Hansenocaris undetermined

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 : 51

Y-nauplius Type AN

Figs 2 , 19I–K

Material examined

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

Description

LAST-STAGE NAUPLIUS (LSN). Lecithotrophic. Body narrowly ovate in dorso-ventral view; about 1.7 times as long as wide; lateral margins tapering gradually towards caudal end with slight discontinuity at posterior end of cephalic shield. No lateral view available, but longitudinal axes of cephalon, trunk and dorso-caudal spine apparently nearly in same plane. Length 320–350 µm (ventral view of mounted exuviae, without dorso-caudal spine), greatest width ca 190 µm, greatest dorso-ventral thickness unknown but body apparently rather flattened. Labrum produced as trapezoidal elevation divided into facets by cuticular ridges; pores not examined in detail. Trunk with rows of 5 µm long spines along margins. Caudal end attenuate, terminating in ca 50 µm long dorso-caudal spine accompanied ventrally and farther forwards by pair of triangular, pointed furcal spines ca 5 µm long. Dorso-caudal spine broad-based but sharply pointed, with irregularly ridged proximal portion bearing a few spinules.

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

Identification and variation

Recognizable by its general shape and by its significantly smaller size compared to the otherwise similar Type Y (see above).

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. 19. Last-stage nauplii of four different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–E. Y-nauplius Type AK. F–G. Y-nauplius Type AO. H. Y-nauplius Type AM. I–K. Y-nauplius Type AN. Shown either in life (A–B, H) or as slide-mounted exuviae (C–G, I–K). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible.