Diplecogaster Fraser-Brunner 1938: 415 (type species: Cyclopterus bimaculatus Bonnaterre 1788 by original designation).
Three and one half gills; gill membranes attached to the isthmus; disc double; dorsal and anal fins normal with strong rays; disc length 3.2 – 5.2 in SL; no spine in subopercular area; 4 – 9 dorsal-fin rays; 3 – 8 anal-fin rays; 20 – 26 pectoral-fin rays; premaxillaries short; maxillaries well forward in position; head lateral-line system with two pores in the lacrymal canal.
A total of six valid species is known in this genus; a checklist of the species and an
identification key are presented below.
Within the genus Diplecogaster, two species groups can be distinguished:
– Diplecogaster-bimaculata group: characterised by a moderate number of 4 – 8 rays in the dorsal fin and 3 – 7 in the anal fin (D.- ctenocrypta group: 9 rays in the dorsal fin, 8 rays in the anal fin), and the position of the anus which is situated in the middle between disc and anal-fin origin (D.- ctenocrypta group: situated closer to the analfin origin than to the end of the disc).
Species. D. bimaculata, D. euxinica, D. megalops, D. pectoralis.
Distribution. Mediterranean Sea, Black Sea, eastern Atlantic Ocean, South Africa.
– Diplecogaster-ctenocrypta group (reviewed in the present paper): characterised by a high number of 9 rays in the dorsal fin and 8 in the anal fin (D.- bimaculata group: 4 – 8 rays in the dorsal fin, 3 – 7 rays in the anal fin), and the position of the anus which is situated closer to the anal-fin origin than to the end of the disc (D.- bimaculata group: situated in the middle between disc and anal-fin origin). The species of the group are further distinguished from the Diplecogaster bimaculata, D. euxinica and D. pectoralis in having 14 – 15 caudalfin rays (18 – 21 in D. bimaculata, D. euxinica and D. pectoralis), and lacking lateral papillae in disc region A (many lateral papillae present in D. bimaculata, D. euxinica and D. pectoralis), and from D. megalops in 13 – 16 rakers on third gill arch (7 – 9 rakers in D. megalops).
Species. D. ctenocrypta, D. tonstricula n. sp.
Distribution. Eastern Atlantic Ocean.
Diplecogaster bimaculata (Bonnaterre [ex Pennant] 1788)
Cyclopterus bimaculatus Bonnaterre [ex Pennant] 1788: 29, pl, 86, figure 355 (seas of England; no types known)
Lepadogaster ocellatus Risso 1810: 74 (Villefranche-sur-Mer, France; no types known). Lepadogaster reticulatus Risso 1810: 77 (Nice, France; no types known).
Lepadogaster mirbeli Risso 1820: 249 (Nice, France; no types known).
Lepadogaster desfontanii Risso 1827: 275, pl. 14, figure 39 (Nice, France; syntypes: MZUF 584-0093, 10 specimens).
Lepadogaster latirostris Costa 1840: Lepadogaster p. 4 (Naples, Italy; no types known). Lepadogaster urifasciatus Costa 1840: Lepadogaster p. 9 (Gulf of Salerno, Italy; no types known).
Lepadogaster norvegicus Düben 1845: 112 (Norway; no types known).
Lepadogaster listellus Nardo [ex Chiereghini] 1847: col. 113 (Italy; no types known).
Lepadogaster raninus Nardo [ex Chiereghini] 1847: col. 113 (Italy; no types known).
Lepidogaster couchii Saville-Kent 1883: 55 – 56 (Devonshire and Cornwall, UK; no types known).
Distribution: Mediterranean Sea, north-eastern Atlantic: Norway and Faroes south to Gibraltar.
Diplecogaster ctenocrypta Briggs 1955: 32, figure 85 (Gran Canaria, Canary Islands; holotype: ZMUC P9037).
Distribution: Canary Islands.
Diplecogaster bimaculata euxinica Murgoci 1964: 229, figure 1 (Romania, Black Sea; holotype: MGAB 55).
Distribution. Black Sea.
Diplecogaster megalops Briggs 1955: 31, figure 84 (off Durban, KwaZulu-Natal, South Africa; holotype: ZMUC P9031).
Distribution: South Africa.
Diplecogaster bimaculata pectoralis Briggs 1955: 30, figure 83 (Gran Canaria, Canary Islands; holotype: ZMUC P9034).
Distribution: Canary Islands, Madeira, Azores, Cape Verde Islands.
Distribution: Canary Islands, Senegal.
Key to the species of the genus Diplecogaster
1. Dorsal-fin rays 4 – 8; anal-fin rays 3 – 7............................................................................................. 2
- Dorsal-fin rays 9; anal-fin rays 8......................................................................................................... 5
2. Eye large, eye diameter 0.5 – 0.6 in bony interorbital, 2.3 – 3.6 (mean 3.25) in head length; no ocelli on sides of body; South Africa............................ Diplecogaster megalops - Eye relatively small, eye diameter 0.7 – 1.2 in bony interorbital, 3.2 – 4.9 (mean 4.2) in head length; at least one ocellus on side of body below pectoral fin; eastern Atlantic, Mediterranean Sea and Black Sea................................................................................................................. 3
3. Snout length 3.7 – 7.7 in head length; upper attachment of axial, dermal flap opposite pectoral-fin rays 10 – 19 (mean 18); principal caudal rays 12 – 14.................................................................................................................... Diplecogaster euxinica - Snout length 3.3 – 3.8 in head length; upper attachment of axial, dermal flap opposite pectoral-fin rays 10 – 13 (mean 12); principal caudal rays 9 – 12............................................... 4
4. Pectoral-fin rays 21 – 24; caudal – peduncle depth 1.2 – 1.5 (mean 1.3); eye diameter 3.7 – 4.9 (mean 4.1) in head length............................................................................ Diplecogaster bimaculata - Pectoral-fin rays 25 – 26; caudal – peduncle depth 1.0 – 1.2 (mean 1.1); eye diameter 3.2 – 3.9 (mean 3.6) in head length................................................................................ Diplecogaster pectoralis 5. Pelvic disc with lateral papillae in region A; disc region B with 5 rows of papillae; mandibular canal with 1 pore; principal caudal-fin rays 16; interorbital distance 5.4 in head length; distance between disc and anus 19% of SL........................ Diplecogaster ctenocrypta - Pelvic disc without lateral papillae in region A; disc region B with 2 rows of weak papillae; mandibular pores missing; principal caudal-fin rays 14 – 15; interorbital distance 4.1 – 4.6 in head length; distance between disc and anus 14 – 17% of SL................................................................................................... Diplecogaster tonstricula n. sp.