Misidentification of mysis stages of Xiphopenaeus kroyeri (Heller, 1862) and Rimapenaeus Pérez-Farfante and Kensley, 1997 (Decapoda: Penaeidae) in the western Atlantic

Abstract

Studies in the western Atlantic have relied primarily on the key of Cook (1966) to identify and discriminate early life stages (ELS) of Xiphopenaeus kroyeri (Heller, 1862) and Rimapenaeus spp. Pérez-Farfante and Kensley, 1997, even though larvae had not been reared successfully past the zoea phase at that time. We surveyed the penaeid literature for descriptions of reared mysis stages of X. kroyeri and Rimapenaeus, compared characters with those of Cook (1966), and found that Cook had reversed illustrations and criteria to discriminate taxa. We also examined plankton-collected mysis stages and identified new characters and previously unrecognized differences between taxa. Mysis stages of X. kroyeri have a slender median spine laterally near the posterior margin of pleomere five, not those of Rimapenaeus, although some early first myses of Rimapenaeus may have a vestigial spine laterally on pleomere five. Rimapenaeus has single dorsomedian spines on pleomeres four through six with the spine on pleomeres five and six >40% (usually about 50%) of fifth pleomere length as measured along the dorsal midline. Rimapenaeus lacks a pterygiostomial spine, although a spine on the distal margin of the developing antennal peduncle near the ventrolateral border of the carapace can be confused with a pterygiostomial spine. Xiphopenaeus kroyeri has a pterygiostomial spine and single dorsomedian spines on pleomeres four through six with the spine on pleomeres five and six <35% (usually about 25%) of fifth pleomere length. Xiphopenaeus kroyeri also has a gap about the width of one spine between the longest and adjacent outer pairs of furcal spines along the posterior margin of the telson, whereas Rimapenaeus has contiguous furcal spines. Differences in spine length dorsally on pleomeres five and six, and the presence or absence of a pterygiostomial spine should be used to discriminate taxa because the low hepatic spine and median spine laterally on pleomere five can be difficult to detect in X. kroyeri, even with a biological stain applied. Likely misidentification of mysis stages and possible overexploitation of X. kroyeri and Rimapenaeus spp. stocks in the western Atlantic emphasizes the need to reassess information on ELS and the necessity of accurate identifications.

A Mysterious World Revealed: Larval-Adult Matching of Deep-Sea Shrimps from the Gulf of Mexico

“…For example, in the Gulf of Mexico, larvae stages are known from the shrimp family Penaeidae [15][16][17], the crab families Menippidae (stone crabs) and Portunidae (swimming crabs) [18][19][20][21] and the spiny lobster family Palinuridae [22]. In the last decade, additional papers have been published for decapod larval stages in the Gulf of Mexico [23][24][25], however more studies are needed. Our knowledge of pelagic or benthic deep-sea decapod larvae is inadequate or even non-existent and is further complicated by the technological demands and expense of sampling in deep oceanic waters.…”