Cynolebias parnaibensis, Costa & Alexandre & Ramos, 2010

Costa, Wilson J. E. M., Alexandre, Telton P. A. Ramos Luisa C. & Ramos, Robson T. C., 2010, Cynolebias parnaibensis, a new seasonal killifish from the Caatinga, Parnaíba River basin, northeastern Brazil, with notes on sound producing courtship behavior (Cyprinodontiformes: Rivulidae), Neotropical Ichthyology 8 (2), pp. 283-288 : 284-286

Cynolebias parnaibensis , new species

Fig. 1

Holotype. UFPB 6719 , 54.5 mm SL, male, Brazil, Estado do Piauí, Município de Jacobina do Piauí, seasonal lagoon at the right side of the road between Conceição do Canindé and Jacobina do Piauí, 08°00’54"S 41°25’26"W, 19 May 2009, T. Ramos, M. Silva & J. Aparecido.

Paratypes. UFPB 6709 , 39.0- 46.2 mm SL, 6 females, UFRJ 6734, 44.3-45.9 mm SL, 2 females; UFRJ 6735, 51.7 mm SL, 1 male, 41.5-41.8 mm SL, 2 females (cleared and stained for bone), collected with holotype. UFRJ 6736, 50.2 mm SL, 1 male, 41.8 mm SL, 1 female, same locality as holotype, 28 June 2009 , T. Ramos, P. Honório & A. Carvalho .

Diagnosis. Cynolebias parnaibensis is distinguished from all other species of the genus, except C. griseus and C. gilbertoi , by having 27-31 neuromasts around eye (vs. 33-46). The new species differs from C. griseus by having 29-33 supraorbital neuromasts (vs. 19-22), 16-18 dorsal-fin rays and 19 anal-fin rays in males (vs. 20-22 and 21-23, respectively), 28-31 caudalfin rays (vs. 33-34), 6 pelvic-fin rays (vs. 5), dorsal-fin origin at a vertical between the base of the 4th or 6th anal-fin ray (vs. base of 1st or 2nd ray), 33-36 scales in the longitudinal series (vs. 29- 31), 3+10 gill-rakers in the first branchial arch (vs. 5+15), absence of second pharyngobranchial teeth (vs. presence), absence of the ventral uncinate process of the second epibranchial (vs. presence), absence of the ventral limb of the posttemporal (vs. presence), and absence of contact organs on the flank scales in both sexes (vs. presence in males). From C. gilbertoi it differs by having 34-35 vertebrae (vs. 32-33), and by the absence of teeth on vomer (vs. 13-15 vomerine teeth). Cynolebias parnaibensis is also distinguished from C. griseus , C. gilbertoi , C. microphthalmus and C. albipunctatus by the presence of transverse series of scales on the anal-fin base (vs. absence).

Description. Morphometric data in Table 1. Dorsal and ventral profiles convex between snout and anterior part of caudal peduncle, nearly straight on caudal peduncle. Body moderately deep, slightly compressed, greatest body depth at level of vertical just anterior to pelvic-fin base. Snout short, blunt.

Dorsal and anal fins pointed in males, rounded in females. Pectoral fin long, rounded, reaching vertical between base of 2nd and 4th anal-fin rays in males, and between pelvic-fin base and anus in females. Tip of pelvic fin reaching between base of 2nd and 3rd anal-fin rays in males, reaching between urogenital papilla and anal-fin origin in females. Pelvic-fin bases medially separated by small interspace. Dorsal-fin origin through base of 5th or 6th anal-fin ray in males, and above base of 4th or 5th anal-fin ray in females; dorsal-fin origin between neural spines of vertebrae 15 and 17 in both sexes. Anal-fin origin between pleural ribs of vertebrae 11 and 12 in males, and pleural ribs of vertebrae 13 and 14 in females. Dorsal-fin rays 16-18 in males, 15-16 in females; anal-fin rays 19 in males, 18-21 in females; caudal-fin rays 28-31; pectoralfin rays 13-14; pelvic-fin rays 6.

Frontal scales irregularly arranged; 11-12 small supraorbital scales. Longitudinal series of scales 33-36; transverse series of scales 14-16; scale rows around caudal peduncle 22. No contact organ on flank. Minute papillate contact organs on inner surface of upper six pectoral fin-rays in males. No contact organs on pelvic and unpaired fins.

Cephalic neuromasts: supraorbital 29-33, parietal 3-4, anterior rostral 3, posterior rostral 3, infraorbital 4+27-31, preorbital 3, otic 6-7, post-otic 7, supratemporal 3, median opercular 2, ventral opercular 3-5, preopercular plus mandibular 44-53, lateral mandibular 9-10, paramandibular 1. One neuromast on each scale of lateral line. Two neuromasts on caudal-fin base.

Basihyal subtriangular, width about 60% of length; basihyal cartilage about 20% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth absent. Gill-rakers on first branchial arch 3+10. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal absent. Total vertebrae 34-35.

Coloration. Males. Side of body light pinkish brown, with narrow pale golden bars; bluish white dots on whole flank; one or two rounded, pale greenish gray humeral blotches. Venter light orangish yellow. Head side yellowish gray, pale golden on opercular region; small dark reddish brown spots along laterosensory series of neuromasts around orbit and on postorbital region. Iris orangish yellow with dark reddish brown bar through center of eye. Unpaired fins yellowish gray on basal and central portions, to pale gray on distal part of dorsal and caudal fins, and pale orange on distal portion of anal fin. Pectoral fin hyaline. Pelvic fin pale orange.

Females. Side of body purplish gray, with narrow pale golden bars; one or two rounded, pale greenish gray humeral blotches; sometimes, rounded black blotch on anterocentral portion of flank. Venter light gray. Head side yellowish gray, pale golden on opercular region; small dark reddish brown spots along laterosensory series of neuromasts around orbit and on postorbital region. Iris orangish yellow with dark reddish brown bar through center of eye. Unpaired fins light gray with faint light gray dots. Paired fins hyaline.

Courtship behavior. Just after induced meetings, the male stays near the bottom whereas the female continuously and slowly swims through the aquarium. This period, herein named as adaptation period, lasted approximately 30 min. After the adaptation period, the courtship begins by the male, which perform a quick and discontinuous swimming towards female. Following the female approximation, the male shakes the head up and downwards producing sound (see sound description below). Just after sound is produced, the female readily starts to swim around male, often scrubbing its snout on the ventral surface of the male trunk, mainly around the genital region. The male swims near the substrate always followed and scrubbed by the female. The male put its snout down into the substrate, in a vertical position, quivering body and fins, which is similar to the stage named as invitation to submerge, described by Belote & Costa (2003) for C. albipunctatus . The time between start of courtship and the invitation to submerge lasted approximately 60 min. Spawning and fertilization were not observed.

Sound. Head shaking male display was synchronized with sound production. The sound consists of a single pulse as a thump. The thump duration ranges from 0.031s to 0.133s (m = 0.081s; sd = 0.024; n = 123). Duration of interthump intervals ranges from 0.020s to 8.319s (m = 0.748; sd = 1.061; n = 122). Repetition rate of thumps per courtship ranges from 0.995 to 1.026 thumps per second (m = 1.011; sd = 0.022; n = 2). Dominant frequency varied between 70.3 and 93.8 Hz (m = 78.5; sd = 11.3; n = 83), although in some thumps the values of dominant frequency were 46.9 and 23.4 Hz. These last values are the dominant frequency of background noise, thus these measured values are possibibly due to the low intensity of some thumps. The frequency bandwidth of each thump is from near to zero to 1 kHz ( Fig. 2 ). There were occasional thumps off the courtship during the adaptation period. Moments with high repetition rate of thumps were observed when the male apparently was more excited.

Distribution and habitat. Cynolebias parnaibensis is known from the type locality, a seasonal lagoon close to the road between Conceição de Canindé and Jacobina do Piauí, Município de Jacobina do Piauí, Piauí State, northeastern Brazil. The type locality is inserted in the Caatinga domain, a semi-arid phytogeographic formation, typical of northeastern Brazil. The lagoon is within the Canindé River drainage, which is part of the Parnaíba River basin. It was about 60 m long, 15 m wide, maximum depth 1 m, average depth 50 cm. The water was turbid, light brown, and the bottom was sandy-muddy. Emerging aquatic vegetation occurred in moderate amount, scattered over the lagoon surface, while large amount of submerged vegetation was found, predominating species of the family Hydrocharitaceae . Margins of the pond were in part densely covered by bushes and low vegetation.

Etymology. The name parnaibensis is a reference to the unique occurrence in the Parnaíba River basin among species of the genus Cynolebias .

Figures

Fig. 1. Cynolebias parnaibensis, Jacobina do Piauí, Piauí, Brazil. (a) UFPB 6719, holotype, male, 54.5 mm SL. (b) UFPB 6709, paratype, female, 46.2 mm SL.

Fig. 2. General thump sequence produced by the male of Cynolebias parnaibensis during the courtship behavior (a), and a single thump expanded (the second one above) (b). Oscilogram above and spectogram below (window function Hann, overlap 99%, FFT size 1,200 points).