Lestrigonus shoemakeri Bowman 1973

Lestrigonus shoemakeri

DERIVATION OF NAME.–After the late Clarence R. Shoemaker, in recognition of his many contributions to amphipod taxonomy.

TYPES.–Holotype ♀, USNM 139096, allotype ♂, USNM 139097, CalCOFI Cruise 9, station 1106, 27°48′N, 119°14′W, west of Punta Eugenia, Baja California, 12 November 1949. 2 ♂ and 2 ♀ paratypes deposited at Scripps Institution of Oceanography.

DIAGNOSIS.–Length of ♀ 2.3–2.7 mm, of ♂ 3.5–4.0 mm. Head slightly more than twice as high as long, about ⅓ as long as pereon. Pereonites 1–4 fused in ♀, but sutures present dorsally, that between pereonites 1–2 shorter than others. Pereonites 1–2 fused in ♂; partial sutures usually absent in adult, present in immature specimens with more than 2 pereonites fused. Gland cone bluntly pointed, overlapping epistome, but not reaching ventral border of buccal mass. Md incisor with 8–9 teeth; lacinia with 7–8 teeth. Mx1 inner lobe with 3 long terminal spines and 1 shorter subterminal spine. Mx2 outer lobe with 1 subterminal and 2 terminal spines; inner lobe with shorter terminal spine. Mxp outer lobes conical, with about 5 spines along inner margin. S2 of P1 with strong bulge on anterior margin; s4 with 2–4 posterodistal spines; carpal process with 5–6 spines; s6 with single spine near anterior margin. P2 with carpal process more than half as long as s6; s6 with 1–2 spines on anterior margin. P3–4, posterior margins of s5–6 with comb of spinules; s5 with 2 spines, s4 with 1 spine on posterior margin. P5–7 with moderately broad s2 armed with a few spines on anterior margin; s5–6 with comb of spinules on anterior margin; s7 of P5 with a few anteroproximal spinules; s6 of P6–7 with spine on distal margin overlapping s7 medially. Telson of ♀ nearly 3/5, of ♂ about half as long as Up3 protopod.


VARIATION.–As in Lestrigonus schizogeneios more pereonites are fused in juveniles than in adults. The youngest free-living individuals have pereonites 1–5 fused. With increasing maturity the number of pereonites fused decreases until the adult condition is reached: pereonites 1–4 fused in the female, 1–2 fused in the male.

DISTRIBUTION.–Thus far I have identified L. shoemakeri only in samples from the warmest stations of the 4 CalCOFI cruises (Figure 34) and in a few samples in the eastern equatorial Pacific: (1) a few miles north of Clipperton Island; (2) west of Nicaragua, 12°35′N, 93°40′W; (3) west of Costa Rica, 10°03′N, 88°52′W; (4) west of Panama, 7°36′N, 85°09′W; (5) near the Galapagos Islands, 00°07′S, 86°55′W. These few records suggest that when better known the distribution of L. shoemakeri may be similar to that of Euphausia eximia and the other euphausiids that Brinton (1962) classifies as eastern Pacific equatorial species.