Hymenopenaeus methalli, Crosnier, Alain & Dall, William, 2004

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 : 17-24

Hymenopenaeus methalli sp. nov. ( Figs. 11–13 ; 14B, C)

Types. Chesterfield Islands: MUSORSTOM 5, Stn CC 384, 19°42.40'S, 158°50.80'E, 756–772 m, 21.10.1986, Ψ holotype 21.9 mm (MNHN­Na 15036); Stn CC 365, 19°42.82'S, 158°48.00'E, 710 m, 19.10.1986, ɗ allotype 18.9 mm (MNHN­Na 15037). The specimens listed in the section "Other Material Examined" are all paratypes.

Other material examined. Chesterfield Islands: MUSORSTOM 5, Stn DW 313, 22°24.31'S, 159°32.53'E, 780–930 m, 13.10.1986, 1 Ψ 19.0 mm (MNHN­Na 15067); Stn CP 363, 19°47.90'S, 158°44.30'E, 685–700 m, 19.10.1986, 1 juv. 9.6 mm; 3 Ψ 10.2–16.4 mm; Stn CP 364, 19°45.30'S, 158°46.50'E, 675 m, 19.10.1986, 2 Ψ 17.1 and 19.8 mm; Stn CC 365, 19°42.82'S, 158°48.00'E, 710 m, 19.10.1986, 1 ɗ 17.7 mm, plus 5 ɗ with bopyrid 14.2–19.5 mm; 4 Ψ 17.7–19.7 mm, plus 2 Ψ with bopyrid 18.2 and 20.7 mm; Stn CC 366, 19°45.40'S, 158°45.62'E, 650 m, 19.10.1986, 7 ɗ 16.7–20.5 mm (with bopyrid); 12 Ψ 15.3–21,6 mm (with bopyrid); Stn CC 384, 19°42.40'S, 158°50.80'E, 756–772 m, 21.10.1986, 3 ɗ 12.3–19.1 mm, 1 ɗ 17.7 mm (figured, MNHN­Na 15039), 1 ɗ 18.3 mm (figured, MNHN­Na 15065), 5 Ψ 12.7–20.5 mm, 1 Ψ 16.5 mm (figured, MNHN­Na 15040), 2 ɗ 18.4 and 18.8 mm (QM), 2 Ψ 19.7 and 20.6 mm (QM); Stn CP 386, 20°56.21'S, 160°51.12'E, 755–770 m, 22.10.1986, 1 juv. 9.5 mm, 1 ɗ 17.9 mm; Stn CP 387, 20°53.41'S, 160°51.12'E, 650–660 m, 22.10.1987, 2 ɗ 13.9 mm and 17.6 mm (with bopyrid); Stn CC 390, 21°00.90'S, 160°50.30'E, 745–825 m, 22.10.1986, 1 juv. 9.0 mm, 2 ɗ 14.2 and 17.9 mm; 3 Ψ 16.2–20.9 mm.

New Caledonia: BIOCAL, Stn CP 31, 23°07.26'S, 166°50.45'E, 850 m, 29.08.1985, 1 ɗ 15.1 mm; 2 Ψ 19.2 and 21.5 mm; Stn CP 52, 23°05.79'S, 167°46.54'E, 540–600 m, 31.08.1985, 1 Ψ 20.7 mm (with bopyrid).

BATHUS 1, Stn CP 709, 21°41.78'S, 166°37.88'E, 650–800 m, 19.03.1993, 4 ɗ 12.1–18.4 mm; 1 Ψ 13.2 mm.

BATHUS 2, Stn CP 765, 22°09.6'S, 166°02.8'E, 600–630 m, 17.05.1993, 2 ɗ 15.5 mm (with bopyrid) and 13.7 mm; Stn CP 766, 22°10'S, 166°01.7'E, 650–724 m, 17.05.1993, 5 ɗ 12.8–16.2 mm; Stn CP 771, 22°09.52'S, 166°01.75'E, 610–800 m, 18.05.1993, 2 ɗ 17.5 and 18.8 mm, 2 Ψ 14.0 and 15.6 mm, plus 4 Ψ 16.8–20.1 mm (with bopyrid).

BATHUS 3, Stn DW 786, 23°54'S, 169°49'E, 699–715 m, 25.11.1993, 1 ɗ 16.7 mm (photograph, MNHN­Na 15038); Stn CP 842, 23°05'S, 166°48'E, 830 m, 1.12.1993, 1 Ψ 15.5 mm.

HALIPRO 1, Stn CH 874, 23°05'S, 166°48'E, 708–830 m, 30.03.1994, 3 ɗ 14.7–15.5 mm; 5 Ψ 11,7– 18.3 mm; 1 Ψ 20.5 mm (figured, MNHN­Na 15066).

BATHUS 4, Stn CP 950, 20°31.93'S, 164°56.11'E, 705–750 m, 10.08.1994, 1 Ψ 16.1 mm.

BERYX 11, Stn CP 59, 23°19.45'S, 167°59.85'E, 750–800 m, 22.10.1992, 2 ɗ 10.9 and 16.4 mm; 1 Ψ 11.5 mm; Stn CP 60, 23°19.00'S, 168°00.37'E, 580–600 m, 22.10.1992, 1 Ψ (with bopyrid).

Loyalty Islands: MUSORSTOM 6, Stn CP 438, 20°23.00'S, 166°20.10'E, 780 m, 18.02.1989, 1 ɗ 14.0 mm; 2 Ψ 12.0 and 19.4 mm.

Vanuatu: MUSORSTOM 8, Stn CC 996, 18°52.41'S, 168°55.73'E, 764–786 m, 24.09.1994, 1 Ψ 17.7 mm.

West Norfolk Ridge: NORFANZ, Stn 043/76, 26°25.94'S, 167°10.87'E, 750–774 m, 18.05.2003, 2 ɗ 15.7 and 17.1 mm; 2 Ψ 16.2 and 20.5 mm (ex QM).

Tonga Islands: BORDAU 2, Stn CP 1625, 23°28'S, 176°22'W, 824 m, 19.06.2000, 2 Ψ 18.1 and 20.4 mm.

Description. Body cuticle smooth, without setae. Rostrum usually straight, rarely slightly downcurved, oriented upwards, varying from fairly robust to slender ( Figs. 11 a– d), with its tip reaching from the level of the base to half the second article of the antennule in the female and not exceeding the first article in the male, save with rare exceptions. The upper edge of the rostrum is armed with 5 or 6 teeth, diminishing gradually in size from the base to the tip, their spacing diminishing similarly; first tooth well in advance of the posterior rim of the orbit. Behind the first rostral tooth is a large space followed by two postrostral teeth of which the anterior is larger and situated just behind the level of the hepatic spine. 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. The posterior rostral tooth has a short extension to the cervical sulcus but does not cross it, so that there is no postrostral carina behind the cervical sulcus. A small dorsal subdistal tubercle, poorly defined, is visible near the posterior mid­dorsal edge of the carapace.

There are four spines on each lateral face of the carapace, antennal, postantennal, hepatic and branchiostegal; the latter, situated behind the anterior edge of the carapace, and the postantennal are of similar size and obviously stronger than the hepatic, which is slender, and the antennal, which is short and wide. There is no orbital spine.

The sulci of the carapace, with the exception of the cervical sulcus and part of the branchiostegal sulcus, are poorly defined.

The eye is large and, in alcohol, brown coloured. The basal article of the antennule bears a short prosartema, only very slightly exceeding the level of the base of the cornea; the stylocerite is equally short and ends at the same level as the prosartema. The scaphocerite, with a length/width ratio of 3.25, has a terminal spine which barely exceeds the tip of the blade.

The third maxillipeds are 1.7 times the length of the carapace (measured from the posterior edge of the orbit to the posterior edge of the carapace); their last segment is equal to 0.7 the length of the penultimate.

The first three pereopods are equal to about 1, 1.4 and 1.6 times the length of the carapace. The first is the strongest and has a merus with a fixed spine on the internal edge at one quarter its length from the tip, and an ischium with a long fixed spine directed anteroventrally. The following pereopods are much more slender and without fixed spines. The fourth and fifth pereopods are very long and slender. The fourth is twice as long as the carapace, its articles, from the ischium to the dactyl, in the proportions of 1, 2, 2.1, 0.6, 0.3. The fifth is 2.6 times the length of the carapace, its articles, from the ischium to the dactyl, in the proportions of 1, 2.5, 2.3, 1,7, 0.3.

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

The fourth, fifth and sixth abdominal segments are dorsally carinated; the third is without a trace of a carina or an ogive shape in transverse section. Only the carina of the sixth segment ends in a spine, whereas those of the fourth and fifth segments are incised to admit the carina of the following segment. The pleurons of the fourth and fifth segments are rounded, without a spine or denticle. The ventral edge of the pleuron of the sixth bears a very small subdistal spine. The length of the sixth segment (measured between the articulation condyle and the lateral posterior point) is equal to 1.55–1.65 times that of the fifth (measured between the articulation condyles). The telson is elongate, the same length as the internal uropods, and bears on each side a long fixed spine at two­thirds its length.

Thelycum ( Fig. 12 ), between the fourth pereopods (sternite XIII), bears a transverse projection reminiscent of the tip of a tongue directed backwards. The sternite behind this projection is excavated to form a feeble depression divided by an indistinct, weak longitudinal median ridge; the posterior part of the sternite forms a surrounding rounded ridge (roll–like) without any projection. Sternite XIV presents a prominent swelling, occupying almost all of its length between the fifth pereopods, and with a median crest which abuts the rounded posterior of the preceding sternite. The posterior part of the sternite forms two rounded ridges much more prominent than those of the preceding sternite, which are clearly interrupted in the middle by a deep depression. These ridges are extended to the rear along the sides of the sternite, leaving between them a trapezoidal space about 5 times as wide at the base as long.

The median lobe of the petasma ( Fig. 13 ) is divided at its extremity into two narrow elongate lobules, separated by a deep V­shaped space, and inclined to the exterior; the anterior lobule has a curved external edge, with the internal edge almost straight and forming a sharp tip; the posterior lobule is of a similar shape, but wider with a more curved external edge and a less acute tip. Below the distal lobules, on the external side and separated from them by a U­shaped space, is a blunt hook­shaped projection with its tip forming a third lobule much shorter and wider than the distal lobules.

The lateral lobe ends in a large blunt point, which reaches the level of one third the length of the distal lobules of the median lobe, passing behind the hook of this lobe; at the base of this hook on the internal side another point separates, much smaller, which is partly recurved to the dorsal side towards the hook of the external lobe. The part bearing the cincinnuli of the median lobe is short, not exceeding one fifth the total length of the petasma.

Coloration. The only colour photograph we have of this species ( Figs. 14 b–c) shows an animal of pink colour, with small white zones mainly on the rostrum, the postrostral spines, certain parts of the branchial area of the carapace, the posterior border of the upper area of the first four abdominal segments, the upper edge of the fifth and sixth abdominal segments, the rami of the pleopods and the distal part of the telson and uropods. It is not known how long after capture this photograph was taken.

Etymology. From the Greek meta which marks a change, joined by elision to halli , the name of the species of Hymenopenaeus described by Bruce in 1966.

Remarks. H. methalli is especially close to H. halli ( Bruce, 1966) . However, it may be distinguished easily by the parts of the genitalia:

The thelycal plate between the fourth pereopods (sternite XIII), has a transverse projection reminiscent of the tip of a tongue directed backwards ( Figs. 12 a, b) (instead of a sharp tooth, either conical or flattened lengthways, Figs. 10 a–e). Also, the posterior part of the same sternite ( Fig. 12 c) forms a smooth roll, separated by a median depression (instead of showing two strong projections separated by a median depression, Fig. 10 c).

On sternite XIV the median carina of the projection between the fifth pereopods abuts against the rounded posterior sternite preceding it, whereas in H. halli it ends well behind the posterior face of sternite XIII (however, this character is not constant and in some specimens this carina does abut the posterior of sternite XIII).

Petasma: the inferior lobule of the median lobe located under the posterior distal lobule is not ovate ( Fig. 10 ) and clearly less developed ( Fig. 13 ) compared with that of H. halli . The posterior edge of the lateral lobe is much less sinuous than that of H. halli and the distal part becomes thinner progressively and regularly to form a wide point. In contrast, that of H. halli shows a strong subdistal narrowing, expanding to a lengthened lobule at the right anterior edge. The distal lobules of the median lobe differ also in that they are less lanceolate ( Fig. 10 g).

This species is frequently parasitised by a bopyrid. The collection made at station 366 on the cruise MUSORSTOM 5 found 7 males and 12 females all parasitised.

Size. The largest female observed had a carapace measuring 21.9 mm, which corresponds with a total length of 80.4 mm. The largest male had a carapace length of 20.5 mm

Distribution. Hymenopenaeus methalli has been collected around New Caledonia, Vanuatu and the Chesterfield Islands, at reliably recorded depths between 600 and 850 m, at the Tonga Islands at 824 m depth, and on the North Norfolk Rise (26°S, 167°E) at depths between 750 and 774 m.

Figures

FIGURE 10. — Hymenopenaeus halli Bruce, 1966, a­b, Ψ 26.9 mm, Chesterfield Islands, MUSORSTOM 5, Stn 384, 756 ­ 772 m (MNHN­Na 15044), a, thelycum, ventral view, b, longitudinal median section of sternites XIII and XIV; c, Ψ 26.4 mm, Vanuatu, MUSORSTOM 8, Stn CP 993, 780 ­ 783 m (MNHN­Na 15064), posterior view of sternite XIII; d, Ψ 21, 0 mm, Vanuatu, MUSORSTOM 8, Stn CP 1127, 1052 ­ 1058 m (MNHN­Na 15045), longitudinal median section of sternites XIII and XIV; e, Ψ 23.6 mm, Chesterfield Islands, MUSORSTOM 5, Stn 384, 756 – 772 m (MNHN­Na 15046), longitudinal median section of the tooth on sternite XIII; f – g, k, ɗ holotype, 22.5 mm, 19 ° 22 ' N, 114 ° 11 ' E, depth, 400 – 435 m, 7.01. 1964 (after Crosnier & Forest, 1973) (NHM 1965.1.7.1), petasma, right half, f, internal face; g, external face; k, posterior face; h, ɗ 18.1 mm, Vanuatu, MUSORSTOM 8, Stn CC 996, 764 – 786 m (MNHN­Na 15047), distal lobules of the median lobes; i, ɗ 20.3 mm, ibidem (MNHN­Na 15048), idem; j, ɗ 21.8 mm, Chesterfield Islands, MUSORSTOM 5, Stn 384, 756 – 772 m (MNHN­Na 15063), idem. Scale, a, b, f, g, 5 mm; c, d, 2 mm; e, h, i, j, k, 1 mm.

FIGURE 11. — Hymenopenaeus methalli n. sp., a, Ψ holotype, 21.9 mm, Chesterfield Islands, MUSORSTOM 5, Stn CC 384, 756 – 772 m (MNHN­Na 15036), anterior region of the body, lateral view; b – d, rostrum and dorsal edge of the carapace, b, Ψ 16.5 mm, Chesterfield Islands, MUSOR­ STOM 5, Stn CC 384, 756 – 772 m (MNHN­Na 15040), c, ɗ 17.7 mm, ibidem (MNHN­Na 15039), d, ɗ 18.3 mm, ibidem (MNHN­Na 15065). Scale, 10 mm.

FIGURE 12. — ­ Hymenopenaeus methalli n. sp., a, Ψ holotype, 21.9 mm, Chesterfield Islands, MUSORSTOM 5, Stn CC 384, 756 – 772 m (MNHN­Na 15036), thelycum, ventral view (modified after Crosnier & Forest, 1973); b, median longitudinal section of sternites XIII and XIV; c, Ψ 20.5 mm, New Caledonia, HALIPRO 1, Stn 874, 708 – 830 m (MNHN­Na 15066), posterior view of sternite XIII. Scale, a, b, 5 mm; c, 1 mm.

FIGURE 13. — Hymenopenaeus methalli n. sp., a – c, ɗ allotype, 18.9 mm, Chesterfield Islands, MUSORSTOM 5, Stn CC 365, 710 m (MNHN­Na 15037), petasma, left half, a, internal face, b, external face, c, posterior view; d – f, distal lobules of the median lobe, d, ɗ allotype, 18.9 mm (MNHN­Na 15037), e, ɗ 18.3 mm, Chesterfield Islands, MUSORSTOM 5, Stn CC 384, 756 – 772 m (MNHN­Na 15065), f, ɗ 17.7 mm, ibidem (MNHN­Na 15039). Scale, a – c, 2 mm; e, f, 1 mm.

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).