Latreutes bicornis ( Kemp, 1925 )

Wicksten, Mary K. & Hancock, Zachary B., 2021, Synonymy of the Caridean Shrimp Genus Paralatreutes Kemp, 1925 with Latreutes Stimpson, 1860 (Decapoda: Hippolytidae), Proceedings of the California Academy of Sciences 67 (8), pp. 247-252 : 248-250

Latreutes bicornis ( Kemp, 1925)

Paralatreutes bicornis Kemp, 1925: 334-338 , figs. 23-24; Holthuis 1993: 245, fig. 242; Chace 1997: 55; Yang 2005: 462.

Material examined.— Female , not ovigerous, carapace length 5.33 mm. Philippine Islands: Luzon , Mabini (Calumpan Peninsula), Balayan Bay , Matotonngil Point , 13.76oN, 120.91oE, 18 m, 27 April 2014, Peri Paleracio, coll., on Porifera; California Academy of Sciences catalog number CASIZ202665 .

Diagnosis.— Body form robust. Rostrum with dorsal margin bearing 8–11 teeth, diminishing in size from posterior to anterior; apex truncate, one sharp apical spine and two spinules, lower margin without teeth; widest at level of peduncle of first antenna. Carapace dorsally carinate with two large teeth posterior to rostrum, submarginal articulated antenna tooth, series of 9–10 spinules along anterior margin. Eyes large, pigmented; ocular peduncle with antero-internal process projecting slightly beyond cornea. First antenna with sharp anterolateral tooth on first segment, flagella equal in length, stylocerite acute, reaching end of first segment; second and third segments unarmed. Antennal scale triangular, three times as long as wide, nearly same length as rostrum, spine exceeding blade. Peduncle of second antennae reaching top end of second segment of antennular peduncle. Mandible without palp. First and second maxilliped with exopods, Third maxilliped without exopod. Epipods on first four pereopods, without arthrobranchs. First to fourth pereopods with epipods. First pereopods shorter than third maxiliipeds, merus with blunt tooth at distal tooth, chelate, fingers shorter than palm. Second pereopod slender, chelate, carpus with three articles. Third pereopod with merus having distolateral sharp tooth, upper margin with blunt tooth, propodus with coarse spinules, dactyl biunguiculate with 4 spines posterior to terminal unguis. Fourth and fifth pereopods similar but shorter. Abdominal somites without dorsal teeth or carinae. Pleura blunt or rounded but posteroventral border of fifth somite with at least one minute tooth. Telson with two pairs dorsal spines, apex with two lateral spines on each side, inner spines longer than outer.

Color in life.— Carapace and abdomen dull, plum-colored or vermilion, with large reddish mid-dorsal patch on carapace; antennal scale and anterior third of rostrum plum-colored or mottled with grey and green, legs red or vermilion or with distal end of merus and carpus pale grey green and propodus purplish orange, propodus of pereopods 3–4 transparent with large deep blue apical spot, fifth dactyl bright red; pleopods dull reddish purple, eggs orange. ( Kemp 1925). Figure 1 shows two views of the specimen in life, and shows the “dorsal patch”on the carapace and marks of tan and red on the pereopods. Photographs of a similar shrimp from Kwajalein show a shrimp that is dark blue with white bands of brown, with hair-like processes on the body (www.underwaterkwaj.com/uw-misc/shrimp/Shrimp-Halimeda-blue. htm).

Type location.—Ross Channel, Port Blair , Andaman Islands , 11o36.1’N, 92o54.5’E, 57 m. The type material, three female specimens, was deposited in the Indian Museum (now the Zoological Survey of India, Calcutta ). Some of the specimens of this or other species described by Kemp were sent to the Natural History Museum in London , the Australian Museum , and other locations. The specimens may still exist (Shane Ahyong, Australian Museum, pers. comm.) but as of this writing, they have not been found.

Genetic analysis.— Whole genomic DNA was extracted from 2–4 pleopods using an EZNA Tissue DNA kit (Omega Bio-tek Inc.) following the manufacturer’s protocol. The 16S ribosomal RNA (16S) was amplified via polymerase chain reaction ( PCR) using primer sets and conditions as described in Cuesta et al. (2012). Forward and reverse strand Sanger sequencing was performed at Psomagen, Inc. (https://psomagen.com /). Chromatograms were manually checked in MEGA 7 ( Kumar et al. 2016), cleaned and filtered, and then a BLAST search was performed to verify the identity of the sequence and evaluated similarity to existing sequences in the NCBI database (https://blast.ncbi.nlm.nih.gov/Blast.cg i). The sequence aligned with 99.18% identity to a 481 bp 16S sequence of Latreutes porcinus ( Kemp, 1916) ( MK 722383; Terossi et al. 2019), indicating that the collected shrimp known as Paralatreute s bicornis should be assigned to Latreutes instead of a separate genus. The sequence has been deposited in GenBank ( MZ 367600). We also sequenced CO1 but the result was of poor quality, possibly due to a pseudogene, and not usable for further analysis. The high genetic similarity between L. bicornis and L. porcinus could indicate that the two are con-specific, but at present this similarity reflects an analysis of only one gene.

The original separation of the monotypic genus Paralatreutes was based on the lack of an exopod on the third maxilliped. This feature has been seen to be variable in other related carideans (G. Jensen, University of Washington, pers. comm). The large dorsal teeth on the carapace are not present in other species of Latreutes but occur in other related genera.

Discussion.—The large carapace teeth and the lack of an exopod on the third maxilliped readily distinguish L. bicornis from other species of Latreutes . (See Chace, 1972 for a key to the species). All four specimens (the three in the type series and the present specimen) are or were females with a ventrally expanded rostrum, as in other species of Latreutes . Male Latreutes have a narrow rostrum with fewer teeth. Latreutes bicornis also may be sexually dimorphic.

The original description of L. bicornis and the specimen we examined both show two very large flat teeth on the dorsal surface of the carapace instead of a series of short more or less equal teeth, as are found in other species such as L. porcinus . Anker and De Grave (2016) provided photos of L. porcinus in which its color resembled that of sea grasses or sand. Color patterns of species of Latreutes tend to be variable but the color pattern of the present specimen of L. bicornis more closely resembles that in the description by Kemp than that seen in photographs of L. porcinus . Pending analysis of additional specimens we prefer to consider L. porcinus and L. bicornis to be separate species.

The family designation of the species of Latreutes remains in question. Stimpson (1860) placed Latreutes within the Hippolytidae , as did Holthuis (1993) and Chace (1997). Yang (2005), on examining the larvae of Latreutes anoplonyx Kemp, 1914 and comparing them with other Latreutes species, noted there were significant differences between the first zoea of these species and those of other species of the Hippolytidae . Christoffersen (1987) suggested that members of the genera Gelastocaris , Gelastreutes , Latreutes , Paralatreutes , Tozeuma and Trachycaris might consist a subfamily, the Latreutinae. Yang disagreed, noting differences in the morphology of the first zoea between Tozeuma carolinense ( Kingsley, 1878) and species of Latreutes . De Grave et al. (2014) using genetical analyses, concluded that the family Hippolytidae sensu Stimpson was polyphyletic. According to this analysis, Latreutes remains in a clade that contains the type genus, Hippolyte . This species may be more widespread in the Indian and Pacific Oceans than previously recorded. We received a photograph likely to be this species taken off Kwajalein Atoll (9.19o N, 167.42o E, Johnson and Johnson, pers. comm.)

Figures

FIGURE 1. A, Latreutes bicornis (Kemp, 1925) (CASIZ 202665), dorsal view showing rostrum and anterior carapace. B, Same specimen, dorsal view showing abdomen and posterior pereopods.