Lestrigonus schizogeneios (Stebbing 1888)

Lestrigonus schizogeneios (Stebbing)

Hyperia schizogeneios Stebbing, 1888:1391–1394, pl. 168.–Bovallius, 1889:221–224.–Chevreux, 1892:233–237, figs. 1–3; 1900:139–143, pl. 17: fig. 1a–m; 1935:188–189.–Vosseler, 1901:66–67.–Lo Bianco, 1902:446 [identification by Vosseler]; 1903: table facing p. 278 [identification by Vosseler].–Stewart, 1913:255–256.–Stephensen, 1924:86–90, Chart 13.–Spandl, 1924b:265.–Chevreux & Fage, 1925:402–404, fig. 402.–Pirlot, 1929:120–122; 1930:16–18.–Candeias, 1934:4.–Irie, 1948:36 [in table]; 1957a:351, fig. 12; 1957b:passim; 1958:107 [in table]; 1959:passim.–Alvarado, 1955:219.–Hure, 1955:47–48, fig. 57a-b; 1961:33.–Bulycheva, 1955:1048 [in list].–Trégouboff & Rose, 1957:456, pl. 132.–Yang, 1960:15–19, figs. 1–3.–Laval, 1965:6197–6198; 1968:passim; 1972:passim.–Vives, 1966:96, table 19; 1968:460, table 1.–Dick, 1971:56–57.–Hure, Scotto di Carlo, & Basile, 1971: passim.–Yoo, 1971:56, fig. 14.

Hyperia promontorii Stebbing, 1888:1385–1387, pl. 166B; 1910:475–476.–Bovallius, 1889:214–218, pl. 11: figs. 3–13.–Vosseler, 1901:64.–Lo Bianco, 1901:446 [identification by Vosseler]; 1903:table facing p. 278 [identification by Vosseler].–Barnard, 1930:411; 1937:183–184.–Dakin & Colefax, 1940:121, fig. 207.–Siegfried, 1963:8.

Hyperia bengalensis (Giles).–Pirlot, 1939:35–36.–Hurley, 1955:137–140, figs. 70–82; 1956:14–15; 1960b:279; 1969:19.–Reid, 1955:17, fig. 4.–Kane, 1962:299–300.–Vinogradov, 1962:24–25.–Brusca, 1967a:388; 1967b:452.

Hyperia zebui Stebbing, 1888:1394.

DERIVATION OF NAME.–From the Greek =I cleave] + [=a chin], referring to the emarginate lower border of the head.

TYPE-LOCALITY.–Off St. Vincent, Cape Verde Is., 16°49′N, 25°14′W.

DIAGNOSIS.–Length of ♀ 2.2–3.5 mm, of ♂ 3.5–4.5 mm. Head about twice as high as long, about half as long as pereon. Pereonites 1–3 fused in ♀, 1–2 in ♂. Gland cone in ♀ conspicuous, rather sharply pointed, extending beyond buccal mass; in ♂ blunter, not quite or barely reaching ventral border of buccal mass. Md incisor with 8 teeth; lacinia with 6–8 teeth. Mx1 inner lobe with 3 long and 2 short terminal spines, 1 subterminal spine. Mx2 outer lobe with 1 subterminal and 2 terminal spines; inner lobe with a shorter terminal spine. Mxp outer lobes conical, about 3 times as long as wide, with 3–4 spines along inner margin. S2 of PI with moderately convex anterior margin; s4 with 2–3 (rarely 4) posterodistal spines; carpal process with 5–6 spines; s6 with 2 (Atlantic specimens) or 3 (Pacific specimens) spines near anterior margin. P2 with carpal process about half as long as s6; s6 with 1–2 spines on anterior margin. P3–4, posterior margin of s5–6 with comb of spinules; s5 also with 2 spines on posterior margin. P5–7 with moderately broad s2 armed with a few spines on anterior margin; anterior margins of s5–6 with comb of spinules; s7 of P5 with a few anteroproximal spinules, s6 of P6–7 with spine on distal margin overlapping base of s7 medially. Telson triangular, in ♀ about half, in ♂ about 2/5 as long as protopod of Up3.

VARIATION.–Specimens from the Atlantic and Pacific are very similar, but have slight differences. I have not studied these differences in detail, but I have examined the armature of the anterior margin of s6 of P1, which was the most obvious difference to me, in my specimens from both oceans. Most of the adult Atlantic specimens had 2 spines on this segment, but occasionally there were 3. One female had 3 spines on the right and 2 on the left P1. Pacific specimens (from CalCOFI collections) usually had 2–3 spines in the adult female (stage 7 of Laval, 1968) and 3–4 in the adult male. The number of spines is less in younger individuals. Stage 5 and younger females have only 1 spine; in stage 6 there are 1–2 spines. Other groups of spines vary in the same way; the older the specimen the more spines in a group.

The number of fused pereonites also varies with maturity, as shown by Yang (1960) and Laval (1968). Laval found that young specimens from the marsupium, characterized by rudimentary pleopods and uropods and named by Laval “protopleon larvae” (stage 1), have all 7 pereonites free. CalCOFI specimens removed from the marsupium also have no fusion of pereonites. Laval observed that after the protopleon larvae leave the marsupium and settle on the host medusa, Phialidium sp., they molt into juveniles with pereonites 1–5 fused (stage 2). Three more instars, stages 3–5, follow in which pereonites 1–5 are fused. The female then enters the stage of prepuberty, stage 6, in which pereonites 1–4 are fused and rudimentary oostegites are present. Stage 7 is the adult, with pereonites 1–3 fused and fully developed oostegites. In the male the flagella of A1–2 remain short and unsegmented in stage 6 (pereonites 1–4 fused) and stage 7 (pereonites 1–3 fused). Stage 8 is the prepuberty stage, with pereonites 1–2 fused and the flagella of A1–2 segmented but only about as long as the pereon. The male does not become fully adult until stage 9, thus he requires 2 more molts than the female to attain maturity.

I have examined many specimens of L. schizogeneios from the CalCOFI collections and have found that the sequence of development agrees closely with that described by Laval.

It is generally agreed that Hyperia schizogeneios and H. promontorii are the female and male respectively of the same species. Both specific names have been used, but although H. promontorii has page precedence, the first revisor, Stephensen (1924), selected the name schizogeneios. Pirlot’s (1939) indiscriminate lumping of 12 nominate species under H. bengalensis has made it difficult to know the real identity of specimens reported as H. bengalensis by subsequent authors. I have, for example, examined those reported by Shoemaker from Bermuda (1945) and Cuba (1948) and found them to be Lestrigonus latissimus, hence Shoemaker’s references are not included in the synonymy given above for L. schizogeneios.

DISTRIBUTION.–Reported from warm waters around the world. In the CalCOFI area it is the second most abundant hyperiid, being exceeded only by Parathemisto pacifica. It extends farther south than the subarctic P. pacifica, but is replaced in the southernmost part of the CalCOFI area by the closely related L. shoemakeri. When its overall distribution in the Pacific becomes known it may prove to be an inhabitant of the transition zone (Brinton, 1962). Its abundance in the samples of the three 1949 CalCOFI cruises was least in March, greater in July, and highest in November, the average number per 1000 m3 for the positive stations increasing from 17 to 64 to 102.