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 : 46

Y-nauplius Type AL

Figs 2 , 18A–F

Material examined

JAPAN – Okinawa, Sesoko I. , laboratory pier, 26°38ʹ09.4ʺ N, 127°51ʹ55.2ʺ E • 3 LSN, 1 of which molted to cyprid; 2018–2019 ( Tables 1 and S1 ).

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body narrowly ovate in dorso-ventral view; about 1.9 times as long as wide; relative length of trunk region quite variable; lateral margins with very slight narrowing in body outline between cephalic shield and trunk. In lateral view, longitudinal axes of cephalon and trunk in approximately same plane (not examined). Length 340 µm (ventral view in life, without dorso-caudal spine), greatest width ca 180 µm, dorso-ventral thickness not measured but body perhaps significantly flattened. Labrum produced as triangular elevation, about as long as wide, with surface divided into facets by cuticular ridges and bearing at least four pores: two in posterior midline and additional pair of pores rather posteriorly along left and right labral margins. Caudal end broadly acute, terminating in 10 µm long dorso-caudal spine with one or two annulate ridges, this spine being flanked ventro-laterally by pair of tiny, pointed furcal spines, these being situated slightly ventral to, and forward from, base of dorso-caudal spine.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body pigmentation varying among examined specimens: one dark brown overall except in marginal areas, and telson with distinct, reddish-brown pigmentation; in another, only telson brown. Telson about as long as wide and half as long as thorax.

Identification and variation

Easy recogniZable by its narrow-ovate form, dorso-ventrally flattened appearance and tiny furcal spines. Some variation was seen in the size of the furcal and dorso-caudal spines and in the pigmentation of the cyprid inside the LSN (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. 18. Last-stage nauplii of two different morphospecies of y-larvae (Facetotecta) from Sesoko Island (Okinawa, Japan). A–F. Y-nauplius Type AL. G–J. Y-nauplius Type AJ. Shown either in life (A–C, G–J) or as slide-mounted exuviae (D–F). Abbreviations: A1 = first antenna; A2 = second antenna; Md = mandible.