Species Accounts - Gobiidae - Anatirostrum
Genus Anatirostrum
Il'in, 1930
This genus comprises only a single species and so its characters are those of the species. The snout is very distinctive and details of neuromasts are not given here as they are not needed in identification, although of importance in relating the genus. The genus is closely related to the tadpole goby clade comprising Benthophiloides-Caspiosoma-Benthophilus and details are give in Miller in Miller (2004). This author also gives an alternative terminology for the arrangement of neuromasts than that of Ahnelt et al. (2000).
Anatirostrum profundorum
(Berg, 1927)
Common names
gavmahi nuk-ordaki (= duckbill goby), gav
mahi-ye poozehderaz.[duckbill tadpole goby].
Systematics
This species was originally described in the genus Benthophilus Eichwald, 1831 by Berg (1927) but later Il'in (1930) erected a new genus because of its unusual and distinctive morphology. The type locality is the Caspian Sea at 37°58'N, 52°22'E at a depth of 294 m (but see below).
There are 14 fish under ZISP 23134 recognised as syntypes in Ahnelt et al. (2000) although Berg (1927) mentions 15 fish in his description. Ragimov (1985) states that Berg described this species from a single young specimen and also visually observed 15 others for a total of 16 in the type series.
Key characters
The duckbill tadpole goby is characterised by the elongate and flattened head which is similar to a duck's bill. Unlike gobies of the genus Benthophilus the body has minute platelets and granules, there are 8 rather than 6, vertical, suborbital series of pit organs, no postorbital occipital series, and no chin barbel or cheek flaps behind the jaw angle (Ahnelt et al., 2000).
Morphology
First dorsal fin with 3-4 spines, usually 4, second dorsal fin with 1 spine followed by 8-11, usually 10, soft rays. Anal fin with 1 spine followed by 8-11 soft rays. Pectoral fin rays 14-16. Gill rakers on the posterior part of the arch are very short and anteriorly are minute. Pit organs on the side of the head are papilliform and clearly visible with the naked eye. Further details of anatomy are given by Ahnelt et al. (2000).
Iranian specimens had the following meristics:- first dorsal fin with 4(4) spines; second dorsal fin with 1(4) spine followed by 10(4) soft rays; pectoral fin rays 14(1), 15(2) or 16(1); anal fin with 1(4) spine followed by 11(4) soft rays; and total vertebrae 29(4).
Sexual dimorphism
Females may retain dermal granules when mature.
Colour
Overall, colour is a light grey or pale fawn fading to a whitish grey on the belly. Various speckles and melanophores are found on the back and upper flank. The dorsal, caudal and pectoral fins have dark grey speckles. The head sides from the snout to the cheek are dark with transversal suborbital papillae series whitish giving the impression of narrow light stripes below the eye and on the cheek. The peritoneum is black or densely covered in fine speckles.
Size
Reaches 11.2 cm, or 13 cm total length (Jolodar and Abdoli, 2004). Females may be larger than males (mean total length 84 mm versus 77 mm).
Distribution
Found in the southern Caspian Sea including Iranian waters (Berg, 1927; Ahnelt et al., 2000).
Zoogeography
Known only from the Caspian Sea and one of the endemic Sarmatian fauna (see Family Account).
Habitat
Found to a depth of 294 m on white silt bottoms according to Berg (1927) but the data in ZISP states 244 sazhems (= 446.5 m). Recent Iranian material is from 45-80 m, at 9.7-16.4°C at 50 m (Ahnelt et al., 2000) and Jolodar and Abdoli (2004) state it lives mainly at 50-100 m depths in the south Caspian Sea.
Age and growth
Unknown.
Food
Unknown but the duck bill may be an adaptation for feeding on silt bottoms (Ragimov, 1986).
Reproduction
Apparently mature eggs reach 1.9 mm in diameter in the Iranian specimen.
Parasites and predators
Unknown.
Economic importance
This species is too rare to be of any economic importance.
Conservation
Conservation requirements are unknown. Kiabi et al. (1999) consider this species to be data deficient in the south Caspian Sea basin according to IUCN criteria.
Further work
More specimens need to be caught to assess its distribution, numbers, variation and biology.
Sources
Type material: See above (ZISP 23134).
Iranian material: CMNFI 1999-0023, 4, 76.1-79.1 mm standard length, Gilan, Caspian Sea off Astara (38º00'N, 49º30'E to 38º20'N, 50º00'E).
© Brian W. Coad (www.briancoad.com)