Parvimysis laminata, Wittmann, 2020

Wittmann, Karl J., 2020, Revision of the genus Parvimysis (Mysida, Mysidae) with descriptions of five new species from coastal waters of the Caribbean, Zootaxa 4742 (1), pp. 1-30 : 10-14

Parvimysis laminata sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:9347D7BE-4D61-472B-8319-4777299A16EC

( Figs 3–5 )

Parvimysis sp. B, Wittmann & Ariani, 2019: figs 1E, F, Table in Suppl.

Type specimens. Holotype ♂ ad. with 2.7 mm body length ( NHMW reg. no. 26570), paratypes 57 ♀ ad. 2.6–3.0 mm, 34 ♂ ad. 2.0– 2.6 mm, 14 subad. ( AMNH IZC 331514 , NHMW 26569 , ZMBN 135401 ), Curaçao, Playa Lagun , 12°19’06’’N 69°09’07’’W, 5–6 m, in loose aggregation above sand, hand net, 28 Aug. 1997, leg. Peter Wirtz.

Non-types from Curaçao (SW-coast, S = 36, leg. Karl J. Wittmann). 47 ♀ ad. 2.3–3.2 mm, 25 ♂ ad. 2.0– 3.1 mm, 5 subad. ( NHMW 26574 ), Porto Mariebaai (Playa Portomarie), 12°13’06’’N 69°05’12’’W, sand flat and reef slope, 1–30 m, 24–26°C, swept with hand net from sand, also from small mysid swarms in rock recesses, 24 Feb. 2014, 15:00 local time ; 33 ♀ ad. 2.9–3.3 mm, 17 ♂ ad. 2.3–2.7 mm, 4 subad. ( NHMW 26572 ), Boca Sint Michiel , Sun Reef, reef slope, 12°08’21’’N 68°59’53’’W, 10–32 m, swept with hand net from brown algae and sand, 26°C, 16 Feb. 2014, about 08:20 local time ; 17 ♀ ad. 2.7–2.9 mm, 17 ♂ ad. 1.9–2.7 mm, 7 subad. ( NHMW 26573 ), Vaersebbaai = Kokomo Beach, reef slope, 12°09’38’’N 69°00’21’’W, swept with hand net from brown and red algae, also from mysid swarms over sand, 8–28 m, 24°C, 18 Feb. 2014, 14:30–15:20 local time .

Non-type from Bonaire. 1 ♀ subad. 2.1 mm ( NHMW 26571 ), Bachelor’s Beach , 12°07’34’’N 68°17’16’’W, 3–26 m, in pooled sample from the sea floor; small hand net, 7 June 2004, daytime, leg. Peter Wirtz.

Type locality. Sublittoral marine waters of Curaçao, Playa Lagun, 12°19’06’’N 69°09’07’’W .

Derivatio nominis. The species name is a Latin adjective with female ending, referring to the series of comparatively long and numerous laminae on the terminal margin of the telson.

Diagnosis. Parvimysis with short, broadly rounded rostrum. Freely projecting portion of the rostrum 0.3–0.5 times the length of the terminal segment of the antennular trunk. Antero-lateral edges of the carapace produced into a short acute process. Cornea large, maximum diameter 1.8–2.4 times the length of the terminal segment of the antennular trunk in dorsal view. Antennular trunk extending beyond trunk of antennal flagellum. Antennal scale with basal segment extending beyond antennular trunk and to varying degree also beyond trunk of antennal flagellum. Cardiac portion of foregut with simple, smooth spines; additional stout, modified spines on lateralia, not so on dorso-lateral infolding. Mandibular palp with terminal segment making up 10–17% total palp length; median segment subterminally with two barbed setae; more proximal portions of this segment smooth or at most with one seta on inner margin, none on outer margin. Maxillary palp with proximal segment 0.3 times total palp length. Exopod of maxilla extends shortly beyond middle of the terminal segment of the palpus. Thoracic exopods 2–5 with 9-segmented flagellum, exopods 6, 7 with (9–8)-segmented flagellum. Endopods 1, 2 without claw; endopods 3–8 with long, slender claw. Length of claw 5 is 11–12 times its width at basis. Endopods 3–8 with oblique articulation between carpus and propodus. Carpus of endopod 5 with comb-like series of setae on inner margin in males, normal setation in females. Oostegites normal. Exopod of fourth male pleopod 3-segmented, ending in large modified seta plus a minute lobe bearing a minute seta. Apical segment of exopod is 0.4–0.5 times the length of the median segment. Scutellum paracaudale terminally well rounded or triangular with broadly rounded tip. Telson short, length 2.6–4.3 times distance between the latero-terminal spines. Shape roughly trapezoid, lateral margins slightly sinusoid, tapering, each armed with 2–5 short spines; each lateral margin ending in a short latero-terminal lobe with apical spine, the latter clearly longer than the lateral spines; margin between these lobes transversely straight or slightly concave, bearing 9–16 laminae with 0.4–0.8 times length of latero-apical spines; no medio-terminal teeth or spines.

Description of types. All features of the diagnosis and those reported further above as common to the six Caribbean species of the present study. Size of adult females 2.6–3.0 mm (n = 54), males 2.0– 2.6 mm (n = 34).

Cephalic region ( Figs 3 , 5 A–D). Cornea dorsoventrally not or only slightly compressed, calotte-shaped in dorsal, (sub)spherical to oviform in lateral view, apparent length 1.1–1.3 times height in lateral view ( Fig. 3B ). Basal segment of antennular trunk longer than combined median and apical segments in females, about equal or longer in males.Antennal scale with apical segment 22–30% length of the basal segment. Third segment of the trunk of the antennal flagellum with 70–82% length of the second segment. Mandibles as in Fig. 3G . Terminal segment of palp with 1–2 smooth setae, 4–5 modified setae bilaterally bearing series of stiff, spine-like barbs; and one longer seta with barbs along most of its distal 70%. Basal segment of maxillary palp with three barbed setae on inner margin, apical segment densely setose at tip and on terminal 50–70% of inner margin, but lined by small hairs in more proximal portions. Each side of the foregut ( Fig. 5 A–D) with one large, apically pronged, serrated spine on mid-posterior part of lateralia; this spine with total of 11–18 teeth, among which 1–4 large teeth at tip ( Fig. 5C ). Group of 4 (3–5) centroapically serrated spines ( Fig. 5D ) in even more posterior position on lateralia; the largest, most proximal spine with total of 9–14 small teeth distributed over distal 50–70% spine length.

Thorax ( Figs 4 , 5E ). Length increases from exopod 1 to 5 and decreases from 5 to 8; length of endopods increases from 1 to 8. Basal plate of thoracic exopods 1–8 terminally well rounded ( Figs 4A , 5E ). Flagellum of exopod 1 with 8 segments; flagellum of exopod 8 with 8 segments in females, and 8–9 in males. Thoracic endopod 8 slender; when stretched, extending forwards shortly beyond the eyes or backwards to or shortly beyond the telson. Dactylus of endopod 2 large, equipped with 4–9 modified setae ( Fig. 4B ) plus a few smooth setae, no spine-like setae. Length of claws increasing in series of thoracic endopods 3–5, not clearly increasing in more caudal endopods. Slenderness not clearly differing among endopods 3–8: claw 3 is 10–13, claw 8 is 10–12 times its width at basis. Penes ( Fig. 5E ) terminally with 5–6 minute setae facing the ejaculatory opening.

Pleon ( Fig. 5 F–R). Male pleopod 5 slender, 1.7–2.0 times length of pleopod 3. Male pleopod 4, when stretched, reaching to end of pleonite 5, its apical seta ends at 80–100% length of pleonite 6. Fourth endopod 0.7–0.9 times length of basal segment of exopod; endopod with 8–10 barbed setae. Uropods with endopod 0.9 times length of exopod or 1.6–1.7 times length of telson (without spines). Length of exopod 6–7 times maximum width. Statoliths mineralized with vaterite, a metastable polymorph of calcium carbonate; shape elliptical to spherical in dorsal view; diameter 60–120 µm (n = 40). Statolith formula 2 + 3 + (4–6) + (5–6) = 14–17. Scanning electron micrographs of a statolith available as Parvimysis sp. B in Wittmann & Ariani (2019: figs 1E, F). Telson length 1.2–1.5 times its width at basis, or 0.5–0.6 times length of exopod of uropods, or 0.6–0.8 times pleonite 6. Laminae with 0.6–1.2 times median length of lateral spines.

Gut contents. Most stomachs empty. Five full foreguts contained mineral particles (‘sand’), fragments of detritus, macerated, unidentifiable material, and diatoms. Content of midgut and hindgut contained mineral particles and particulate to fully macerated, unidentifiable material. The contents suggest that the mysids graze ‘detritus’ on the sediment surface. They also indicate that the secondary filter does not fully prevent infiltration of mineral particles into the midgut.

Eggs and larvae. Among 150 adult females examined in this respect, 65 showed empty brood pouch, 38 were with eggs, 30 with nauplioid larvae, and 17 with postnauplioid larvae. Size of breeding females 2.4–3.3 mm, each carrying 3–4 (5) eggs or larvae. Egg diameters 0.23–0.32 mm, length of nauplioids 0.5–0.6 mm at substage N2, 0.5–0.7 mm at N3, 0.6–0.8 mm at N4, postnauplioids 0.7–0.9 mm at P2, 0.8–1.0 mm at P3 (n = 50 eggs; 39, 37, 34, 22, or 35 larvae, respectively). The larvae attain 23–35% parental length (n = 10 parents) shortly before they moult to the free-living juvenile stage.

Distribution and habitat. Coasts of Curaçao and Bonaire, both islands located in the south-western part of the Lesser Antilles. In euhaline waters, on the sea floor in 1–32 m depth. Observed in swarms and loose aggregations hovering a few cm above the substrate (sand, algae, overgrown rock), over and inside rock recesses. Without direct observation, swept with hand net from the substrate surface during the day.

Figures

FIGURE 3. Parvimysis laminata sp. nov. from Curaçao, holotype male with body length 2.7 mm (A, B), paratypes female 2.6 mm (C, G), 3.2 mm (D, E, J), 2.1 mm (F, H), 2.7 mm (K); A, anterior body region of male (setae omitted from antennal scale), detail (B) shows right eye in lateral view; C, carapace expanded on slide; D, female antennula, dorsal aspect; E, antenna, ventral; F, labrum; G, mandibles, caudal; H, labium; J, maxillula, caudal; K, maxilla, caudal.

FIGURE 4. Thoracopods 1–7 in Parvimysis laminata sp. nov. from Curaçao, paratypes female with body length 2.5 mm (A), 3.2 mm (B, H), 2.9 mm (C, D), 3.1 mm (J), 3.0 mm (K), and males 2.8 mm (E), 2.5 mm (F, G); A, thoracopod 1 with sternites 1–4; B, endopod 2; C, endopod 3, detail (D) shows dactylus; E, endopod 4; F–H, endopod 5 in female (F) and male (G), detail (H) shows dactylus; J, endopod 6; K, endopod 7 with oostegite.

FIGURE 5. Parvimysis laminata sp. nov. from Curaçao, paratypes female with body length 2.7 mm (A–D, L–O), 3.2 mm (P, R), and males 2.2 mm (E–K), 1.9 mm (Q); A, foregut in dorsal view (dorsal wall omitted), details (B–D) show modified spines of lateralia; E, endopod 8 with penis; F–K, series of male pleopods 1–5; L–N, series of female pleopods 1, 3, 5; O, P, variants of scutellum paracaudale, lateral; Q, tail fan (setae omitted, dorsal wall of left endopod drawn as transparent); R, additional telson variant; S, nauplioid larva, lateral.