Petalidium suspiriosum Burkenroad, 1937

Petalidium suspiriosum Burkenroad, 1937

( Fig. 2 View Figure 2 )

Petalidium suspiriosum Burkenroad, 1937: 325 , figs. 8–12.— Pearcy and Forss, 1966: 1136–1140 (parsim).— Pearcy and Forss, 1969: 757 (Table 1).— Wasmer, 1974: 160, figs. 1–8.— Walters, 1976: 824.— Word and Charwat, 1976: 27–28 (textfig.).— Hanamura, 1983: 73.— Krygier and Wasmer, 1988: 71.— Hendrickx and Estrada-Navarrete, 1989: 110.— Hendrickx and Estrada-Navarrete, 1996: 75–76, figs. 47–48.— Pérez- Farfante and Kensley, 1997: 193.— Wicksten 2002: 131.— Poupin et al. 2009: 216 (table).— De Grave and Fransen, 2011: 244 (list).— Wicksten, 2012: 30 View Cited Treatment , fig. 5N–S.

Petalidium suspiniosum .— Ebeling et al., 1969: 12.

Material examined. TALUD X cruise, station 10 (27º48’30”N 112º17’12”W), Feb 10, 2007, 1 male ( CL 10.2 mm) GoogleMaps , benthic sledge operating at 1396–1422 m (ICML-EMU-8097).

Geographic distribution. Northeastern Pacific, from 51°40.9’N 138°30.3’W to 20°36’N 115°07’W; Clarion Island (type locality); SW off the Baja California Peninsula (about 13°28’N 120°07’W and 23°N 125°W) ( Hanamura, 1983); off Hawaiian Islands ( Walters, 1976); Central Gulf of California(material examined); a possible record off NE Japan ( Hanamura, 1983). An unpublished record is available in the United States National Museum catalogue ( USNM 170359). This material, identified by F. A. Chace is from off Ensenada (32°01’30”N 117°13’30”W), Mexico, collected on May 27, 1957, in a plankton net (reported depth: 1372 m). There are therefore three records for western Mexico EEZ ( Fig. 1 View Figure 1 ).

Depth distribution. According to Wicksten (2012), P. suspiriosum occurs in a wide depth range, from 150 to 1750 m. Records from off Oregon indicate a maximum population density in 200–1000 m using a multiple plankton sampler ( Pearcy and Forss, 1966; Wasmer, 1974).

Remarks. The general shape of the carapace of the specimen examined ( Fig. 2A View Figure 2 ) fits well with the illustrations provided by Burkenroad (1937: type material) and by Wasmer (1974), with the exception of the pointed tip of the rostrum observed in the type material but not in the Oregon material ( Wasmer 1974). The eye ( Fig. 2B View Figure 2 ) possesses the typical, welldeveloped tubercle at the base of the cornea and the additional, shallow projection, further proximally, as described by Burkenroad (1937) and by Wasmer (1974). The inferior antennal flagellum ( Fig. 2C View Figure 2 ) also fits well with the illustration provided by Wasmer (1974), including the number of blunt, spatulate spines (16) on the inferior margin of prolongation of third article and on the superior margin of the prolongation of the fourth article (9 instead of 10), the latter also featuring a strong, subconical (instead of rounded) distal protuberance. The petasma of the unique male available in this study ( Fig.2D View Figure 2 ) matches the illustration provided by Wasmer (1974), including the position and proportion of the branches of the lobus armatus, of the processus ventralis, and of the lobus terminalis, with their respective series of crochets. The shape and proportion of the telson-uropods ( Fig. 2E View Figure 2 ) are also similar to what was described by Burkenroad (1937) and Wasmer (1974): telson a little more than half as long as external margin of uropodal exopodite, narrowing abruptly to a small terminal spine flanked by a pair of fixed lateral spines, uropodal exopodite slender, longer that endopodite by about half its length. Lateral spines of the examined specimen, however, are reduced or wanting probably due to damage.

Considering the higher number of deep, midwater samples collected in western Mexico during the TALUD cruises, from 1989 to 2014 (see Hendrickx, 2012; Hendrickx and Hernández-Payán, 2018), it is rather surprising that only one specimen of P. suspiriosum was found during these extensive exploratory cruises. In contrast, Wasmer (1974) indicated that over 1000 specimens of this species were obtained during sampling operations in the NW Pacific between 1961 and 1974, and Hanamura (1983) reported on 105 specimens in four samples taken near seamounts off western Mexico in 1979. Were it not for the unique record within the Gulf of California included herein, P. suspiriosum would appear to be restricted to the California Current area (Oregon, California, Baja California area) and to the North Equatorial Current (seamount at 13°28’N 120°07’W). The Gulf of California material of P. suspiriosum , if part of a more abundant population, might be somehow isolated from the main distribution area of this species. Records available from off western Mexico ( Burkenroad, 1937; USNM material; this study) do not allow for precise information about depth at which the few specimens were captured.