Cymadusa imbroglio Rabindranath 1972
Creators: name: Hughes, L. E.
name: Lowry, J. K.
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Ampithoidae
Cymadusa
Cymadusa imbroglio

description: Cymadusa imbroglio Rabindranath, 1972   
(Figs 19, 20, Pl. 1F)  
 Cymadusa imbroglio Rabindranath, 1972: 175, fig 9. — Myers, 1985: 29, figs 20, 21 (key). — Peart, 2004: 320, figs 12– 15 (key).   
 Cymadusa filosa forme imbroglio. — Ledoyer, 1984: 5, 15, figs 5, 6 (male, 11 mm, stn 70).   
 Material examined. Male, photo 5, AM P70682 (QLD 1640); male, 7.8 mm, 3 slides, AM P76749 (QLD 1648); female, 8.6 mm, 2 slides, AM P76750 (QLD 1648); 1 ‘C’ male, AM P76751, 12 mm, (SEL /LZI-5-2); many unsexed, AM P76752 (SEL /LZI-5-2).   
 Type locality. Manoli Island, Gulf of Mannar, India (~ 9°12'N 79°7'E), intertidal.   
 Description. Based on male, 7.8 mm, AM P76749.   
 Head. Head as long as deep. Antenna 1 longer than antenna 2; primary flagellum 46 articles; accessory flagellum with 1 article. Antenna 2 flagellum 17 articles. Upper lip directed nearly straight down, lateral margins each with midlateral notch. Mandible molar well developed, triturating, accessory setal row with 8 serrate setae; palp 3–articulate, article 3 apically setose; article 1 shorter than article 2; article 2 slightly shorter than article 3; article 3 longer than article 1. Lower lip outer plates notched, forming a medial excavation; mandibular lobe with straight margins, rounded apically. Maxilla 1 inner plate with 4 setae; palp article 2 broad. Maxilla 2 inner plate narrower than outer plate. Maxilliped outer plate with row of large robust setae along medial margin.   
 Pereon. Coxae 1–4 deeper than broad. Gnathopod 1 smaller than gnathopod 2; coxa distinctly larger than coxa 2, anteroventrally produced, anterior margin convex, anteroventral corner rounded; basis subequal in length to coxa, anterodistal lobe absent; merus posterodistal lobe subacute; carpus about 2 x as long as broad, subequal in length to propodus, anterior margin with slender setae, posterior margin convex; propodus broad, subovoid; palm acute, sinusoidal, with rounded posterodistal corner, with 1 robust seta defining palm; dactylus subequal in length to palm, inner margin crenate. Gnathopod 2 basis with sparse slender setae, anterodistal lobe small, rounded, not reaching beyond ischium, corner without setae; merus margin with short, rounded anterodistal lobe; carpus much shorter than propodus, subtriangular; propodus broad, less than 1.5 x as long as broad, subquadrate, not produced into an anterodistally setose lobe; palm acute, excavate, with midmedial, subquadrate projection, with short posterodistal tooth, (length 1 x breadth), apically subacute, without palm defining robust setae; dactylus shorter than palm, tapering evenly, apically acute, inner margin crenate. Pereopods 3–4 basis narrow; merus subequal in length to carpus. Pereopods 5–7 simple. Pereopod 5 basis without medial slender setae; distal articles slender; propodus not expanded distally, without anterodistal striated robust setae; dactylus strongly curved. Pereopod 6 basis posterior margin weakly sinusoidal, with several marginal robust setae; distal articles slender; propodus not expanded distally, without anterodistal striated robust setae; dactylus strongly curved. Pereopod 7 similar to pereopod 6.   
 Pleon. Epimeron 2 posteroventral corner forming a small rounded cusp. Epimeron 3 posteroventral corner narrowly rounded. Uropod 1 peduncle with 9 robust setae, with long fringe of slender setae (greater than 0.5 x length of peduncle), with large, acute distoventral spine; outer ramus with 5 lateral robust setae; outer ramus with 9 lateral robust setae. Uropod 2 peduncle with 3 robust setae; outer ramus with 6 lateral robust setae; inner ramus with 8 lateral robust setae. Uropod 3 peduncle longer than broad, less than 2 x length of rami, marginal slender setae rounded, with 4 distal peduncular robust setae, with 3 distal slender setae; outer ramus with 2 large recurved distal robust setae, with 1 lateral robust seta and 4 lateral slender setae; inner ramus with 5 apical slender setae and 1 robust seta, without lateral robust setae. Telson subtrapezoidal, apically truncated, without apicolateral cusp on each distolateral corner, 2 pair of oblique medial slender setae, 3 pair of apical slender setae, and with 1 pair of lateral and 1 pair of apical plumose setae.   
 Female (sexually dimorphic characters). Based on female, 8.6 mm, AM P76750. Gnathopod 1 subequal in size to gnathopod 2; coxa anterior margin concave, with a tuft of long and short slender setae in the posteroventral corner; basis with fringe of long, slender marginal and medial setae; anterodistal lobe absent, with 1 slender seta; merus anterodistal lobe subacute; palm convex, without robust setae defining palm; dactylus overreaching palm. Gnathopod 2 coxa with a tuft of long or short slender setae in the posteroventral corner; basis with fringe of long, slender setae; carpus shorter than propodus; propodus with shallow midmedial tooth, posterodistal corner, acute; dactylus overreaching palm.   
 Colour. Body clear to white with green-brown patches and spots, eyes with red ommatidia in a white matrix.   
 Habitat. Green algae, Udotea sp.   
 Remarks. The original description of C. imbroglio Rabindranath, 1972, based on specimens from the Gulf of Manaar in south-eastern India, is not extensive, but the species is distinctive. The only reports of the species since Rabindranath (1972) have been Ledoyer (1984), based on specimens from New Caledonia, Myers (1985) on specimens from Fiji and Peart (2004) on specimens from New South Wales, Australia. The most apparent differences between the Indian Ocean population and the Pacific Ocean populations are the shape of the palm of male gnathopod 2 and the number of distal robust setae on the peduncle of uropod 3. Myers (1985) considered these differences as variation. We have material representing a range of sizes. Our observations indicate that the distinctive midmedial projection reduces with increasing size/age of the male individuals. In specimens ~ 8 mm in length the tooth is a long subquadrate platform that eventually reduces to a tiny vestigial tooth in males 12 mm long. The overall propodus becomes increasingly calcified and more subovoid with age.   
 Peart (2007a) considered that the Indian and Pacific Ocean populations might not be conspecific. However, our material shows that changes with growth stages encompasses the variation figured by all authors. The Indian population of C. imbroglio (Rabindranath, 1972) are hyperadults at 8.4 mm. In the GBR populations males are mature at 7.8 mm and hyperadults at 12 mm.   
 Distribution. Australia. Queensland: Lizard Island (current study). New South Wales: Botany Bay (Peart 2004). Fiji. Viti Levu: Momi Bay, Nasese, Mburelevu, Nananui Ra (Myers 1985). India. Gulf of Mannar, Manoli Island (Rabindranath 1972). New Caledonia. Récif Abore (Ledoyer 1984).
description: Published as part of Hughes, L. E. & Lowry, J. K., 2009, Ampithoidae *, pp. 153-219 in Zootaxa 2260 (1) on pages 184-188, DOI: 10.11646/zootaxa.2260.1.8, http://zenodo.org/record/5322208