Malagodon honahona, Carr & Martin & Sparks, 2024

Carr, Emily M., Martin, Rene P. & Sparks, John S., 2024, A New Extinct Species of Malagodon (Cyprinodontiformes: Pantanodontidae) from Southeastern Coastal Madagascar, with a Discussion of its Phylogenetic Relationships and a Redescription of the Genus, American Museum Novitates 2024 (4012), pp. 1-16 : 5-10

Malagodon honahona , new species

Figures 2–6 ; table 1

Pantanodon n. sp. “manombo”: Sparks and Stiassny, 2003: table 9.1.

Pantanodon n. sp. “manombo”: Sparks and Stiassny, 2008: table 1.

Pantanodon n. sp. “manombo”: Sparks and Stiassny, 2022: tables 10-1 and 10-9.

Pantanodon n. sp. “manombo”: Sparks and Smith, 2022.

Malagodon spec. ‘Manombo Reserve’ (yet undescribed): Meinema and Huber, 2023.

HOLOTYPE: UMMZ 240245 ; male, 23.9 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 94-4; P. Reinthal, J. Sparks, and K. Riseng, 16 Jun. 1994.

ALLOTYPE: UMMZ 254162 ; female, 18.9 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 97-2; P. Reinthal et al., Oct. 1997.

PARATYPES: AMNH 278989 (formerly UMMZ 240245 ); 2 ex. C&S (1 male and 1 female), 18.6–20.2 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 94-4; P. Reinthal, J. Sparks, and K. Riseng, 16 Jun. 1994 . AMNH 278990 (formerly UMMZ 254161 ); 2 ex., 20.4–20.7 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 97-2; P. Reinthal et al., Oct. 1997 . UMMZ 254159 (formerly UMMZ 240245 ); 2 ex., 19.4–20.2 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 94-4; P. Reinthal, J. Sparks, and K. Riseng, 16 Jun. 1994 . UMMZ 254160 ; 5 ex., 16.2–23.2 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 94-3; P. Reinthal, J. Sparks, and K. Riseng, 15 Jun. 1994 . UMMZ 254161 , 13 ex., 15.3–21.8 mm SL; Madagascar: Fianarantsoa Province: Réserve Spéciale de Manombo; small Pandanas swamp at edge of intact forest; 23° 3′ S, 47° 42′ E; PNR 97-2; P. Reinthal et al., Oct. 1997 .

DIAGNOSIS: The new species is readily distinguished from Malagodon madagascariensis , its only congener, by the following apomorphic features: lower anal-fin ray count (15–17 vs. 18–19), longer caudal peduncle (26.8–39.8 vs. 21.9–26.7% SL), and notably expanded and platelike neural spine on arch of fifth vertebral centrum in both sexes (vs. thin and spinelike in M. madagascariensis ). In addition, neural spines on both sixth and seventh vertebral centra in new species also somewhat expanded and platelike dorsally versus narrow and spinelike in P. madagascariensis .

DESCRIPTION: Morphometric and meristic data presented in table 1. Pigmentation pattern in life and preservation, as well as external and internal morphological features, shown in figures 2–6. Body similar in overall shape to M. madagascariensis , and relatively elongate and dorsoventrally flattened anteriorly. Body width of males becoming gradually more laterally compressed posteriorly, whereas body width of females becoming significantly laterally compressed posterior to pelvic fins. Head extremely dorsoventrally flattened. Snout pointed and oriented dorsally. Orbit very large. Eyes dorsolaterally oriented. Interorbital width approximately half of orbit diameter. Mouth wide, superiorly oriented, and jaws short. Posterior margin of maxilla extending posteroventrally to vertical approximately at midpoint of orbit. Upper lip large and thickened medially. Lower lip thin. Lower jaw greatly protrudes anterior to upper jaw.

Three rows of sharp lingually curved villiform teeth restricted to the premaxilla, becoming reduced to a single row posterolaterally. Tooth size decreasing laterally from premaxillary symphysis. Lower jaw with two distinct rows of lingually curved villiform teeth at symphysis of dentary, slightly decreasing in size posterolaterally. Paired 5th ceratobranchial bones (IF = inferior pharyngobranchials of Rosen, 1965: fig. 3) with 10 rows of sharp, slightly posteriorly recurved villiform teeth. Tooth number decreasing anteriorly with 12–13 teeth in the most posterior row decreasing to one tooth in the most anterior row. Pharyngobranchials 3,4 (PB 3,4 of Rosen 1965: fig. 3) with eight rows of sharp, slightly posteriorly recurved villiform teeth. Tooth number greatest in medial rows, with 7–8 teeth, decreasing anteriorly and posteriorly to 3–4 teeth per row. Second pharyngobranchial elements (PB 2? of Rosen, 1965: fig. 3) weakly ossified, large and elongate, tapering to a point rostrally, and with numerous associated toothplates (many weakly associated and floating in adjacent tissue as opposed to directly fused to PB 2? bones).

Suborbital series comprised of the lacrimal and the dermosphenotic. Posterior margin of preopercle smooth, lacking serrations. Opercle lacking spines. Operculum extending posterior to pectoral-fin base. Gill membrane joined to isthmus, but sides meet without a connecting membrane. Lower limb of first gill arch with two rows (one inner and one outer) of 32–35 elongate, triangular rakers. Lower limb of gill arches two through four with inner and outer row rakers of a similar morphology and count (32–35 in each row) as first arch. Five branchiostegals present.

All scales cycloid, relatively uniform in size, and covering entire body. Smaller scales on caudal fin extending approximately 1/6 length of fin. Scales on nape laterally oblong. Cheek and ventrum fully scaled. Lacrimal asquamate. Snout and occiput fully scaled. Fourteen scales in diagonal from dorsal margin of opercle to origin of dorsal fin. Twenty-two predorsal scales along dorsal midline. Twenty-eight to 29 lateral line scales present.

Fin ray counts as follows: dorsal 7–8; anal 15–17; pectoral 8–9; pelvic 6; caudal 25–27. Anal fin frequently with one or two feeble leading spinelike unbranched rays (rarely three), especially in larger individuals. Pelvic fin with hooked spinelike processes (thickened rays) present in males, with both number of spinelike processes and associated hooks variable and generally increasing over ontogeny (i.e., sexually mature males generally have both more thickened spinelike rays and associated hooks; fig. 6A, C, E): (A) no spinelike process, first ray with single hook; (C) one spinelike process present, exhibiting single hook, and following ray with paired hooks; (E) two spinelike processes present, with first exhibiting single hook, second with paired hooks, and third ray with paired hooks. All females lack hooks on pelvic-fin rays regardless of size or sexual maturity. Vertebral count 17 precaudal + 13–15 caudal = 30–32 total vertebrae. Anteriormost precaudal vertebra lacking pleural ribs. Pectoral fin extending posteriorly to near vertical of longest pelvic-fin ray when both adducted. Anterior origin of dorsal fin at approximate midpoint of anal fin. Anal fin originating at vertical greater than three-quarters of predorsal distance and terminating slightly posterior to last dorsal-fin ray. Caudal fin evenly rounded to lanceolate in larger males

(fig. 4).

Neural spines (= processes) notably expanded and platelike on first five vertebral

FIGURE 4. Live adult male Malagodon honahona , centra in both sexes, not thin and spinelike (fig.

UMMZ 240245 , holotype, 23.9 mm SL, photo- 5A, B). Additionally, neural spines on both graphed shortly after capture. (Photo by P. Reinthal sixth and seventh vertebral centra somewhat and J.S. Sparks.)

expanded and platelike dorsally.

PIGMENTATION IN LIFE: Coloration of recently collected male shown in figure 4. Base body color orangish-brown. Head with a purplish-blue blotch that continues posteriorly as thin stripe along midline to caudal peduncle. Reddish-orange spots present on snout and bases of both pectoral and caudal fins. Unpaired fins, especially anal and caudal, reddish orange with darker margins.

PIGMENTATION IN PRESERVATIVE: Coloration in alcohol shown in figures 2 and 3. Overall coloration light grayish brown with very small dark spots covering body and visible only under microscope.

DISTRIBUTION AND HABITAT: The new species is known only from a single, small, isolated

Pandanas swamp in southeastern coastal Madagascar, located within the Réserve Spéciale de

Manombo (23° 3′ S, 47° 42′ E), south of the coastal town of Farafangana (fig. 1). Although the species was first collected in 1994, it has not been collected since the late 1990s despite repeated attempts and is presumed to be extinct. The habitat was a small, turbid swamp, with only a thin layer of clear water over a much more extensive highly sedimented layer. All specimens of M.

honahona were collected from this thin top layer of clear water.

Members of Malagodon are omnivorous. In aquaria, M. honahona fed on algae, zooplank-

ton, and chironomid larvae. These fishes are oviparous, and fertilization is external. This species was kept in aquaria for several years (at UMMZ). However, efforts to induce reproduction failed. Little else is known regarding reproductive behavior of either species of Malagodon .

CONSERVATION STATUS: Based on the most recent Red List assessment (IUCN, 2023),

Malagodon madagascariensis is considered to be extinct (Ravelomanana et al., 2018; Sparks and

Smith, 2022). Although the newly described species from southeastern coastal Madagascar was not assessed by IUCN in 2016 ( Sparks, 2016), which limits assessments to formally described species, extensive collecting efforts over the past three decades by our research team and others have failed to locate additional individuals, therefore, it can be presumed that M. honahona is also extinct. Both species of Malagodon exhibited extremely restricted ranges in eastern coastal

Madagascar. Malagodon madagascariensis was known only from forested areas in the region of

Mahambo (17° 29′ S, 49° 28′ E), about 80 km north of the port city of Toamasina (Tamatave) ,

and no additional specimens have been collected from the region since collection of the type series in late 1962 by Arnoult (figs. 1, 7). Malagodon honahona was first collected in 1994 by our research team from a single, small lowland Pandanus swamp within the Réserve Spéciale de Manombo (23° 3′ S, 47° 42′ E), located to the south of Farafangana, its only known locality (figs. 1, 2, 4). Unfortunately, introduced Gambusia were prevalent at this locality and likely competing with M. honahona , and specimens of the new species of Malagodon have not been collected at the type locality since 1997. The region upstream of their only known habitat lies outside the Réserve Spéciale de Manombo protected area and is afforded no protection. As a result, the watershed has experienced rapid deforestation in recent decades such that the fragile type locality has suffered severe degradation. It is likely M. honahona became extinct in the late 1990s, not long after it was first discovered. Despite the similar spelling of the type localities for M. madagascariensis and M. honahona , it is clear from the description and accompanying notes made by Arnoult (1963) that the specimens he collected were from forested swamps located to the north of Toamasina, near Mahambo, which is approximately 650 km (400 miles) to the north of the Réserve Spéciale de Manombo, type locality of M. honahona (fig. 1).

LOCAL NAME: None known.

ETYMOLOGY: Named for the swampy Pandanas dominated habitat in which this species occurred within the Réserve Spéciale de Manombo, in southeastern coastal Madagascar. Hohahona translates as swamp or swampy in Malagasy. The epithet, honahona , is used as a noun in apposition.

Figures

FIGURE 2. Malagodon honahona, new species, holotype, UMMZ 240245, adult male, 23.9 mm SL. Réserve Spéciale de Manombo, southeastern coastal Madagascar. Preserved in ethanol.

FIGURE 3. Malagodon honahona, new species, allotype, UMMZ 254162, adult female, 18.9 mm SL. Réserve Spéciale de Manombo, southeastern coastal Madagascar. Preserved in ethanol.

FIGURE 5. Comparison of adult male and female cleared-and-stained Malagodon species. Malagodon honahona: A, male, AMNH 278989, 20.2 mm SL, and B, female, AMNH 278989, 18.6 mm SL. Malagodon madagascariensis: C, male, AMNH 20526, 22.3 mm SL, and D, female, MNHN 1963-166, 22.2 mm SL. Asterisks (*) mark the neural spine on the fifth vertebral centrum for comparison. Inset on C is of same specimen with additional alizarin staining to visualize neural spines more easily. Scale bars = 1 mm.

FIGURE 6. Ontogenetic series comparing pelvic-fin development during ontogeny in Malagodon males. Malagodon honahona: A, UMMZ 254159, 20.2 mm SL; C, UMMZ 254161, 18.3 mm SL; E, UMMZ 240245, holotype, 23.9 mm SL. Malagodon madagascariensis: B, MNHN 1963-166, 11.8 mm SL; D, MNHN 1963-166, 21.6 mm SL; F, MNHN 1963-166, 26.1 mm SL. S = spinelike process with associated hook. Numerals 1–4 designate hooked segmented rays in series, following thickened spinelike processes, if present. Both spinelike processes and associated hooks increase in number over ontogeny, with sexually mature males possessing both more spinelike processes and hooks: (B) no thickened spinelike process, no hook; (A) no spinelike process, first ray with single hook; (C, D) one spinelike process present, exhibiting single hook, and following ray with paired hooks; (E) two spinelike processes present, with first spinelike process exhibiting single hook, second with paired hooks, and following ray with paired hooks; and (F) three spinelike processes present, all exhibiting paired hooks, and following ray also with paired hooks.