Cyamus monodontis Lutken 1870
Creators: name: Iwasa-Arai, Tammy
name: Carvalho, Vitor Luz
name: Serejo, Cristiana Silveira
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Cyamidae
Cyamus
Cyamus monodontis

description: Cyamus monodontis Lütken, 1870   
(Figures 1 and 2)  
 Cyamus monodontis Lütken, 1870: 279. – Lütken 1873: 282. – Leung 1967: 285, fig. 4c. – Lincoln and Hurley 1974b: 68. – Leung 1976: 160. – Berzin and Vlasova 1982: 157, 158. – Margolis and Arai 1989: 12. – Haney 1999: 124–128, figs 47–49. – Martin and Heyning 1999: 28.   
 Cyamus (Cyamus) monodontis – Margolis et al. 2000: 71–74, fig. 4.   
 Material examined (host Monodon monoceros)   
 Lectotype. One male, 9.4 mm, Greenland, ZMUC-CRU-8685. Paralectotypes: four males, 8.5– 9.3 mm, Greenland, ZMUC CRU- 467. Allotype: one female, 7.2 mm, Thule, Greenland, ZMUC CRU-8686. Other non-type material: one female, 5.4 mm, Greenland, ZMUC CRU-7641; three males, 5.2–7.2 mm, 3 females, 7.1–7.8 mm, Thule, Greenland, ZMUC CRU-8570.   
 Hosts   
 Monodon monoceros, Delphinapterus leucas (Pallas).   
 Diagnosis   
Pereonite 2 without knoblike process on the posterior margin. Lateral gills stout, uniramous; male accessory gills asymmetrically bilobed, anterior lobe shortest, female accessory gills oval. Pereonite 5 smooth, male pereonites 6 and 7 with two pairs of acute ventral processes, female P6 with three pairs and P7 with one pair of acute ventral processes.  
 Redescription   
Lectotype, male, 9.4 mm, ZMUC CRU-8685. Body compact and dorso-ventrally depressed. Eyes small and ovoid. Head quadrangular, partially fused with pereonite 1; lateral incision between head and pereonite 1 absent. Pereonite 1 with lateral expansion. Pereonite 2 with squared process on posterolateral margin. Pereonites 3 and 4 shorter in length than pereonites 1, 2 and 5–7, subequal in width to pereonite 5, with terminal posterior projections, without pereopods, each bearing one pair of gills and one accessory gill. Pereonite 5 smooth. Pereonites 6 and 7 each bearing two pairs of acute ventral processes (ventral spines), the first pair antero-directed, the second, latero-directed. Pereonite 7 triangular. Penes large, stout (Figure 1).  
Antenna 1 long, 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; other articles sparsely setose. Antenna 2 with 4 articles, with setae on terminal article; article 3 the longest. Upper lip with distomedial invagination, producing distally rounded left and right subequal lobes, epistome moderate, not reaching distomedial invagination. Lower lip outer lobes longer than inner lobes; outer lobes broad, triangular; inner margin setose; inner lobes partially fused, rounded distally. Left mandible with palp absent; incisor five-toothed; lacinia mobilis five-toothed; spine row short, with three setae; molar process absent. Right mandible with palp absent; right incisor five-toothed; lacinia mobilis multituberculate with two teeth; spine row of three setae; molar process absent; submolar setae lacking. Maxilla 1 with seven denticulate setae on outer lobe; palp 1 onearticulate, with long setae. Maxilla 2 with distomedial expansion of inner lobe bearing two setae. Maxillipeds with inner plate lacking setae; outer plate with 3–4 setae, palp 4- articulated, sparsely setose (Figure 2).  
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 blunt process on anterolateral corner, large blunt expansion located proximally of process; carpus and propodus fused; proximal process of interior margin of propodus oval, propodus with subacute palmar tooth, subequal in length to proximal process, dactylus large and unornamented, reaching propodus’ oval 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 bilobed medial (accessory) gill; accessory gill much shorter than lateral gill, also arising as coxal epipod. Accessory gill lobes asymmetrical, posterior lobe the longest. Pereopods 5–7 coxae not fused with pereon. Basi-ischium with large, acute process, distally directed, located distally on antero-ventral face. Anterior margin of ischium uniform, unornamented. Inferior margin of merus uniform. Carpus with anterolateral expansion. Propodus subelliptical; with no teeth or spines. Dactylus acute, angle of recurve dactylus extreme, approximately 90° (Figure 1).  
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, 7.2 mm, ZMUC CRU-8686 – 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 without ventral acute processes, genital valves present; medial margin of genital valve well rounded, bearing cluster of short setae. Pereonite 6 bearing three pairs of ventral acute processes, forwardly, laterally and backwardly directed, pereonite 7 with one pair of ventral acute processes, laterally directed; pleon lacking pleopods.  
 Remarks   
 The syntype series of Cyamus monodontis was available from the Zoologisk Museum, University of Copenhagen, which made it possible for us to designate a lectotype and paralectotypes, and provide a redescription using modern standards. Cyamus monodontis was described originally as an ectoparasite of Monodon monoceros from Greenland (Lütken, 1870). Its body shape is similar to that of Cyamus nodosus, which co-occurs on Monodon monoceros, and to that of Cyamus ceti (Linnaeus, 1758), ectoparasite of bowhead whales Balaena mysticetus Linnaeus, 1758 and gray whales Eschrichtius robustus (Lilljeborg). Lateral gills of C. monodontis are more similar to those of C. nodosus, while its accessory gills are more similar to those of C. ceti, which are asymmetrically bilobed. Cyamus monodontis differs from them by the spination on the ventral face of pereonites 5–7 and the absence of knob-like processes on the posterior margin of pereonite 2.   
 Despite C. monodontis being recorded for both M. monoceros and D. leucas, all the examined material was collected from a single host species, M. monoceros. Delphinapterus leucas was recorded by Margolis (1954) and Grüner (1975) as host, but it seems that the majority of the available material in collections is from M. monoceros (Margolis 1954; Lincoln and Hurley 1974b; Haney 1999). A description of C. monodontis specimens from D. leucas is available in Margolis et al. (2000).
description: Published as part of 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, pp. 2225-2245 in Journal of Natural History (J. Nat. Hist.) (J. Nat. Hist.) 51 (37 - 38) on pages 2228-2231, DOI: 10.1080/00222933.2017.1365965, http://zenodo.org/record/4746859