Common names:

* proposed name

Synonyms:

Etymology:
'Periophthalmus' is a compound name from the Greek 'peri' (around), and 'ophthalmôn' (eye), which refers to the wide visual field of these species

'chrysospilos' probably comes from 'chrusos' (gold), and 'spilos' (stone), (= gold nugget?), which refers to the yellow speckles on head and flanks

Maximum recorded length:
100 mm TL (pers. obs.)

Live colouration (Murdy, 1989, pers. obs.: Peninsular Malaysia):
ground colour pale to dark grey; head and trunk with numerous orange speckles larger than the underlaying scales, also ventrally on gill cover, prepelvic area, and chin; dorsal dusky saddle-like bars may be visible; D1 membrane anteriorly dusky, medially and proximally red, posteriorly and inframarginally black, and with a thin translucent margin; D2 with a distal reddish margin, a black stripe medially, and proximally translucent with a series of dark spots on membrane; caudal fin dusky, distally paler; anal fin transparent; pectoral fins dusky; pelvic fins white

Colouration on preservation (Murdy, 1989; pers. obs.):
ground colour dorsally and laterally grey to tan brown, ventrally whitish to yellowish; sometimes whitish speckles are visible on throat and opercula; banded pattern rarely observable in the posterior part of body; D1 markedly heterogeneous in colour, posteriorly blackened; D2 with dark to dusky medial stripe and proximal series of dusky spots, transparent for the rest; caudal and pectoral fins dusky; pelvic fins whitish to yellowish

Diagnosis (Murdy, 1989):
D1 VII-X; total D2 elements 12-13; total anal fin elements 11-13; TRDB 15-19; longitudinal scale count 64-77; head width 12.6-21.8%SL; pelvic fin length 12.4-16.8%SL; length of anal fin base 16.7-20.6%SL; length of D2 base 16.3-24.3%SL; pelvic fins totally fused in a disc, pelvic frenum conspicous; dorsal fins not connected by membrane; no stripes or spots on D1; species-specific sexual dimorphism: first two D1 spines elongated in males.
The genus is yet undefined by synapomorphies

Diet:
it seems that this species (Khoo, 1966, quoted by Lim, 1971) alternates its feeding regimes from totally herbivorous (diatoms, filamentous algae - pers. obs. - and other plant material), to carnivorous (crustaceans, harpacticoid copepods, worms, etc.). Moderate to drastic shifts in the feeding regimes were found in other congeneric species (e.g. P. sobrinus= P. argentilineatus: Colombini et al., 1996; P. barbarus: King & Udo, 1998), and seem to be related to different behaviours of sexes during the reproduction, or seasonal changes, respectively

Reproduction:
males jump to attract females inside the burrows to spawn (Polunin, 1972, pers. obs.).
Sex in this species can be discriminated by observing D1 in adults: the 1st and 2nd spines are elongated in males. Males dig reproductive burrows in front of the marine fringe of mangrove forests (Macnae, 1968; pers. obs.).

middle: a male at the opening of its reproductive burrow

(Photo: G. Polgar, Tg. Piai, peninsular Malaysia, 2006)

Ecological notes (pers. obs.: Malaysia peninsulare):
locally very abundant on open mudflats at low tide.
At ebb tide P. chrysospilos gathers in small schools of 20-40 individuals which follow the water edge to feed on the mudflat; with the flood tide the fishes follow the tide in the opposite direction to enter the pioneer mangrove forest, perching on roots and trunks to escape marine predators.

left: a pioneer Avicennia mangrove forest, a typical habitat where P. chrysospilos takes refuge during high tide (Sementa, peninsular Malaysia)

right: the open mudflat, where these fishes go to feed (Tg. Piai, peninsular Malaysia)

(Photos by G. Polgar, 2006)

Distribution (Murdy, 1989):
from east coast of India, to Gulf of Thailand and Java Sea; type locality: Banka Is., Indonesia

Photographs of Periophthalmus chrysospilos:

A: a freshly dead female, note the absence of elongated D1 spines (photo G. Polgar; specimen collected in Kuala Selangor, peninsular Malaysia, 2006); B: ventral view of the pelvic disc of a specimen attached to the glass of an aquarium (photo G. Polgar, 2006); C: a specimen in aquarium (photo G. Polgar, 2006); D: an individual on the open mudflat at low tide (photo G. Polgar; Tg. Piai, Peninsular Malaysia, 2007); E, F: schooling individuals following the ebb tide to the mud flat (photo G. Polgar; Kukup Is., Peninsular Malaysia, 2006); G: perching individuals on prop roots of Rhizophora mucronata at high tide (photo G. Polgar; Tg. Piai, Peninsular Malaysia, 2006); H: another shot of perching P. chrysospilos at high tide; note how smaller and larger individuals remain close to each other while perching (photo G. Polgar; Tg. Piai, Peninsular Malaysia, 2006); I: a perching individual flagging at a mosquito, visible nearby its eye (photo G. Polgar; Kukup Is., Peninsular Malaysia, 2007); J: another shot of schooling individuals at ebb tide (photo G. Polgar; Morib, Peninsular Malaysia, 1996); K: P. chrysospilos perching on a pneumatophore of Avicennia sp.; L: school at ebb tide: note the homogeneous direction of all individuals (photo K, L: Yuko Ikebe) - * with permission

Drawings of Periophthalmus chrysospilos:

cephalic sensory and nasal pores of Periophthalmus spp.: an= anterior nostril; pn= posterior nostril (modified from Murdy, 1989)* - * with permission