Last update: 01 June 2014

Common names:

* proposed name

Synonyms:

Etymology:
'Boleophthalmus' depicts the capability of these fishes to rapidly raise their eyes above the level of their orbits, as if they were ejected out of their orbits: from 'bolê' (ejected), and 'ophthalmôn' (eye) (Cuvier & Valenciénnes, 1837)

'pectinirostris' is a compound Latin form, from 'pecten' (comb, rake) and 'rostrum' (beak, snout), which probably refers to the incised teeth of the mandible

Maximum recorded length:
155 mm SL (Murdy, 1989)

Live colouration (Murdy, 1989; Polgar & Crosa, 2009):
ground colour greenish grey; head covered by numerous small pale blue speckles, becoming larger and scattered on flanks and dorsum; 7 dark blotches on flanks and at the base of the caudal fin, above the lateral midline; in adults, the epidermis below orbits (dermal cups) is sky blue (Malayan populations). D1 greenish to dark grey with numerous small sky blue spots (young do not have a different D1 coloration pattern, as in B. boddarti); D2 greenish grey with columns of 3-8 sky blue spots between rays; caudal fin greenish grey to dark grey with either series of sky blue speckles or elongated flecks on the interradial membrane; anal fin proximally reddish to dark grey, distally dusky to hyaline; muscular base of pectoral fins with small sky blue speckles; pectoral fins dusky for the rest; pelvic fins dusky to dark grey

Colouration on preservation (Murdy, 1989; pers. obs.: Peninsular Malaysia, Indonesia, southern China, southern Japan):
ground colour whitish to tan brown; dorsal and caudal fins bluish-grey, all other ones light brown; spotting pattern often retained only on fins; on some specimens, 1-4 diagonal dark bands are visible on dorsum on the posterior portion of the body; some specimens exhibit large, dark brown blotches on head

Diagnosis (Murdy, 1989; Polgar & Crosa, 2009):
total elements of D2 23-26; longitudinal scale count 84-123; predorsal scales 26-48; caudal fin length 18.3-22.2%SL; head length 24.3-28.0%SL; length of D2 base 41.5-46.1%SL; first D2 element usually segmented and branched; lower jaw teeth notched (bifid).
Malayan populations: in adults, the epidermis below orbits (dermal cups) is sky blue; sexual dimorphism; D1 spines much elongated in adult females; in males, large blotches darker than background are present on the margin of the D1 membrane, behind the first 2-3 spines.
The genus is characterised by the greatly thickened epidermis of the head and dorsum, covered by dermal papillae; and by a rectangular piece of cartilage spanning the width of the pelvic girdle (see drawing)

Diet:
benthic feeder, herbivorous, feeding on microalgal assemblages (Yang, 1996; Yang et al., 2003) which are scraped from the mud surface with side-to-side movements of the head, then sieving the mixture of mud and algae in shallow pools (see photo J). Chen et al. (2007) found two types of territories (Fujian, China): with or without mud walls; the former ones were associated with greater population densities and higher diatom concentrations, especially during the cold season (mud-walled territories were also found in B. dussumieri by several authors). Also the bacterial flora of the gut of these fishes has been investigated (Morii & Kasama, 1989; 1990).
All congeneric species present almost identical feeding behaviours (e.g. see the video clip of B. boddarti) and probably have very similar diets

Reproduction:
males jump to attract females inside the burrows to spawn.
In Japanese populations, adult females exhibit an elongated 2nd spine of D1 (MudskipperWorld, by Yuko Ikebe). Similarly in Malayan populations, adult females' D1 spines are more elongated than in males (Polgar & Crosa, 2009). This was also observed in Malayan and Thai specimens of B. boddarti (Polgar & Crosa, 2009; Swennen et al., 1995), and in New Guinean specimens of B. caeruleomaculatus (Polgar et al., 2010).
B. pectinirostris was artificially propagated through induced ovulation and larval rearing (Chen & Ting, 1986; Chung et al., 1991; Hong et al., 1988; Hong & Wang, 1989; Zhang et al., 1987; Zhang et al., 1989; Zhang and Zhang, 1988).
Age and growth were studied through the analysis of the radials of pectoral fins (Washio et al., 1991; Nanami & Takegaki, 2005)

left: female

right: male

(Photos modified from MudskipperWorld, by Yuko Ikebe)

Ecological notes:
locally very abundant on open mudflats.
Malayan populations (Polgar & Crosa, 2009; Polgar & Bartolino, 2010) were not clearly distributed according to an ecological spatial partition between different size classes along the intertidal zone, such as that observed in different habitats of the same ecosystem in B. boddarti, Oxuderces dentatus and Periophthalmus gracilis (Polgar & Bartolino, 2010); nonetheless, the largest individuals are exclusively present on lower unvegetated mudflats, while smaller individuals exhibit a more irregular distribution, occurring both on open mudflats and along ephemeral inlets inside mangrove forests and pneumatophore zones (Polgar & Bartolino, 2010).
During winter, fishes living in Southern Japan hybernate, laying at the bottom of their burrows (Takegaki et al., 2006)

left: typical habitat of B. pectinirostris: the main openings of the fishes' burrows are visible (Japan, Saga Prefecture, Ariake Sea)

right: resin cast of a burrow of an adult: note the "Y" shape with two openings; the whole burrow was about 1.5 m deep

(Photos: modified from Hiro Masa Matsumoto, 1999)

Distribution:
Taiwan, China and Southern Japan; type locality: Canton, China (Murdy, 1989).
Recently it was recorded in South-East Asia (Peninsular Malaysia) and Indonesia (Polgar & Crosa, 2009), where is sympatric with B. boddarti. Malayan, Chinese and Japanese populations exhibit slightly different colouration patterns and morphologies (see below, Remarks)

left: an example of "mudskipper architecture"

right: a wooden decoration inspired by the "mutsugoro"

(Photos by Hiro Masa Matsumoto: Saga prefecture, Japan, 1999)

Remarks:
this species is extensively farmed and consumed in Japan, Taiwan and Southern China, where it is considered as a culinary delicacy (Clayton, 1993). In Japan this fish is very popular, and it is captured by a traditional fishing method called mutsukake, handed down from father to son. The most important tools are a very long rod, a harpoon-like hook and a sort of mud-slide called oshiita. Another technique consists in some bamboo traps that simulate the fishes' burrows and are deeply inserted into the mud. According to Polgar and Crosa (2009), the Malayan populations of his species were misidentified as B. dussumieri by Takita et al., 1999 and Polgar & Khaironizam, 2008.

Takegaki (2008) prompted for urgent action to save southern Japanese populations of this species, threatened by intense habitat destruction in this region (Stanley, 2011).

Molecular phylogenetic analyses suggest that this species includes two criptic species, with different geographic distributions: one in the South China Sea (from the Guf of Tonkin to the Taiwan Strait) and in the East China Sea, up to the Korea Strait (B. pectinirostris s.s.), and another species distributed in the Strait of Malacca (possibly northward to Taiwan: pers. obs.) (Chen et al., 2014).

left: hook (photo by Hiro Masa Matsumoto, 1999)

middle: traditional Japanese traps (photo by Hiro Masa Matsumoto, 1999)

right: a fisherman on an oshiita collecting mutsugoro (© Ariake lawsuit, 2007)

Photographs of Boleophthalmus pectinirostris:

A: B. pectinirostris in aquarium (photo: © fishing-forum, Kumamoto prefecture, Japan, 2003); B: a female specimen from Taiwan (photo: Hans Ho, Taipei market, Taiwan, 2006); C: a male specimen from Taiwan (photo: Naomi Delventhal, Taipei market, Taiwan, 2006); D: a Chinese specimen: note the different colouration pattern (photo: anonimous, Meizhou, China, 2006); E: an agonistic encounter between two males; F: a female; G: jumping reproductive males (photos E-G: © BlueNativeFactory, Ariake Sea, Japan, 2006)*; H: a territorial dispute between two males; a female is out of focus in the foreground (photo: G. Polgar, Kukup town jetty, Peninsular Malaysia, Johor, 2006); I: another shot of a jumping male, right in the moment when it pushes itself with its tail (photo: Yuko Ikebe, Ariake Sea, Japan, 2003)*; J: a specimen "sieving" in a small pool the mixture of mud and algae scraped from the mud surface: note the ripples on the water surface made by the rapid movements of the mandible (photo: G. Polgar, Kukup town jetty, Johor, Peninsular Malaysia, 2006); K: a Chinese specimen bought in a market (photo: Ray Cui, Guangzhou, China, 2006)*; L: a female of B. pectinirostris and a reproductive male of Periophthalmus chrysospilos: note the opening of this latter species' burrow in the lower right corner of this picture (photo: G. Polgar, Tanjung Piai, Peninsular Malaysia, Johor, 2007) - * with permission

Drawings of Boleophthalmus pectinirostris:

A	B	C
D	E	F

A: cephalic sensory and nasal pores of Boleophthalmus spp.: an = anterior nostril; ao = anterior oculoscapular canal pore; pn = posterior nostril (modified from Murdy, 1989)*; B: Gobius pectinirostris Linnaeus, 1758: the first scientific drawing of a mudskipper (Linnaeus, 1759: detail of fig. 3, p. 260) Göttinger Digitalisierungs - Zentrum, Goettingen State and University Library*; visited: 08/2007); C: a Korean specimen (Kim, 1997); D: ventral view of pelvis of B. boddarti (pelvic fin elements removed from left side: modified from Murdy, 1989)*: PIC = pelvic intercleithral cartilage; Plv = pelvis; RC = rectangular cartilage; Plsp = pelvic fin spine; E: Boleophthalmus pectinirostris (Linnaeus) (Bleeker, 1983)*; F: Boleophthalmus chinensis (Osbeck) (Herre, 1927) - * with permission