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 : 50

Y-nauplius Type AO

Figs 2 , 19F–G

Material examined

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

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body shape lanceolate in dorso-ventral view; about 2.2 times as long as wide; lateral margins tapering gradually towards caudal end, with very slight narrowing apparent at posterior end of cephalic shield. No lateral view obtained, but longitudinal axes of cephalon, trunk and dorso-caudal spine apparently in nearly same plane. Length 366 µm (based on exuvia on slide, without dorso-caudal spine), greatest width 170 µm, greatest dorso-ventral thickness unknown but body apparently rather flattened. Labrum not examined in detail but with straight posterior margin and with surface undivided into facets; pores not examined. Caudal end attenuate, terminating in 90 µm long, spinose dorso-caudal spine accompanied by slightly more ventrally and forward-positioned pair of ca 17 µm long furcal spines.

CYPRID VIEWED THROUGH CUTICLE OF LSN. The only available information on live specimens is from the slide label, which reports that the tip of the [cyprid] tail is brown.

Identification and variation

Recognizable by its great length relative to width, relatively long and slender dorso-caudal spine and relatively long furcal spines.

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.