Cyamus nodosus Lütken, 1861

Iwasa-Arai, Tammy, Carvalho, Vitor Luz & Serejo, Cristiana Silveira, 2017, Updates on Cyamidae (Crustacea: Amphipoda): redescriptions of Cyamus monodontis Lütken, 1870 and Cyamus nodosus Lütken, 1861, a new species of Isocyamus, and new host records for Syncyamus ilheusensis Haney, De Almeida and Reis, 2004, Journal of Natural History (J. Nat. Hist.) 51 (37 - 38), pp. 2225-2245 : 2232-2235

Cyamus nodosus Lütken, 1861

( Figures 3 and 4 )

Cyamus nodosus Lütken, 1861: 591 . – Lütken 1870: 280. – Lütken 1873: 282. – Leung 1967: 286, fig. 3c. – Lincoln and Hurley 1974b: 68–69. – Berzin and Vlasova 1982: 157–158. – Margolis and Arai 1989: 12. – Martin and Heyning 1999: 28. – Haney 1999: 128–133, figs 50–52. – Margolis et al. 2000: 74.

Paracyamus nodosus – Stephensen 1942: 451–452. – Margolis 1955: 128.

Material examined (host Monodon monoceros )

Lectotype. One male, 8.6 mm, Greenland, ZMUC CRU-8687 . Paralectotypes: four males, 5.8–7.2 mm, Greenland, ZMUC CRU- 494. Allotype: one female, 7.1 mm, ZMUC CRU-8688 . Other non-type material: two males, 6.4–7.0 mm, one female, 5.4 mm, one juvenile, 3.8 mm, Greenland, ZMUC CRU-7641 ; 15 males, 6.5–7.0 mm, 13 females, 5.9 mm – 7.1 mm, 16 juveniles, not measured, Thule , Greenland, ZMUC CRU-8570 .

Hosts

Monodon Monoceros , Delphinapterus leucas .

Diagnosis

Dorsal face of pereonites 2–7 with broad protuberances; Lateral gills stout, uniramous; accessory gills of male subtriangular, uniramous; pereonite 5 of male smooth, pereonites 6 and 7 of male bearing one pair of blunt ventral processes.

Redescription

Lectotype, male, 8.6 mm, ZMUC CRU-8687. Body compact and dorso-ventrally depressed, dorsal surface uneven, with broad protuberances. Eyes small and ovoid. Head quadrangular, partially fused with pereonite 1; lateral incision between head and pereonite 1 absent. Pereonite 1 without lateral expansion. Pereonite 2 with knob-like process on posterolateral margin. Pereonites 3 and 4 subequal in length to other somites, wider than pereonite 5–7; pereonite 4 with posterolateral projection, without pereopods, each bearing one pair of gills and one accessory gill. Pereonite 5 smooth. Pereonites 6 and 7 each bearing one pair of blunt ventral processes (ventral spines) antero-directed. Pereonite 7 triangular. Penes large, stout ( Figure 3 ).

Antenna 1 with 4 articles, terminal article narrow and long, bearing apical tuft of setae, and brush-like setal groupings on the internal margin of terminal article; subterminal article sparsely setose. Antenna 2 four-articulate, with setae on terminal article; article 3 the longest. Upper lip with distomedial invagination, producing distally rounded left and right subequal lobes, setose on inner margin of both lobes, epistome moderate, not reaching distomedial invagination. Lower lip outer lobes longer than inner lobes; outer lobes slender, triangular; inner margin setose; inner lobes partially fused, rounded distally. Left mandible with palp absent; incisor seven-toothed; lacinia mobilis seven-toothed; spine row of three or more setae; molar process absent, submolar setae long. Right mandible with palp absent; right incisor five-toothed; lacinia mobilis multituberculate with four teeth; spine row of two setae; molar process absent; submolar setae present. Maxilla 1 with seven denticulate setae on outer lobe; palp 1onearticulate, with long setae. Maxilla 2 with distomedial expansion of inner lobe bearing two setae. Maxillipeds with inner plate setose; outer plate with 4–6 setae, palp absent ( Figure 4 ).

Gnathopod 1 approximately one-fourth size of gnathopod 2, coxa not fused with pereon, anterior margin of propodus with elongate expansion. Gnathopod 2 coxa not fused with pereon; ventral face of basi-ischium with large blunt expansion on anterior margin; carpus and propodus fused; proximal process of interior margin of propodus triangular, propodus with subacute palmar tooth, subequal in length to proximal process, dactylus large and unornamented, reaching propodus’ triangular proximal process. Pereopods 3 and 4 absent. Pereonites 3 and 4 bearing stout, uniramous and outwardly directed lateral gill; lateral gill cylindrical, 3.5 times longer than wide. Pereonites 3 and 4 bearing subtriangular medial (accessory) gill; accessory gill much shorter than lateral gill, also arising as coxal epipod. Coxae of pereopods 5–7 not fused with pereon. Basi-ischium uniform, lacking anterolateral acute process on ventral face. Anterior margin of ischium uniform, unornamented. Inferior margin of merus uniform. Carpus without anterolateral expansion. Propodus subelliptical; with no teeth or spines. Dactylus acute, angle of recurve dactylus extreme, approximately 90° ( Figure 3 ).

Pleon reduced with one pair of pleopods, fused basally and separate distally; with each pleopod ending in a spherical lobe and bearing short setae along its lateral margins.

Female, 7.1 mm, ZMUC CRU-8688 – Pereonites 3 and 4 broader than those of male, subequal in width to pereonites 5 and 6, bearing triangular oostegite. Margins of oostegites lined with short, simple setae. Pereonites 3 and 4 bearing small round accessory gills, posterior margin smooth. Pereonite 5 with a pair ventral acute processes on posterolateral margin of genital valves; medial margin of genital valve well rounded, bearing cluster of short setae. Pereonite 6 bearing two pairs of ventral blunt processes, pereonite 7 with one pair of ventral blunt processes; pleon lacking pleopods.

Remarks

The syntype series of Cyamus nodosus was available from the Zoologisk Museum, University of Copenhagen, which made it possible to designate a lectotype and paralectotypes, and provide a redescription following modern standards. Cyamus nodosus is easily distinguishable from other Cyamus species by the presence of broad tubercles on its pereon. It was described by Lütken (1861) for M. monoceros from Greenland.

Cyamus nodosus was described for Monodon monoceros , and later recorded for Delphinapterus leucas by Margolis (1954), who emphasised the host specificity of whale-louse species and suggested that contact between host species should provide the parasite’ s horizontal transfer, by the observation of rare occurrence of C. nodosus and C. monodontis on D. leucas .

Figures

Figure 3. Cyamus nodosus Lütken, 1861. Lectotype, male, 8.6 mm, ZMUC CRU-8687. AG: accessory gill; Gn: gnathopod; P: pereopod. Scale bars = 1 mm.

Figure 4. Cyamus nodosus Lütken, 1861. Lectotype, male, 8.6 mm, ZMUC CRU-8687. Ant: antenna; LL: lower lip; lMd: left mandible; rMd; right mandible; Mx: maxilla; Mxp: maxilliped; UL: upper lip. Scale bars: antenna 1 = 1 mm; all others = 100 μm.