Machado, Valéria N.; Pereira, Victória D.; Ota, Rafaela P.; Collins, Rupert A.; Ândrade, Marcelo; Garcia-Ayala, James R.; Jégu, Michel; Farias, Izeni P.; Hrbek, Tomas

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Original Article • Neotrop. ichthyol. 22 (2) • 2024 • https://doi.org/10.1590/1982-0224-2023-0095 copiar

Integrative taxonomy of the black-barred disk pacus (Characiformes: Serrasalmidae), including the redescription of Myloplus schomburgkii and the description of two new species

Autoria SCIMAGO INSTITUTIONS RANKINGS

Resumo

Atualmente, Myloplus schomburgkii representa a espécie mais facilmente reconhecida entre os serrasalmídeos, por apresentar uma barra preta vertical no meio do corpo. No entanto, através de uma ampla revisão taxonômica, incluindo DNA barcoding e análises morfológicas, conseguimos identificar e descrever duas novas espécies que também compartilham a barra vertical escura no flanco. Além disso, redescrevemos M. schomburgkii, designando um neótipo e restringindo a localidade-tipo ao rio Negro, Barcelos, Estado do Amazonas, Brasil. As três linhagens de pacus de barra preta apresentam altas divergências moleculares (7,9–11%) e podem ser morfologicamente distinguidas por diferenças na forma da barra vertical, forma da nadadeira anal nas fêmeas, número de vértebras totais, número de raios ramificados na nadadeira dorsal, entre outros caracteres. Embora a existência dessas duas novas espécies tenha sido ocultada devido a grandes semelhanças morfológicas, principalmente pela presença da barra vertical preta, as três linhagens não compõem um grupo monofilético, com uma das novas espécies sendo recuperada como irmã de Ossubtus xinguense. Este resultado reforça a necessidade da redefinição dos gêneros de Myleini.

Palavras chave:
Bacia Amazônica; COI; DNA barcode; Myleini; Neótipo

Sociedade Brasileira de Ictiologia Neotropical Ichthyology, Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura, Universidade Estadual de Maringá., Av. Colombo, 5790, 87020-900, Phone number: +55 44-3011-4632 - Maringá - PR - Brazil
E-mail: neoichth@nupelia.uem.br

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[1] Edited-by

Bruno Melo

Measurements	Description of the measurements with the landmarks
Standard length	From the anteriormost point of the snout (1) to the distal margin of the hypurals (2)
Body depth	From dorsal-fin insertion (3) to the pelvic-fin insertion (4)
Head length	From the anteriormost point of the snout (1) to the posteriormost point of the opercle, not including the opercular membrane (5)
Supraoccipital process	From the Supraocciptal’s base (6) to the Supraocciptal’s distal tip (7)
Predorsal length	From the anteriormost point of the snout (1) to the dorsal-fin insertion (3)
Postdorsal length	From the dorsal-fin insertion (3) to the distal margin of the hypurals (2)
Prepectoral length	From the anteriormost point of the snout (1) to the pectoral-fin insertion (8)
Prepelvic length	From the anteriormost point of the snout (1) to the pelvic-fin insertion (4)
Preanal length	From the anteriormost point of the snout (1) to the anal-fin insertion (9)
Dorsal-fin length	From the dorsal-fin insertion (3) to the distal tip of the longest dorsal-fin unbranched ray (10)
Interdorsal length	From the dorsal-fin origin (11) to the anterior end of the adipose-fin base (12)
Pectoral-fin length	From the pectoral-fin insertion (8) to the pectoral-fin distal tip (13)
Pelvic-fin length	From the pelvic-fin insertion (4) to the pelvic-fin distal tip (14)
First anal-fin lobe length	From the anal-fin insertion (9) to the distal tip of the longest anal-fin unbranched ray (15)
Second anal-fin lobe length	From the base of the longest branched ray of the second anal-fin lobe (16) to its tip (17)
Adipose-fin length	From the anterior end of the adipose-fin base (12) to the distal end of the anterodorsal margin of the adipose fin (18)
Dorsal-fin base length	From the dorsal-fin insertion (3) to the dorsal-fin origin (11)
Adipose-fin base length	From the anterior end of the adipose-fin base (12) to the posterior end of the adipose-fin base (19)
Anal-fin base length	From the anal-fin insertion (9) to the posterior end of the anal-fin base (20)
Caudal-peduncle depth	The shortest distance between the dorsal and ventral profiles of the caudal peduncle (21 to 22’)
Width of peduncle	Point in which the caudal peduncle is wider (33 to 33’)
Supraoccipital to dorsal-fin	From the supraocciptal’s base (6) to the dorsal-fin insertion (3)
Snout to Supraoccipital	From the anteriormost point of the snout (1) to the supraocciptal’s distal tip (7)
Snout to base of supraocciptal	From the anteriormost point of the snout (1) to the supraocciptal’s base (6)
Pelvic-anal distance	From the pelvic-fin insertion (4) to the anal-fin insertion (9)
Pectoral-pelvic distance	From the pectoral-fin insertion (8) to the pelvic-fin insertion (4)
Dorsal-fin origin to anal-fin origin	From the dorsal-fin insertion (3) to the anal-fin insertion (9)
Dorsal-fin end to anal-fin origin	From the dorsal-fin origin (11) to the anal-fin insertion (9)
Dorsal-fin end to anal-fin end	From the dorsal-fin origin (11) to the posterior end of the anal-fin base (20)
Head width	Point in which the head is wider (32 to 32’)
Postorbital distance	From the posteriormost margin of the eye (23) to the posteriormost point of the opercle, not including the opercular membrane (5)
Fourth infraorbital width	From the middle point of the anteromargin of the fourth infraorbital (23) to the middle point of its posterior margin (24)
Third infraorbital width	From the middle point of the anterordorsal margin of the third infraorbital (25) to the middle point of its posteroventral margin (26)
Cheek gap width	From the middle point of the third infraorbital posteroventral margin (26) to the internal angle of the preopercle (27)
Interorbital width	Between the dorsalmost point of the orbits (28 to 28’)
Eye vertical diameter	From the dorsalmost point of the orbit (28) to its ventralmost point (29)
Snout length	From the anteriormost point of the snout (1) to the anteriormost point of the orbit (30)
Mouth length	From the anteriormost point of the snout (1) to the distal end of the maxilla (31)
Mouth width	Between the distal tip of the maxillae (31 to 31’)

Species	Number samples	Number drainages	Number localities	Number haplotypes
Acnodon normani	2	1	1	2
Acnodon oligacanthus	15	1	6	5
Acnodon senai	2	1	1	1
Mylesinus paraschomburgkii	15	3	3	4
Mylesinus paucisquamatus	5	2	2	3
Myleus micans	7	1	3	5
Myleus planquettei	7	2	6	4
Myleus setiger	29	8	14	13
Myloplus arnoldi	24	5	11	8
Myloplus asterias	21	7	9	15
Myloplus levis	2	1	1	1
Myloplus lobatus	31	5	8	7
Myloplus lucienae	6	1	4	1
Myloplus nigrolineatus	68	11	18	20
Myloplus rubripinnis	49	6	13	16
Myloplus schomburgkii	89	13	32	36
Myloplus sp.	35	6	11	16
Myloplus tiete	1	1	1	1
Myloplus zorroi	14	1	2	4
Ossubtus xinguense	6	1	3	4
Paramyloplus ternetzi	33	1	11	4
Prosomyleus rhomboidalis	33	4	13	7
Tometes ancylorhynchus	8	1	2	4
Tometes camunani	6	2	4	4
Tometes kranponhah	13	2	3	4
Tometes lebaili	13	1	8	6
Tometes makue	1	1	1	1
Tometes siderocarajensis	8	3	5	4
Tometes sp.	15	1	3	6
Tometes trilobatus	1	1	1	1
Utiaritichthys longidorsalis	5	1	1	2

	Holotype	N	Range	Mean	SD
Standard length (mm)	213.0	27	53.4–309.3	–	–
Percentages of standard length
Body depth	72.4	27	59.2–79.9	73.1	4.7
Head length	29.0	27	26.2–33.7	29.7	2.0
Supraoccipital process	15.8	27	12.1–18.0	14.8	1.4
Predorsal length	61.2	27	57.2–64.5	60.5	1.7
Postdorsal length	55.1	27	51.1–66.5	57.3	3.5
Prepectoral length	29.2	27	28.0–33.8	30.4	1.5
Prepelvic length	60.8	27	57.5–64.8	60.6	1.8
Preanal length	80.1	27	76.3–84.0	79.7	1.8
Dorsal-fin length	23.6	20	22.4–47.7	29.1	8.4
Interdorsal length	9.0	27	7.0–11.8	9.8	1.2
Pectoral-fin length	21.3	27	18.0–23.6	21.3	1.3
Pelvic-fin length	13.8	27	12.8–17.2	16.1	1.5
First anal-fin lobe length	19.2	25	18.6–37.0	25.1	5.0
Second anal-fin lobe length	30.1	3	13.2–14.2	13.2	0.5
Dorsal-fin base length	34.3	27	31.1–37.1	34.5	1.6
Adipose-fin base length	6.4	27	5.0–7.7	6.3	0.7
Anal-fin base length	33.8	27	32.6–40.9	37.0	2.5
Caudal-peduncle depth	10.4	27	8.9–11.5	10.3	0.7
Width of peduncle	4.2	27	2.3–5.8	4.1	1.0
Supraoccipital to dorsal-fin	48.5	27	32.9–48.6	44.5	3.0
Snout to Supraoccipital	29.9	27	27.9–35.6	31.0	2.1
Snout to base of supraocciptal	13.4	21	13.4–18.8	16.4	1.6
Pelvic-anal distance	23.5	27	19.9–24.6	21.9	1.3
Pectoral-pelvic distance	29.8	27	28.0–33.3	30.5	1.3
Dorsal-fin origin to anal-fin origin	74.5	27	64.4–82.2	75.5	4.1
Dorsal-fin end to anal-fin origin	50.9	27	44.6–57.7	53.4	3.1
Dorsal-fin end to anal-fin end	24.5	27	23.4–28.6	25.3	1.3
Percentages of head length
Head width	17.9	27	13.6–19.4	17.1	1.4
Postorbital distance	41.4	27	25.0–41.4	31.0	4.2
Fourth infraorbital width	20.4	27	7.4–20.4	14.4	3.0
Third infraorbital width	14.9	27	6.9–15.3	11.9	2.6
Cheek gap width	14.6	27	10.8–23.2	15.4	2.3
Interorbital width	58.0	27	38.4–63.6	50.6	6.2
Eye vertical diameter	26.3	27	26.3–40.9	29.6	3.8
Snout length	37.9	27	22.0–38.9	28.7	6.3
Mouth length	43.3	27	19.2–47.9	32.5	8.9
Mouth width	35.3	27	29.2–45.3	34.5	3.8
Percentages of adipose-fin base length
Adipose-fin length	0.8	21	0.7–1.1	0.8	0.1

	Holotype	N	Range	Mean	SD
Standard length (mm)	166.4	32	38.9–166.4	–	–
Percentages of standard length
Body depth	66.1	32	66.1–76.1	71.7	2.7
Head length	29.6	32	27.0–32.9	30.0	1.3
Supraoccipital process	18.5	32	13.8–19.4	16.7	1.6
Predorsal length	60.3	32	59.6–66.1	62.4	1.6
Postdorsal length	56.5	32	50.2–58.9	54.4	1.9
Prepectoral length	29.2	32	27.5–34.4	29.9	1.5
Prepelvic length	54.5	32	54.5–61.1	58.3	1.6
Preanal length	73.4	32	73.4–82.5	77.8	2.0
Dorsal-fin length	14.1	25	24.8–69.8	37.4	9.8
Interdorsal length	14.3	32	8.0–14.9	12.3	1.7
Pectoral-fin length	24.2	32	20.6–25.3	22.9	1.0
Pelvic-fin length	16.8	32	14.2–18.3	16.2	1.1
First anal-fin lobe length	22.9	31	20.3–48.7	28.2	5.7
Second anal-fin lobe length	19.4	5	12.7–22.0	19.0	3.3
Dorsal-fin base length	27.0	32	25.6–29.1	27.7	0.9
Adipose-fin base length	8.7	32	7.1–9.7	8.4	0.6
Anal-fin base length	34.8	32	34.8–41.4	38.6	1.4
Caudal-peduncle depth	10.7	32	10.4–11.6	11.0	0.3
Width of peduncle	4.8	32	2.6–5.1	3.6	0.6
Supraoccipital to dorsal-fin	43.9	32	37.9–47.9	43.7	2.5
Snout to Supraoccipital	35.9	32	32.3–42.2	36.8	2.5
Snout to base of supraocciptal	18.5	9	18.1–19.6	18.7	0.5
Pelvic-anal distance	21.9	32	20.7–26.5	22.4	1.6
Pectoral-pelvic distance	26.2	32	24.2–31.1	27.9	1.4
Dorsal-fin origin to anal-fin origin	69.1	32	69.1–79.3	74.7	2.3
Dorsal-fin end to anal-fin origin	51.9	32	51.9–61.3	57.2	2.0
Dorsal-fin end to anal-fin end	30.0	32	27.8–32.0	29.7	1.1
Percentages of head length
Head width	19.8	32	15.1–22.7	17.7	1.4
Postorbital distance	30.4	32	25.7–32.0	29.0	1.3
Fourth infraorbital width	17.1	32	12.3–21.1	15.8	1.8
Third infraorbital width	19.3	32	12.7–20.1	16.6	2.1
Cheek gap width	16.1	32	12.5–17.1	15.2	1.2
Interorbital width	50.0	32	40.7–53.5	47.3	3.3
Eye vertical diameter	27.7	32	27.5–43.6	33.5	3.4
Snout length	30.4	32	24.5–35.7	32.4	3.5
Mouth length	38.1	31	31.4–42.4	37.1	2.9
Mouth width	36.7	32	30.5–41.8	34.9	2.7
Percentages of adipose-fin base length
Adipose-fin length	0.5	21	0.4–0.6	0.5	0.1

	Neotype	N	Range	Mean	SD
Standard length (mm)	203.9	100	43.3–236.8	–	–
Percentages of standard length
Body depth	60.9	99	59.3–78.8	69.0	3.6
Head length	27	100	23.8–34.6	28.7	2.1
Supraoccipital process	17.8	96	12.5–24.5	16.1	2
Predorsal length	54.4	99	54.4–64.4	59.3	1.8
Postdorsal length	56.4	99	49.2–62.4	56.7	2.2
Prepectoral length	28.5	99	24.5–34.1	28.8	2
Prepelvic length	54.6	98	51.7–63.7	58.3	2.3
Preanal length	73.5	99	68.8–82.5	78.5	2.2
Dorsal-fin length	21.8	56	20.3–74.2	35.9	13.3
Interdorsal length	10.6	99	6.2–13.8	11.1	1.7
Pectoral-fin length	20.5	97	17.7–24.1	21.8	1.2
Pelvic-fin length	16.1	97	12.7–18.2	16.4	1.2
First anal-fin lobe length	19.2	84	10.0–39.4	27.6	6.5
Second anal-fin lobe length	19.5	23	11.8–26.5	17.5	4.2
Dorsal-fin base length	35.3	98	29.2–36.7	33.4	1.9
Adipose-fin base length	4.9	97	4.6–7.2	6.0	0.7
Anal-fin base length	34.4	99	31.4–41.3	35.4	1.9
Caudal-peduncle depth	10.4	99	8.0–13.4	10	0.8
Width of peduncle	4.1	98	2.0–5.3	3.9	0.7
Supraoccipital to dorsal-fin	39	97	35.2–47.1	41.4	2.8
Snout to Supraoccipital	34.3	96	15.2–42.8	35	4.2
Snout to base of supraocciptal	16.1	62	15.1–26.8	17.1	2.7
Pelvic-anal distance	20.6	99	18.8–26.1	22.9	1.6
Pectoral-pelvic distance	27	99	24.7–34.4	29.8	1.8
Dorsal-fin origin to anal-fin origin	66.9	98	64.9–81.1	73.1	3.3
Dorsal-fin end to anal-fin origin	46.9	99	45.8–62.0	52.5	3
Dorsal-fin end to anal-fin end	24.4	99	21.7–28.8	25.8	1.5
Percentages of head length
Head width	17	100	14.0–20.4	17.1	1.1
Postorbital distance	32.2	100	21.1–33.6	28	2.4
Fourth infraorbital width	15.8	98	8.1–18.4	15.2	2
Third infraorbital width	16.4	98	7.8–18.7	14.5	2.2
Cheek gap width	11.8	98	10.3–18.4	13.9	1.9
Interorbital width	50.5	99	34.9–60.8	49	5.6
Eye vertical diameter	32.4	99	26.4–46.1	33.2	4.2
Snout length	36	99	21.0–39.7	32.7	4.7
Mouth length	41.5	99	24.8–43.5	36.3	3.6
Mouth width	33.7	98	24.0–38.0	33.6	2.6
Percentages of adipose-fin base length
Adipose-fin length	0.7	90	0.5–1.0	0.8	0.1

Species	Clade biogeographic subset (delimitation code)	Posterior probability (speciation)	Posterior probability (monophyly)	Max. intraspecific p-distance	Min. interspecific p-distance	Closest interspecific clade
Myloplus sauron	Xingu (1a)	0.97	1	0.01	0.097	1c
Myloplus aylan	Upper Amazon, Madeira, Branco (1b)	0.96	1	0.005	0.079	1c
Myloplus schomburgkii	Brazilian Shield and Guiana Shield (1c)	0.54	1	0.029	0.079	1b
Myloplus schomburgkii	Brazilian Shield including Teles Pires (2a)	0.27	0.66	0.013	0.018	2b
Myloplus schomburgkii	Guiana Shield including Orinoco-Cassiquiare (2b)	0.04	0.47	0.021	0.018	2a
Myloplus schomburgkii	Brazilian Shield excluding Teles Pires (3a)	0.16	0.93	0.009	0.005	3b
Myloplus schomburgkii	Teles Pires (3b)	0.14	0.78	0	0.005	3a
Myloplus schomburgkii	Guiana Shield excluding Orinoco-Cassiquiare (3c)	0.26	0.63	0.008	0.015	3d
Myloplus schomburgkii	Orinoco-Cassiquiare (3d)	0.32	0.99	0.005	0.015	3c