Ocypodidae Rafinesque, 1815

Kumar, Austin A. J. & Al-Aidaroos, Ali M., 2022, Fig. 5 in Fig. 2 in An Updated Checklist of Sea Slugs (Gastropoda, Heterobranchia) from Hong Kong Supported by Citizen Science., Zoological Studies 61 (70), pp. 1-23 : 3-13

Family Ocypodidae Rafinesque, 1815 Austruca albimana (Kossmann, 1877) ( Figs. 1–15 )

Zoea I

Size (mean ± sd): CL = 0.3 ± 0.05 mm; RDL = 0.59 ± 0.09 mm.

Carapace ( Fig. 2a): Smooth; rostrum short, dorsal spine small, curved posteriorly, smaller than rostrum; lateral spines absent; ventral margin without setae; eyes sessile.

Antennule ( Fig. 3a): Endopod absent; exopod unsegmented with 2 long, 3 short aesthetascs.

Antenna ( Fig. 4a): Biramous. Protopodal process bilaterally spinulate up to distal margin; exopod with two terminal simple setae.

Mandible ( Fig. 5a): Incisor with five blunt teeth, molar process present, posterior margin with three teeth; palp absent.

Maxillule ( Fig. 6a): Epipod seta absent; coxa with 2 subterminal plumodenticulate, 3 terminal cuspidate setae; basis with 5 terminal setae (4 cuspidate, 1 plumodenticulate); endopod 2-segmented, distal segment with two plumodenticulate terminal setae.

Maxilla ( Fig. 7a): Coxa bilobed, proximal lobe with 2 cuspidate, 1 plumodenticulate setae, basis with 2 plumodenticulate setae; basis bilobed, proximal segment with 4 cuspidate terminal setae, distal segment with 3 plumodenticulate terminal setae; endopod bilobed with 1+2 terminal plumose setae; scaphognathite with 4 plumose setae.

First maxilliped ( Fig. 8a): Basis with 2+2+3+2 sparsely plumose setae; endopod 5-segmented with 2 (plumose), 2 (plumose), 1 (plumose), 2–3 (plumose), 5 (2 plumose subterminal, 3 plumodenticulate terminal) setae; exopod 2-segmented, distal segment with 4 natatory plumose setae.

Second maxilliped ( Fig. 9a ): Basis with 1+1+1+1 plumose setae; endopod 3-segmented with 0,0,5 (3 simple, 2 plumodenticulate setae); exopod bisegmented with 4 terminal plumose setae.

Pleon ( Fig. 10a ): Five somites; somite II with pair of anteriorly directed dorsolateral processes; somite III with pair of posteriorly directed dorsolateral processes; somite IV broader than others, posterolateral margin overlapping with Vth somite; somite I without seta; somites II–V with pair of posterodorsal simple setae.

Telson ( Fig 10a ): Inner margin with 3 pairs of setae; minute spines on lateral sides of forks of telson.

Zoea II

Size (mean ± sd): CL = 0.35 ± 0.02 mm; RDL = 0.8 ± 0.05 mm.

Antenna ( Fig. 4b): Endopod bud present.

Mandible ( Fig. 5b): Incisor with six blunt teeth, all margins of molar process toothed.

Maxillule ( Fig. 6b): Basis with 5 cuspidate, 1 plumodenticulate setae; epipod seta present.

Maxilla ( Fig. 7b): Coxa bilobed, proximal lobe with 1 cuspidate, 4 plumodenticulate setae, distal lobe with 3 plumodenticulate setae; basis bilobed, proximal segment with 1 cuspidate, 5 plumodenticulate setae, distal segment with 1 cuspidate, 3 plumodenticulate setae; scaphognathite with 8 plumose setae.

First maxilliped ( Fig. 8b): Endopod with 2,2,1,3,6 (2 subterminal plumose, 4 terminal plumodenticulate) setation; exopod with 6 natatory setae.

Second maxilliped ( Fig. 9b ): Exopod with 6

natatory setae.

Pleon ( Figs. 10b ; 13 a, b ): Pleopod buds appear.

Zoea III

Size (mean ± sd): CL = 0.57 ± 0.05 mm; RDL = 0.9

± 0.09 mm.

Carapace ( Fig. 2c): Small hairs on anterodorsal margin.

Antennule ( Fig. 3c): Three aesthetascs, two spines.

Antenna ( Fig. 4c): Endopod about one half length of protopod.

Mandible ( Fig. 5c): Incisor with around eight blunt teeth, posterior margin of molar process with large tooth, other margins smooth.

Maxillule ( Fig. 6c): Coxa with 2 cuspidate, 2 plumodenticulate, 1 simple setae; basis with 7 cuspidate, 2 plumodenticulate setae.

Maxilla ( Fig. 7c): Proximal segment of coxa with 4 plumodenticulate, 1 cuspidate setae, distal segment with 3 cuspidate setae; proximal segment of basis with 3 cuspidate, 2 plumodenticulate setae, distal segment with 2 cuspidate, 3 plumodenticulate setae; scaphognathite with 13 plumose setae.

First maxilliped ( Fig. 8c): Coxal seta; basis with 2,2,3,3 plumose setae; exopod with 8 plumose natatory setae.

Second maxilliped ( Fig. 9c ): Exopod with 8 plumose natatory setae.

Pereiopods ( Fig. 11a). Segmentation incomplete.

Pleon ( Fig. 10c ): Six somites; somites III–V with well-developed posterolateral processes; pleopod buds more developed.

Telson ( Fig. 10c ): Inner margin with four pairs of setae.

Zoea IV

Size (mean ± sd): CL = 0.6 ± 0.05 mm; RDL = 1.4 ± 0.1 mm.

Carapace ( Fig. 2d): Twelve pairs of ventral setae.

Antennule ( Fig. 3d): Eight aesthetascs arranged in two groups (4+4).

Antenna ( Fig. 4d): Endopod longer than exopod.

Mandible ( Fig. 5d): Incisor with eight teeth, all margins of molar process toothed.

Maxillule ( Fig. 6d): Two epipodal setae; coxa with 2 cuspidate, 3 plumodenticulate (1 subterminal, 2 terminal) setae; basis with 3 terminal cuspidate, 6 plumodenticulate setae (3 subterminal).

Maxilla ( Fig. 7d): Proximal lobe of coxa with 5 plumodenticulate setae, distal segment with 3 cuspidate setae; proximal lobe of basial with 2 cuspidate, 4 plumodenticulate setae, distal segment with 3 cuspidate, 2 plumodenticulate setae; scaphognathite with 24 plumose setae (20 Plumose, 4 simple).

First maxilliped ( Fig. 8d): Exopod with 10 plumose natatory setae.

Second maxilliped ( Fig. 9d ): Exopod with 10 plumose natatory setae.

Third maxilliped ( Fig. 9f ): Present, not well developed.

Pereiopods ( Fig. 11b): Well developed, segmented.

Pleon ( Figs. 10d, e , 14a, b, 15 ): Somite I with 5 dorsal setae; pleopods well developed.

Megalopa

Size: CW = 0.86 mm; CL = 1.1 mm.

Carapace ( Fig. 2e): Longer than broad; sparsely setose dorsally, posterolateral margins with few setae; rostral spine truncated, naked; eyes stalked.

Antennule ( Fig. 3e): Peduncle 3-segmented with 3,1,0 plumose setae; endopod small, unsegmented with 2 plumose, distal setae; exopod three-segmented with 0, 6 (aesthetascs), 4 (3 aesthetascs, 1 seta) setation.

Antenna ( Fig. 4e): 3-segmented peduncle with 1,1,1 plumose setae; flagellum 7-segmented with 0,0, 2,0,2,2,2 setae, segments 1–6 with plumose setae, 7th segment with simple setae.

Mandible ( Fig. 5e): Palp two-segmented; distal segment with 3 terminal simple setae.

Maxillule ( Fig. 6e): Coxa with 8 cuspidate, 6 plumodenticulate setae; basis with 5 cuspidate, 2 plumose and 2 plumodenticulate setae; endopod bisegmented, distal segment terminates with seta; single protopod plumose seta.

Maxilla ( Fig. 7e): Coxa bilobed, proximal segment with 13 setae, distal segment with 5 setae, all plumodenticulate; basis bilobed, proximal segment with 7 simple setae, distal segment with 6 simple, 1 plumose setae; endopod unsegmented without setae; scaphognathite with 51 plumose setae.

First maxilliped ( Fig. 8e): Coxa, basis with 5, 6 plumodenticulate setae, respectively; endopod with 2 subterminal setae; exopod 2-segmented, proximal segment with two distal setae, distal segment with 3 setae, all plumose; epipod with 7 long setae.

Second maxilliped ( Fig. 9e ): Endopod 4-segmented with 0, 0, 4 (all plumodenticulate), 7 (4 cuspidate, 3 plumodenticulate) setation; exopod 2-segmented, distal segment with 4 plumose setae.

Third maxilliped ( Fig. 9g ): Protopod naked; endopod 5-segmented with 9 (5 plumodenticulate, 4 simple), 7 (4 simple, 3 plumodenticulate), 2 (plumodenticulate), 6 (plumodenticulate), 5 cuspidate setae; exopod 3-segmented without setation, epipod with 20 (18 simple, 2 plumose) setae.

Pereiopods ( Fig. 11c–g): Inner margins of fused basis, ischium, merus, superior border of carpus of chelae with 1 or 2 spines each; fingers cross each other; inner margins of segments of pereiopods II–IV with few spines; coxa of Vth pereiopods with three stout plumose setae; superior margins of carpus and propodus with 1 or 2 spines; tips of dactyl with 3 long setae.

Pleon ( Fig. 10f ): Six somites; somites I, III, IV with 1 pair of setae each, somite II with 2 pairs of setae, one each on anterior and posterior borders, V and VI with two pairs of posterior setae each; somite III with 3 pairs of setae; somite V with well-developed lateral processes.

Telson ( Fig. 10f ): Tip rounded: 5 pairs of plumose setae; three pairs anteriorly, two pairs posteriorly.

Pleopods ( Fig. 12a–d): Endopods of somites I– V with three cincinnuli each, pleopod of somite VI without endopod; exopods of pleopods of somite II–VI with 13S, 12S, 14S, 12S plumose setae, respectively.

Uropod ( Fig. 12e): Exopod with 9 plumose setae, protopod with plumose seta.

Figures

Fig. 1. Austruca albimana (Kossmann, 1877), dorsal view of the berried female.

Fig. 9. Austruca albimana (Kossmann, 1877), second maxilliped: a) zoea I; b) zoea II; c) zoea III; d) zoea IV; e) megalopa; f) third maxilliped of zoea IV; g) third maxilliped of megalopa.

Fig. 10. Austruca albimana (Kossmann, 1877), dorsal view of pleon: a) zoea I; b) zoea II; c) zoea III; d) zoea IV; e) fork of the telson of zoea IV; dorsal view of pleon: e) megalopa.

Fig. 13. Austruca albimana (Kossmann, 1877), SEM images of the telson of zoea II; a) at magnification 6000×; b) at magnification 10000×.

Fig. 15. Austruca albimana (Kossmann, 1877), SEM images of the telson of zoea IV at magnification 40000×.