Heteromysis (Heteromysis) korntalensis, Wittmann & Abed-Navandi & Dubois & Chevaldonné, 2021

Wittmann, Karl J., Abed-Navandi, Daniel, Dubois, Maude & Chevaldonné, Pierre, 2021, Three new species of Heteromysis (Crustacea: Mysida) from coral reef aquaria in Florida and Central Europe, Zootaxa 4980 (3), pp. 490-520 : 500-505

Heteromysis (Heteromysis) korntalensis sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:4FE5E9E2-6D23-4CC4-A029-6C0000618759

Figs 5–7

Holotype. Adult male with 4.6 mm body length ( NHMW –27019), tanks of the wholesaler ‘ Whitecorals’, Korntal, Germany, Sept. 2020, leg. Christian Kapaun.

Paratypes. 1 M ad. 3.6 mm, 1 F ad. 4.2 mm ( MNINGA MYS 441 ) in vial, 1 F ad. 3.5 mm ( NHMW –27020), 1 M ad. 4.4 mm ( NHMW –27018) on slides, same sample as for holotype .

Material sequenced. 18S and COI barcodes here provided for 1 M ad. from same sample as for holotype, deposited in GenBank under accession numbers MW591698 and MW596476 .

Type locality. Not defined because the locality of origin ought to be indicated according to Art. 76.1.1. of the nomenclatorial code ( ICZN, 1999). The species was first discovered from tanks of the wholesaler ‘Whitecorals’ in Korntal ( Germany).

Derivatio nominis. The species name is a Latinized adjective with feminine location suffix, referring to the city of Korntal ( Germany) from where the type material was obtained.

Diagnosis. Carapace normal, rostrum triangular with narrowly rounded to acute tip, 0.4–0.8 times length of terminal segment of antennular trunk, covering <1/3 of eyestalks. Antero-lateral edges of carapace well rounded. In dorsal view, the eyes appear moderately large, subquadrate, almost ovate ( Fig. 5A ). The eyestalks expand beyond obliquely laterally implanted cornea; no disto-mesial spiniform extension.

Eyes ( Fig. 5A–C ). Eyestalks dorsoventrally compressed by a factor of 1.7–2.0 (length by maximum height), dorsal face flattened. Lateral aspect of eyestalks wedge-like in males ( Fig. 5B ), anterior margin with apically rounded, triangular protrusion with margins converging at 80–90 angular degrees. This aspect oviform, with weaker anterior protrusion in females ( Fig. 5C ). Small cornea located mid-laterally on stalk, where it extends over about 20% eye surface; its ommatidia compound, structure normal, functional. Cornea calotte-shaped in dorsal view ( Fig. 5A ), diameter 0.7–1.0 times the length of terminal segment of antennular trunk. Cornea ovate to almost circular in lateral view ( Fig. 5B–C ), dorsoventrally compressed by a factor of 1.1–1.6.

Antennulae ( Fig. 6A–H ). Antennular trunk with setae only, without spines; setae non-dimorphic. Basal segment of trunk with large dorsal apophysis bearing one long, flagelliform seta, medially accompanied by one shorter whip seta ( Fig. 6B, F ), and laterally by several shorter barbed setae. Lateral lobe with barbed setae only. Median segment without apophysis, its anterior margin mid-dorsally with seta group formed by one whip seta laterally accompanied by a few normal setae; additional group of that kind on disto-mesial edge. Anterior margin of terminal segment with the usual mid-dorsal apophysis. Disto-mesial edge of terminal segment with two large whip setae facing opposite directions. Appendix masculina small, with dense tuft of long setae.

Antennae and mouthparts ( Fig. 6I–J ). Antennal sympod with small spiniform extension on lateral face. Scale ( Fig. 6I ) reaches to 60–90% length of terminal segment of antennular trunk in both sexes. Scale length 3.0–3.6 times maximum width. Scale with small apical segment. Mouthparts normal; labrum with short, rounded, rostral protrusion ( Fig. 6J ).

Thorax. Only males with median processes ( Fig. 7D ) extending from thoracic sternites 1–8, not counting the usual, large lobe on first sternite. Flagellum ( Fig. 7F ) of thoracic exopods 1–8 with 8, 9, 9, 9, 9, 9, 8–9, and 8–9 segments, respectively. Carpopropodus ( Figs 6K , 7F ) of thoracic endopods 1–8 with 2, 2, 2, 5–4, 5–6, 5, 5, and 5–4 segments, respectively. Claw of endopod 3 ( Fig. 6O–P ) measured along its median line, 4–5 times dactylus length and 32–44% carpopropodus. Claw 3 weakly curved, large, the strongest; claw 1 with 40% length of claw 3, straight, strong; claw 2 ( Fig. 7E ) with half the length of claw 3, curved, strong as well; claw 4 with 1/3 length of claw 3, weakly curved, less strong, slender; claws 5–8 with 1/4 length of claw 3, more strongly curved, slender as well. Claw of endopods 1, 5–8 subapically serrated on mesial margin, claw 2 serrated in median portions, and claws 3, 4 smooth. Penes tube-like ( Fig. 7F ), 0.6–0.8 times length of ischium 8, and 0.9–1.1 times merus 8. Proximal half of penes with 2–3 whip setae increasing in length distally (the large, most distal seta occasionally accompanied by a shorter barbed seta); distal half without setae. Each penis terminally truncate, with, if any, two short, rounded apical lobes.

Gnathopods ( Fig. 6K–P ). Thoracic endopod 3 with most of mesial margin of ischium and merus rugose by small projections each bearing a whip seta at its tip. Merus terminally with triangular, apically acute ridge ( Fig. 6L ) on caudal face in both sexes. Carpus, propodus, and dactylus separated by distinct sutures. Carpopropodus length is 11–14% body length in females, 15–18% in males. Carpopropodus swollen, its length 3.5−4.2 times maximum width in both sexes; mesial margin of carpus with 8–10 strong spines. Propodus without spines; its paradactylary setae modified, dimorphic, longer than claw in males ( Fig. 6O ; due to more proximal insertion not or only shortly extending beyond claw), less strongly modified and only half the length of claw in females ( Fig. 6P ).

Pleon. Pleopods ( Fig. 7H–I ) non-dimorphic, reduced to small, setose, obscurely bilobate plates, without spines. Uropods ( Fig. 5D ) normal, entire; exopod reaches with 7–24% of its length beyond endopod. Endopod armed with linear series of 7–12 spines, about equally spaced along mesial margin from statocyst to 8–15% endopod length below apex. Telson ( Fig. 7K ) subtriangular, length 1.2–1.3 times maximum width and 0.8–0.9 times exopod of uropod. Lateral margins of telson with 7–13 spines on distal 50–60%, proximal portion smooth. Disto-lateral lobes each with two spines on narrowly truncate apex; latero-apical spines are 10–13% telson length; medio-apical spines are 0.6–0.8 times length of latero-apical spines. Proximally well rounded, U-shaped apical cleft occupies 22–23% length of telson. Cleft armed with 8–12 acute laminae along basal 60–70% of its margins, distal portions smooth.

Description. All features of the diagnosis plus the above listed features shared by the three here described species. General appearance, pleopods ( Fig. 7H–I ), and nauplioid larvae as in H. gulfarii . Body size of adults is 3.5–4.2 mm (n = 2) in females and 3.6–4.6 mm (n = 3) in males. Cephalothorax comprises 29–32% body length, pleon without telson 52–55%, telson 12–14%, carapace without rostrum 27–30%, and rostrum 3–4%. Frons with triangular subrostral process ( Fig. 5A ). Posterior margin of carapace leaves 0.5–1.0 ultimate thoracic somite middorsally exposed. Abdominal somites 1–5 measure 0.6–0.7, 0.7–0.8, 0.6–0.8, 0.6–0.8, and 0.6 times the length of somite 6, respectively.

Eyes ( Fig. 5A–C, E ). Anterior margin of eyestalk not wrinkled in both sexes. Stalk with, if any, small fields of minute scales on mesial and lateral basal edges. Cornea diameter 0.6–0.9 times the length of eyestalk.

Antennulae ( Fig. 6A–H ). Trunk extends 40–60% its length beyond eyes. Measured along dorsal midline, the basal segment is 44–46% trunk length, median 16–20%, and terminal 36–39%. Basal segment on basal half of its lateral face with 2–3 small setae bearing long barbs (as in Fig. 2E ). Its dorsal apophysis with 4–5 barbed setae and two whip setae; the mesial whip seta ( Fig. 6B, F ) shorter than the laterally adjoining whip seta. Lateral lobe of basal segment with 3–5 barbed setae. Median segment about mid-dorsally, closely behind distal margin, with seta group formed by three barbed setae plus one short whip seta. On disto-mesial edge of the median segment, an additional set formed by a plumose seta and a shorter whip seta ( Fig. 6C, G ). Terminal segment 1.1–1.5 times longer than wide in both sexes. Its mid-dorsal apophysis as in H. gulfarii . In both sexes the lateral antennular flagellum is thicker than the mesial one by a factor of 1.4–1.6 when measured near basis of flagella. Male lobe as in H. gulfarii , its length (antero-posterior extension) is 20–29% width of terminal segment of trunk, and lobe width is 18–28%. Epi-antennular process forms an evenly rounded shield; hypo-antennular process forms a triangular, tooth-like projection ( Fig. 6E ).

Antennae ( Fig. 6I ). Sympod as in H. gulfarii , its crescent-shaped shield 2.0–3.1 times longer than maximum width. The three-segmented antennal peduncle with basal segment 16–19% peduncle length, second 45–51%, and third 33–37%. Basal segment of peduncle dorsally with field of triangular scales (as in Fig. 2K ). Antennal scale extends to 20–80% length of third segment of antennal peduncle. Scale as in H. gulfarii , its short, broad apical segment 7–10% total scale length.

Mandibles. Palp most similar to Fig. 2L , segments 1–3 contributing 11–13%, 63–65%, and 22–24% to total palp length, respectively. Proximal segment with 2–3 whip setae on lateral margin, no additional setae. Median segment 2.3–2.5 times longer than its maximum width; 15–19 whip setae distally increasing in length almost all along lateral margin, the distal 1–2 setae with sparsely barbed handle; 12–14 basally thick setae along subbasal to subterminal portions of mesial margin, most setae of proximal half unilaterally barbed in both sexes; one large whip seta close to disto-mesial edge. Proximal half of median segment with large field of minute triangular scales (as in Fig. 2M ) on rostral face in both sexes. Terminal segment strongly setose. Pars molaris with well-developed grinding surface in both mandibles. Pars incisiva with 4–5 teeth, digitus mobilis with 3–4 teeth, and pars centralis with three spiny teeth.

Maxillula and maxilla. Distal segment of maxillula terminally with 11–12 strong spines, the innermost spine being thickest and longest; the two innermost spines microserrated in median portions of their outer (= lateral) margin. Setae of distal segment and of endite as in H. gulfarii . Maxilla with 13–16 plumose setae all along lateral margin of exopod, the two apical setae larger than the remaining ones. Basal segment of endopod with four basally thick, barbed setae. Terminal segment 1.6–2.2 times longer than wide.

Thoracic sternites ( Fig. 7D ). All male sternites with median processes. Male sternites 4–7 with larger processes compared to sternites 1–3, 8. Processes 2–7 clearly triangular. Processes 3–6 in part with pair of triangular secondary processes. Sternite 1 with large anterior lobe whose distal half is triangular with narrowly rounded apex in both sexes.

Thoracopods general ( Figs 6K–P , 7E–G ). Length of flagella as well as of basal plates increases from exopod 1 to 4, remain subequal from exopods 4 to 7, and is shorter in exopod 8. Basal plates weakly expanded, length 2.2–2.7 times maximum width in both sexes. Lateral margin of plates ends in a rounded edge ( Fig. 7F ). First thoracopod with large, leaf-like, smooth epipod. Relative size of endopods 1–8 and respective presence of apophyses as in H. gulfarii . Series of endopods 1–8 with slenderness of ischium and relative length of ischium, merus, and dactylus as in H. gulfarii . Combined praeischium plus ischium of endopod 2 is 0.8–1.0 times merus length, carpopropodus plus dactylus 0.8–1.2 times merus. Dactylus 2 with 9–12 modified setae; further details as described above for H. gulfarii . Distal 3–4 segments of the carpopropodus of endopod 4 each with one modified seta bearing minute teeth (modified barbs) along its thickened handle (as in Fig. 2R ), no such setae in endopods 5–8. Relative length of endopod 8 ( Fig. 7F ) as in H. gulfarii .

Gnathopods ( Figs 5E , 6K–P ). Thoracic endopods 3 form a powerful subchela. Basis with indistinct endite. Ischium 2.1−2.7 as long as wide (maximum width); merus 3.4−4.1 as long as wide and 1.4−1.7 times length of ischium. Mesial margin of ischium with 15–19 whip setae implanted on small (minute) projections; merus with 9–20 such setae on the tips of such projections ( Fig. 6K ). Distribution and structure of whip setae on lateral face of merus as in H. gulfarii . Carpopropodus 1.0–1.2 times merus length, 1.5–2.0 times ischium. Carpus with arrangement and structure of spines and setae ( Fig. 6K , M−P) as described in H. gulfarii .

Marsupium. Oostegite 1 near basis with 6–10 setae which are microserrated along their distal half, oostegite 2 with 2–3 such setae. Ventral and rostral portions of outer face of oostegite 2 with 9–18 small whip setae. Thoracopod 6 with terminally well-rounded rudimentary oostegite distally bearing one small barbed seta and two long setae microserrated along their distal half.

Tail fan ( Figs 5D , 7J–K ). Scutellum paracaudale and shape of exopod of uropods ( Fig. 5D ) as in H. gulfarii . Exopod extends 20–36% its length beyond telson; endopod 9–21% its length beyond telson (partly due to telson inserting more rostrally). Most spines of endopod subequal in length, proximal 0–2 spines occasionally smaller. Endopod ( Fig. 5D ) basally with large statocyst, statolith diameter 65–85 µm (n = 7 statoliths from four specimens). Statoliths discoidal with shallow fundus and distinct tegmen. Statolith formula 2 + (2–3) + (0–1) + (4–8) + (5–10) = 16–20 (n = 4). Telson ( Fig. 7K ) length 1.0–1.1 times length of sixth pleonite and 0.9–1.0 times endopod of uropod. Additional notes on telson structure as given above in the paragraph ‘Tail fan’ for H. gulfarii .

Foregut ( Fig. 7A–C ). As in H. gulfarii , except for different structure of certain teeth ( Fig. 7B–C versus Fig. 4B–C ). Each lateral margin of superomedianum, in addition to setae and normal spines, with 4–8 comparatively large smooth spines ( Fig. 7C ).

Gut contents of four specimens were mostly masticated, unidentifiable material (‘detritus’) and mineral particles; no crustacean remains identified.

Figures

FIGURE 2. Heteromysis gulfarii sp. nov. from aquaria in Florida, paratypes, male with body length 3.8 mm (A–E, L–M, O–S: NHMW–27017) and female 3.7 mm (F–K, N: NHMW–27015); A, male antennula together with associated processes from frons, dorsal; B–D, details of male antennula (A) showing whip setae from segments 1–3 of antennular trunk; E, detail of male antennula (A) showing stout barbed setae laterally on basal segment; F, female antennula, dorsal; G–I, details of female antennula (F) showing whip setae from segments 1–3 of antennular trunk; J, antenna, dorsal; K, detail of antenna (J) showing scales dorsally on basal segment of the antennal peduncle; L, mandibular palp, rostral; M, detail of mandibular palp (L) showing scales on rostral face; N, maxillula, caudal; O, male thoracic sternites 1–8; P, dactylus with nail of thoracic endopod 1, setae omitted; Q, tarsus of thoracic endopod 4, rostral; R, detail of tarsus 4 (Q) showing modified seta on rostral face; S, detail of tarsus 4 (Q) showing dactylus with nail, setae omitted.

FIGURE 4. Heteromysis gulfarii sp. nov. from aquaria in Florida, paratypes, male with body length 3.8 mm (A–D, F–G, J–K: NHMW–27017) and females 3.7 mm (E, H: NHMW–27015), 4.5 mm (I: MNINGA MYS 440); A–C, modified spines of foregut; D, male pleopod 1, caudal; E, female pleopod 2, caudal; F, male pleopod 3, rostral; G, male pleopod 4, rostral; H, female pleopod 5, caudal; I, scutellum paracaudale, lateral; J, uropods, ventral; K, telson; L, nauplioid larva at late substage N3, anteriorly distorted, lateral; M, tip of nauplioid abdomen in another specimen, lateral.

FIGURE 5. Heteromysis korntalensis sp. nov. from aquaria in Korntal (Germany), holotype, male with body length 4.6 mm (B, E: NHMW–27019), paratypes males 4.4 mm (A: NHMW–27018), 3.6 mm (D: MNINGA MYS 441), and female 4.2 mm (C: MNINGA MYS 441); A, eyes of male, dorsal, white dotted line enhances contour of left eyestalk, black dotted line that of subrostral process, dashed line that of anterior margin of carapace; B, left eye of male, lateral, dashed line enhances contour of left eyestalk; C, left eye of female, lateral; D, uropods, ventral; E, anterior body region of male, lateral. A–E, ethanol-fixed materials in petri dishes (A–C, E) and slides (D).

FIGURE 6. Heteromysis korntalensis sp. nov. from aquaria in Korntal (Germany), paratypes male with body length 4.4 mm (A–D, I–O: NHMW–27018) and female 3.5 mm (E–H, P: NHMW–27020); A, right male antennula, dorsal; B–D, details of male antennula (A) showing whip setae of basal (B), median (C) and terminal (D) segments of trunk; E, left female antennula together with associated processes from frons, dorsal; F–H, details of female antennula (E) showing whip setae of basal (F), median (G) and terminal (H) segments of trunk; I, antenna, ventral, arrow points to scale field below drawing plane on dorsal face; J, labrum, ventral; K, right male gnathopod, rostral, details show ridge on disto-mesial edge of merus (L) and (M–N) modified spines of carpus; O, propodus plus dactylus of right male gnathopod, rostral; P, dactylus of right gnathopod in female, caudal.

FIGURE 7. Heteromysis korntalensis sp. nov. from aquaria in Korntal (Germany), holotype male with body length 4.6 mm (J: NHMW–27019), paratypes female 3.5 mm (A–C, E, H: NHMW–27020) and male 4.4 mm (D, F–G, I, K: NHMW–27018); A–C, modified spines of foregut; D, male thoracic sternites 1–8; E, dactylus with nail of thoracic endopod 2, setae omitted; F, male thoracopod 8 with penis, detail (G) shows dactylus with nail; H, right female pleopod 2, rostral; I, left male pleopod 4, rostral; J, scutellum paracaudale, lateral; K, telson.