Cymothoa hermani, Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2011

Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2011, Cymothoa hermani sp. nov. (Isopoda, Cymothoidae, Crustacea), a parasitic isopod, collected off the Zanzibar coast, Tanzania from the mouth of a parrotfish (Scaridae), Zootaxa 2876, pp. 57-68 : 58-67

Cymothoa hermani sp. nov.

Figures 1–7

Material examined. Holotype. Ψ 28 mm, Miwi Island, Kiwani Bay, Unguja Island, Zanzibar, Tanzania, 06°21’S, 39°20’E, 26 April 2008, coll. H. Van der Bank ( SAMC A47890).

Paratypes. Ψ 23 mm (mouthparts dissected), 2 ɗ 14 mm, 15 mm, same data as holotype ( SAMC A47891).

Type host. Removed from the buccal cavity of Leptoscarus vaigiensis ( Quoy & Gaimard, 1824) Host held in the South African Institute for Aquatic Biodiversity ( SAIAB 96718).

Ovigerous female. Length 28.0 mm, width 17.0 mm.

Body 1.9 times as long as greatest width, dorsal surfaces rugose; widest at pereonite 3, most narrow at pereonite 7, lateral margins subparallel. Cephalon twice as long as wide, triangular and not visible from dorsal view. Frontal margin rounded, forming blunt rostrum. Eyes absent. Pereonite 1 anterolateral angle rounded and produced past frontal margin of cephalon, with unique bulbous orientation; posterior margins of pereonites smooth and straight. Coxae 2–3 with posteroventral angles rounded; coxae 4–7 with small, distinct points. Pereonites 1–3 increasing in length and width posteriorly; pereonites 4–7 decreasing in length and width posteriorly; pereonites becoming progressively more rounded posteriorly. Pleon visible in dorsal view, pleonites posterior margin concave; posterolateral angles of pleonite 2 forming acute point, 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 slightly concave. Pleotelson 0.5 times as long as anterior width, dorsal surface with 2 submedial depressions, lateral margins concave, posterior margin truncate.

Antennule comprised of 8 articles; peduncle articles 1 and 2 distinct and articulated; article 2 as long as article 1; article 3 as long as wide, 0.4 times as long as combined lengths of articles 1 and 2. Antenna peduncle article 3 1.5 times as long as article 2, 1.8 times as long as wide; article 4 as long as wide, 0.6 times as long as article 3; article 5 as long as wide, as long as article 4. Antenna flagellum with 4 articles, article 4 without setae. Labrum lateral margins straight, diverging slightly towards anterior, anterior margin rounded, with median indentation, without small median point. Mandibular process ending in acute incisor, mandible palp article 2 and 3 without setae. Maxillule simple with 4 terminal robust setae. Maxilla mesial lobe partly fused to lateral lobe and covered in pectinate scales; lateral lobe with 3 recurved robust setae; mesial lobe with 3 large recurved robust setae. Maxilliped covered in pectinate scales, oostegite lobe lamellar. Maxilliped palp article 2 with 20 simple setae, article 3 with 9 recurved robust setae. Oostegites smooth, without setae.

Pereopod 1 basis 2.2 times as long as greatest width; ischium 1.3 times as long as basis; merus proximal margin without bulbous protrusion; carpus with rounded proximal margin; propodus 1.8 times as long as wide; dactylus slender, 1.4 as long as propodus, 3.5 times as long as basal width. Pereopod 2 propodus 1.9 as long as wide; dactylus 1.6 as long as propodus. Pereopod 3-6 similar to pereopod 2 and gradually increasing in size towards posterior, all without robust or simple setae. Pereopod 7 basis 1.2 times as long as greatest width; ischium 1.4 as long as basis; merus proximal margin with slight bulbous protrusion, merus 0.3 as long as ischium, 0.6 times as long as wide, with slight bulbous protrusion; carpus 0.5 as long as ischium, 1.2 times as long as wide; propodus 0.8 as long as ischium, 1.8 times as long as wide; dactylus slender, 1.3 as long as propodus, 3.5 times as long as basal width.

Pleopods with slight depression on central dorsal surface of each pleopod ramus. Pleopod 1 exopod 0.8 times as long as wide, lateral margin weakly convex, mesial margin weakly produced; endopod as long as wide, lateral margin straight, mesial margin slightly convex; peduncle 2.3 times as wide as long. Pleopods 2–3 simple, similar to pleopod 1, mesial margins becoming more strongly produced. Pleopods 3–5 endopods proximal borders extending below exopod to peduncle; large medial lobes present and increasing in size from pleopod 1 to 5.

Uropod half as long as pleotelson, peduncle 1.1 times as long as rami, lateral margin without setae, rami not extending beyond pleotelson, marginal setae absent, apices narrowly rounded. Endopod apically slightly pointed, 2.9 times as long as greatest width, lateral margin weakly convex, setae absent, mesial margin weakly convex. Exopod not extending to end of endopod, narrower and slightly shorter than endopod, 4 times as long as greatest width, apically rounded, lateral margin weakly convex, without setae, mesial margin weakly convex.

Male. Length 14.0–15.0 mm, width 6.0– 6.2 mm.

Males similar to females but smaller. Body rectangular, 1.5 times as long as wide. Cephalon visible in dorsal view, with less obvious bulbous ornamentation on pereonite 1. Antenna with 10 articles. Setae present on mandibular palp article 3. Pleopods simple, with less folds on endopod. Pleopod 2 appendix masculina with parallel margins, as long as endopod, distally narrowly rounded.

Colour. Tan in ethanol preserved specimens.

Distribution. Currently only known from the type location, off Miwi Island, Kiwani Bay, Unguja, Zanzibar, Tanzania. The host, Leptoscarus vaigiensis is found from the northern Red Sea to South Africa and eastwards to Japan and New Zealand.

Etymology. Named after Prof. Herman van der Bank (University of Johannesburg) who collected this species on one of his research trips.

Remarks. Cymothoa hermani sp.nov. can be identified by the unique bulbous ornamentation on pereonite 1, anterolateral angles on pereonite 1 rounded and produced past frontal margin of cephalon, long and slender dactyli and the numerous lobes on pleopods 4 and 5 in the ovigerous female. No other species in the genus shows this unique combination of characters. There are currently no other described species of Cymothoa known from parrotfishes, although at least one species has been collected from parrotfish in Queensland (Museum of Tropical Queensland, QM W8961). The host, Leptoscarus vaigiensis , (‘marbled parrotfish’) is known from the Indo-Pacific (northern Red Sea and South Africa to Easter Island, north to southern Japan, south to Poor Knight's Island in New Zealand and Rottnest Island in Australia), and from the southeast Atlantic (False Bay, South Africa). It is known to inhabit seagrass areas or areas with hard substrates heavy with algal cover as it feeds on the seagrass and algae ( Froese & Pauly 2010).

Three species of Cymothoa are recorded from the south-western Indian Ocean to date, namely C. borbonica , C. eremita and C. rotundifrons . Cymothoa borbonica is similar to C. hermani but differs in having shorter uropods and a larger pleotelson which has a rounded posterior margin compared to the small rectangular pleotelson seen in C. hermani . Cymothoa rotundifrons differs from C. hermani in having two lateral depressions on pereonites 3 and 4, three near-parallel lines of sunken pits on pereonites 5 and 6, and the pleon not narrowing posteriorly.

Cymothoa eremita , the only other Cymothoa species known from Zanzibar, differs in that it does not show the characteristic bulbous ornamentation on pereonite 1 that is present in C. hermani . The cephalon of C. eremita is visible dorsally, the anterolateral margin of pereonite 1 is not produced past the cephalon, and the lateral pereonite margins are more acutely produced than in C. hermani . Furthermore, the pleonite posterior margins are irregular in C. eremita with the pleonite 5 appearing to have very distinctly produced sub-medial points; C. eremita has a much wider than long cephaloson compared to the much longer than wider C. hermani cephalon. The host species for C. eremita in Zanzibar is not known, but hosts for C. eremita elsewhere include a diverse range of species from the families Coryphaenidae , Stromateidae , Chloropthalmidae and Psettodidae ( Trilles 1994) .

Figures

FIGURE 1. Cymothoa hermani sp. nov., female holotype (28.0 mm) (SAMC A 47890). A, full length dorsal view; B, front view of pereonite 1 and cephalon; C, dorsal view of pleotelson; D, lateral view of body.

FIGURE 2. Cymothoa hermani sp. nov., female paratype (23.0 mm) (SAMC A 47891). A, right mandible; B, right maxillule; C, antennule; D, antenna; E, tip of maxilla; F, tip of maxillule; G, left maxilla; H, maxilliped article 3; I, left maxilliped.

FIGURE 3. Cymothoa hermani sp. nov., female holotype (28.0 mm) (SAMC A 47890). A, pereopod 1; B, pereopod 2; C, pereopod 6; D, pereopod 7; E, uropod; F, ventral view of cephalon; G, oostegites.

FIGURE 4. Cymothoa hermani sp. nov., female paratype (23.0 mm) (SAMC A 47891). A, dorsal pleopod 1; B, dorsal pleopod 2; C, dorsal pleopod 3; D, dorsal pleopod 4; E, dorsal pleopod 5; F, ventral pleopod 1; G, ventral pleopod 2; H, ventral pleopod 3; I, ventral pleopod 4; J, ventral pleopod 5.

FIGURE 5. Cymothoa hermani sp. nov., male paratype (14.0 mm) (SAMC A 47891). A, full length dorsal view; B, antennule; C, antenna; D, dorsal view of pleotelson; E, lateral view of body.

FIGURE 6. Cymothoa hermani sp. nov., male paratype (14.0 mm) (SAMC A 47891). A, right mandible; B, left maxilliped; C, maxilliped article; 3, D, left maxillule, E, uropod; F, maxillule tip; G, left maxilla; H, pereopod 1; I, pereopod 7.

FIGURE 7. Cymothoa hermani sp. nov., male paratype (14.0 mm) (SAMC A 47891). A, dorsal pleopod 1; B, dorsal pleopod 2; C, dorsal pleopod 3; D, dorsal pleopod 4; E, dorsal pleopod 5; F, ventral pleopod 1; G, ventral pleopod 2; H, ventral pleopod 3; I, ventral pleopod 4; J, ventral pleopod 5.