Isocyamus indopacetus Iwasa-Arai and Serejo, 2017
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publication ID |
https://doi.org/ 10.1080/00222933.2017.1365965 |
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publication LSID |
lsid:zoobank.org:pub:451A4857-9CFC-4C81-AF70-8DFD0D7CEB16 |
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persistent identifier |
https://treatment.plazi.org/id/03FC878B-FFD0-FFF9-FEA5-FD8051A6F98B |
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treatment provided by |
Carolina |
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scientific name |
Isocyamus indopacetus Iwasa-Arai and Serejo |
| status |
sp. nov. |
Isocyamus indopacetus Iwasa-Arai and Serejo View in CoL , sp. nov.
( Figures 5–7 View Figure 5 View Figure 6 View Figure 7 )
Material examined
Holotype, male, 9.2 mm, Baie de la Somme (22.329°S; 166.824°E), New Caledonia, from Indopacetus paci fi cus, C. Garrigue et al. col., November 2013, MNHN-IU-2014-12863. GoogleMaps
Diagnosis
Maxilliped inner lobes rounded, with distal outer lobes. Gnathopod 2 with proximal palmar expansion and triangular palmar tooth. Accessory gills subtriangular; lateral gills with a pair of spine-like processes at the base. Maxilla 2 with reduced outer lobes. Lower lip with inner lobes fully fused. Pereopod 5–7 basi-ischium with anterolateral acute process distally directed.
Etymology
The specific epithet refers to the host genus, Indopacetus Moore).
Description
Holotype, male, 9.2 mm, MNHN-IU-2014-12863. Body compact and dorso-ventrally depressed, dorsal surface smooth. 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 typical anterodorsal epaulet-like cuticular infoldings and knob-like process on posterolateral margin ( Figures 5 View Figure 5 and 7 View Figure 7 (a)). Pereonites 3 and 4 subequal in length to other somites, slightly narrower than pereonite 5, without pereopods, each bearing one pair of sausage-like gills, one subtriangular accessory gill and two accessory spine-like processes arising from each lateral gill ( Figures 5 View Figure 5 and 7 View Figure 7 (b)). Pereonites 5, 6 and 7 each bearing one pair of acute ventral processes (ventral spines), antero-directed ( Figures 5 View Figure 5 and 7 View Figure 7 (d)). Pereonite 7 triangular. Penes large, stout.
Antenna 1 four-articulate, terminal article narrow and long, bearing a continuous band on the internal margin of terminal article; subterminal article sparsely setose. Antenna 2 three-articulate, with sparse setae. 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; terminal margin heavily setose and inner margin setose; inner lobes fully fused, triangular. Left mandible with palp absent; incisor five-toothed; lacinia mobilis five-toothed; spine row of three setae; molar process absent. Right mandible with palp absent; right incisor six-toothed; lacinia mobilis multituberculate with two teeth; spine row absent; molar process absent; submolar setae lacking. Maxilla 1 with seven denticulate robust setae on outer lobe; palp one-articulate, with long setae, not reaching outer lobe setae. Maxilla 2 with distomedial expansion of inner lobe; outer lobe fused. Maxillipeds with inner plate lacking setae, fused basally, maxillipeds outer plate present, anteriorly directed; palp absent ( Figures 6 View Figure 6 and 7 View Figure 7 (c)).
Gnathopod 1 approximately one-fourth size of gnathopod 2, coxa not fused with pereon, anterior margin of propodus with proximal broad expansion. Gnathopod 2 coxa not fused with pereon; basi-ischium with large triangular expansion on anterior margin; carpus and propodus fused; proximal interior margin of propodus with a small blunt projection, propodus with subacute palmar tooth, larger than proximal expansion, dactylus large and unornamented, reaching propodus’ proximal expansion. Pereopods 3 and 4 absent. Pereonites 3 and 4 bearing stout, uniramous and outwardly directed lateral gill; lateral gill cylindrical, 7.5 times longer than wide. Pereonites 3 and 4 bearing triangular, leaf-shaped medial (accessory) gill; accessory gill subequal in length to lateral gill, also arising as coxal epipod; pair of spine-like process arising from each gill, laterally directed. Coxae of pereopods 5 through 7 not fused with pereon. Basi-ischium with anterolateral acute process on ventral face, distally directed. 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 5 View Figure 5 ).
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.
Remarks
Until the present study Isocyamus included four species that are ectoparasites of different hosts ( Table 2). Isocyamus indopacetus sp. nov. is close to I. deltobranchium in the subtriangular shape of accessory gills, which is an exclusive character of these species. However, I. indopacetus sp. nov. presents two spine-like processes at the base of each lateral gill, whereas I. deltobranchium has only one process per gill ( Figures 5 View Figure 5 and 7 View Figure 7 (b); Table 3). Also, Isocyamus indopacetus sp. nov. exhibits the maxilliped with outer plate, an unique character among other Isocyamus ( Figures 6 View Figure 6 and 7 View Figure 7 (c)). Nonetheless, while other species of Isocyamus have the dactyl of gnathopod 1 with a combed ridge, it is smooth in I. indopacetus sp. nov. ( Figure 5 View Figure 5 ).
Longman’ s beaked whale is considered one of the rarest and least well known cetaceans ( Garrigue et al. 2016). This is the first record of a whale-louse species parasitising the Longman beaked whale, though Yamada et al. (2012) reported that Indopacetus paci fi cus often carried unidentified whale lice, and highlighted the importance of having more research on external parasites of these beaked whales.
Key to species of Isocyamus View in CoL (modified from Sedlak-Weinstein 1992b)
1. One pair of ventral acute processes on segments 5–7....................................................... 2
– No ventral processes on segments 5–7........................................................................ I. kogiae View in CoL
2. Accessory gills in males shorter than lateral gills, subtriangular or clavate, pereonite 2 with anterodorsal epaulet-like cuticular infoldings ........................................................... 3
– Accessory gills in males equal in length to lateral gills, cylindrical, pereonite 2 anterodorsal margin straight .............................................................................................. I. delphinii View in CoL
3. One spine-like process on basis of lateral gills ...................................................................... 4
– Two spine-like processes on basis of lateral gills ...... ...... I. indopacetus View in CoL sp. nov. ( Figure 2 View Figure 2 )
4. Accessory gills in males triangular, palm of gnathopod 2 of female with posterior tooth only... ................................................. ................................................. I. deltobranchium View in CoL
– Accessory gills in males clavate, palm of gnathopod 2 of female with anterior and posterior pointed teeth ...................................................................................................... I. antarcticensis View in CoL
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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