (1884) synonymised C. stromatei with C. eremita .

The holotype for Cymothoa limbata Schioedte & Meinert, 1884 (SMNH 4933) from Cape York, Australia, was not examined. A single non-ovigerous female was originally described but no other collections have been made of it since, making comparisons difficult. This species strongly resembles C. eremita and C. oestrum . Cymothoa oestrum has the same uropod length and subtruncate cephalon seen in C. limbata but the anterolateral angles of pereonite 1 do not seem as large and as long as those in C. oestrum which extend to the anterior margin of the cephalon or further. However, C. limbata shares a similar pleon and morphology with C. eremita , as well as shorter, more acute anterolateral projections of pereonite 1 similar to C. eremita . Trilles (1994) suggested synonymising C. limbata with C. eremita and after reviewing the type drawings of C. limbata , this synonymisation seems viable but a personal observation of the holotype would be necessary for absolute confidence in this regard.

The Cymothoa sp. (an. eremita Brünnich, 1783 ) [sic] of Monod (1934) also shows many of the species characteristics of C. eremita . Trilles (1994) placed Monod’s (1934) record into synonymy with C. pulchrum but we disagree as C. pulchrum has pleonite 1 less visible, wider anterolateral angles on pereonite 1 and lateral projections on pereonite 1 that Monod’s (1934) specimen does not have. These characters correspond with C. eremita , where we now place that record.

Cymothoa cinerea Bal and Joshi, 1959 was described from India with the authors noting that the species was very similar to Cymothoa stromatea [sic] parasitic on Parastromateus niger , differing in having a longer thorax, shorter and tuberculate abdomen and slightly punctuate sides of its body. Both species were collected from the same host species off India. Comparing the figures of C. cinerea to C. eremita , it is proposed that these C. cinerea is a junior synonymy of Cymothoa eremita .

It is clear that Cymothoa eremita is a common species in the Indian and Pacific Oceans. It has often been repeatedly misidentified or thought to be a new species and a redescription of the syntypes was necessary. A number of species have also already been synonymised with C. eremita and two of those ( C. mathoei and C. leschenaultii ) were examined as part of this study ( Figs 4–5 ) and their status as junior synonyms confirmed herein.

Figures

FIGURE 3. Cymothoa eremita (Brünnich, 1783), female lectotype (26 mm) (ZMUC-CRU- 10078). A, dorsal view; B, anterodorsal view of pereonite 1 and cephalon; C, ventral view of cephalon; D, pereopod 1; E, pereopod 7; F, lateral view.

FIGURE 4. Cymothoa eremita female (31 mm), syntype of C. mathoei Leach, 1818 (BMNH 1979.407.2). A, dorsal view; B, antero-dorsal view of pereonite 1 and cephalon; C, pereopod 7; D, lateral view.

FIGURE 5. Cymothoa eremita female (36 mm), holotype of C. leschenaultii Leach, 1818 (BMNH 1979.406.1). A, dorsal view; B, antero-dorsal view of pereonite 1 and cephalon; C, pereopod 7; D, lateral view.