Hansenocaris cristalabri 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 : 24-25

Hansenocaris cristalabri Olesen & Grygier, 2022

Figs 2 , 5C , 9A–B

Hansenocaris cristalabri Olesen & Grygier, 2022: 304 , figs 1–5, tables 1–2.

Hansenocaris cristalabri – Dreyer et al. 2023b: fig. 1d.

One of “three known larval types of ‘y-larvae’” – Olesen 2024: fig. in upper right corner on p. 17.

Material examined

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

Description

LAST-STAGE NAUPLIUS (LSN) . Lecithotrophic. Body spoon-shaped in dorso-ventral view; about twice as long as wide (without dorso-caudal spine); cephalic shield broadly rounded, with sharp discontinuity in body outline leading into trunk. In lateral view, body only slightly bent, trunk axis downturned 15–20° relative to cephalic axis. Length ca 330 µm (ventral view in life, without dorso-caudal spine), greatest width 180 µm, greatest dorso-ventral thickness ca 100 µm. Labrum with goblet-shaped outline in ventral view and posterior margin free; labral surface divided into facets by cuticular ridges; midline of labrum extending ventrally as huge, cockscomb-like, spine-bearing crest. Cephalic shield with spines bordering pair of pits at postero-lateral corners. Trunk dorsum with two longitudinal rows of spines. Caudal end attenuate, terminating in 120 µm long, robust, and conical dorso-caudal spine armed with smaller spines and accompanied ventrally at base by pair of curved, 15 µm long furcal spines; dorso-caudal spine upturned 20° relative to trunk axis.

CYPRID VIEWED THROUGH CUTICLE OF LSN. Body weakly brownish with darker brown pigmentation in parts of thorax and telson. Telson less than half as long as thorax.

Identification and variation

Easily recognizable by its huge and unique labral crest-like process, the spines near the postero-lateral corners of the cephalic shield, the two longitudinal rows of spines dorsally 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. 5. Scanning electron micrographs of three significantly different kinds of last-stage lecithotrophic (non-feeding) y-nauplii (Facetotecta) illustrating key characters (general body size and shape, and morphology of labrum and caudal spines) used herein to separate and describe 34 y-naupliar morphospecies, with various measurements explained directly on the figure. A–B. Hansenocaris demodex Olesenet al., 2022, ventral view with detail of labral area.C. Hansenocaris cristalabri Olesen & Grygier, 2022 (holotype, NHMD), lateral view. D–F. Type K, lateral view with details of labrum and caudal spines. A–B from Olesen et al. (2022); C from Olesen & Grygier (2022).

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).