Hypsolebias hamadryades Costa

Costa, Wilson J. E. M., Amorim, Pedro F. & Mattos, Jose Leonardo O., 2018, Cryptic species diversity in the Hypsolebiasmagnificus complex, a clade of endangered seasonal killifishes from the Sao Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae), ZooKeys 777, pp. 141-158 : 141

Hypsolebias hamadryades Costa sp. n. Figure 4, Table 3

Holotype.

UFRJ 6893, male, 26.9 mm SL; Brazil: Minas Gerais state: Janaúba municipality: temporary pool near road MG-401 at the town of Janaúba, floodplains of Gorutuba River, Verde Grande River drainage, São Francisco River basin, 15°48'06"S, 43°19'19"W, altitude about 530 m a.s.l.; W. J. E. M. Costa et al., 17 January 2017.

Paratypes.

UFRJ 6895, 4 males, 17.4-26.1 mm SL, 1 female, 21.2 mm SL; UFRJ 6894, 3 males, 22.6 - 26.1 mm SL, 2 females, 15.9-21.0 mm SL (C&S); UFRJ 11473, 4 males, 15.5-17.9 mm SL (DNA); collected with holotype. - UFRJ 6892, 2 females, 21.0-23.7 mm SL; same locality and collectors, 21 April 2017.

Diagnosis.

Hypsolebias hamadryades is distinguished from all other species of the H. magnificus complex by the absence of dark greenish grey bars on the anterior portion of the flank in males (vs. presence) and presence of transverse blue stripes on the unpaired fins in males wider than interspace (vs. transverse series of dots or stripes narrower than interspace). It also differs from all other species of the complex by the following combination of character states relative to the male colour pattern: dorsal fin with transverse blue stripes and one basal row of blue dots (vs. rows of blue dots on the whole fin in H. picturatus ); anal fin with transverse blue stripes on most portion of the fin (vs. dots and short vermiculate marks arranged on most part of the fin in H. gardneri , H. harmonicus and H. picturatus ); and most portion of caudal fin with blue bars (vs. anterior half of caudal fin with transverse rows of blue dots, posterior half with transverse blue bars in H. gardneri and H. harmonicus , or dots on the entire fin in H. picturatus ), and the presence of eight to ten light red bars between humeral region and the anterior part of the caudal peduncle (vs. six or seven in H. magnificus , H. harmonicus and H. gardneri ). Hypsolebias hamadryades is further distinguished from H. gardneri and H. picturatus by having the dorsal-fin origin anterior to anal-fin origin in males (vs. just posterior anterior) and from H. harmonicus by having 23 or 24 caudal-fin rays (vs. 21 or 22).

Description.

Morphometric data appear in Table 3. Body relatively deep, compressed. Greatest body depth at vertical just anterior to pelvic-fin base. Dorsal and ventral profiles of head and trunk slightly convex, approximately straight on caudal peduncle. Head narrow, sub-triangular in lateral view. Jaws short, teeth numerous, conical, irregularly arranged; outer teeth hypertrophied, inner teeth small and numerous. Vomerine teeth absent. Gill-rakers on first branchial arch 3 + 9, gill-rakers short, straight, without denticles. Urogenital papilla conical in males, pocket-shaped in females, slightly projecting over anterior part of anal fin.

Dorsal and anal fins relatively short, extremities rounded to slightly pointed in both sexes, without filamentous rays. Caudal fin rounded. Pectoral fin elliptical, posterior margin reaching base of 7th anal-fin ray in males, reaching anus in females. Pelvic fin small, tip reaching between base of 2nd and 3rd anal-fin rays in males, reaching urogenital papilla in females; pelvic-fin bases medially united. Dorsal-fin origin anterior to anal-fin origin in males, anal-fin origin at vertical between base of 1st and 3rd dorsal-fin rays; dorsal-fin origin posterior to anal-fin origin in females, dorsal-fin origin at vertical between base of 1st and 3rd anal-fin rays in females. Dorsal-fin rays 22-26 in males, 15-17 in females; anal-fin rays 20-23 in males, 18-19 in females; caudal-fin rays 23-24; pectoral-fin rays 12-13; pelvic-fin rays 5-6. In males, minute papillate contact organs on inner surface of dorsal-most pectoral-fin ray. Second proximal radial of dorsal fin between neural spines of 5th and 7th vertebrae in males, between neural spines of 10th and 12th vertebrae in females; first proximal radial of anal fin between pleural ribs of 7th and 9th vertebrae in males, between pleural ribs of 8th and 10th vertebrae in females; total vertebrae 27-29.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 25% of caudal-fin base; no scales on dorsal, anal and pectoral-fin bases. Frontal squamation E-patterned; E-scales overlapping medially; no row of scales anterior to H-scale; one supraorbital scale. Longitudinal series of scales 26; transverse series of scales 11; scale rows around caudal peduncle 12. One minute contact organ per scale of anteroventral portion of flank. Cephalic neuromasts: supraorbital 14-16; parietal 2; anterior rostral 1, posterior rostral 1; infraorbital 2 + 18-20; preorbital 2; otic 2-3, post-otic 2; supratemporal 1; median opercular 1, ventral opercular 1; pre-opercular 12-15, mandibular 10; lateral mandibular 5, paramandibular 1.

Colouration in life.

Males. Flank light blue on middle, light pink ventrally, and pale reddish orange dorsally and posteriorly; eight to ten light red bars between humeral region and anterior part of caudal peduncle, more conspicuous anteriorly; minute vertically elongated metallic blue spots per scale, on whole flank. Dorsum pale reddish orange, venter white. Head light blue, margin of scales of dorso-posterior region reddish orange. Iris yellow, with dark reddish brown bar through orbit centre. Unpaired fins red with bright blue transverse stripes, sometimes interrupted, including four or five on dorsal and anal fins, and six or seven on caudal fin; stripes broader than interspace; each unpaired fin with one row of small bright blue spots along basal portion and black line along distal margin. Paired fins red with black margin; faint blue dots on pelvic fin. Females. Flank light grey, with faint vertically elongated grey spots and one or two small black spots on flank centre, at vertical between pelvic-fin base and urogenital papilla; scale border pale yellow on dorsal portion of flank and head. Dorsum light grey, venter white. Head side pale grey with pale golden iridescence on opercle. Iris silver, with dark grey bar through orbit centre. Fins hyaline.

Colouration in alcohol.

Males with similar colour pattern as in life, but iridescence is lost and red marks substituted by grey or inconspicuous. Females with similar colour pattern as in life, but iridescence in head is lost.

Distribution and conservation.

Hypsolebias hamadryades is only known from a pool in the floodplains of the Gorutuba River, within the town of Janaúba, Minas Gerais, Brazil (15°48'06"S, 43°19'19"W, altitude about 530 m a.s.l.; Figure 3). This area has been studied since January 2002 (Costa, 2006), but H. hamadryades was first collected only in 2017. Previous field studies revealed two endemic seasonal killifishes, H. janaubensis (Costa, 2006) and Cynolebias gorotuba Costa, 2017, as well as an intense process of urbanization which result in the complete extirpation of all temporary pools studied between 2002 and 2010 ( Costa 2017). The type locality pool of H. hamadryades was only found in January 2017, since it was hidden by a dense Caatinga forest. The pool occupied an area of about 100 m2 and was about 1 m deep. The whole pool was densely populated by adult specimens of H. janaubensis , whereas individuals of H. hamadryades , mostly juvenile specimens below 20 mm SL including, were found only in a small part of the pool containing shaded zones, near the pool margins, where bushes were concentrated. The largest males exhibited damaged caudal fins, indicating possible territorial disputes as commonly occurring in other seasonal killifishes. A new collecting trip was made in April 2017, when physical conditions of the pool were nearly identical to the first collection, except that the pool was shallower (about 0.5 m at deepest places). At that time, however, only two females and no males of H. hamadryades were found. According to local people, pools in the region did not dry between January and the period of the second collection.

Etymology.

The name hamadryades is an allusion to the occurrence of the new species in the forested part of a Caatinga temporary pool. This name was used by the Bavarian naturalist Karl Friedrich Philipp von Martius for the Caatinga in his classification of vegetation formations of Brazil, in which he used names of Greek mythological beings to name each Brazilian phytogeographical province. The name is opportune by referring to hamadryades , a particular kind of Greek nymph entity that is believed to be associated to trees, vanishing when trees die. Similarly, field studies have shown that populations of species of the H. magnificus group became extinct after marginal deforestation (see discussion below).