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Variation in body shape of known material large, yet all relative dimensions of head, especially length of snout and jaws appear to be shorter on average in L. indica than in the members of the L. arborifera-group; except for diameter of eyes, which on average distinctly greater in L. indica females.
Preopercular and sphenotic spines well developed, the latter curved and directed anteriorly in all specimens examined; projection of margin of frontal bone above eye not acutely pointed, its anterior and posterior margins forming an angle of about 90 degrees; lower jaw without symphysial spine, posterior angle not distinctly pointed. Jaw teeth of females arranged in same pattern as all other species of Linophryne examined, having four longitudinal series in upper jaw and three in lower; number of teeth increasing with standard length, from 13–20 in each premaxilla, 11–14 in each dentary; total number of teeth falling within variation observed in specimens of L. arborifera-group of similar length, but with a slight tendency towards higher values in posterior series; vomer with a single pair of teeth; dorsal-fin rays 3; anal-fin rays 3 (37-mm female, SIO 73149, with anal-fin rays 2); pectoral-fin rays 14–18. Length of illicium 12–19% SL; pattern of escal appendage of 36.5 and 37 mm females (SIO 71-297, SIO 73-149) in full agreement with that of 35-mm female described by Regan and Trewavas (1932:110, fig. 169; ZMUC P92143), while those of three slightly larger females (42–51 mm, LACM 36046-11, LACM 33319-4, SIO 70-306) show various aberrations as follows: Common to three smaller specimens: (1) a low median distal papilla with three short filaments; (2) an anterior distal pair of fringed appendages, with length two-thirds to nearly one and one-half times diameter of escal bulb, bearing short, unbranched side branches regularly decreasing in length towards tip; (3) stout median and posterior distal pairs of filaments, one and one-half times diameter of bulb in length, simple or with a few short side branches near base (filaments of median distal pair emerging close to base of distal papilla, those of posterior pair emerging more laterally on distal surface of escal bulb); (4) a stout, unbranched posterior filament, somewhat longer than diameter of bulb, situated behind the escal pore. Common to slightly aberrant escae of three larger females: 1) distinct distal papilla absent, but an irregularly branched group of filaments situated between bases of fringed anterior pair of appendages; anterior pair of appendages somewhat shorter (about one-half diameter of bulb) and more irregularly branched; 2) posterior appendage short, less than one-half diameter of the bulb.
A 44-mm female (LACM 33319-4) differing further in having 1) three simple, relatively stout filaments behind median cluster of branched filaments mentioned above, and 2) filaments of median distal pair short (less than one-half diameter of bulb) and bifurcated at base. In 51-mm female (SIO 70-306) this median pair appears to be torn away; well-preserved esca of 42-mm female (LACM 36046-11) with only a single distal pair posterior to anterior fringed pair of appendages. Barbels of five of seven available metamorphosed females appear to form a natural developmental series; 44-mm female (LACM 333194) with somewhat aberrant branching.
All specimens with darkly pigmented, relatively short undivided stems, 10–17% SL in length. Smallest specimen (35 mm, ZMUC P92143) with tip of barbel bearing a series of six short, unpigmented branches along posterior edge, decreasing in width and length distally and anteriorly, and terminating at same level; each branch with a globular terminal photophore and a distal, more or less branched filament.
Barbels of three somewhat larger females (36.5–42 mm; SIO 71-297, SIO 73-149, LACM 36046-11) representing very similar developmental stages: six branches relatively thicker, two shortest anterior branches with tendency to fuse at base; while posterior branch remaining largest, intermediate branches of 42-mm specimen varying more irregularly in length; distal filaments in greater number and relative length, carrying numerous stalked, sessile, internal photophores; in addition to large terminal photophore of each branch, numerous photophores of various sizes present inside and on surface of distal part of branches. In 51-mm female (SIO 70-306), barbel divided into three primary branches, each branch with an undivided, pigmented proximal part; posterior and anterior branches about equal in length, with a gradually tapering, unpigmented distal part carrying filaments and photophores; median branch truncated, with about six short, unpigmented, more or less fused branches, each bearing short distal filaments and sessile photophores. Barbel of 44-mm female (LACM 33319-4) with an anterior and posterior primary branch, each pigmented proximally, gradually tapering and longer than intermediate branches, emerging from common base; differing from those of other specimens in having intermediate group divided into about 10 slender branches, each gradually tapering into filaments and carrying numerous small photophores, nearly all placed on separate slender stalks; internal, terminal, enlarged photophores (present in each branch of other specimens) absent.
Unique pattern of subdermal pigmentation present in all known specimens, including larvae, free-living males, holotype of Linophryne corymbifera, lectotype of Linophryne indica, and female and parasitic male recorded as L. corymbifera; in three primary concentrations: (1) Pigment of body consisting of two rows of relatively large, well-separated melanophores situated along sides of body, extending anteriorly to or near base of pectoral fin; dorsolateral row lying just above midline of body, usually consisting of a single series of melanophores; ventrolateral row 2 or 3 melanophores wide; similar lateral rows of melanophores present in species of Linophryne arborifera-group and in Haplophryne mollis; in smaller larvae (less than 8 or 9 mm) of these latter two taxa, no other distinguishing characters have been found. Lectotype of L. indica and other metamorphosed males, females, and larger larvae, with lateral rows of melanophores widening posteriorly to form a more dense group of melanophores at base of caudal fin; a similar distinct caudal group of melanophores may be present in Haplophryne mollis but absent or very indistinct in L. arborifera-group. (2) In all material examined greater than about 8 mm, subdermal pigmentation differing from that of all other known linophrynids in having a dense concentration of melanophores on posterior part of peritoneum, prolonged in larvae and males to form a short empty sack behind sinistral anus; in ventral view pigmentation V- or U-shaped in males and larvae, visible through a slit in skin of metamorphosed females, appearing as a very distinct black spot; especially dense cluster of melanophores present dorsally and laterally on anterior part of peritoneum, divided on each side into two groups by an unpigmented zone along postcleithrum. (3) In contrast to other linophrynids, subdermal pigment present on posterior angle of lower jaw, developing in larvae of about 8 mm; larger larvae with pigment spreading dorsally behind preopercle, especially well developed in 15-mm larval female (SIO 73-329); largest females (42–51 mm; LACM 36046-11, SIO 70-306) with pigmentation less distinct, but present as scattered melanophores embedded in cavities of posterior part of articular bones.
Free-living males of L. indica are distinguished from those of the L. arborifera-group only on the basis of the pattern of subdermal pigmentation. Like the latter, and in contrast to all other known Linophryne males, L. indica males lack pointed sphenotic spines. The number of olfactory lamellae seems to vary between 9 and 11, but exact counts are not possible without dissection; similarly, the number of denticular teeth appears to vary within the limits found in members of the L. arborifera-group (3–6 upper, 9–14 lower), but exact counts are possible only on cleared and stained specimens. For these reasons, no attempt to examine possible differences from other Linophryne males in average numbers of olfactory lamellae and denticular teeth has been made.
Parasitic males, both within length distribution observed in free-living metamorphosed males, attached by separate outgrowths from snout and tip of lower jaw to belly of female in front of and below sinistral anus, without distinct degeneration of eyes or olfactory organs; differing from free-living males in body shape, having relatively larger heads (probably due to degeneration of body muscles); 15-mm parasitic male of mature 51-mm female (SIO 70-306) with abdomen slightly swollen by enlarged testes.
Metamorphosed females of Linophryne indica differ from those of all other species of the genus in having the following escal and barbel characters: escal bulb with a distal pair of fringed anterior filaments; a medial distal papilla with short filaments present in some specimens; one or two pairs of stout distal posterior filaments (simple or with a few short lateral branches); a simple tapering appendage emerging from behind escal pore. Barbel with a short, stout, undivided stem, its length 10–17% SL to base of a series of 5 or 6 short branches, each with a number of branched filaments at distal tip; filaments and transparent distal part of primary branches with numerous, small, globular luminous organs, internal, sessile, or set on short stalks; each primary branch with one larger, internal, terminal luminous organ. Lower jaw without symphysial spine. Males without pointed sphenotic spines. Larvae, males, and juvenile females with two lateral rows of large subdermal melanophores along side of body, with a concentration at base of caudal fin; melanophores extending anteriorly beyond anterior margin of dorsal and anal fins; a concentration of subdermal pigment on posterior angle of lower jaw, and on posterior tip of peritoneum behind anus.
All known specimens of L. indica were caught in the Indo-Pacific region, the greater part between 60–135°E and 10°S–35°N in Indian, Indo-Malayan, and Western Pacific waters.
Three of the females (SIO 71-297, SIO 73-149, LACM 333194) and several males came from off Hawaii; a single male (SIO 75-452) was collected in the Gulf of Panama.
Pietsch TW. 2009. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkley: University of California Press. 638 p.
Regan CT, Trewavas E. 1932. Deep-sea anglerfish (Ceratioidea). Dana Rept 2:113 pp.
The ovaries of the three non-parasitized females (35–37 mm) are small and immature, with tiny oocysts. In the 42-mm parasitized female (LACM 3604611), the ovaries are about 10 mm long, containing immature eggs about 0.1 mm in diameter. The 51-mm parasitized female (SIO 70 -306) appears to be nearly mature with enlarged ovaries about 20 x 15 mm, containing numerous eggs 0.3–0.4 mm in diameter.
Parasitized females have a single attached male, in contrast to the linophrynid genera Haplophryne and Borophryne (and the ceratiid genera Ceratias and Cryptopsaras) in which females with two or more males are known. In all known cases parasitized females of the family, the male is directed forward with respect to the female and attached in nearly the same position on the ventral midline of the female, somewhat in front of and below the sinistral anus; with only one or two exceptions, all are attached upside down with respect to the female. This is again in contrast to the linophrynid genera Haplophryne and Photocorynus (and the ceratiid genus Cryptopsaras) in which males may attach in any direction and almost anywhere on the head and body of the female. In all known examples, the males are attached by both upper and lower jaws, leaving prominent openings on each side that lead into their mouths and opercular cavities; there is no papilla of tissue projecting from the female into the mouth of the male.
Known from 11 metamorphosed females (24–51 mm), two parasitic males (9.5–14.5 mm), 31 free-living males (11–16 mm), and 17 larvae (7.5–22 mm).
VALDIVIA station 230, 2°43'S, 61°12'E, 1500 m, 3 March 1899 (by subsequent designation of Bertelsen, 1981:2).
Lectotype of Aceratias macrorhinus indicus: ZMB 17715, male, 16 mm.
