Pilumnus minutus (De Haan, 1835)

Manikandan, K, Megalaa, N, Valliappan, Subramanian, Nandini, K, Rani, Lourdu V, Dakshinamurthi, Senthil & Nagappan, Nagappan, 2022, Crabs (Crustacea, Decapoda) from the Seas of East and Southeast Asia Collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 3. Sahul Shelf, Bulletin of the National Museum of Nature and Science. Series A, Zoology 48 (2), pp. 35-83 : 72-74

Pilumnus minutus (De Haan, 1835)

( Fig. 18D )

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 29, 3 $$ ( CB 7.0 mm excluding lateral spines×CL 5.1 mm – 11.7× 7.6 mm), NSMT-Cr 30755. — Sta. 32, 1Ə ( CB 8.9 mm excluding lateral spines×CL 6.1 mm), NSMT-Cr 30756; 1 Ə (8.2× 6.6 mm), 1$ (7.7× 6.2 mm), NSMT-Cr 30757; 1 $ (7.8× 6.2 mm) with a Sacculina , 1$(6.5× 4.8 mm) with 3 Sacculina , NSMT-Cr 30758.

Remarks. Pilumnus hirsutus Stimpson, 1858 , has been considered to be synonymous with P. minutus (De Haan, 1835) first by Parisi (1916), and then followed by Sakai (1939, 1965, 1976) and Takeda and Miyake (1968). The original description of P. hirsutus was translated from Latin to English, with an illustration and some additional information ( Stimpson, 1907), and as rightly mentioned, the original description of P. minutus is short, and the figure is too small and poor for subsequent definite identification. However, Stimpson`s description and figure of P. hirsutus (1858, 1907) based on the specimens from the northern China Sea (=East China Sea), Ousima (=Amami-Oshima Island), and the Bonin Islands (=Ogasawara Islands) also lacks the sufficient detail for the accurate identification. According to Takeda and Miyake (1968), P. minutus is the most abundant species of Pilumnus in Japanese shallow waters, and therefore, it is reasonably considered that P. minutus and P. hirsutus reported from Japanese waters represent the same species, and some differences in carapace dorsal granulation and setation, and the ambulatory armature with spines, spinules or sharp granules between both species are not specific and may be referred to individual variation.

There are many records of P. hirsutus from the wide area in the Indo-West Pacific before the 1960s. Dai and Yang (1991: fig. 178, pl. 49-5) recorded P. minutus , without mention of P. hirsutus, and the photograph is not always clear, but the G1 is close to the figures given by Takeda and Miyake (1968: fig. 9d, as P. minutus ) and Chopra and Das (1937: fig. 11, as P. hirsutus ) in having the brush-like setae near the distal part, which is not seen in the other species of Pilumnus.

Distribution. Widely distributed in the Indo-West Pacific from Japan to Australia and to South Africa, down to about 200 m depth, but usually 30 to 50 m depth (cf. Takeda and Miyake, 1968).

Figures

Fig. 18.ɹA–B: Pilumnus rotundus Borradaile, $ (NSMT-Cr 30760; CB 10.6×CL 7.5 mm) from sta. 29. C: Pilumnus semilanatus Miers, $ (NSMT-Cr 30761; CB 14.7×CL 11.1mm) from sta. 29. D: Pilumnus minutus (De Haan), Ə (NSMT-Cr 30755; CB 8.9×CL 6.1mm) from sta. 29. E–F: Pilumnus longicornis Hilgendorf, Ə (NSMT-Cr 30754; CB 11.2×CL 8.6mm) from sta. 29.