Hepatus chiliensis

Hepatus chiliensis is a crab of the family Aethridae, whose name is listed as accepted in WoRMS ^[1]. The IMARPE catalogue lists the common name cangrejo de arena for it ^[2]. It lives in the infralittoral zone, on sand and stone bottoms with abundant algae, mostly between 2 and 42 m deep, and ranges from Ecuador to Valparaíso, in Chile ^[2]. Its type locality is Valparaíso, in Chile ^[3].

Henri Milne Edwards described it in 1837 in his Histoire naturelle des Crustacés; according to Rathbun, the type locality is Valparaíso and the type specimen is kept in the Paris museum ^[3].

The epithet has been written in two ways: the original form is Hepatus chiliensis, and Milne Edwards and Lucas wrote Hepatus chilensis in 1843 ^[3]; both spellings are still in use, for example in the IMARPE report on Callao in 2014 ^[4]. In 1857 Kinahan applied the name Hepatus angustata to this species, a name Fabricius had given in 1798 to a different species ^[3].

In Rathbun's diagnosis, the front is truncate and barely extends beyond the line of the suborbital cavities; the posterior and posterolateral margins bear elongate tubercles and have no teeth; and the sixth segment of the male abdomen has a median terminal tubercle ^[3]. The back shows 8 lines of tubercles, those on the branchial and cardiac regions being arched; the upper edge of the palm has 4 low, blunt-tipped tooth-like projections, and the dactyli of the walking legs carry a strip of fur above and below ^[3].

Rathbun described it in 1910 as a crab of good size, with a broad oval carapace with crenulate margins, stout chelipeds that fold against the body and compressed legs without spines; the width he gave was 70 to 85 mm ^[5]. A male measured by Rathbun had a carapace length of 56.5 mm and a width of 84 mm ^[3]. The 4 specimens from Ancón that Moscoso examined measured between 45.0 and 55.1 mm in carapace length ^[2].

Colour varies by author: Dana described a yellowish or ochre base covered with a fine brownish-purple network, and Miers a nearly uniform pink with light yellow spots and lines, both cited by Rathbun ^[3]. In the Ancón specimens, Moscoso noted a colour between light orange and brown, with dark chocolate-brown marks ^[2].

Similar species

• Hepatus kossmanni: It is also recorded in Peru, as far as the Chincha Islands; its carapace is bright yellow with cream spots ringed by a thin scarlet-red circle, whereas Hepatus chiliensis ranges from light orange to brown with dark brown marks ^[2].

It is known from Ecuador to Valparaíso and Juan Fernández Island, in Chile ^[2]; Rathbun already gave it for Ecuador, Peru and Chile ^[5]. For Peru, the IMARPE catalogue cites Paita, Ancón Bay, Callao, San Lorenzo Island, the Chincha Islands, Paracas Bay, Independencia Bay and Mollendo ^[2].

It is an infralittoral species of sand and stone bottoms with abundant algae, mainly between 2 and 42 m deep, according to the catalogue, which relies on Méndez and colleagues (1979) and on Garth (1957) ^[2]. Rathbun recorded specimens dredged near the northeast side of San Lorenzo Island and others from Callao ^[5]. Moscoso collected 4 specimens in Ancón Bay, on 24 June 1990, on a sandy infralittoral bottom ^[2].

In 2014 IMARPE monitored 7 fixed stations every two months on the east side of San Lorenzo Island, in Callao, at depths under 20 m, using semi-autonomous diving for 10 to 15 minutes per station ^[4]. Hepatus chiliensis was counted among the crustaceans recorded, together with Cancer plebejus, Cancer porteri and Platymera gaudichaudii ^[4].

Its density showed two periods, from April to June and in December; the highest mean density was 2.14 individuals and 110.1 g per 10 minutes of diving, in April, and in August it fell to 0.15 individuals ^[4].

Published records for Peru run from Paita to Mollendo ^[2]. In the 2014 IMARPE monitoring it appeared at 6 of the 7 stations on the east side of San Lorenzo Island, at depths under 20 m, with sampling done from a shellfish-diving boat equipped with dive gear ^[4].