A. nattereri HELLER (1857) : 103 KRøyER (1863) : 23 THORELL (1864) : 60 WILSON (1902) : 720 THIELE (1904) : 23 MOREIRA (1913) : 8 Argulus silvestrii LAHILLE (1926) : 10 Argulus salminei MEEHEAN (1940) : 502 A. nattereri RINGUELET (1943) : 57 WILSON (1944) : 552 THATcHER (2006) : 393 A new species of Argulus (Crustacea, Branchiura, Argulidae) from the skin of catfish, with new records of branchiurans from wild fish in the Brazilian Pantanal wetland Tavares, Luiz E. R. Zootaxa 2017 2017-09-18 4320 3 447 469 Heller, 1857 Heller 1857 [151,516,924,950] Maxillopoda Argulidae Argulus Animalia Arguloida 11 458 Arthropoda species nattereri     A. nattereri:  HELLER (1857): 103–106, PL. II, fIGS. 4–12;  KRøyER (1863): 23–25, 29, PL. I, fIGS. 3A–D;  THORELL (1864): 60;  WILSON (1902): 720, PL. XXII, fIG. 63;  THIELE (1904): 23–25, fIGS. 43–52;  MOREIRA (1913): 8, PL. II, fIG. 1;  Argulus silvestrii LAHILLE, 1926:  LAHILLE (1926): 10–11, 16, fIG. 3;  Argulus salminei KRøyER, 1863: PART  MEEHEAN (1940): 502;  A. nattereri:  RINGUELET (1943): 57–62, PL. III, fIGS. 1–6;  WILSON (1944): 552, 573–574, PL. 24, fIGS. 74–78; LEMOS DE CASTRO (1985): 10, fIGS, 11– 13;  THATcHER (2006): 393, 395, 398, fIG. 9.5    Typehost.  Hydrocyon brevidens(=  Salminus brasiliensis[Cuvier 1816]) ( Heller 1857)    Typelocality. Undefinedlocation in Brazil( Heller 1857).  Other hosts and localities.  Salminus brevidens(=  S. brasiliensis), state of Mato Grosso, Brazil( Moreira 1912, 1913);  P. corruscans,  S. brevidens(=  S. brasiliensis), ParanaRiver in Zona de  San Pedro, Argentina( Ringuelet 1943);  Pimelodus albicans(Valenciennes, 1840),  P. corruscans, Ysoró Stream, municipality of Cuatro Bocas, province of Corrientes, and in the ParanaRiver, province of Entre Ríos, both in Argentina( Barzanti 1976; Chemes & Takemoto 2011);  P. tigrinumand  Pseudoplatystoma fasciatum(Linnaeus, 1766), Beniand Ichilo Rivers Bolívia, ( Mamani et al.2004).   Material deposited.3 vouchers: 1 adultfemale ZUEC-CRU 3516, in ethanol 70%,  3 June 2004,  Salminus brasiliensis, skin, ParaguayRiver, Corumbá-MS, Brazil( 18°59'53.17"S, 57°36'44.43"O);  1 adultmale ZUEC- CRU 3517, in ethanol 70%, and 1 adultmale INPA 2307, in Hoyer’smedium,  4 July 2008, skin,  Pseudoplatystoma corruscans, Cuiabá River, Parque Nacionaldo Pantanal Matogrossense( 17°49′37.77″ S, 57°22′53.38″ W).   Measurements.Based on 2 malesand 1 female. Total length (mm) 4.54 (3.7–5.3) in males, 4.5 infemales. Carapace length 4.55 (2.6–4.5) in males, 4.6 infemale; maximum carapace width 3.5 (2.6––4.4) in males, 4.6 infemale. Carapace posterior sinus length 1.3 (1.2–1.35) in males, 1.1 infemale; width 1 (0.9–1.1) in males, 1.2 infemale. Cephalothorax length 2.2 (1.8–2.6) in males, 2.5 infemale; anterior width 2.1 (1.7–2.5) in males, 2.5 infemale. Abdomen length 0.9 (0.8–1) in males, 0.5 infemale; width 0.7 (0.6–0.75) in males, 0.5 infemale. Abdomen posterior sinus length 0.2 (0.15–0.3) in males, 0.13 infemale; width 0.13 (0.11–0.15) in males, 0.04 infemale. Eyes diameter (µm) 175 left and 225 right in one male, 150 left and 182 right in female; transverse distance between eyes (µm) 800 inone male, 800 infemale. First maxillae outer diameter (µm) 837 left (675–1000) and 899.4 right (724–1075) in males, 1300 left and 1250 right in female; inner diameter 650 left (525–775) and 616 right (508–725) in males, 1075 left and 975 right in females. Number of support rods in suction cups 64–70 inmales, 66–69 infemale; number of sclerites per support rod 6–9 inmales, 7–9 infemale.   Remarks.Among the species of  Argulusfrom freshwater environments of South America, only  A. nattereri( Figs. 8A–B) and  Argulus juparanaensisLemos de Castro, 1950have the carapace alae covering all four legs, although males of  A. pestiferalso display this characteristic ( Heller 1857; Lemos de Castro 1950; Ringuelet 1943), as do females of  A. salmineiaccording to Meehean (1940)but not according to Ringuelet (1943). The morphology of the sclerites of rods of the suction cups of  A. nattereriand  A. pestifer, is similar, although as well as being smaller in  A. nattereri, there is variation in numbers, with 8–10 inspecimens of  A. nattereri( Figs. 8E–F) and just two in  A. pestifer( Fig. 9E). Specimens of  A. nattereriexhibit a strong chitin plate from the dorsal to the second antennae, which narrows and runs laterally and forwards ( Thiele 1904) ( Fig. 8D). This structure is also present in  A. pestifer, although in this species these plates are also in the frontal and median region of the cephalothorax ( Ringuelet 1948). The preoral stylet, which was observed in its inverted state ( Fig. 8G), and the presence of flagellum on the first two pairs of legs ( Figs. 8K–L) in both males and females, differentiates  A. nattererifrom  A. pestifer. The presence of ventral spines along the length of the carapace alae ( Figs. 8M, 8D) is also an important diagnostic characteristic of  A. nattereri, as these spines are absent in  A. pestifer( Ringuelet 1948)and are limited to the frontal region, more specifically to the anterolateral sinuses, in  A. juparanaensis(Lemos de Castro 1950). Additionally, the morphology of the antenna, antennules, postantennal spines, and the robust and acute spine, which emerges from the carapace towards the basal segment of the antennae ( Fig. 8D), the socket on the 3rd leg and the peg on the 4th legs of males ( Fig. 8M) allow identification of  A. nattereri. Nevertheless,  A. nattereriis distinguished from all species above by the presence of naked setae regularly scattered at the dorsal side of cephalothorax and carapace alae ( Figs. 8A, 8C), structures which are absent in  A. salminei,  A. pestiferand  A. juparanaensis( Heller 1857; Lemos de Castro 1950; Ringuelet 1943, 1948; Thiele 1904). We observed some morphological differences in our specimens of  A. natterericomparing with the description of other authors. The morphology of the carapace alae of the female was in accordance with Heller (1857)( Figs. 8O–P) but differed from Wilson (1944), because the posterior lobes of the carapace did not overlap. The number of sclerites of the suction cup was lower, with 6–9 sclerites per support rod in males and 7–9 infemales, whereas 9–10 ( Ringuelet 1943) and 14–16 ( Wilson 1944), have been previously recorded. Coarse-pectinate scales were observed by Thiele (1904), but the sensilla on the mouth tube ( Figs. 8I, J), similar to those previously observed in  Argulus yucatanus Poly, 2005from  Mexico( Poly 2005), were also observed in the  A. nattereriof the present study. We observed, as indicated by Ringuelet (1943), two pairs of small, thick and blunt accessory spines ( Fig. 8H), although Wilson (1944)has stated that this structure was missing for this species. We also observed that the endopods and exopods of the third and fourth legs were of similar size, rather than the longer exopods viewed by Ringuelet (1943). We observed smaller endopods only on the first and second legs, in accordance with Thiele (1904), although we did not see the 3-segmented extension of the first endopod, as per Ringuelet (1943). A finger-like papillae, resembling the tactile papillae of some females such as those of  Argulus americanus Wilson, 1902( Wilson 1904), was observed rooted at the base of the natatory lobes of the fourth leg of the male of  A. nattereri( Fig. 8N). While tactile papillae are situated on either side of the opening of the oviduct between the bases of the posterior legs of females and are not found in males, we observed a differently located structure. Ventrally, erect coarse pectinate scales cover the thorax, abdomen and legs of  A. nattereri( Fig. 8Q). 1638540581 [199,850,1256,1281] Brazil Undefined 11 458 1 holotype 1638540588 2004-06-03 ZUEC-CRU Brazil -18.998102 Paraguay 1 57.61234 11 458 ZUEC-CRU 3516 1 1 Paraguay 1638540585 2008-07-04 INPA Brazil -17.82716 Hoyer's 1 -57.381493 Pantanal Matogrossense 11 458 INPA 2307 2 2 Paraguay