Parvimysis brattegardi, 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 : 14-18

Parvimysis brattegardi sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:71B95044-2B20-4BB2-9203-20C7243D0356

( Figs 6 , 7 )

Type specimens. Holotype ♂ ad. with 2.1 mm body length ( NHMW reg. no. 26564), paratypes 102 ♀ ad. 2.3–3.4 mm, 90 ♂ ad. 1.8–3.2 mm, 43 subad. ( AMNH IZC 331515 , NHMW 26563 , ZMBN 135400 ), Curaçao, SW-coast, reef slope 1 km to the west of Piscadera Baai , 12°07’43’’N 68°58’45’’W, 4–12 m, mysid swarms around block of corals, hand net, 20 Aug. 1997, day, leg. Peter Wirtz.

Non-types (SW-coast of Curaçao, S = 36, leg. Karl J. Wittmann). 44 ♀ ad. 2.3–2.8 mm, 45 ♂ ad. 1.7–2.4 mm, 7 subad. ( NHMW 26565 ), 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 ; 28 ♀ ad. 2.1–2.7 mm, 38 ♂ ad. 1.5–2.5 mm, 6 subad. ( NHMW 26566 ), same station as before, reef slope, 15–30 m, hand net, mysid swarms over rock recesses in 15 m depth, and over sand in front of rock recesses in 20 m; swept from algae and rock, 24°C, 17 Feb. 2014, about 08:30 local time ; 25 ♀ ad. 2.5–2.7 mm, 42 ♂ ad. 2.0– 2.5 mm, 9 subad. ( NHMW 26567 ), same station as before, reef flat and reef slope, 7–21 m, swept with hand net from brown and red algae, and from sand within rock recesses, 24°C, 19 Feb. 2014, 19:30–20:30 local time, night ; 23 ♀ ad. 2.0–3.0 mm, 39 ♂ ad. 1.6–2.5 mm, 9 subad. ( NHMW 26568 ), 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 netted from small mysid swarms in rock recesses, 24 Feb. 2014, 15:00 local time .

Type locality. Sublittoral marine waters of Curaçao, SW-coast at 12°07‘43‘‘N 68°58‘45‘‘W .

Derivatio nominis. The species name is a Latinized noun in genitive singular, dedicated to Torleiv Brattegard (Bergen, Norway) in recognition of his most ample and important contributions to mysid taxonomy and faunistics of the Caribbean.

Diagnosis. Parvimysis with subtriangular, apically rounded rostrum. Freely projecting portion of the rostrum 0.4–0.8 times the length of the terminal segment of the antennular trunk. Antero-lateral edges of the carapace produced into a short acute process. Maximum diameter of the cornea 1.5–1.7 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 not reaching to the end of the antennular trunk; apical segment extending by about half its length 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 apical segment making up 16–22% total palp length. Median segment subterminally with only two barbed setae; more proximal portions of this segment with 1–0 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 2–7 with 9-segmented flagellum. Endopods 1, 2 without claw; endopods 3–8 with long, slender claw. Length of claw 5 is 10–14 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 (sub)triangular with acute to narrowly rounded tip. Telson short, length 2.6–6.8 times distance between the latero-terminal spines. Shape roughly trapezoid to subtriangular; its lateral margins slightly sinusoid, tapering, each armed with 2–5 short spines; each lateral margin ending in a short, partly inconspicuous, latero-terminal lobe with apical spine, the latter longer than the lateral spines; margin between these lobes weakly concave, bearing 4–12 laminae with 0.2–0.5 times length of latero-apical spines; no medio-terminal teeth and 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 2.3–3.4 mm (n = 111), males 1.8–3.2 mm (n = 101).

Cephalic region ( Figs 6 A–J). Cornea dorsoventrally compressed, reniform in dorsal, obliquely reniform-oviform in lateral view, length 1.3–1.7 times height in lateral view ( Fig. 6B ). Basal segment of antennular trunk about equal or slightly longer than combined median and apical segments in both sexes. Antennal scale with apical segment 25–28% length of the basal segment. Third segment of the trunk of the antennal flagellum with 74–87% length of the second segment. Apical segment of mandibular 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 50–70%. Basal segment of maxillary palp with three barbed setae on inner margin, apical segment densely setose at tip and on terminal 30–50% of inner margin, whereas lined by small hairs in more proximal portions. Each half of the foregut with 1 (2) large, apically pronged, serrated spine ( Fig. 6F ) on mid-posterior part of lateralia; this spine with total of 15–27 teeth, among them 3–5 large teeth at tip. Group of four centrally serrated spines ( Fig. 6G ), often similar in structure to the centro-apically serrated spines ( Fig. 6H ), in even more posterior position on lateralia; the largest, most proximal spine ( Fig. 6G ) with total of 4–8 small teeth distributed over apical 50–70% of spine length.

Thorax ( Figs 6 K–N, 7A, B). Length increases from exopod 1 to (4–6) and decreases from 6 to 8; length of endopods increases from 1 to 8. Basal plate of thoracic exopods 1–8 well rounded. Flagellum 8-segmented in exopod 1, and (8–9)-segmented in exopod 8. Thoracic endopod 8 slender; when stretched, extending forwards up to the eyes or backwards to the telson. Dactylus of endopod 2 large, equipped with 6–9 modified setae (as in Fig. 4B ) plus a few smooth setae, no spine-like setae. Length of claws increases in series of thoracic endopods 3–5, not clearly increasing in more caudal endopods. Claws are most slender in intermediate endopods, claw 5 is 10-14 times width at basis, claw 3 as well as claw 8 are 9–11 times that width. Penes ( Fig. 7A ) terminally with 4–5 minute setae facing the ejaculatory opening.

Pleon ( Figs 7 C–O). Male pleopod 5 slender, 1.6–1.9 times length of pleopod 3. Male pleopod 4, when stretched, reaching to end of pleonite 5, its large apical seta ends 60–100% length of pleonite 6. Fourth endopod 0.7–1.0 times length of basal segment of exopod; endopod with 8–10 barbed setae. Uropods with endopod 0.9 times length of exopod or 1.7–1.9 times length of telson (without spines). Length of exopod 6–8 times maximum width. Statoliths mineralized with vaterite (n = 40). One statocyst contained a small calcite particle in addition to a normal vaterite statolith. Such abnormalities are rarely found in nature, but may be artificially induced in laboratory (Ariani et al., 1999). Shape elliptical to spherical in dorsal view; diameter 50–90 µm. Statolith formula 2 + 3 + (4–7) + (5–7) = 15–19. Telson length 1.0–1.4 times its width at basis, or 0.5–0.6 times length of exopod of uropods, or 0.6–0.9 times pleonite 6. Laminae with 0.3–0.6 times median length of lateral spines.

Gut contents. Five full foreguts contained mineral particles (‘sand’), fragments of detritus, filiform algae, and macerated, unidentifiable material. The content of the 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 200 adult females examined in this respect, 101 showed empty brood pouch, 40 were with eggs, 31 with nauplioid larvae, and 28 with postnauplioid larvae. Size of breeding females 2.2–3.4 mm, each carrying 3– 5 eggs or larvae. Egg diameters 0.21–0.26 mm, length of nauplioids 0.3 mm at substage N1, 0.4–0.5 mm at N2, 0.5–0.6 mm at N3, 0.6–0.7 mm at N4, postnauplioids 0.7 mm at P1, 0.7–0.8 mm at P2, 0.8–0.9 mm at P3 (n = 50 eggs; 44, 28, 28, 21, 31, 25, or 26 larvae, respectively). The larvae attain 31–36% parental length (n = 7 parents) shortly before they moult to the free-living juvenile stage.

Distribution and habitat. In euhaline coastal waters of Curaçao, depth 1– 32 m. Large numbers of these mysids were observed in situ during daytime and sampled from swarms and loose aggregations hovering a few centimetres above the substrate (sand, algae, overgrown rock, corals), over and inside rock recesses. Without direct observation, swept from substrate surface during day and night.

Figures

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 6. Parvimysis brattegardi sp. nov. from Curaçao, holotype adult male with body length 2.1 mm (A, B), paratypes males 2.3 mm (C, E, J, M), 2.4 mm (G, N), 2.5 mm (H), 2.2 mm (K), and female with 2.3 mm (D, F, L); A, anterior body region of male, dorsal aspect (setae omitted from antennal scale), detail (B) shows right eye in lateral view; C, carapace expanded on slide; D, female antennula, dorsal; E, antenna, ventral (setae omitted from scale); F–H, modified spines from lateralia in foregut; J, maxillula, caudal; K, thoracic endopod 3; L, M, thoracic endopod 5 in female (L) and male (M); N, dactylus of thoracic endopod 5 in another male.

FIGURE 7. Parvimysis brattegardi sp. nov. from Curaçao; holotype adult male with body length 2.1 mm (L), paratypes males 2.5 mm (A, B, F), 2.3 mm (C–E, G), 2.1 mm (O), and females with 2.5 mm (H–K, M), 2.7 mm (N); A, eighth thoracic endopod with sympod and penis, detail (B) shows dactylus; C–G, series of male pleopods 1–5; H–K, series of female pleopods 1, 4, 5; L, M, variants of scutellum paracaudale, lateral; N, O, telson variants.