Of the five species in the genus Acromitus, Acromitus hardenbergi is easily distinguished from its congeners by the absence of a terminal thread-like appendage on each mouth arm (see Kitamura & Omori, 2010: 109). It has been suggested that Acromitus maculosus is the only species in the genus, and the rest (including Acromitus hardenbergi) are merely varieties of it (see World Register of Marine Species, 2008b; Maaden, 1935). However, this is not universally accepted (see Kitamura & Omori, 2010: 109). Acromitus hardenbergi can be found at mouths of rivers (see Kitamura & Omori, 2010: 109) and even further inland, up to about 24 km upstream from the river mouth (Stiasny, 1934: 1). The medusae of live individuals of Acromitus hardenbergi have been reported to be white or slightly brown and lightly pink or purple (see Kitamura & Omori, 2010: 109), but not blue (as in Fig. 1). Closer examination of the medusa’s oral arms, gastric canals and sub-genital projection (to be seen from the oral side of the jellyfish) is required for a better diagnosis. The present identification should, therefore, be regarded as tentative. Another possible candidate would be Acromitus flagellatus which inhabits coastal areas, sometimes in brackish or silty waters, and is distributed from the western Indian Ocean to the central Pacific. Some individuals of Acromitus flagellatus do not have the long terminal filaments (see World Register of Marine Species, 2008a) and can be mistaken for Acromitus hardenbergi. However, the length of the oral arms of Acromitus flagellatus is approximately as long as the diameter of the bell, while the oral arm to bell diameter ratio is halved in Acromitus hardenbergi (see Stiasny, 1934: 5). In this aspect, the featured example resembles Acromitus hardenbergi.

Green iguanas are not native to Singapore. Adult and juvenile individuals, very likely abandoned pets and their progeny, have been recorded in the western and northern parts of Singapore, including Bukit Batok (Tay, 2015), Jurong (Low et al., 2016), Sungei Buloh Wetland Reserve (Chua, 2007) and Kranji Reservoir around Sungei Tengah (Ng & Lim, 2014; Khoo, 2016). This appears to be the first published record in the central part of the island, at the edge of the Central Catchment Nature Reserve.

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature