Heteronika nesisi ( Burukovsky, 1986 )

Hendrickx, M. E., 2019, Redescription of the rare shrimp Heterocarpus nesisi (Burukovsky, 1986) (Crustacea: Caridea: Pandalidae) rediscovered off western Mexico, with the proposal of a new genus, Zootaxa 4565 (1), pp. 49-60 : 51-59

publication ID	https://doi.org/ 10.11646/zootaxa.4565.1.3
publication LSID	lsid:zoobank.org:pub:F4B6A917-1EA8-40E4-850B-4507F1E92DBE
DOI	https://doi.org/10.5281/zenodo.5943212
persistent identifier	https://treatment.plazi.org/id/5934E94B-FFAB-FFAF-FF21-8143FEE5FE1D
treatment provided by	Plazi
scientific name	Heteronika nesisi ( Burukovsky, 1986 )
status

Treatment

Heteronika nesisi ( Burukovsky, 1986) View in CoL new. comb.

( Figs. 1 View FIGURE 1 –5)

Heterocarpus nesisi Burukovsky, 1986: 62 View in CoL , fig. 1, fig. 3 (distribution map), Table 1.― Crosnier, 1988: 90 (key), 92.― Chace, 1989: 87. Plesionika nesisi View in CoL .― Poupin 1996; Pl. 4e.― Chan & Crosnier 1997: 197, figs. 5–10, 28.― De Grave & Fransen, 2011: 449.

Material examined. TALUD XV, St. 1 (23°18'40" N, 111°19'37" W), August 4, 2012, benthic sledge, 750–850 m depth, 1 female (CL 32.95 mm) (ICML-EMU-12110), 1 female (CL 33.88 mm) (ICML-EMU-12111), 2 males (CL 26.07–29.75 mm), and 4 females (CL 23.75–30.80 mm) (ICML-EMU-12112) GoogleMaps .

Description. (based on material examined) Rostrum about 0.82–0.87 times as long as carapace, proportionally shorter in larger specimens, slightly upturned in distal half; 11–13 fixed dorsal teeth, regularly spaced, 4–5 on carapace, 7–8 fixed ventral teeth, a small dorsal tubercle near posterior margin ( Figs. 1B View FIGURE 1 , 2 View FIGURE 2 A–B). Antennal spine ( Fig. 2 View FIGURE 2 A–B) strong, acute. Pterygostomian spine ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 ) stout, similar in size to antennal spine. Carapace with a distinct, strong lateral, postorbital carina originating above antennal spine, extending posteriorly to about 2/ 5 o carapace length, followed by a strong X-shape carina, and extending as a slightly curved carina almost to posterior margin of carapace ( Figs. 1 View FIGURE 1 , 2A View FIGURE 2 ). Tegumental scales absent.

Abdomen ( Fig. 1A View FIGURE 1 , 2A View FIGURE 2 ) pleura smooth; somites without posterodorsal tooth, 3rd with weakly marked dorsal boss ( Fig. 2A, C View FIGURE 2 ) demarked by two submesial, almost parallel shallow sulcus, somite dorsally extended to cover part of somite 4 ( Fig. 2C View FIGURE 2 ); pleura of 3–4 posterior margin rounded (one exception in a male specimen; see Fig. 2I View FIGURE 2 ); pleura of 5th somite with acute posterior projection; sixth somite about twice as long as fifth, armed posteroventrally and posterolaterally with sharp tooth ( Fig. 2A, H View FIGURE 2 ). Telson ( Fig. 2F, G, I View FIGURE 2 ) about 1 and 1/2 as long than sixth abdominal somite, deeply sulcate middorsally, armed with four pairs of strong dorsolateral spines; distal margin with distinct medial tooth, 3 pairs of spines, the intermediate pair the longest.

Eye ( Fig. 2 A, D View FIGURE 2 ) with subspherical cornea broader than stalk; ocellus not well defined.

Basal segment of antennular peduncle without ventromesial tooth; stylocerite narrowly tapering to sharp point, reaching half length (or slightly beyond) of second article of antennular peduncle, lateral margin straight; intermediate segment 0.5 times as long as basal segment; ultimate segment short, 0.5 times as long as intermediate segment ( Fig. 2D, E View FIGURE 2 )

Scaphocerite longer than antennular peduncle ( Fig. 2D View FIGURE 2 ); distolateral tooth reaching distal margin of lamina. Basicerite with strong lateral tooth.

Incisor process of left mandible with 6 teeth, ventral tooth largest; molar process straight with a shallow sulcus ventrally ( Fig. 3A, B View FIGURE 3 ). Incisor process of right mandible similar to left, with 5 teeth, ventral tooth largest; molar process similar to left mandible. Mandibular palp ( Fig. 3A, B View FIGURE 3 ) three-segmented; basal segment short, widening distally, laterally produced, penultimate segment slightly shorter than basal segment, ultimate segment slightly longer than basal segment.

First maxilla (maxillula) ( Fig. 3C View FIGURE 3 ) with lower and upper endites well developed; upper endite broad, with distal rows of setae; lower endite distally acute, with many simple setae; palp bilobed, with each lobe ending in several slender setae.

Second maxilla ( Fig. 3D View FIGURE 3 ) with lower endite reduced; upper endite bilobed, upper lobe largest; palp well developed, tapering distally; scaphognathite large, posterior lobe rounded, projecting.

First maxilliped ( Fig. 3E View FIGURE 3 ) with separated endites of basis and coxa; palp slender, faintly 2-segmented, terminal segment slender; exopod distal part long and slender, with well developed caridean lobe; epipod bilobed.

Second maxilliped ( Fig. 3F View FIGURE 3 ) with ultimate segment broad; penultimate segment oblong, wider near base; carpal segment subrectangular, as long as wide; meral segment nearly twice as long as its distal width; basis and ischium partly fused; exopod well developed.

Third maxilliped ( Fig. 3H, G View FIGURE 3 ) long and slender, reaching beyond scaphocerite by about half of ultimate segment; ultimate segment about 1.5 times as long as penultimate segment, with lateral row of closely-set, short setae and one mesial row of spines; penultimate segment with lateral row of closely-set, short setae and one subdistal spine; antepenultimate segment 2.4 times as long as penultimate; exopod long, about 0.7 times length of antepenultimate segment; strap-like epipod well developed.

First pereiopods ( Fig. 4 View FIGURE 4 A–C) extending slightly over distal margin of scaphocerite, indistinctly subchelate; propodus about 0.7 times as long as carpus, with rows of densely-set short setae and one row of stronger setae in proximal 3rd, tufts of long setae in distal 2/3rd; carpus unarmed, with regularly spaced tufts of long setae and a subterminal, oblique row of short setae; merus equal to carpus length, with irregularly set tufts of long setae; ischium about 2/3 merus length, unarmed.

Second pereiopods ( Fig. 4 View FIGURE 4 D–E) different in form and length, left much slender and longer than right, overreaching scaphocerite distal margin by chela length; right extending to about 2/3 of scaphocerite length. Right pereiopod ( Fig. 4D View FIGURE 4 ) short, stout; chela massive, about 2.5 times longer and 2.5 times higher than chela of left pereiopod, palm slightly longer than finger; carpus 1.25 times as long as merus, 5-segmented, proximal segment equal to 4 distal segments, 3 subdistal segments excavated to receive merus, distal segment as long as combined length of 3 subdistal segments; merus straight, unarmed; ischium slightly longer than merus. Left second pereiopod ( Fig. 4E View FIGURE 4 ) slender; carpus 1.8 times longer than merus, with 17–19 segments (in some specimens intermediate segments not distinctly articulated); merus slightly longer than merus; ischium with row of slender curved ventromedial spines.

Third, fourth and fifth pereiopods ( Fig. 4 View FIGURE 4 F–I) similar in shape and of about the same length.

Third pereiopod ( Fig. 4F View FIGURE 4 ). Dactyl short, flexor margin with 4 movable spines, unguis simple, strong; propodus about 7 times dactylus length, armed with 16–18 movable spines; carpus 0.9 times propodus length, with one sharp movable spine at about mid-length; merus about 1.7 times as long as carpus, with 11 strong movable spines; ischium about 1/3 merus length, with one sharp movable spine.

Fourth periopod ( Fig. 4 View FIGURE 4 G–H). Dactyl short, flexor margin with 4 movable spines, unguis simple, well developed; propodus about 7 times dactylus length, armed with row of about 10–12 movable spines; carpus 0.8 times propodus length, with two sharp, movable spines in proximal half; merus about 1.3 times as long as carpus, with 10 strong movable spines; ischium about 1/3 merus length, with two sharp movable spines.

Fifth pereiopod ( Fig. 4I View FIGURE 4 ). Dactyl mising. Propodus unarmed; carpus 0.8 times propodus length, with one strong, movable spine at about mid-length; merus about 1.7 times as long as carpus, with 6 strong movable spines; ischium about 1/3 merus length, unarmed.

Pereiopods 1–5 with strap-like epipod ( Fig. 4J View FIGURE 4 ).

Uropods slightly longer than telson; one fixed (external) and one movable spines at posterior corner of exopod.

Pleopod II of male (Fig. 5A–D) with appendix masculina slightly longer than appendix interna, the latter with a pear-shaped patch of 63 cincinnuli.

Distribution. Known from two (three?) localities. Type locality (13°34' N, 120°33' W), on a seamount about 1000 km off western Mexico, ca. 800 m depth ( Burukovsky 1986). Off western Mexico (23°18'40" N, 111°19'37" W; material examined), 750–850 m depth. If the specimen reported by Chace (1989: 87) proves to belong to Heteronika nesisi , new comb., there would be a third known locality for this species (22°48'20" N, 109°52'40" W; off Cabo San Lucas, Baja California Sur, Mexico) (see Fig. 6 View FIGURE 6 ).

Ecology. Same depth range as the holotype and the specimen of the "Albatross" St. 5682. Bottom level environmental conditions: oxygen, 0.11 ml/l; temperature, 5.75°C; salinity, 34.54; sediments, 13.4 clay, 18.7 sands, 67.9 silt; organic carbon content, 3.93%.

Remarks. The original description of this species (see Appendix), transferred to Plesionika by Chan & Crosnier (1997), was based on a single male (holotype) of 76 mm (measured from the base or rostrum to the end of telson) captured in 1975 on a seamount located off the northeast coast of America ( Burukovsky 1986).

While reviewing the taxonomic status of Heterocarpus alexandri A. Milne-Edwards, 1883 , Chace (1989) suggested that a specimen identified by W.L. Schmitt as H. alexandri , from of San Lucas Bay ("Albatross" St. 5682), on the southern tip of the Baja California Peninsula, probably belongs to " H. nesisi ". Chace (1989) provided several characteristics of this material that clearly match the original description by Burukovsky (1986) and provided some additional observations made with this Baja California specimen, including: rostral structure 4/7+7; pterygostomian spine close to antennal spine; no transverse grooves on somites 1–2; no dorsal boss on tergum of somite 3; telson deeply sulcate dorsally with 5 pairs of [dorso] lateral spines; pereopods 1–4 with epipod; pereopods 2 with 5 (right) and 15 (left) carpal segments; dactyl of pereiopod 3 with 4 spines on flexor margin, plus distal tooth [unguis]. These characteristics fit well with the description of the material examined.

Chace (1989: 88) suggested that the group of species "... clustered around Heterocarpus laevis and H. alexandri might eventually constitute a valid separate genus". Based on the illustrations and description provided by Chace (1989) for H. alexandri , it is not clear if that species features a lateral carina as (or nearly as) strong as in H. nesisi . In his key to species of Heterocarpus , however, Chace (1986: 20) clearly included the presence of "1 longitudinal carina on lateral surface [of carapace]" to separate H. alexandri from H. laevis (no longitudinal carina in that species).

FIGURA 5. Heteronika nesisi (Burukovsky, 1996) . Male (CL 26.07 mm; ICML-EMU-12112), left second pleopod. A, appendix interna and appendix masculina; B, close-up of appendix interna; C, same, distal tip; D, same, close-up of cincinnuli.

In his review of the species of Heterocarpus from the SW Indian Ocean, Crosnier (1988: 89, key) clearly included H. alexandri and " H. nesisi " in the group of species with a single lateral carina on the carapace, this lateral carina originating posterior to the orbit, just above the antennal spine (opposed to a second group of species in which the anterior part of this carina is confused or in line with the antennal spine). The material examined herein clearly fits with the first group of species considered by Crosnier (1988).

In all the specimens examined, the posterior margin of pleura 3–4 is rounded, without tooth, except in the 29.75 mm CL male where a small, but clearly spiny postero-lateral corner was observed on both side of the somite of pleura 4 ( Fig. 2H View FIGURE 2 ).

When compared with the type species of Heterocarpus , H. ensifer A. Milne Edwards, 1881 , Heteronika nesisi new comb. presents stricking differences, including: the presence of only one lateral carina on the carapace, the later originating near the orbital margin, above the antennal spine vs. two carina in H. ensifer , the upper carina in line with the antennal spine; the absence of dorsal tooth on abdominal somites 3–4 vs. one long (3) and one shorter (4) acute tooth on both somites in H. ensifer ; the absence of a dorsal carina on somites 1–2 vs. the presence of a weak carina in H. ensifer (Chace 1985, Crosnier 1988). The blade of the scaphocerite of H. ensifer is, according to Chace (1985: 28), atypical when compared with the rest of the species of Heterocarpu s (i.e., "... blade tapering strongly toward the distolateral spine vs. broadly rounded or subtruncate distally").

Chan & Crosnier (1997) reported material of Plesionika nesisi from several localities in the western Pacific ( French Polynesia to the Philippines) and in the Indian Ocean ( Seychelles Islands and Madagascar). They provided a color photograph of one specimen from French Polynesia, illustrations of the carapace-rostrum in lateral view, of the abdominal somites in lateral (2–6) and dorsal (3) views, of the propodus-dactyl of the third pereiopod, and of the tip of the telson. None of the illustrations of the carapace in lateral view provided by Chan & Crosnier (1997: figs. 5, 6, 7b) shows the typical strong, well-marked lateral carina described by Burukovsky (1986) and observed in all the specimens of the Mexican material. Instead, Chan & Crosnier (1997) drawings show a weak carina, almost obsolete in some specimens. The typical oval depression at about mid-length of the lateral carina illustrated by Burukovsky (1986) and also present in the material examined (see Fig. 2C View FIGURE 2 ) does no show on any of Chan & Crosnier (1997) illustrations. The carina of the pterygostomial spine as shown by Chan & Crosnier (1997) is always weak and short, weaker than in Burukovsky (1986) description and than in the Mexican material. The dorsal boss observed by Chan & Crosnier (1997: figs. 8e, c) in their material was not reported by Burukovsky (1986) and not clearly observed in the Mexican material; similarly, the pair of mesial furrows they observed and described as " [abdominal somite III] ... generally [bearing] a pair of distinct submedian furrows ..." was not reported by Burukovsky (1896), although in their re-examination of the holotype Chan & Crosnier (1997: fig. 8a) indeed presented an illustration showing a pair of weak submedian furrows on this somite; this was also observed in the Mexican material. The terminal spines in the tip of the telson of one of the French Polynesia specimen is similar to what was observed in the Mexican material; however, the tip of the telson as illustrated by Chan & Crosnier (1997: fig. 8d) is clearly spine-like, while in the Mexican material it is acutely triangular.

Little can be concluded from the illustrations of the propodus and dactyl of the third pereiopod provided by Chan & Crosnier (1997: fig. 10) for their Indo-Pacific material. Pereiopods 3 of the holotype were missing and not described. The Mexican material feature a rather slender dactyl, with 4 spines on the flexor margin and a strong, moderately long unguis; the material reported by Chan & Crosnier (1997) is quite variable in this respect, with 2–4 spines. The propodus of the Mexican material is armed with 18 spines vs. 13–16 in the Indo-Pacific material examined by Chan & Crosnier (1997: fig. 10).

Based on these observations, it seems reasonable to conclude that the material reported by Chan & Crosnier (1997) as Plesionika nesisi actually belongs to another species, not to the Heterocarpus nesisi of R.N. Burukovsky.

Chan & Crosnier (1997: fig. 7a, 8a, b) also re-examined the holotype of H. nesisi (reportedly in bad shape) and provided illustration of the carapace (rostrum missing), of adominal somites 2–6 in lateral view, and of the telson. The carapace is, of course, very similar to Burukovsky' s (1986) illustration but the proportion between the carapace length and height is different: 1.59 in Burukovsky' s (1986) illustration vs. 1.67 in Chan & Crosnier (1997) drawing. The lateral view of somites 3–5 of the holotype is similar in both cases ( Burukovsky 1986; Chan & Crosnier 1997) and fit well with the Mexican material. The telson of the holotype drawn by Chan & Crosnier (1997: fig. 8b) is similar to what was observed in the Mexican material, with 4 pairs of dorsal spines and 3 pairs of terminal spines.