Lestrigonus bengalensis Giles 1888

Lestrigonus bengalensis Giles

Lestrigonus bengalensis Giles, 1887:224–227, plates 6–7.

Hyperia bengalensis (Giles).–Bovallius, 1889:199–201, fig. [copied from Giles].–Walker, 1904:235; 1909:51.–Nayar, 1959:46–47, plate 16: figs. 1–5.

Hyperia dysschistus Stebbing, 1888:1388–1391, plate 167.–Bovallius. 1889:204–206, plate 11: figs. 1–2.–Spandl, 1924a:23; 1924b:265.

Hyperia thoracica Bovallius, 1889:233–236, plate 11: figs. 37–41.–Vosseler, 1901:73–74, plate 6: figs. 1–4.–Stephensen, 1924:91.–Lewis and Fish, 1969:9.

Hyperia gilesi Bovallius, 1889:236–239.

Hyperia atlantica Vosseler, 1901:67–70, plate 6: figs. 5–15.–Yang, 1960:28–33, figs. 6–7.–Dick, 1970:55.

Hyperia latissima Bovallius.–Barnard, 1930:410–411 [misidentification].

Hyperia hydrocephala Vosseler.–Dakin and Colefax, 1940:121, fig. 206 [misidentification].

DERIVATION OF NAME.–Not given, presumably geographical (Bay of Bengal).

TYPE-LOCALITY.–“About 100 miles from land in the Bay of Bengal, the depth of the water in the locality being 850 fathoms.”

DIAGNOSIS.–Length of ♀ 2–2.5 mm, of ♂ 2.8–3.4 mm. Head of ♀ about twice, of ♂ about 1.6 times as high as long. Pereonites 1–5 fused in ♀, 1–4 fused in ♂. Gland cone of ♀ produced anteroventrally, overlapping and extending anterior to epistome; apex bluntly rounded; posterior margin subparallel to body axis. Gland cone of ♂ produced ventrally as rounded lobe, extending only slightly anterior to epistome. Md incisor with 8 teeth; lacinia with 7 teeth. Mx1 inner lobe with 3 long terminal spines and 1 shorter subterminal spine. Mx2 outer lobe with 1 subterminal and 2 slender terminal spines; inner lobe with 1 shorter terminal spine. S2 of P1 with strong bulge on anterior margin; s4 with 2 posterodistal spines; s5 with 1–2 spines on posterior margin and 3 on carpal process; s6 with single spine near posterior margin. S2 of P2 quite broad for a Lestrigonus; carpal process slightly less than half as long as s6, with 7 marginal spines. P3–4, posterior margins of s5–6 with comb of spinules; s4–5 with posterodistal spine. P5–7 with moderately broad s2 armed with 2–4 spines on anterior margin; s5–6 with comb of spinules on anterior margin; s7 of P5 7/8 as long as s7 of P6–7, armed with a few anteroproximal spinules; s7 of P6–7 sometimes with 1–2 anteroproximal spinules; s6 of P6–7 with spine on distal margin overlapping s7 medially. Telson of ♀ slightly more than ½, in ♂ about 3/8 as long as Up3 protopod.

VARIATION.–It is entirely possible that more than 1 species of Lestrigonus agrees with the above diagnosis. There is a noticeable variation in some characters in different populations included here under L. bengalensis, and illustrations are provided to show some of the variation in the armature of the distal segments of P5–7. Until sufficient collections for an adequate study of variations are available, I am including all Lestrigonus with 5 pereonites fused in the ♀ and 4 in the ♂ under L. bengalensis, realizing that this may be a gross oversimplification. There is some indication from available collections that L. bengalensis inhabits coastal waters, which would lead to populations becoming isolated and tending to differentiate from one another.

Stebbing’s (1888) drawing of an immature male H. dysschistus in lateral view (plate 167) shows a complete suture between pereonites 1 and 2 and fusion of pereonites 2–5. This suture is not mentioned in Stebbing’s description, which states that pereonites 1–5 are fused. I have examined the holotype of H. dysschistus and can confirm the complete fusion of pereonites 1–5. Nevertheless, Bovallius (1889) considered a free pereonite 1 to be the outstanding diagnostic character of H. dysschistus and stated that he had examined specimens which exhibited this peculiar segmentation. Spandl (1924a, 1924b) also claimed to have identified similar specimens of H. dysschistus.

Among the hundreds of specimens of Lestrigonus that I have examined, I have never found one with pereonite 1 free and succeeding pereonites fused, and I am convinced that such a condition does not exist in this genus. I suggest that Stebbing, Bovallius, and Spandl all mistook muscle bands or some other structure beneath the integument for a suture. Such a mistake can be expected in the study of small hyperiids, where sutures and other markings on the rather delicate and semitransparent cuticle are often less apparent than subcuticular structures. Such internal structures have frequently been mistaken for sutures between the coxae and their pereonites. In his lateral view of Hyperia dysschistus Stebbing shows free coxae, as he also does for Hyperia schizogeneios on plate 168. Bovallius (1889) shows distinct coxae on Hyperia fabrei, H. promontorii, H. crucipes, H. latissima, and H. thoracica, none of which have them. Other carcinologists who have portrayed species of Lestrigonus with what appear to be sutures between the coxae and their pereonites are Chevreux, Hurley, Irie, and Stephensen.

Giles (1887) described Lestrigonus bengalensis as having 7 free pereonites, but remarked on “the junction between the pleura and the coxal plates being hard to make out, as are also the junctions of the terga of the first 5 thoracic segments.” In his illustrations the adult male has 7 free pereonites, but an immature male is shown with pereonites 1–5 fused and a female with pereonites 1–5 fused. Bovallius (1889) placed H. bengalensis among the species with 7 free pereonites, but it seems evident that Giles portrayed correctly the condition of the female and young male; L. bengalensis has pereonites 1–5 fused in the ♀ and 1–4 in the male.

The specimens that Barnard (1930) identified as Hyperia latissima are placed here under L. bengalensis because of Barnard’s statement “The present specimens have segments 1–4 in ♂, 1–5 in ♀ coalesced.”

DISTRIBUTION.–Worldwide in tropical waters, tending to occur in coastal waters.

V. Hyperietta, new genus

DIAGNOSIS.–Small species, with body rather compressed laterally. Head rather short anteroposteriorly; eyes occupying most of its surface. Pereonites 1–2 fused in both sexes. Coxae fused with pereonites. Telson inserted distinctly anterior to insertion of Up3 peduncle; ♀ telson at least half as long as Up3 protopod. Epistome small, inconspicuous. ♀ Al 2–merous. ♀ A2 1–merous, rudimentary; gland cones rather inconspicuous, in anterior view converging medially. Md with smooth incisor and dentate lacinia; molar narrow; palp absent in ♀. Mx1 outer lobe with 3 terminal spines. Mxp outer lobes fused medially; inner lobe rudimentary. P1 simple, weakly subchelate, or barely chelate. P2 chelate, with spoon-shaped carpal process bearing marginal spines. ♀ P3–4 with 1 conspicuous spine on posterior margin of s4, 2 spines on posterior margin of s5; ♂ P3–4 with shorter spines in same positions. Distal margin of s6 of P6–7 and sometimes of P5 produced into spinose lobe medial to base of s7; s7 unarmed. Up 1–3 slender; margins of rami smooth or with extremely fine serrations.

DERIVATION OF NAME.–Diminutive of Hyperia, gender feminine.

TYPE-SPECIES.–By present designation, Hyperia luzoni Stebbing.