Page 150 - 《水产学报》2026年第2期

2 期 PASSMORE Roland Madziva，等：银灰半棱鳀仔稚鱼的脊柱和附肢骨骼发育 50 卷

complete sinking. Specimens were then cleared with a portion starting on hypural 1 (Plate Ⅰ-5). Uroneural 2
30 mL saturated borax solution in 70 mL distilled formed via intramembranous ossification dorsal to a
water and 1 g trypsin. The solution was replaced every flexed notochord. Ural centra (U1 and U2) formed by
1-2 days or when it turned blue. To accelerate clear- intramembranous ossification. Ural centrum 2 formed
ing, samples were incubated in a water bath at 37 ℃ first, prior to uroneural 1, and was closely associated
until they softened and became transparent. Following with hypurals, Hy3, Hy4 and Hy5, whereas ural
clearing, the specimens were stained with Alizarin Red centrum 1, and was associated with hypurals, Hy1 and
to visualise the ossified bone, which turned reddish- Hy2. By 10.24 mm SL, hypural 5 had lost its associ-
purple. The specimens were bleached and cleaned ation with ural centrum 1 (U1) at its base. Preural
overnight through a graded series of 0.5% KOH solu- centra (PU1, PU2 and PU3) ossified prior to their
tion-glycerine mixtures (3∶1, 1∶1, and 1∶3 v/v) associated neural and haemal arches. Two epurals
until completely immersed in each. Specimens were appear as cartilaginous ovals posterior-dorsal to the
stored in pure glycerol for long-term preservation. notochord (Plate Ⅰ-6), then epural 3 at 13.10 mm SL
(Plate Ⅰ-7). Epurals (Ep1 and Ep2) fused at 34.56
Specimens were observed under a Nikon SMZ745T
and photographed with a CCD camera (HTC1600ISP). mm SL, forming a rod-like anterior-dorsal epural com-
pound (Plate Ⅰ-8). Radial cartilage was first observed
All animal experimental procedures were
at 34.56 mm SL ventral and close to the parhypural
reviewed and approved by the Institutional Ethics
and preceding haemal spine. Principal fin ray segment-
Committee of the College of Fisheries and Life Sci-
ation was evident at 10.24 mm SL and greater.
ence, Shanghai Ocean University, Shanghai, China
Hypural 6 ossified last after hypurals 1-5. All hypur-
and were performed in accordance with the guidelines
als, Hy1 to Hy6, epurals (Ep 1+2) and Ep3, haemal
of Shanghai Ocean University Laboratory Animal Eth-
and neural spines, and parhypural remain with their
ics Committee on the care and use of animals in sci-
cartilaginous distal margins by 34.56 mm SL.
entific research.
2.2 Dorsal fin development
2 RESULTS
Dorsal fin development was initially character-
ised by the presence of dorsal anlagen in specimens
2.1 Caudal complex
ranging from 3.78 to 4.54 mm NL. As development
Two hypurals (Hy1 and Hy2) appeared as car-
proceeded, proximal radials emerge around 5.20 mm
tilaginous structures before notochord flexion at a size NL (Plate Ⅱ-1), forming anteriorly. In larger speci-
of 5.55 mm NL, followed by the formation of parhy- mens beyond 5.20 mm NL, posterior distal radials
pural cartilage (Plate Ⅰ-1). At notochord flexion in become apparent, with new elements also forming
6.08 mm NL (Plate Ⅰ-2), 3 more hypurals, Hy3, Hy4 anteriorly (Plate Ⅱ-2). Both structures are composed
and Hy5 emerge. The first haemal arch formed prior to of cartilage. Dorsal fin rays appear as cartilaginous,
the neural arches. Parhypural was fused to hypural 1 soft projections but later elongate at 5.68 mm NL. And
by a temporary cartilaginous bridge proximally. 13 proximal radials and 13 distal radials present by
Uroneural 1 appears as cartilage and later ossifies at 9.58 mm SL. In the posteriormost region of speci-
7.38 mm NL. Principal fin rays developed by mens measuring 10.24-18.08 mm SL (Plate Ⅱ-3), a
intramembranous ossification by 6.32 mm NL. Seg- stay bone appears consistently as a small cartilaginous
mentation of these fin rays was evident by 10.24 mm projection out-growth elongating posteriorly. The
SL. The first neural arch was observed at 7.38 mm NL anterior process of the first proximal radial formed,
(Plate Ⅰ-4). In postflexion larvae (9.58 mm SL), initially as cartilage at 13.20 mm SL and became
hypural 6 appears as a cartilaginous bud, and parhy- learly discernible by 18.08 mm SL. By this stage, the
pural and hypural, Hy1 to Hy5 begin ossifying mid- count of both distal and proximal radials is 13. At the

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