Sestrostoma balssi ( Shen, 1932 )

Kornienko, Elena S. & Korn, Olga M., 2011, Morphology of the complete larval development of the symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae), Zootaxa 2990, pp. 45-58 : 46-55

publication ID	https://doi.org/ 10.5281/zenodo.206824
DOI	https://doi.org/10.5281/zenodo.6192354
persistent identifier	https://treatment.plazi.org/id/038B87E0-F906-5E03-FF63-C14AD4CDF877
treatment provided by	Plazi
scientific name	Sestrostoma balssi ( Shen, 1932 )
status

Treatment

Sestrostoma balssi ( Shen, 1932) View in CoL

Acmaeopleura balssi Shen, 1932: 155 View in CoL , 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 View in CoL – Davie & N.K. Ng, 2007: 265, figs 7, 8.

The development of S. balssi View in CoL 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 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 . Only morphological changes are described for the second to fifth zoeal stages.

Description of larval stages. ( Figs 1–8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

First zoea ( Fig. 1 View FIGURE 1 )

Material examined. CL = 0.46±0.02 mm, DRL = 1.20±0.04 mm, N = 10.

Minimal duration. 6 days.

Carapace ( Fig. 1 View FIGURE 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 View FIGURE 1 C). Uniramous, endopod absent; exopod conical, unsegmented, with 2 long, 1 short terminal aesthetascs, 2 short terminal setae.

Antenna ( Fig. 1 View FIGURE 1 D). Protopod pointed, with 2 rows of sharp spinules; exopod as a small bud with 1 simple terminal seta.

Mandible ( Fig. 1 View FIGURE 1 E). Asymmetrical; without palp.

Maxillule ( Fig. 1 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 2 )

Material examined. CL = 0.57±0.02 mm, DRL = 1.57±0.06 mm, N = 10.

Minimal duration. 5 days.

Carapace ( Fig. 2 View FIGURE 2 А). Eyes stalked. Four pairs of setae on surface of carapace; each ventral margin with 2 setae.

Antennule ( Fig. 2 View FIGURE 2 B). Exopod with 4 long terminal aesthetascs.

Antenna ( Fig. 2 View FIGURE 2 C). Unchanged.

Mandible ( Fig. 2 View FIGURE 2 D). Unchanged.

Maxillule ( Fig. 2 View FIGURE 2 F). Basial endite with 5 plumodenticulate cuspidate, 2 plumodenticulate setae; exopod seta present.

Maxilla ( Fig. 2 View FIGURE 2 F). Proximal part of scaphognathite with 5, distal part with 3 densely plumose setae.

First maxilliped ( Fig. 2 View FIGURE 2 G). Exopod with 6 terminal plumose natatory setae.

Second maxilliped ( Fig. 2 View FIGURE 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 View FIGURE 3 )

Material examined. CL = 0.63±0.04 mm, DRL = 1.96±0.04 mm, N = 7.

Minimal duration. 6 days.

Carapace ( Fig. 3 View FIGURE 3 A). One pair of setae on dorsal spine; each ventral margin with 4 setae.

Antennule ( Fig. 3 View FIGURE 3 B). Exopod with 3 terminal aesthetascs.

Antenna ( Fig. 3 View FIGURE 3 C). Unchanged.

Mandible ( Fig. 3 View FIGURE 3 D). Unchanged.

Maxillule ( Fig. 3 View FIGURE 3 E). Basial endite with 1 lateral seta; epipod seta present.

Maxilla ( Fig. 3 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 3 I). The sixth pleonal somite differentiated.

Telson ( Fig. 3 View FIGURE 3 I). Posterior margin with 4+4 plumodenticulate setae.

Fourth zoea ( Fig. 4 View FIGURE 4 )

Material examined. CL = 0.88±0.05 mm, DRL = 2.77±0.16 mm, N = 10.

Minimal duration. 7 days.

Carapace ( Fig. 4 View FIGURE 4 A). Two pairs of setae on dorsal spine; each ventral margin with 7 or 8 setae.

Antennule ( Fig. 4 View FIGURE 4 B). Exopod with 4 terminal, 1 subterminal aesthetascs.

Antenna ( Fig. 4 View FIGURE 4 C). Biramous, endopod about of 1/3 of protopod.

Mandible ( Fig. 4 View FIGURE 4 D). Unchanged.

Maxillule ( Fig. 4 View FIGURE 4 E). Coxal endite with 7 plumodenticulate setae; basial endite with 12 or 13 plumodenticulate setae (5 cuspidate, 2 lateral).

Maxilla ( Fig. 4 View FIGURE 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 View FIGURE 4 G). Endopod setal formula progressing distally 2, 3, 2, 2, 2+4; exopod with 10 terminal plumose natatory setae.

Second maxilliped ( Fig. 4 View FIGURE 4 H). Exopod with 10 terminal plumose natatory setae.

Third maxilliped ( Fig. 4 View FIGURE 4 I). Biramous.

Pereiopods ( Fig. 4 View FIGURE 4 J). Pereiopod I chelated.

Pleon ( Fig. 4 View FIGURE 4 K). Somite 1 with 3 dorsomedial setae; somites 2–5 with uniramous pleopod buds. Telson ( Fig. 4 View FIGURE 4 K). Unchanged.

Fifth zoea ( Fig. 5 View FIGURE 5 )

Material examined. CL = 1.05±0.06 mm, DRL = 3.20±0.12 mm, N = 8.

Minimal duration. 11 days.

Carapace ( Fig. 5 View FIGURE 5 A). Three pairs of setae on dorsal spine; each ventral margin with 8–12 setae; posterodorsal arch with 2 setae.

Antennule ( Fig. 5 View FIGURE 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 View FIGURE 5 C). Endopod slightly shorter than protopod, incompletely segmented.

Mandible ( Fig. 5 View FIGURE 5 D). Palp bud present.

Maxillule ( Fig. 5 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 5 H). Exopod incompletely 2-segmented, with 12 terminal plumose natatory setae.

Third maxilliped ( Fig. 5 View FIGURE 5 I). Increased in size, incompletely segmented.

Pereiopods ( Fig. 5 View FIGURE 5 J). Increased in size, incompletely segmented.

Pleon ( Fig. 5 View FIGURE 5 K). Somite 1 with 5 dorsomedial setae; somite 2–5 with biramous pleopods, somite 6 with uniramous uropods.

Telson ( Fig. 5 View FIGURE 5 K). Posterior margin with 5+5 plumodenticulate setae.

Megalopa ( Figs 6–8 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Material examined. CL = 1.45±0.09 mm, СW = 1.22±0.05 mm, N = 4.

Minimal duration. Undetermined.

Carapace ( Fig. 6 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 6 D). Palp 2-segmented, distal segment with 8 setae.

Maxillule ( Fig. 6 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 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 View FIGURE 8 F). With 5 pairs of setae in anterior part.

Pleon ( Fig. 8 View FIGURE 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 View FIGURE 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 View FIGURE 8 H). Nearly rectangular; width somewhat greater than length; posterior margin with 1 pair of small tubercles; 4 pairs of setae on dorsal surface.