Actinopterygii (Gigaclass) > Actinopteri (Class) > Teleostei (Subclass) > Gobiiformes (Order) > Apogonoidei (Suborder) > Apogonidae (Family) > Apogoninae (Subfamily) > Foa (Genus)

Fo cardinalfish, Samoan cardinalfish, Samoan fo, Weedy cardinalfish, Taiwan matoi shimochi, タイワンマトイシモチ, 菲律宾腭竺鱼,

Synonymes
Apogonichthys fo (Jordan & Seale, 1905)
Apogonichthys zuluensis (Fowler, 1934)
Foa zuluensis (Fowler, 1934)

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Description
Dorsal spines (total): 9, third spine longest and strongest, sixth radial free in advance of hidden nubbin representing eighth spine; Dorsal soft rays (total): 9; Anal spines: 2; Anal soft rays: 8; Pectoral fin rays: 12; Pelvic fin rays: I, 5; Principal caudal fin rays: 1-8 + 7 + 1; Lateral line scales: 23 with 14 pored and 9 partial pores and pits; Transverse scale rows above lateral line: 1; Transverse scale rows below lateral line: 4; Median predorsal scales: 4; Circumpeduncular scale rows: 12 (5 + 2 + 5); Gill rakers + rudiments: 14, well developed rakers: 8, upper arch: 2 rudiments and 1 raker, lower arch: 7 rakers and 4 rudiments; Second arch with rudiments on hypobranchial and ceratobranchial with one raker at angle. Villiform teeth in a band on the premaxilla and dentary; 2-3 rows on vomer; 3 rows on the palatine; None on ectopterygoid, endopterygoid or basihyal. Vertebrae: 10 + 14 = 24; Five free hypurals; One pair of short, slender uroneurals; Three epurals, the first two expanded, a free parhypural; Three supraneurals, no procumbent spines (spurs); Two supernumerary spines on first dorsal pterygiophore, no procumbent spines (spurs); Basisphenoid reduced to upper portion (meningost); Supramaxilla thin and reduced in length; Posttemporal smooth on posterior margin; Preopercle smooth on vertical and horizontal edges, ridge smooth; Infraorbitals smooth, infraorbital shelf present on third bone; Interhaemal gap: 1 + 4. Peripheral ctenoid scales on cheek, subopercle, opercle, isthmus, base of pectoral fin, ctenoid behind pectoral fin and on body, nape and predorsal scales ctenoid; Two large cycloid scales on base of pelvic fin, no axillary scale; Cycloid scales onto caudal fin about same size as scales on caudal peduncle. Head of lectotype with skin congealed, obscuring pore openings and without evidence of sensory neuromasts; Anterior end of supra-orbital canal as a broad slit at edge of upper lip curving up distally; Lachrymal with large anterior pore near flat posterior nare opening, two large ventral slit pores along edge of lachrymal; Anterior portion of dentary with dentary (anterior) and mental (ventral) pores, posterior with a large articular pore; Supratemporal canal with posterior canals onto first nape and predorsal scales. Head of lectotype with most free neuromasts missing. Free neuromasts on snout, interorbit and temporal areas in, a split line becoming one line of neuromasts from snout interrupted over eye, offset, not overlapping, continuing onto side of head below posttemporal, short lines generally perpendicular to long lines, short medial lines associated with commissure region, supratemporal neuromasts missing; Several rows of neuromasts between nares and anterior infraorbital oriented horizontally and vertically; A long linear line of neuromasts from first infraorbital (lachrymal) past posterior corner of maxilla dividing on to lower cheek horizontally as well as downward, short lines of neuromasts radiate from ventral and posterior edge of eye; Three or four rows of neuromasts on anterior third of lower jaw grading posteriorly to one row near edge of articular pore, gular free neuromasts in chevron rows except for anterior two rows; Preopercle with single long vertical line of neuromasts on upper arm from posterior part of lower arm; Preopercle flap (horizontal arm) with short rows of various orientations; Opercle with short vertical row of neuromasts on upper anterior scale, a long vertical row near preopercular edge, a row on posterior scale, and two areas with neuromasts on opercular flap; Pored lateral line scales with vertical rows of neuromasts above and below canal pore; First scale with pit with a reduced row above pit, free neuromasts on other pit scales and several small caudal scales, no free neuromasts observed on other basicaudal scales; Free neuromasts associated with 11 principal caudal fin-rays in single linear lines on ventral edges of upper branched rays (3-8) and on dorsal edges of lower branched rays (11-15), middle two caudal rays (9-10), upper unbranched and branched caudal rays (1-2), and lower unbranched and branched caudal rays (16-17) lack free neuromasts. Anterior nare tubular, posterior nare flat. Caudal fin rounded, broken in lectotype; Second dorsal and anal fin with rounded distal edges. Max. length: 3.5 cm SL. Depth range: 0 - 82 m, usually: 0 - 15 m.

Color
Head, body, first dorsal and pelvic fins brown with white spots and markings; Darker brown bar-like markings on head and body, a cheek mark from eye to upper jaw, a mark above preopercle over anterior nape, one or two short marks above opercle not reaching base of first dorsal fin, an irregular bar from near mid-base of first dorsal fin to side of abdomen, an irregular bar from base of soft anal rays to base of soft dorsal rays, an anterior caudal peduncle mark, and diffuse basicaudal marks; Lips brownish with narrow alternating white marks; Edge of eye with alternating brown and white markings; Irregular whitish spots on body and caudal peduncle, a white spot at upper pectoral fin base, a white spot at mid-base of soft dorsal rays, a white spot and posterior base of soft dorsal fin, three basicaudal white spots; Membranes between second to fourth dorsal spine more whitish than brownish, fourth to seventh membranes more brownish than whitish; Base of pelvic rays to tip of spine whitish, remainder of fin brownish; Soft dorsal, anal and caudal fin rays with tiny white spots on translucent fins.

Etymology
Both parts of the name are derived from fō, the Samoan name for cardinal fishes (Apogonidae). The genus name Foa, apparently a latinization of fō, was proposed by Jordan & Evermann in the same publication. Just five letters long, Foa fo, the Samoan Cardinalfish, is the shortest name of any valid species of Recent fish.
Original descripiton: Foa fo Jordan & Seale, 1905 - Type locality: Negros, Cavite, Luzon Island, Philippines, Manila Bay, South China Sea, western Pacific.

Distribution
Red Sea; Indo-West Pacific: South Africa, East Africa, Comoros, Mozambique Channel, Mascarenes, Maldives and Chagos Archipelago, east to Philippines and Society Islands (French Polynesia), north to Amami Islands (southern Japan), south to Western Australia, Queensland (Australia), New Caledonia, Tonga and Rapa (French Polynesia).

Biology
Nocturnal species; Occurs inshore. Enters estuaries and quiet coastal bays, usually on mud or silty substrate with algae-rock outcrops or isolated soft corals. Solitary or in small groups. Are mouthbrooders. Distinct pairing during courtship and spawning.

Similar species
Species of Foa all share very similar body proportions and morphometrics; Radiographs also show that there are no distinctive osteological characters to differentiate species. Apparently, the only reliable features to distinguish these species are marking patterns and the pores and neuromast patterns on the lower jaw. The presence of irregular indistinct bars on the body and caudal peduncle are diagnostic, but typically are not present on old bleached museum specimens, which often cannot be assigned to species.