Hymenopenaeus obliquirostris ( Bate, 1881 )

Crosnier, Alain & Dall, William, 2004, Redescription of Hymenopenaeus obliquirostris (Crustacea, Decapoda, Penaeoidea, Solenoceridae) and descriptions of two new species of Hymenopenaeus from the Indo­West Pacific, Zootaxa 600, pp. 1-26 : 3-10

Hymenopenaeus obliquirostris ( Bate, 1881) ( Figs. 3–5 , 9 A, 14A)

Haliporus obliquirostris Bate, 1881: 186 ; 1888: 286, pl. 41: fig. 2.

Hymenopenaeus obliquirostris Crosnier & Forest, 1973: 264 , fig. 87e; Burukovsky, 1974: 46 (key); 1983: 62 (key). — Crosnier, 1989: 49, figs. 2c, 4a–b. — Pérez Farfante & Kensley, 1997: 173. — Lee et al., 2001: 58, figs. 2G–K, 3K, L, 4F, pl. 1D.

Non Haliporus obliquirostris de Man, 1911: 36 (= Hymenopenaus halli Bruce, 1966 ).

Types. Kermadec Islands: Challenger, Stn 170, 29°55'S, 178°14'W, 951 m, 14.07.1874, 5 Ψ 12.7, 18.3, 19.7, 19.9, 24.2 mm (and not 24.7 mm as shown in Crosnier & Forest 1973), all in very poor condition. A sixth specimen, with a carapace measuring about 12 mm, has desiccated with time and is of limited use. These specimens are registered under NHM 1888.22

Other Material Examined. New Caledonia: BIOCAL, Stn CP 57, 23°43.26'S, 166°58.06'E, 1490–1620 m, 1.09.1985, 2 Ψ 17.7 and 31.1 mm; Stn CP 61, 24°11.68'S, 167°31.37'E, 1070 m, 2.09.1985, 1 Ψ 11.0 mm (MNHN­Na 15033); 3 Ψ 9.9–12.1 mm.

HALIPRO 2, Stn BT 42, 25°34'S, 167°22'E, 1132–1160 m, 15.11.1996, 1 juvenile %, very damaged; 1 Ψ 20.8, 1 Ψ 22.3 mm (MNHN­Na 15041); Stn BT 74, 24°47'S, 167°41'E, 1213–1246 m, 20.11.1996, 1 % 11.9 mm; Stn BT 85, 23°40'S, 168°05'E, 935–1100 m, 23.11.1996, 1 Ψ 12.7 mm; Stn BT 95, 24°00'S, 162°08'E, 1224–1233 m, 25.11.1996, 1 Ψ 20.8 mm; Stn BT 96, 23°59'S, 161°55'E, 1034–1056 m, 25.11.1996, 1 Ψ 13.4 mm; Stn BT 106, 25°27'S, 163°16'E, 1315–1357 m, 27.11.1996, 1 % 14.1 mm; 1 Ψ 30.5 mm (MNHN­ Na 15034).

West Norfolk Ridge: NORFANZ, Stn 114/011, 32°35.22'S, 167°47.67'E, 1021–1052 m, 30.05.2003, 2 % 20.1 (MNHN­Na 15042) and 20.5 mm (MNHN­Na 15035); Stn 146/ 0 12, 34°14.33'S, 161°21.18'E, 1195–1202 m, 3.06.2003, 3 Ψ 19.7–27.3 mm.

Description. Body cuticle smooth, without setae. Rostrum rather variable, more or less robust, oriented obliquely upwards, curved or straight, reaching about as far as half the second article of the antennular peduncle (rarely as far as three quarters). The upper margin usually bears 5 or 6 teeth, rarely 4 or 7, their size diminishing very slightly from the base to the extremity of the rostrum and their spacing also diminishing from the first to the penultimate; the first tooth is slightly in advance of the orbit (exceptionally level with it); the last tooth is subdistal and very close to the penultimate ( Fig. 3 b), but in specimens with five rostral teeth, the space between the last and penultimate tooth is as large or slightly larger than that between the two preceding teeth. Behind the first rostral tooth is a large space followed by two postrostral teeth; the anterior of these is larger and sometimes situated at the same level as the hepatic spine, but in most cases it is situated slightly in front of it, in which case the hepatic spine is roughly midway between the two postrostral teeth. The lower edge of the rostrum is unarmed and, except for the tip, is fringed with a row of long setae (also, short setae are present between the dorsal teeth). The rostrum bears an adrostral carina, which arises in the upper orbit and extends to the tip of the rostrum.

A postrostral carina interrupts the cervical sulcus and extends three­quarters the distance to the posterior rim of the carapace; a mid­dorsal tubercle is located near the posterior rim of the carapace. Each lateral face of the carapace bears four spines, antennal, postantennal, hepatic and branchiostegal, the last­named being the largest and based on the carapace, with tip reaching to or beyond the edge of the carapace; the postantennal spine almost as large, with the hepatic and antennal spines very small. There is no orbital spine.

The cervical sulcus is well defined and extends almost to the mid­dorsum; the hepatic sulcus, equally well defined, is extended by the branchiocardiac sulcus, which runs obliquely upwards almost to the dorsal region of the carapace, is bordered on its lower edge by a strong carina. At the junction of the hepatic and branchiocardiac sulci there is a weak carina, which makes an angle of about 45° to the branchiocardiac sulcus, then turns, following the inferior edge of the carapace, progressively weakening.

The eye is deep­black and relatively small ( Fig. 9 ; eye diameter/carapace length approx. 0.11). The basal article of the antennal peduncle bears a prosartema, its tip reaching to the level of the cornea; the stylocerite is short and ends at the same level as the prosartema. The scaphocerite has a terminal spine which barely exceeds the lamella, the ratio of whose length to maximum width is around 3.25.

The third maxillipeds are about 1.5 times the length of the carapace (measured from the posterior orbit to the posterior edge of dorsum); their last article is equal to 0.7 the length of the penultimate article.

The first three pereopods are of increasing length, their relative lengths respectively 1, 1.5 and 2 times the length of the carapace. The first is robust, the ischium with a large fixed distal spine directed antero­ventrally, but lacks a fixed spine on the merus. The second and third pereopods are much more slender and are without fixed spines. The fourth and fifth pereopods are very long and slender. The fourth is 2.8 times the length of the carapace, and its articles from the ischium to the dactyl are in the proportions, 1.0, 3.0, 3.5, 0.7, 0.23. None of the specimens examined had complete fifth pereopods, but basis­ischium­merus­carpus was 2.85 times the length of the carapace.

The distribution of gills, epipods and exopods is that usual for this genus ( Pérez Farfante & Kensley, 1997, 172).

Each of the fourth, fifth and sixth abdominal segments has a dorsal carina, the third ogive­shaped in transverse section, but with no true carina. Only the carina of the sixth segment ends in a spine, while those of the fourth and fifth are incised posteriorly to receive the following carina. The pleura of the fourth and fifth segments are rounded, without spines or denticles, while the ventral edge of the sixth bears a very small subdistal spine. The length of the sixth segment (measured between the articular condyle and the posterior lateral projection) is equal to 1.65–1.75 that of the fifth (measured between the articular condyles). The slender telson is the same length as that of the uropodal endopods and bears on each edge a long fixed spine at two­thirds its length.

The thelycal plate between the fourth pereopods (sternite XIII) is a prominent, dentiform projection, more or less trihedral, the anterior face flat and oriented vertically in relation to the body of the animal, the posterior part forming two lateral oblique faces joining posteriorly and enclosing a more or less definite crest. (fig. 4). Behind this projection there is a shallow cup­shaped depression on the sternite, which is partly divided by a weak longitudinal ridge; the posterior part of the sternite forms a vertical wall formed into two weakly developed lobes separated by a small median depression ( Fig. 4 c). The sternite of the fifth pereopods (sternite XIV) resembles a swollen escutcheon which occupies the length of the sternite and with a well­defined median longitudinal ridge, which terminates in an obtuse tooth abutting or almost abutting the posterior part of the preceding sternite ( Fig. 4 a, b); The posterior part of sternite XIV forms a wall similar to that of sternite XIII, but with the median depression better defined; the extremities of this wall extend rearwards along the sides of a trapezoidal space about 1.5 times as wide as long.

The shape of the dentiform projection between the fourth pereopods varies with the size of the specimen ( Fig. 4 d–g). It begins as a small projection arising from the bulging sternite, then the anterior part projects further to form the adult tooth, which becomes rounded with age.

The extremity of the median lobe of the petasma ( Fig. 5 ) is divided by a narrow Vshaped space into two elongated lobules with pointed tips, strongly inclined towards the exterior. The inner and external edges of the anterior lobule are nearly straight, while those of the posterior lobule are curved. A little below the distal lobules, on the external edge, is an inferior lobule, also strongly curved towards the exterior and much wider than long (ratio W/L about 1.6), with strongly rounded lateral edges, the distal edge weakly rounded. The lateral lobe has a spoon­shaped distal lobule which reaches the base of the distal lobules of the median lobe. This lobule is attached by a strong peduncle and partially curves the internal face of the inferior lobule of the median lobe, described above. On the external face of the lateral lobe, at the base of the peduncle of the ovoid lobule, there is a diverticulum in the form of a long point with rounded extremity which goes round the base of the inferior lobule of the median lobe. The cincinnular part of the median lobe is short and approximately one fifth the total length of the petasma.

Coloration. Fig. 14a is from a colour transparency taken at the time of capture. The body is generally red­orange, sometimes paler, the rostrum translucent, the thoracic appendages with whitish bands and the uropods becoming brown distally. Lee et al. (2001: pl. 1D) published a colour photograph of this species which corresponds closely with ours. T.­ Y. Chan (pers. com.) considers that the differences in coloration to be sex related, with the males having a deep­red colour and the females being pink to somewhat yellowish.

Size. The largest female observed had a carapace measuring 31.1 mm, corresponding to a total length of 113 mm.

Remarks. Bate (1881) had only female specimens at his disposal for the description of the species (he did not give the exact number). Six of these females, in poor state, are currently in the collection of The Natural History Museum, London. We have no doubt that our material is conspecific with the type material.

The entire female illustrated by Bate appears to be lost. Bate's (1888) figure shows a rostrum slightly curved upwards, similar to that shown here ( Fig. 3 a). All existing female syntypes have an obliquely ascending but straight rostrum (as is usually the case for the females we have collected), which is fairly elongate ( Fig. 3 b). The form of the rostrum of H. obliquirostris females appears to be quite variable, but similar variability has been noted in other Hymenopenaeus (cf. Crosnier 1989: 45, figs. 1a–d).

With the exception of H. fallax n. sp., described and compared with H. obliquirostris under the account of the former, H. obliquirostris is closest to H. halli ( Bruce, 1966) . It is distinguished by the following:

﹤ The smaller eyes. ( Fig. 9 )

﹤ The presence of a well defined postrostral carina extending for three­quarters the distance between the cervical sulcus and the posterior edge of the carapace (absent in H. halli or barely defined, mostly in large females).

﹤ The presence of a very large branchiostegal spine, whose tip often exceeds the edge of the branchiostegite (while it never attains the edge in H. halli ).

﹤ The absence of a strong, fixed spine on the ventral border of the merus of the first pereopods.

﹤ On abdominal segments 2 and 3, the portion that is overlapped by the preceding segment, is separated from the visible portion by a transverse sulcus, better defined in the dorsal part (an exception was, however, observed in a specimen of H. halli from Taiwan, which had a sulcus like that of H. obliquirostris ).

﹤ The rostral teeth are fewer (usually 5 or 6, whereas H. halli usually has 6 or 7). ﹤ In the female, the dentiform thelycal plate between the bases of the fourth pereopods is massive and extends transversely (instead of being narrower and extending longitudinally). In H. halli this tooth can sometimes be conical with a slightly incurved tip, but it never extends transversely.

﹤ In the female, the median carina on sternite XIV is relatively longer in H. obliquiros ­ tris and abuts, or nearly abuts, the posterior edge of sternite XIII, whereas in H. halli this carina is usually much shorter and does not reach sternite XIII (cf. Crosnier 1989: figs. 4a, d). (These features are not always absolute and in some H. halli the carina may abut the posterior edge of sternite XIII.)

﹤ For the females it is not certain that the relative proportions of the trapezoidal space of the posterior of sternite XIV are valid for distinguishing the two species. We have observed important variations in this respect in H. halli from Polynesia which closely approach those of H. obliquirostris .

﹤ For the male, the inclination towards the exterior of the distal lobules of the median lobe approaches 90°, whereas in H. halli the lobules are inclined at about 45°. ﹤ The colour in life appears to be different. From colour photographs of H. obliquirostris (the present publication and Lee et al. 2001) seems to be mainly red­orange. Conversely, H. halli , from our memory, has a duller coloration, often yellowish, but from various photos, the coloration seems to be variable (see below in the section devoted to this species).

De Man (1911: 36) identified a female caught near the Kei Islands, Indonesia (5°53.8'S, 132°18.8'E, 560 m) as H. obliquirostris . Crosnier (1978: 123) indicated that this was an error in identification and that this specimen is H. halli .

Eldredge et al. (1998) mentioned the presence of H. obliquirostris in the Hawaiian Islands, citing Pérez Farfante & Kensley (1997: 173). At present, we have been unable to confirm the source of the latter authors’ information. Crosnier (1989) noted that the specimens mentioned by Rathbun (1906: 905) under the name Haliporus equalis did not belong to this species and would have to be redescribed at a future date. The identification of these specimens as H. obliquirostris by Burkenroad is probably an error, and is perhaps the source for Pérez Farfante & Kensley’s Hawaiian record.

Lee et al. (2001: 58, figs. 2G, H, 3K, L, 4F, pl. 1D) described H. obliquirostris from around Taiwan, giving figures of the rostrum, petasma and thelycum and a colour photograph. This occurrence is much further north of locations known up to this time. (These authors erroneously stated that this species had been recorded in Hawaii by Bate (1888)). Lee et al. (2001) gave the depths of four captures from around Taiwan, 471–480, 626– 632, 948–1020, 978– 1008 m. While the two latter depths correspond with that of the type (951 m) and the samples of the present study (935–1100 m, 1490–1620 m), the two former depths are much shallower than expected. Figure 3 L in Lee et al. (2001) from a specimen collected at 625–632 m appears to be from H. obliquirostris , but we are not convinced that the same applies to the specimen from 471–480 m, which we believe is too shallow for this species. Unfortunately, it was not possible to reexamine the material studied by Lee et al. (2001) to confirm the identifications.

Distribution. Described off the Kermadec Islands (29°55'S, 178°14'W) at 951 m depth by Bate (1888), this species had not been recorded again until 2001 when Lee et al. recorded it off Taiwan at reliable depths between 632 and 978 m (see above). Now it is reliably recorded in the environs of New Caledonia at depths between 1034 and 1490 m and on the West Norfolk Ridge between 969 and 1345 m.

Figures

FIGURE 3. Hymenopenaeus obliquirostris (Bate, 1881), a, Ψ 30.5 mm, New Caledonia, HALIPRO 2, Stn BT 106, 1315 – 1357 m (MNHN­Na 15034), anterior region of the body, lateral view; b, Ψ syntype, 19.9 mm, Kermadec Islands, Challenger, Stn 170, 951 m (NHM 1888.22), rostrum and dorsal edge of the carapace. Scale, a, b, 1 cm.

FIGURE 4. Hymenopenaeus obliquirostris (Bate, 1881), a – b, Ψ syntype, 24.2 mm, Kermadec Islands, Challenger, Stn 170, 951 m (NHM 1888.22), a, thelycum, ventral view (after Crosnier, 1989), b, longitudinal median section of sternites XIII and XIV (after Crosnier, 1989, modified); c, Ψ 22.3 mm, New Caledonia, HALIPRO 2, Stn BT 42, 1132 – 1160 m, posterior view of sternite XIII (MNHN­Na 15041); d – g, development of the median tooth of sternite XIII with four females of increasing size (top part, side view and rear view), d, Ψ 11.0 mm, New Caledonia, BIOCAL, Stn CP 61, 1070 m (MNHN­Na 15033), e, Ψ syntype 18.3 mm, Kermadec Islands, Challenger, Stn 170, 951 m (NHM 1888.22), f, Ψ syntype 19.7 mm, ibidem (NHM 1888.22), g, Ψ syntype 24.2 mm, ibidem (NHM 1888.22). Scale, a – g, 1 mm.

FIGURE 5. Hymenopenaeus obliquirostris (Bate, 1881), a – c, % 20.5 mm, West Norfolk Ridge, NORFANZ, Stn 114 / 011, 1021 – 1052 m (MNHN­Na 15035), petasma, right half, a, internal view; b, external view, c, posterior view; d – e, distal lobules of median lobe, d, % 20.5 mm, ibidem (MNHN­Na 15035), e, % 20.1 mm, ibidem (MNHN­Na 15042). Scale, a – c, 5 mm; d, c, 1 mm.

FIGURE 9. — Shape of the eye, a, Hymenopenaeus obliquirostris (Bate, 1881), Ψ 23.9 mm, syntype, Kermadec Islands (NHM 1888.22); b, Hymenopenaeus halli Bruce, 1966, Ψ 23.5 mm, CIDARIS, northeast coast of Australia, Stn 45 ­ 3, 17 ° 33,12 ' S, 146 ° 55,92 ' E, 908 – 926 m (MNHN­Na 15043); c, Hymenopenaeus halli Bruce, 1966, Ψ 22.1 mm, Madagascar, northwest coast, VAUBAN, Stn CH 85, 12 ° 39,4 ' S, 48 ° 12,8 ' E, 550 m (MNHN­Na 7370). All figures are to the same scale.

FIGURE 14. — a, Hymenopenaeus obliquirostris (Bate, 1881), New Caledonia, HALIPRO 2, Stn BT 106, 1315 – 1357 m, Ψ 30.5 mm (tip of telson broken) (MNHN­Na 15034). Photo P. Hamel (IRD, Nouméa); b – c, Hymenopenaeus methalli n. sp., Chesterfield Islands, MUSORSTOM 5, Stn DW 313, 780 – 930 m, Ψ 19.0 mm (MNHN­Na 15067). Photos P. Laboute (IRD, Nouméa).