Twospot Cardinalfish

The species Cheilodipterus novemstriatus, commonly known as the 🌊 Indian Ocean twospot cardinalfish, is a member of the family Apogonidae, endemic to the 🌊 Indian Ocean. Since 2011, it has expanded its range to the eastern Mediterranean Sea via the Suez Canal (🇪🇬 Egypt).

Morphologically, Cheilodipterus novemstriatus exhibits a slender body characterized by a short snout and a terminal mouth fitted with canine-like teeth in both jaws, albeit lacking teeth at the symphysis of the lower jaw. This species also features large eyes. It has two dorsal fins, with the first fin originating slightly posterior to the pelvic fin's origin. The anal fin aligns with the second dorsal fin and the caudal fin is notably forked. Its body presents a predominant silver-grey coloration, accentuated by five distinctive longitudinal black stripes. The upper stripe runs near the base of the dorsal fin, the middle stripe extends from the snout across the eye to the caudal peduncle, and the lower stripe follows along the ventral surface arc, often becoming indistinct towards the anal fin's base. Among other features, the caudal peduncle exhibits a large oval black spot surrounded by a yellow background and another spot on its dorsal surface. The species reaches a maximum length of 8 cm (3.1 inches), with a more typical length range of 2–6 cm (0.79–2.36 inches).

Cheilodipterus novemstriatus is native to the western 🌊 Indian Ocean, ranging from the 🌊 Red Sea to the 🌊 Persian Gulf. Since being identified in the Mediterranean off 🇮🇱 Israel in 2011, its presence has extended to Lebanon (2012), southeastern 🇹🇷 Turkey (2014), and Cyprus (2015). It is currently established in the Levantine Sea, with its introduction likely attributed to migration from the 🌊 Red Sea through the Suez Canal (🇪🇬 Egypt).

The species thrives in shallow, sheltered aquatic environments, typically at depths of 1–10 meters (3.3–32.8 ft) amidst rocky reefs or coral featuring structural complexity such as holes and ledges. In addition, it is known to seek refuge among the spines of sea urchins (genus Diadema) with group sizes contingent on the relative dimensions of the fish and urchin. Notably, it has been observed at a shipwreck in the Mediterranean at a depth of 30 meters (98 ft) in cohabitation with the native Mediterranean cardinalfish Apogon imberbis, as well as on hard substrates encrusted with calcareous algae and near rocky crevices and overhangs. This species is also seen sharing habitat with juveniles of the native wrasse Coris julis.

Primarily nocturnal, C. novemstriatus vacates its daytime hideouts to forage in open areas. Its nocturnal lifestyle likely facilitated its successful establishment in the eastern Mediterranean, where indigenous nocturnal competition is minimal. Feeding predominantly on zooplankton, this species is frequently found at night along sandy shores in the 🌊 Red Sea at depths ranging from 0.5 to 1.5 meters. C. novemstriatus is social, forming large aggregations in both its native and newly established habitats. Like other cardinalfish species, it demonstrates pairing behavior during courtship, with males exhibiting oral brooding of eggs.