Paracallisoma coecum (Holmes, 1908)

Kilgallen, Niamh M. & Lowry, James K., 2015, A review of the scopelocheirid amphipods (Crustacea, Amphipoda, Lysianassoidea), with the description of new taxa from Australian waters, Zoosystematics and Evolution 91 (1), pp. 1-43 : 14-15

Paracallisoma coecum (Holmes, 1908) Figure 24

Scopelocheirus coecus Holmes, 1908: 500, figs 10-12. - Shoemaker 1945: 186 (in part, part ? Paracallisoma platepistomum ). - J.L Barnard 1954: 54, figs 4, 5. - Gurjanova 1951: 241 (key).

Paracallisoma coecum . - Hurley 1963: 61, fig. 18. - Barnard and Karaman 1991: 511. - Thurston 2001: 685 (table 2).

Paracallisoma coecus . - J.L. Barnard 1958: 97 (list). - J.L. Barnard 1964: 319, fig. 3. - Brusca 1967: 384, 385, table 4. - Childress and Nygaard 1974: 228, table 1. - Childress 1975: 788 (table 1a). - Quetin et al. 1980: table 1. - Smith and Baldwin 1982: 292 (table 3). - Austin 1985: 601. - Vermeer and Devito 1988: 65, 67, table 2. - Ikeda 2013: 342 (table 1).

Paracallisoma alberti . - Birstein and Vinogradov 1955: 223, 279 (in part). - Birstein and Vinogradov 1958: 228. - Birstein and Vinogradov 1960: 176, fig. 5, 233, fig. 33. - Gurjanova 1962: 309, fig. 102. - Nagata 1963: 1. - Birstein and Vinogradov 1970: table 1, table 3. - Hatch 1983: 194, 195, table 3. - Nysewander 1983: 328, table 7. - Hatch 2013: 275.

Type material.

Holotype, female, 20 mm, USNM 38538.

Type locality.

Off San Clemente Island, California, United States, 1196-1287 m depth.

Depth range.

549-4023 m ( Shoemaker 1945, Barnard 1964). Some depth records (e.g. 0-9000 m, Birstein and Vinogradov (1958)) are excluded from this range as exact depth of capture is unknown due to the sampling technique.

Distribution.

Pacific Ocean: off San Clemente Island, California, United States ( Holmes 1908); Pacific City, Oregon, United States (from the stomach of a duck) ( Shoemaker 1945); San Nicolas Basin and off Santa Barbara Island, California, United States ( Barnard 1954); outer Santa Barbara Passage, California, United States ( Hurley 1963); off Kamchatka, Russia ( Shoemaker 1945, Gurjanova 1962); Gulf of Alaska ( Barnard 1964); Kuril-Kamchatka Trench ( Birstein and Vinogradov 1958); near the Tenji Seamount, south-south-west of the Aleutian Trench ( Birstein and Vinogradov 1958); near the Makarov Seamount ( Birstein and Vinogradov 1960); Japan Trench ( Nagata 1963).

Discussion.

Schellenberg (1926) first considered Paracallisoma coecum to be a junior subjective synonym of Paracallisoma alberti , a move that was accepted by many subsequent authors. However, Barnard (1964), and many more recent works (e.g. Thurston 1990, Barnard and Karaman 1991, Thurston et al. 2001) have again treated Paracallisoma coecum as a valid species, a decision with which we agree. Paracallisoma coecum can be differentiated from Paracallisoma alberti by following characters: gnathopod 1 coxa much longer than wide, margins slightly tapering distally (coxa slightly longer than wide, margins subparallel in Paracallisoma alberti ); gnathopod 1 propodus margins tapering distally (gnathopod 1 propodus margins subparallel in Paracallisoma alberti ); gnathopod 2 propodus subovate, palm transverse to slightly acute, dactylus fitting palm (gnathopod 2 propodus diverging distally, palm acute, dactylus shorter than palm in Paracallisoma alberti ).

Due to its taxonomic history, many records of Paracallisoma coecum have erroneously been attributed to Paracallisoma alberti . Pacific Ocean material reported as Paracallisoma alberti has now been confirmed as or is presumed to be Paracallisoma coecum ( Thurston 1990). According to Thurston (1990), the record of Shoemaker (1945) of Paracallisoma coecum (as Scopelocheirus coecus ) from Bermuda is referable to Paracallisoma platepistomum Andres, 1977. Indian Ocean material recorded as Paracallisoma alberti is unconfirmed.