Cymothoa ianuarii Schioedte & Meinert, 1884

Ribeiro, Felipe Bezerra, Huber, Augusto Frederico & Araujo, Paula Beatriz, 2021, Redescription of the fish-parasitic isopod Cymothoa ianuarii Schioedte & Meinert, 1884 and further records of C. excisa Perty, 1833 and C. oestrum (Linnaeus, 1758) (Isopoda: Cymothoida: Cymothoidae) from Brazil, Papéis Avulsos de Zoologia 61, pp. 1-10 : 2-7

Cymothoa ianuarii Schioedte & Meinert, 1884 ( Figs. 2-4 , 6 ; Table 1)

Cymothoa Ianuarii Schioedte & Meinert, 1884: 246-248 , tab. VI (Cym. XXIV), figs. 19-20.

Cymothoa ianuarii Trilles, 1994 : Thatcher et al., 2003: 551, fig. 80. Luque et al., 2013: 1454.

Cymothoa januarii Sartor & Pires, 1988: 146-156 . [erroneus spelling].

Material examined: BRAZIL: São Paulo: three ovigerous females, Enseada de Ubatuba , 03/ V /2007 ( UFRGS 6515 ) ; one ovigerous female, Enseada de Ubatuba , coll. F. Mantelatto, 02/ VI /2008 ( UFRGS 6516 ) [illustrated] ; one ovigerous female, Enseada de Ubatuba , 15/ VI /2003 ( UFRGS 6517 ) ; one female, Enseada de Ubatuba , 15/ VI /2003 ( UFRGS 6518 ) ; one ovigerous female, Enseada de Ubatuba , X/2002 ( UFRGS 6520 ) [illustrated] .

Redescription (based on seven females)

Body 1.8 times as long than wide ( Table 1), widest at pereonite 5, narrowest at pereonite 1 ( Fig. 2A ).

Cephalon: longer than wide, frons transversely truncat- ed, visible in dorsal view, immersed on pereonite 1; eyes visible ( Figs. 2A, C, D ).

Pereon: Convex. Pereonite 1 with anterolateral angles surpassing eyes; pereonites 1 and 4 largest; pereonites 2 and 3 subequal; pereonites 5 and 6 subequal; pereonite 7 shorter and narrower than pereonite 6. Coxae 2 and 3 morphologically similar and bent downwards; 4-7 morphologically similar to each other and falciform( Fig.2A,C ).

Pleon: Immersed in pereonite 7; pleonites similar in length with posterolateral margins not overlapped by lateral margins of the subsequent pleonite ( Figs. 2A, E ). Pleotelson sub-rectangular and 0.46 times as long as wide; posterior margin sinuous; dorsal surface smooth; lateral margins convex ( Fig. 2A, E ).

Antennula: with eight articles, the first two being stout- er, distal article with five small apical setae ( Figs. 2B , 3A ).

Antenna: comprised of nine articles, terminal article without setae; extending to posterior margin of cephalon. Labrum lateral margins concave, without median point ( Figs. 2B , 3C ).

Mandible: with chitinous and acute incisor and straight molar process. Palp shorter than mandible ( Fig. 3D ).

Maxillula: bilobed with four apical stout robust setae ( Figs. 3E, F ).

Maxilla: mesial lobe with four recurved robust setae, partly fused to lateral lobe with two recurved robust setae ( Fig. 3G, H ).

Maxilliped: Maxilliped article 3 with three recurved robust setae ( Figs. 3I, J ).

Oostegite: smooth, with marginal setae (not illustrated) ( Fig. 2B ).

Pereopods: 1-3 smaller than 4-7, which gradually increase in size and with carina on basis. Pereopod 1 basis 1.1 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 1.6 times as long as wide; dactylus slender, 1.3 as long as propodus, 3.2 times as long as basal width. Pereopod 2 propodus 1.4 times as long as wide; dactylus 1.7 times as long as propodus;Pereopod 3 basis 1.5 times as long as greatest width;ischium 0.5 times as long as basis; propodus 1.2 times as long as wide; dactylus slender, 1.7 as long as propodus, 2.4 times as long as basal width. Pereopod 4 basis 1.67 times as long as greatest width; ischium 0.5 times as long as basis; propodus 1.4 times as long as wide; dactylus slender, 1.43 as long as propodus, 2.1 times as long as basal width. Pereopod 5 basis 1.3 times as long as greatest width; ischium 0.6 times as long as basis; propodus 1.07 times as long as wide; dactylus slender, 2.03 as long as propodus, 2.18 times as long as basal width. Pereopod 6 basis 1.3 times as long as greatest width; ischium 0.6 times as long as basis; propodus 1.6 as long as wide; dactylus 1.2 times as long as propodus.Pereopod 7 basis 1.5 times as long as greatest width; ischium 0.4 times as long as basis, with large proximal bulbous protrusion; merus proximal margin with slight protrusion, 0.3 times as long as ischium, 0.4 times as long as wide; carpus without bulbous protrusion; propodus 0.8 times as long as ischium, 1.6 times as long as wide; dactylus slender, 1.8 times as long as propodus, 2.6 times as long as basal width.

Pleopods: without setae, lobes decreasing in size from pleonites 1 to 5, exopod larger than endopod. Pleopod 1 exopod 1.1 times as long as greatest width,lateral margin straight, distal margin sinuous, mesial margin straight; endopod as long as wide, lateral margin convex, distally narrowly rounded, mesial margin convex; peduncle 2.75 times as wide as long. Pleopods 1-3 endopod proximal borders decreasing in size and increasing in size in pleopods 4-5; with fleshy folds absent and medial lobes present and decreasing in size ( Figs. 4 H-L).

Uropods: shorter than pleotelson. Peduncle 0.8 times as long as rami; lateral margins without setae. Endopod apically rounded, 2.8 times as long as greatest width, lateral margin weakly convex, mesial margin weakly convex. Exopod 0.9 times as long as endopod, 2.5 times as long as greatest width and without setae ( Figs. 2A, C, E ; 4M ).

Remarks: Adult females of Cymothoa ianuarii can be distinguished mainly by the cephalon with conspicuous eyes and not deeply immersed in pereonite 1, anterolateral angles of pereonites 1 surpassing eyes, pereonites 5-6 much wider than 4, pleotelson twice wide as long and pleopods 1-5 decreasing in size. Males are unknown ( Thatcher et al., 2003). This is the first record from the state of São Paulo, particularly in the northern portion of the coast (23°29′38.72″S, 45°05′16.0″W). This new record represents the rediscovery of this species after a hiatus of approximately 136 years since its original description from material collected in Rio de Janeiro in the 1880’s.We provided the redescription of this species based on the analyzed specimens.

Hosts: The host of present specimens is unknown. However, C. ianuarii was already found parasitizing fishes of the families Priacanthidae and Pleuronectidae ( Schioedte & Meinert, 1884) .

Distribution: Rio de Janeiro ( Schioedte & Meinert, 1884) and São Paulo, Brazil ( Fig. 6 ).

Figures

Figure 2. Cymothoa ianuarii Schioedte & Meinert, 1884 (UFRGS 6516): (A) habitus dorsal view (UFRGS 6516); (B) habitus ventral view (UFRGS 6516); (C) habitus lateral view (UFRGS 6516); (D) cephalon frontal view (UFRGS 6516); (E) pleotelson dorsal view (UFRGS 6520). Scale bar: A-C = 5 mm; D = 2.5 mm;E = 1 mm.

Figure 3. Cymothoa ianuarii Schioedte & Meinert, 1884: (A) antennule (UFRGS 6516); (B) apical article of antennule (UFRGS 6516); (C) antenna (UFRGS 6516); (D) mandible (UFRGS 6515); (E) maxilulle (UFRGS 6520); (F) apex of maxillula (UFRGS 6520); (G) maxilla (UFRGS 6515); (H) maxilla distal portion (UFRGS 6515); (I) maxilliped with oostegite (UFRGS 6515); (J) maxilliped articles 2 and 3 (UFRGS 6515). Scale bar: A, C and D = 0.5 mm; E and G = 0.3 mm; B = 0.125 mm; F,H and J = 0.1 mm; I = 1 mm.

Figure 4. Cymothoa ianuarii Schioedte & Meinert, 1884 (UFRGS 6516): (A-G) pereopods 1-7; (H-J) pleopods 1-5 dorsal view; (M) uropod.Scale bar: E-G = 2 mm; A-D,H-J = 1 mm;D = 2.5 mm; M = 0.5 mm.

Figure 6. Map with the records of Cymothoa excisa (▲), C. ianuarii (⬛) and C.oestrum (⬤) in Brazil.Symbols in dark gray indicate literature records and white indicatesnewrecords.Abbreviations:PA =Pará;MA = Maranhão;PE= Pernambuco;SE = Sergipe;BA = Bahia;RJ = Rio de Janeiro;SP = São Paulo; SC = Santa Catarina.