Austinograea rodriguezensis Tsuchida & Hashimoto, 2002

Kihara, Terue Cristina, Clark, Paul F. & Meyn, Klaas H., 2024, First zoeal stage of the Indian Ocean hydrothermal vent crab, Austinograea rodriguezensis Tsuchida & Hashimoto, 2002 (Decapoda: Brachyura: Bythograeidae), Zootaxa 5476 (1), pp. 192-206 : 194-198

Austinograea rodriguezensis Tsuchida & Hashimoto, 2002

( Figs. 2–6 )

Material examined. 2 specimens, Indian Ocean , Central Indian Ridge, Kairei Hydrothermal Vent field, 25.320°S, 70.040°E, depth 2423 m, 11 January 2016, stn INDEX16 _ 6RO, sample I16_6RO_RE1B_1, SMF 61980 and SMF 61981 .

Description of zoea I. Size: RDL = 1.25–1.50 mm (Mean= 1.37, N = 2).

Carapace ( Fig. 2 ): multispinulate, dorsal spine long, spinulate and curved distally, longer than rostral spine; rostral spine, long, longer than antennal protopod and with 4 spines, 2 proximal, 2 distal; lateral spines long, straight and spinulate; 1 pair of anterodorsal setae; 1 pair of posterodorsal setae; 1 anterodorsal and posterodorsal protuberance, ventral margin presence of a spine posterior to the notch, marginal setae absent.

Cephalon

Eyes ( Fig. 2 ): sessile with spines on or near circumcorneal margin.

Antennule ( Fig. 3A ): primary flagellum unsegmented with 3 terminal aesthetascs of unequal length and 3 terminal setae of unequal length; accessory flagellum absent.

Antenna ( Fig. 3B ): biramous; protopodal process distally bilaterally spinulate, shorter than rostral spine, 1 small basal spine (not visible in the figure); endopod spine present; exopod half of the length of protopod, possessing 3 (1 long subterminal + 2 unequal terminal) setae and 2 small medial lateral spines.

Mandible ( Fig. 3C–D ): palp absent.

Maxillule ( Fig. 4A ): uniramous; epipod seta absent; coxal endite with 7 setae; basial endite with 5 setal processes; endopod comprising 2 articles, proximal article with 1 seta; distal article with 1 subterminal and 4 terminal setae; exopod seta absent.

Maxilla ( Fig. 4B ): biramous; coxal endite bilobed with 8+4 setae; basial endite bilobed with 5+4 setae; endopod bilobed with 3+4 (1 subterminal+3 terminal) setae; exopod (scaphognathite) margin with 4 setae and 1 long distal stout process.

Pereion

First maxilliped ( Fig. 4C–D ): biramous; coxa with 1 seta ( Fig. 4D ); basis with 10 (2+2+3+2) setae; endopod comprising 5 articles with 3,2,1,2,5 (2 subterminal+3 terminal) setae respectively; exopod comprising 2 articles, distal article with 4 long terminal plumose natatory setae.

Second maxilliped ( Fig. 4E–F ): biramous; coxa without setae; basis with 4 (1+1+1+1) setae; endopod comprising 3 articles, with 1,1, 6 (3 subterminal+3 terminal) setae respectively; exopod comprising 2 articles, distal article with 4 long terminal plumose natatory setae. Variability: SMF 61980 setation of the terminal endopodal article of the left second maxilliped with 7 (3 subterminal+4 terminal) setae ( Fig. 4F ).

Third maxilliped: absent.

Pereiopods: absent.

Pleon

Pleon ( Figs. 5A–B , 6A ): 5 pleomeres present; pleomeres 3–5 each with 1 pair of middorsal and 1 pair of dorsolateral processes, 1 pair of posterodorsal setae and distal margin spinulate; pleomeres 4–5 with additional 1 pair of middorsal processes and pairs of dorsolateral processes (1 pair in pleomeres 4 and 2 pairs in pleomere 5); pleopod buds absent.

Telson ( Figs. 5A–B , 6B ): each fork long, gradually curved distally and spinulate; 1 pair of dorsal medial spines; 2 pairs of dorsolateral spines, 1 pair of dorsolateral glands and 1 pair of anterodorsal spines; 1 pair of middorsal spines; 1 pair of dorsolateral setae and 1 pair of posterodorsal setae; 3 pairs of stout spinulate setae on posterior margin.

Figures

FIGURE 2. CLSM images of Austinograea rodriguezensis Tsuchida & Hashimoto, 2002, zoea I, SMF 61980: A, lateral view; B, dorsal view. Scale bars = 100 µm.

FIGURE 3. Drishti images of Austinograea rodriguezensis Tsuchida & Hashimoto, 2002, zoea I, SMF 61980: A, antennule; B, antenna; C, mandible, anterior view; D, mandible, posterior view. Scale bars = 100 µm.

FIGURE 4. CLSM images of Austinograea rodriguezensis Tsuchida & Hashimoto, 2002, zoea I, SMF 61980:A, maxillule; B, maxilla; C, first maxilliped; D, setation of first maxilliped coxal article; E, right second maxilliped; F, setation of the terminal endopodal article of the left second maxilliped. Scale bars = 50 µm.

FIGURE 5. Austinograea rodriguezensis Tsuchida & Hashimoto, 2002, zoea I, pleon and telson, dorsal view, SMF 61980: A, CLSM image; B, Drishti image. Scale bars = 100 µm.

FIGURE 6. Austinograea rodriguezensis Tsuchida & Hashimoto, 2002, zoea I, dorsal view, SMF 61980: A, pleon, schematic illustration of pleomeres 3–5; B, telson. Scale bar = 100 µm.