Ajargo

Perception Channels: tactile ; chemical

Relatives of D. holocanthus are popular in Asian sushi restaurants. However, D. holocanthus is not normally consumed. Dried, inflated bodies of D. holocanthus are however, a relatively common novelty for tourists on vacation in tropical areas (FLMNH).

The teeth of both the upper and lower jaws of D. holocanthus are fused, forming a solid, heavy beak (Hobson 1974; Waikiki Aquarium 1999). This beak makes cracking the shells of snails, sea urchins and hermit crabs a breeze. With the help of its relatively large eyes, D. holocanthus feeds at night on these delicacies of the coastal zone (Waikiki Aquarium 1999). As for catching its prey, D. holocanthus certainly does not rely on speed. It is actually a slow-swimming predator (Waikiki Aquarium 1999). What D. holocanthus can do is maneuver into tricky positions using its pectoral, pelvic and anal fins. This is especially helpful in complex habitat such as coral reefs. D. holocanthus uses its tail primarily for steering and for occasional bursts of speed (Waikiki Aquarium 1999).

Diodon holocanthus is a nocturnal predator and remains hidden during the day (Hobson 1974; Waikiki Aquarium 1999; FLMNH). Individuals have been observed resting near ledges and shallow caves of the rocky sea floor in the Gulf of California and ledges or holes in the Florida Keys in the daytime (Hobson 1974). In coral reefs around Hawaii and the West Indies, D. holocanthus' main food source is pagurid crabs (hermit crabs) and prosobranch gastropods, which include familiar marine organisms such as abalones, limpets, top shells, periwinkles, boat shells, conchs, moon snails, and whelks (Hobson 1974; FLMNH;Randall 1967; Waikiki Aquarium 1999).

Diodon holocanthus is distributed circumtropically throughout the world (Hobson 1974; FLMNH). In the U.S. it is found along the Pacific coast, the Florida Keys and Hawaii (Hobson 1974; Waikiki Aquarium 1999). It is widespread in the Caribbean and eastern Asia (Hobson 1974; FLMNH).

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

Adult balloonfish are found in relatively shallow areas of the ocean. They prefer grassy flats, coral reefs, and mangrove areas (Randall 1967; FLMNH; Nagelkerken et. al 2000). The larvae however, are found in the pelagic (open water) zone (FLMNH). They bob around in their shells for about 4 days before hatching (FLMNH).

Aquatic Biomes: reef ; coastal

Diodon holocanthus, also known as the balloonfish or spiny puffer, can reach lengths from about 30.5 to 61 cm. It has dark patches along its sides and back, but perhaps its most telling feature is the long spines that protrude from all over its body, excluding the fins and face. The spines are actually modified scales, which lay flat against its body most of the time (Waikiki Aquarium 1999). In some relatives of the balloonfish, a toxic chemical, tetrodotoxin, is found in the skin and spines. However, only trace amounts of tetrodotoxin have been found in balloonfish, mainly concentrated in the ovaries (Chen and Chou 1998). In appearance, D. holocanthus resembles its closest cousin, D. hystrix, also known as the porcupinefish. However, an easy way to tell these two apart (without getting too close) is by checking for spots on the fins: D. hystrix has them, while D. holocanthus does not (FLMNH).

Balloonfish expand by swallowing mouthfuls of air or water when attacked by a predator. The balloonfish swallows air, when attacked by avian predators, or water, when attacked by piscine predators (Brainerd 1994). After ingestion through the mouth, the air or water reaches the highly elastic stomach, which has been described as a "large dilatable sac with robust esophageal and pyloric sphincters" (Rosen, 1912). The stomach, which has lost its digestive function, plays a key role in the inflation process (Brainerd 1994). In Diodontidae, the stomach is a simple sac, whereas in Tetraodontidae the stomach is divided into two parts by a pyloric sphincter. As the stomach expands, it pushes the peritoneal lining into the ample peritoneal space. The peritoneal cavity expands towards the head to the mandible and towards the tail to enclose the unpaired fins (Brainerd 1994).

The skeletal structure of D. holocanthus also facilitates inflation. Because the balloonfish lacks pleural ribs and a pelvic girdle, expansion is not as strictly inhibited as in most fish. The vertebral column is also highly flexible. It bends in an arc towards the dorsal side of the fish, allowing D. holocanthus to attain its characteristic spherical shape upon inflation (Brainerd 1994).

In addition to the elastic stomach, generous peritoneal space and skeletal structure, balloonfish skin is also specialized for inflation (Brainerd 1994). The skin of D. holocanthus is highly elastic because of microfolds in the epidermis and collagen fibers of the dermis. These allow D. holocanthus to extend through 40% of its initial length before it begins to stiffen (Brainerd 1994).

Other Physical Features: bilateral symmetry

Diodon holocanthus reproduces through sexual processes, just like most other fish. Sexual reproduction maintains genetic diversity within the species, which is important for preventing disease and adapting to changes in the environment over time. During spawning season, a male pushes a female to the surface and they immediately spawn (FLMNH). The round eggs float in the water. Until they are 10 days old, D. holocanthus larvae retain a thin shell covering, which is then lost (FLMNH). At this time, D. holocanthus begins to develop spines. The larvae metamorphosize after about 3 weeks (FLMNH). After this metamorphosis, fins and fin rays are present, the teeth are formed, and adult olive and brown coloring develops (FLMNH). Dark spots appear on the belly, which may help camouflage the juveniles in floating sargassum from underwater predators such as the mahi mahi (FLMNH). The juvenile loses this underside spotting when it reaches the adult stage. At this point in development, spine elongation and body growth occur. The larval stage of D. holocanthus is yellow with red spots and well-developed functional mouth, eyes and gas bladder (FLMNH ).

Like all species in the family Diodontidae, Long-spined Porcupinefish (Diodon holocanthus) can inflate themselves by swallowing water (or air). As in other species in the genus Diodon, this swelling causes the erection of the long movable spines covering the body. The Long-spined Porcupinefish is a robust fish with rounded dorsal and anal fins. Spines on the forehead of the Long-spined Porcupinefish are slightly shorter to much longer than are those immediately behind the pectoral fin base. Long-spined Porcupinefish have a broad dark bar through the eyes and, usually, four dark saddles on the back. The rest of the body is brownish yellow, paler below, with dark brown spots of moderate size (no spots on the fins beyond their bases). These spots are larger than the diameter of the spines. No spines are wholly on the caudal peduncle. Pelagic juveniles are around 6 to 9 cm. Maximum adult standard length (i.e., excluding tail) is around 30 cm, with a maximum total length of around 45 to 50 cm. In North American waters, the similar Spotted Porcupinefish (Diodon hystrix) is larger (to 91 cm), lacks the dark bars on the back and through the eyes, is covered with small dark spots that are around the same diameter as the spines, has the longest spines posterior to the pectoral fins, and has one or more spines wholly on the caudal peduncle. The Long-spined Porcupinefish has a circumtropical distribution in the Atlantic, Pacific, and Indian Oceans (except that it seems to occur only peripherally on the Pacific Plate). It is found in the Atlantic from Florida and the Bahamas to Brazil and in the Pacific from the Gulf of California to Peru (see Leis 2006 for more details on geographic distribution). Long-spined Porcupinefish are nocturnal and usually solitary. They feed on hard-shelled invertebrates. Larger individuals are found in a variety of benthic habitats from shallow reefs to open, soft bottoms to at least 100 m. In some areas, Long-spined Porcupinefish are harvested and dried in their inflated state for sale to tourists. See Leis (2006) for a comprehensive key to identify the seven or eight genera and 18 or 19 species in the family Diodontidae that are recognized as valid by the author. (Boschung et al. 1983; Eschmeyer and Herald 1983; Robins and Ray 1986; Leis 2003, 2006)

Inhabits lagoon and seaward reefs (Ref. 37816, 58534) to open shallow, soft bottoms. Occurs on open muddy substrates as well as on rich soft-bottom and coral reefs. Also in areas with rocky substrata. Young and sub-adults may form small groups (Ref. 48637). Juveniles pelagic to about 6-9 cm. Solitary. Feeds on mollusks, sea urchins, hermit crabs, shellfish and crabs at night (Ref. 9680, 54301). Mobile-invertebrate feeder (Ref. 57615, 57616). Sessile invertebrate feeder (Ref. 126840). A relatively poor swimmer (Ref. 9710). A relatively poor swimmer (Ref. 9710).

Dorsal spines (total): 0; Dorsal soft rays (total): 13 - 15; Analspines: 0; Analsoft rays: 13 - 15

Pelagic juveniles with spots, particularly prominent on belly; adults with dark blotches across back and spots between the blotches; fins without spots (Ref. 4423). 14 to 16 spines in an approximate row between snout and origin of dorsal fin; with a large brown bar above and below each eye; a broad transverse brown bar on occipital region of head (Ref. 13442).

Lymphocystis Disease. Viral diseases

Inhabit shallow reefs to open, soft bottoms. Also in areas with rocky substrata. Sometimes form groups (Ref. 9710, 48637). Occur on open muddy substrates as well as on rich soft-bottom and coral reefs. Juveniles often with floating Sargassum rafts. Young and sub-adults may form small groups (Ref. 48637). Benthopelagic (Ref. 58302). Juveniles pelagic to about 6-9 cm. Solitary. Feed on mollusks, sea urchins, hermit crabs, and crabs at night (Ref. 9680). Relatively poor swimmers (Ref. 9710). Used in Chinese medicine (Ref. 12166). Captured at the surface using a hand net (Ref. 26165).

fisheries: minor commercial; aquarium: commercial; price category: unknown; price reliability:

分布於全世界各熱帶海域。台灣各地海域均產。

沿岸常見魚種，流刺網、一支釣、手釣等皆可捕獲，無食用經濟價值，但常被飼養於水族館供人觀賞。

體短圓筒形，頭和體前部寬圓。尾柄錐狀，後部側扁。吻寬短，背緣微凹。眼中大。鼻孔每側2個，鼻瓣呈卵圓狀突起。口中大，前位；上下頜各具1喙狀大齒板，無中央縫。頭及體上的棘甚堅硬而長；尾柄無小棘；眼下緣下方無1指向腹面的小棘。各棘具2棘根，可自由活動。背鰭一個，位於體後部，肛門上方，具軟條13-15；臀鰭與其同形，具軟條13-15；胸鰭寬短，上側鰭條較長，具軟條20-24；尾鰭圓形，具軟條9。體背側灰褐色，腹面白色，背部及側面有一些深色的斑塊，另有一些黑色小斑點分布；無喉斑；背、胸、臀及尾鰭淡色，無任何圓形小黑斑。

熱帶海洋性底層魚類，主要棲息於淺海礁石區、軟質底海域或開放性水域。一般行獨居生活，有時會聚集成群；幼魚則行大洋漂游性生活。主要於夜間捕食軟體動物、海膽、寄居蟹及螃蟹等無脊椎動物為食。

The long-spine porcupinefish (Diodon holocanthus), also known as the freckled porcupinefish among other vernacular names, is a species of marine fish in the family Diodontidae.

Inhabits shallow reefs to open, soft bottoms to at least 100 m . Also in areas with rocky substrata. Sometimes forms groups (Ref. 9710). Juveniles pelagic to about 6-9 cm. Solitary. Feeds on molluscs, sea urchins, hermit crabs and crabs at night (Ref. 9680). A relatively poor swimmer (Ref. 9710).

Feeds on mollusks, sea urchins, hermit crabs, and crabs at night

circumtropical in distribution; Western Atlantic: Near Georges Bank to Brazil

Inhabits shallow reefs to open, soft bottoms. Also in areas with rocky substrata. Sometimes forms groups.

benthic

Known from seamounts and knolls