Phalloceros elachistos, Lucinda, 2008

Lucinda, Paulo Henrique Franco, 2008, Systematics and biogeography of the genus Phalloceros Eigenmann, 1907 (Cyprinodontiformes: Poeciliidae: Poeciliinae), with the description of twenty-one new species, Neotropical Ichthyology 6 (2), pp. 113-158 : 129-131

Phalloceros elachistos , new species

Figs. 21 , 22

Phalloceros sp. n. U Lucinda & Reis (2005).

Holotype. MCP 30468, córrego Limoeiro, at Praça Oito, approximately 19 o 55’S 40 o 50’W, Itarana, Espírito Santo, Brazil, 18 Oct 2000, R.L. Teixeira & P.S. Miller .

Paratypes. BRAZIL. Espírito Santo. Rio Doce Drainage: MCP 30023, 90/5*, collected with the holotype. MCP 30021, 6, Itarana, córrego Jaboticas, 18 Oct 2000, R.L. Teixeira & P.S. Miller. MCP 30022, 1, Itarana, córrego Limoeiro, at Praça Oito, 8 Feb 2001, R.L. Teixeira & P.S. Miller. Rio Santa Maria da Vitória drainage: MNRJ 11645, 13, Santa Leopoldina, rio da Prata along road ES-080, 16 Feb 1988, P.A. Buckup et al. UMMZ 215314, 13, same data as for MNRJ 11645. Rio Jucu drainage: USNM 257031, 13, southern branch of rio Jucu between Isabel and Viana on road BR 262, 13 Nov 1982, N.A. Menezes et al . Rio Timbuí drainage: MCP 29435, 3, Santa Teresa, rio da Penha, Sítio do Rubinho, 24 Oct 2001, R.L. Teixeira. MNRJ 11640, 29, Santa Tereza, córrego at Valsugana Velha, 16 Feb 1988, P.A. Buckup et al. UMMZ 215307, 31/4*, same data as for MNRJ 11640.

Diagnosis. Phalloceros elachistos can be distinguished from P. anisophallos , P. megapolos , P. spiloura , P. reisi , P. buckupi , P. alessandrae , P. lucenorum , P. uai , P. pellos , and P. malabarbai by the female urogenital papilla straight along midline and located between the anus and the base of first anal-fin ray (vs. curved to the right, located laterally; border of the anal aperture in contact with the first anal-fin ray). Phalloceros elachistos can be distinguished from P. tupinamba , P. leptokeras , and P. aspilos by (1) the female urogenital papilla straight along midline (vs. slightly left turned); (2) absence of a lateral ramus of the female urogenital papilla (vs. lateral ramus present); and (3) small and simple hook in gonopodial appendix (vs. large sickle like hook) ( Fig. 22 ). Phalloceros elachistos can be distinguished from P. caudimaculatus , P. heptaktinos , P. ocellatus , P. mikrommatos , and P. leticiae by the possession of a hook in the gonopodial appendix (vs. hook absent). Phalloceros elachistos is readily distinguished from P. titthos by the absence of symphyseal papillae on mandible of large females (vs. symphyseal papillae present); and from P. enneaktinos by the possession of seven or eight dorsal-fin rays (vs. nine) (see remarks). Phalloceros elachistos can be distinguished from P. harpagos by the hook of gonopodial appendix, which is very small in adults, forming a minute lateral protuberance ( Fig. 22 ) (vs. not forming a lateral protuberance – see remarks on P. harpagos description). In juveniles hook (usually) is absent or (rarely) minuscule. When present in juveniles hook never situated on the appendix corner (vs. present and located on the appendix corner). Juveniles never present skin covering the tip of appendix (vs. skin present). Distal half of appendix approximately as wide as (or slightly narrower than) proximal half (vs. narrower than proximal half).

Description. Morphometric data in Tables 9 and 10 . Range of SL: 15.1 to 27.8 mm (females), 14.9 to 18.5 mm (males). Dorsal-fin rays: 7 [1], 8* [47], 9 [1]. Branched pectoral-fin rays: 6 [8], 7* [15]. Pelvic-fin rays: 5* [13] (males), 5 [31] (females).Anal-fin rays of females: 10 [1], 11 [29].Anal-fin rays of males: 8 [2], 9* [15]. Branched caudal-fin rays: 10 [1], 11 [21], 12* [22], 13 [1]. Predorsal scales: 13 [2], 14 [20], 15* [1]. Longitudinal series of scales: 28* [9], 29 [39], 30 [3]. Series of scales around caudal peduncle: 16* [55]. Transverse series of scales: 6 [1], 7* [54]. Serrae on R4p: 9 [3], 10 [6], 11* [6], 12 [1]. Epipleural ribs: 14 [3], 15 [2]. Pleural ribs: 14 [4], 15 [1]. Vertebrae: 31 [1], 32 [3], 33 [1]. Female urogenital papilla straight, located along midventral line and between anus and base of first anal-fin ray. Gonopodial appendix hook small sized. Appendix hook very small in adults, forming lateral minute protuberance ( Fig. 22 ). Hook (usually) absent or minute (rarely) in juveniles. When present in juveniles hook never situated on appendix corner. Juveniles never possess skin-covering tip of appendix. Distal half of appendix approximately as wide as (or slightly narrower than) proximal half ( Fig. 22 ).

Color in alcohol. Eye black with greenish brown pupil. Ground color pale brown, darker in upper half. Border of scales and subjacent skin replete with brown chromatophores, more concentrated at short distance from scale border, forming v-band conferring reticulate pattern to body sides, mainly on upper half. Brown chromatophores scattered through whole body, more concentrated on dorsal portion, mainly on head, snout, opercle, and ventral surface of mandible. Lateral dark brown spot very small, inconspicuous or absent. When present located approximately on 18th scale of longitudinal series covering approximately one scale on both horizontal and vertical directions. Inconspicuous vertical bars along flanks. Dorsal-fin membrane hyaline bearing dark band of chromatophores on distal border of dorsal fin and another near dorsal-fin base. Pectoral-, pelvic- and caudal-fin rays dusky. Dark brown line along R3.

Etymology. Specific name from the Greek ελαχυς, −εια [= elachis, -eia], adj. m. nom. sg.], small, short, little, plus the superlative ending −ιστος [= -istos]. Ελαχιστος, −η, −ον, [ = elachistos , -e, -on], meaning the least, which alludes to the small size of the specimens. An adjective, gender masculine.

Distribution. Drainages of rio Doce, Santa Maria da Vitória, Jucu, and Timbuí, coastal drainages of Espírito Santo State of Brazil ( Fig. 18 ).

Remarks. One out of 48 studied specimens presented nine dorsal-fin rays.

Figures

Fig. 21. Phalloceros elachistos. (A) Holotype, male, 19.9 mm SL, MCP 30468, córrego Limoeiro, at Praça Oito, Itarana, Espírito Santo, Brazil; (B) paratype, female, MCP 30023, 31.5 mm SL, collected with the holotype.

Fig. 22. Gonopodium tip of Phalloceros elachistos, MCP 30023.R3, R4a, R4p, R5a, R5p indicate gonopodial rays. Scale bar 1 mm.

Fig. 18. Collection localities of Phalloceros elachistos (fivepointed star, 1), P. leptokeras (triangle, 2), P. aspilos (circle, 3), P. alessandrae (inverted triangle, 4), and P. megapolos (square, 5). Some symbols represent more than one lot or locality. Numbers represent type localities. The inset is the range of the genus.

Tables

Table 9. Descriptive morphometrics of female specimens of Phalloceros reisi, P. elachistos, P. enneaktinos, and P. harpagos. Measurements 1-10 are percents of standard length and measurements 11-13 are percents of head length.

	Phalloceros reisi		Phalloceros elachistos		Phalloceros enneaktinos		Phalloceros harpagos
Character	n = 71		n = 36		n = 8		n = 407
	Range	Mean	Range	Mean	Range	Mean	Range	Mean
Standard length (mm)	23.2-49.9	33.6	15.1-27.8	20.8	23.5-35.8	29.6	18.4-46.8	29.2
1-Head length	18.4-25.4	21.3	19.9-24.1	22.3	20.1-23.8	21.7	16.5-25.8	20.9
2-Snout-occipital distance	15.0-22.5	18.6	20.9-24.9	22.8	22.6-25.6	24.3	17.5-26.5	21.9
3-Predorsal distance	60.3-64.6	62.3	59.7-63.8	62.2	59.4-63.2	61.2	57.3-66.9	62.0
4-Dorsal-fin base length	7.6-13.8	10.5	8.0-11.7	10.1	9.1-12.4	11.1	6.9-13.6	10.8
5-Anal-fin base length	6.6-13.2	9.5	7.5-12.4	9.7	8.5-10.3	9.2	7.1-12.1	9.7
6-Body depth	22.3-28.2	25.1	19.2-28.8	23.8	25.6-29.0	27.3	21.1-30.7	25.5
7-Pre-pelvic length	41.0-45.9	43.6	40.5-44.9	42.9	42.2-45.3	43.7	39.7-47.9	43.3
8-Preanal length	56.2-60.0	57.9	53.8-59.9	57.1	54.5-59.2	57.0	52..0-62.4	58.0
9-Postanal length	33.9-39.2	36.2	32.6-39.2	36.3	35.4-39.2	37.6	31.5-43.3	35.9
10-Caudal peduncle depth	13.2-16.2	14.7	13.6-16.9	15.1	15.3-16.5	16.1	12.5-17.2	14.9
11-Snout length	19.3-31.4	25.6	17.8-27.0	22.1	18.3-28.2	22.3	15.3-33.3	21.5
12-Orbital diameter	28.6-42.7	35.9	37.6-48.0	42.5	35.1-43.4	38.5	30.2-48.6	39.6
13-Postorbital length	35.3-47.8	41.3	35.1-45.9	42.0	32.9-45.5	42.4	35.0-55.2	46.2