Hansenocaris aquila Olesen & Grygier, 2022

Olesen, Jørgen & Grygier, Mark J., 2024, Taxonomic diversity of marine planktonic ‘ y-larvae’ (Crustacea: Facetotecta) from a coral reef hotspot locality (Japan, Okinawa), with a key to y-nauplii, European Journal of Taxonomy 929 (1), pp. 1-90 : 26

Hansenocaris aquila Olesen & Grygier, 2022

Figs 2 , 9D–E

Hansenocaris aquila Grygier &Olesen, 2022: 307 , fig. 6.

Hansenocaris aquila – Olesen et al. 2024: fig. 2.

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 2 LSN; 1991–2005 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body spoon-shaped in dorso-ventral view; about twice as long as wide; cephalic shield broadly rounded, with sharp discontinuity in body outline leading into trunk. In lateral view, trunk axis bent downwards ca 40° with respect to cephalic axis. Length 400 µm (ventral view of mounted exuvia, without dorso-caudal spine), greatest width ca 210 µm, dorso-ventral thickness ca 120 µm. Labrum with goblet-shaped outline in ventral view, its free posterior margin extending into large medial spine (‘stem’ of ‘goblet’), preceded by four small spines on labral midline; labral surface divided into facets by cuticular ridges. Trunk dorsum with four longitudinal rows of spines. Caudal end attenuate, terminating in 100 µm long, robust dorso-caudal spine armed with many smaller spines and accompanied ventrally at base by pair of small, ca 5 µm long furcal spines; long axis of dorso-caudal spine upturned 15° with respect to trunk axis.

CYPRID VIEWED THROUGH CUTICLE OF LSN. No live specimens examined.

Identification and variation

Easily recognizable by its labrum with the posterior margin extended into a large, eagle-beak-like median spine preceded by ca four small spines on the midline; also distinguished by the four dorsal rows of longitudinal spines on the trunk and the very long, robust and distinctly spinose dorso-caudal spine.

Distribution

Japan (Sesoko Island, Okinawa).

Figures

Fig. 2. Y-naupliar (Facetotecta) diversity at Sesoko Island (Okinawa, Japan). A. Schematic life cycle of y-larvae (modified from Itô 1991; Glenner et al. 2008). B. Overview of 34 morphospecies of lecithotrophic last-stage y-nauplii obtained by laboratory rearing of earlier-stage nauplii collected in the plankton; three of them represent formally described species while 31 remain undescribed. C. Nine types of planktotrophic y-larvae, of which only Type A* is treated in detail in this paper. All photos in B and C are to the same scale. Figure also used in Olesen (2004). Examples of live video of most of the y-naupliar morphospecies can be seen at https://youtu.be/er0mYLswV-c and are also deposited at Figshare.com: https://doi.org/10.6084/m9.figshare.24953568.v1.

Fig. 9. Last-stage nauplii of four different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–C. Hansenocaris cristalabri Olesen & Grygier, 2022. D–E. Hansenocaris aquila Olesen & Grygier, 2022. F–H. Y-nauplius Type AC. I–N. Y-nauplius Type AH*. Shown either in life (A–B, F–H, I–J), as slide-mounted exuviae (D–E, K–N) or in SEM (C). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible. A–E from Olesen & Grygier (2022).