Sestrostoma balssi Shen 1932
Creators: name: Kornienko, Elena S.
name: Korn, Olga M.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Varunidae
Sestrostoma
Sestrostoma balssi

description: Sestrostoma balssi (Shen, 1932)
Acmaeopleura balssi Shen, 1932: 155, figs 98, 100; tab. 6, figs 1, 2 [type locality: Shangdong Province, northeastern China]; Itani et al., 2002: 46 –47, figs 2, 3.
Sestrostoma balssi – Davie & N.K. Ng, 2007: 265, figs 7, 8.
The development of S. balssi included five zoeae and one megalopa. The minimal time required for larvae to reach the megalopal stage was about 35 days at a temperature of 20–22°C. The body outlines and appendages are illustrated in Figures 1–8. Only morphological changes are described for the second to fifth zoeal stages.
Description of larval stages. (Figs 1–8)
First zoea (Fig. 1)
Material examined. CL = 0.46±0.02 mm, DRL = 1.20±0.04 mm, N = 10.
Minimal duration. 6 days.
Carapace (Fig. 1 А, B). Eyes sessile. Rostral, dorsal, lateral spines present. Rostral, dorsal spines straight, nearly equal carapace length; rostral spine two times longer than antenna; lateral spines longer than 1/2 carapace width. One pair of setae on surface of carapace, at base of dorsal spine.
Antennule (Fig. 1 C). Uniramous, endopod absent; exopod conical, unsegmented, with 2 long, 1 short terminal aesthetascs, 2 short terminal setae.
Antenna (Fig. 1 D). Protopod pointed, with 2 rows of sharp spinules; exopod as a small bud with 1 simple terminal seta.
Mandible (Fig. 1 E). Asymmetrical; without palp.
Maxillule (Fig. 1 F). Coxal endite with 5 plumodenticulate setae; basial endite with 3 plumodenticulate cuspidate, 2 plumodenticulate setae; endopod 2-segmented, proximal segment with 1 simple seta, distal segment with 4 marginal, 1 submarginal plumodenticulate setae.
Maxilla (Fig. 1 G). Coxal endite with 7 plumodenticulate setae; basial endite bilobed, proximal lobe with 4 or 5, distal lobe with 4 plumodenticulate setae; endopod unsegmented, bilobed, with numerous microtrichiae, each lobe with 2 plumodenticulate setae; scaphognathite with 4 marginal densely plumose setae, with long distal process.
First maxilliped (Fig. 1 H). Coxa unarmed; basis with 10 plumodenticulate setae arranged 2, 2, 3, 3; endopod 5- segmented, setal formula progressing distally 2, 2, 1, 2, 1+4, third segment with numerous microtrichiae; exopod unsegmented, with 4 terminal plumose natatory setae.
Second maxilliped (Fig. 1 I). Coxa unarmed; basis with 4 plumodenticulate setae arranged 1, 1, 1, 1; endopod 3-segmented, setal formula progressing distally 0, 1, 3+3; exopod unsegmented, with 4 terminal plumose natatory setae.
Third maxilliped. Absent.
Pereiopods. Absent.
Pleon (Fig. 1 J). Five somites; somite 2, 3 each with a pair of dorsolateral processes; somites 2–5 each with a pair of posterodorsal simple setae; pleopods absent.
Telson (Fig.1 J). Bifurcated, furcal rami longer than proximal part of telson, without lateral spines; distal part slightly curved upwards, with 2 rows of spinules; posterior margin with 3+3 plumodenticulate setae, with fairly deep median notch.
Second zoea (Fig. 2)
Material examined. CL = 0.57±0.02 mm, DRL = 1.57±0.06 mm, N = 10.
Minimal duration. 5 days.
Carapace (Fig. 2 А). Eyes stalked. Four pairs of setae on surface of carapace; each ventral margin with 2 setae.
Antennule (Fig. 2 B). Exopod with 4 long terminal aesthetascs.
Antenna (Fig. 2 C). Unchanged.
Mandible (Fig. 2 D). Unchanged.
Maxillule (Fig. 2 F). Basial endite with 5 plumodenticulate cuspidate, 2 plumodenticulate setae; exopod seta present.
Maxilla (Fig. 2 F). Proximal part of scaphognathite with 5, distal part with 3 densely plumose setae.
First maxilliped (Fig. 2 G). Exopod with 6 terminal plumose natatory setae.
Second maxilliped (Fig. 2 H). Exopod with 6 terminal plumose natatory setae.
Third maxilliped. Presents as a small bud.
Pereiopods. Absent.
Pleon. Somite 1 with 1 dorsomedial seta.
Telson. Unchanged.
Third zoea (Fig. 3)
Material examined. CL = 0.63±0.04 mm, DRL = 1.96±0.04 mm, N = 7.
Minimal duration. 6 days.
Carapace (Fig. 3 A). One pair of setae on dorsal spine; each ventral margin with 4 setae.
Antennule (Fig. 3 B). Exopod with 3 terminal aesthetascs.
Antenna (Fig. 3 C). Unchanged.
Mandible (Fig. 3 D). Unchanged.
Maxillule (Fig. 3 E). Basial endite with 1 lateral seta; epipod seta present.
Maxilla (Fig. 3 F). Coxal endite incompletely bilobed; proximal, distal lobes of basial endite each with 5 setae; proximal part of scaphognathite with 8 or 9, distal part with 5 densely plumose setae.
First maxilliped (Fig. 3 G). Coxa with 1 plumose seta; third segment of endopod with addition sparsely plumose seta; exopod with 8 terminal plumose natatory setae.
Second maxilliped (Fig. 3 H). Exopod with 8 terminal plumose natatory setae.
Third maxilliped. Increased in size to a little degree.
Pereiopods. Present as buds.
Pleon (Fig. 3 I). The sixth pleonal somite differentiated.
Telson (Fig. 3 I). Posterior margin with 4+4 plumodenticulate setae.
Fourth zoea (Fig. 4)
Material examined. CL = 0.88±0.05 mm, DRL = 2.77±0.16 mm, N = 10.
Minimal duration. 7 days.
Carapace (Fig. 4 A). Two pairs of setae on dorsal spine; each ventral margin with 7 or 8 setae.
Antennule (Fig. 4 B). Exopod with 4 terminal, 1 subterminal aesthetascs.
Antenna (Fig. 4 C). Biramous, endopod about of 1/3 of protopod.
Mandible (Fig. 4 D). Unchanged.
Maxillule (Fig. 4 E). Coxal endite with 7 plumodenticulate setae; basial endite with 12 or 13 plumodenticulate setae (5 cuspidate, 2 lateral).
Maxilla (Fig. 4 F). Coxal endite bilobed; proximal lobe of coxal endite with 4 or 5, distal lobe with 3 plumodenticulate setae; proximal lobe of basial endite with 7, distal lobe with 6 plumodenticulate setae; scaphognathite with 19–21 plumose setae.
First maxilliped (Fig. 4 G). Endopod setal formula progressing distally 2, 3, 2, 2, 2+4; exopod with 10 terminal plumose natatory setae.
Second maxilliped (Fig. 4 H). Exopod with 10 terminal plumose natatory setae.
Third maxilliped (Fig. 4 I). Biramous.
Pereiopods (Fig. 4 J). Pereiopod I chelated.
Pleon (Fig. 4 K). Somite 1 with 3 dorsomedial setae; somites 2–5 with uniramous pleopod buds. Telson (Fig. 4 K). Unchanged.
Fifth zoea (Fig. 5)
Material examined. CL = 1.05±0.06 mm, DRL = 3.20±0.12 mm, N = 8.
Minimal duration. 11 days.
Carapace (Fig. 5 A). Three pairs of setae on dorsal spine; each ventral margin with 8–12 setae; posterodorsal arch with 2 setae.
Antennule (Fig. 5 B). Antennular base broadened, with 2 short setae; endopod bud present; exopod with 10 aesthetascs in tree tiers (3+2+5), 1 short simple terminal seta.
Antenna (Fig. 5 C). Endopod slightly shorter than protopod, incompletely segmented.
Mandible (Fig. 5 D). Palp bud present.
Maxillule (Fig. 5 E). Coxal endite with 9–11 setae; basial endite with 15–17 setae of different size (6 or 7 cuspidate, 3 lateral); two epipod setae present.
Maxilla (Fig. 5 F). Proximal lobe of coxal endite with 6 or 8, distal lobe with 3 setae; proximal lobe of basial endite with 8 or 9, distal lobe with 8 setae; scaphognathite with 27–32 plumose setae.
First maxilliped (Fig. 5 G). Coxa with 3 plumodenticulate setae (2 long, 1 short); exopod 2-segmented, with 12 terminal plumose natatory setae; small unarmed triangular epipod presents.
Second maxilliped (Fig. 5 H). Exopod incompletely 2-segmented, with 12 terminal plumose natatory setae.
Third maxilliped (Fig. 5 I). Increased in size, incompletely segmented.
Pereiopods (Fig. 5 J). Increased in size, incompletely segmented.
Pleon (Fig. 5 K). Somite 1 with 5 dorsomedial setae; somite 2–5 with biramous pleopods, somite 6 with uniramous uropods.
Telson (Fig. 5 K). Posterior margin with 5+5 plumodenticulate setae.
Megalopa (Figs 6–8)
Material examined. CL = 1.45±0.09 mm, СW = 1.22±0.05 mm, N = 4.
Minimal duration. Undetermined.
Carapace (Fig. 6 A). Pear-shaped, with small paired tubercles behind eyes, one posterodorsal tubercle. Carapace surface covered with scattered short simple setae; each ventral margin with 30–40 plumose setae. Rostrum short, directed ventrally. Ocular peduncle with 3 short setae on frontal margin; cornea not wider than ocular peduncle.
Antennule (Fig. 6 B). Biramous; peduncle 3-segmented, setal formula 8, 2, 1; endopod unsegmented, with 1+3 setae; exopod 4-segmented, setal formula 4 or 5 aesthetascs, 5 or 6 aesthetascs, 5 or 6 aesthetascs+2 sparsely plumose setae, 5 aesthetascs (4 long, 1 short)+1 terminal sparsely plumose seta.
Antenna (Fig. 6 C). Consists of 11 segments; peduncle 3-segmented, with 1, 1 or 2, 1 or 2 setae; flagellum 8- segmented, setal formula 0, 0, 2 or 3, 2–4, 1, 4, 2 or 3, 3; four distal segments with long serrate setae, rest segments with short simple (rarely sparsely plumose) setae.
Mandible (Fig. 6 D). Palp 2-segmented, distal segment with 8 setae.
Maxillule (Fig. 6 E). Coxal endite with 18–21 plumodenticulate setae; basial endite with 22 or 23 marginal (9 plumodenticulate, 12 or 13 plumodenticulate cuspidate), 3 or 4 lateral sparsely plumose or simple setae; endopod reduced, unsegmented, with 6 setae; at base of maxillule 4 plumodenticulate setae.
Maxilla (Fig. 6 F). Coxal endite bilobed, proximal lobe with 11–14, distal lobe with 5 setae; basial endite bilobed, proximal lobe with 12–14, distal lobe with 10–14 setae; endopod reduced, 2 or 3 setae similar to scaphognathite setae in proximal part, 1 or 2 plumodenticulate or simple setae in distal part; scaphognathite with 52–60 densely plumose marginal setae, with 4 or 5 simple setae on surface.
First maxilliped (Fig. 7 A). Epipod triangular, with 3 or 4 setae in proximal part, with 7–9 plumodenticulate setae in distal part; coxa with 12–18 plumodenticulate setae; basis with 14–20 setae; endopod reduced, incompletely segmented, with 2 or 3 lateral simple setae, 3 or 4 terminal plumodenticulate setae; exopod 2-segmented, proximal segment with 2 distal short plumose setae, distal segment with 4 or 5 terminal plumose setae.
Second maxilliped (Fig. 7 B). Epipod with 1 plumose seta in proximal part, 3–5 setae in distal part; coxa, basis fused, with 3 or 4 setae; endopod 4-segmented, setal formula 2, 0, 6 or 7, 8–10; exopod 2-segmented, proximal segment with 1–3 lateral short simple setae, distal segment with 5 or 6 terminal plumose setae.
Third maxilliped (Fig. 7 C). Epipod with 11 or 12 plumodenticulate setae in proximal part, 19–23 setae in distal part; coxa, basis fused, with 8–12 setae; endopod 5-segmented, setal formula 11 or 12, 5–9, 4 or 5, 10–12, 9; exopod 2-segmented, proximal segment with 2 or 3 simple setae, distal segment with 6 terminal plumose setae.
Pereiopods (Fig. 8 A–E). Covered by rare short simple setae. Cheliped short, not longer than antenna, palm nearly equal dactylus, dactylus and fixed finger crossed. Dactyli of pereiopods 3–4 each with 1 appreciable spine in centre of inner margin; dactylus of pereiopod 5 with 2 terminal, 1 subterminal long curved serrate setae, small claw. Propodi of pereiopods 3–4 each with strong serrate seta in distal part.
Sternum (Fig. 8 F). With 5 pairs of setae in anterior part.
Pleon (Fig. 8 G, H). Consists of 6 somites, covered by simple setae (somite 1 with 8 setae, somite 2 with 14 setae, somite 3 with 12 setae, somite 4 with 12 setae, somite 5 with 10 setae, somite 6 with 6 setae). Somites 2–4 with small posterolateral processes; somites 2–5 with biramous pleopods, somite 6 with uniramous uropods.
Pleopods (Fig. 8 I, J). Exopods of pleopods 1–3 each with 14–16 plumose natatory setae, exopod of pleopod 4 with 12 or 13 plumose natatory setae; endopods of pleopods 1–4 each with 3 cincinnuli; uropod with 8 or 9 plumose setae on exopod, 1 seta on basal segment.
Telson (Fig. 8 H). Nearly rectangular; width somewhat greater than length; posterior margin with 1 pair of small tubercles; 4 pairs of setae on dorsal surface.
description: Published as part of Kornienko, Elena S. & Korn, Olga M., 2011, Morphology of the complete larval development of the symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae), pp. 45-58 in Zootaxa 2990 on pages 46-55, DOI: 10.5281/zenodo.206824