Palaemonella jamila, Anker & Benzoni, 2023

Anker, Arthur & Benzoni, Francesca, 2023, Hidden in plain sight: two new species of decapod crustaceans (Palaemonidae and Porcellanidae) discovered in the Red Sea on a university campus in Saudi Arabia, Zootaxa 5278 (1), pp. 78-102 : 79-87

publication ID	https://doi.org/ 10.11646/zootaxa.5278.1.3
publication LSID	lsid:zoobank.org:pub:7B68BAD4-FA98-45B3-8267-F2652F03CDE9
DOI	https://doi.org/10.5281/zenodo.7900228
persistent identifier	https://treatment.plazi.org/id/15405E79-EB0E-FF81-FF7E-C683C4A2C98A
treatment provided by	Plazi
scientific name	Palaemonella jamila
status	sp. nov.

Treatment

Palaemonella jamila sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type material. Holotype: male, pocl 4.2 mm, cl 7.4 mm, FLMNH UF 71319 , Saudi Arabia, Makkah Province, Thuwal, King Abdullah University of Science and Technology ( KAUST), near King Abdullah Monument , 22°20’26.2”N 39°05’15.1”E, shallow sand-rubble flat between small mangrove and deeper channel, in burrow of Alpheus sp. , suction (yabby) pump, depth: 1 m, leg. A. Anker, A. Assayie & V. Peinemann, 10.01.2023 [fcn AA-22- 457] GoogleMaps . Paratype (not deposited, specimen lost, see text): ovigerous female, pocl 4.4 mm, cl 7.8 mm, Saudi Arabia, Makkah Province, Thuwal, King Abdullah University of Science and Technology ( KAUST), near King Abdullah Monument , 22°20’26.2”N 39°05’15.1”E, shallow sand-rubble flat between small mangrove and deeper channel, in burrow of Alpheus sp. , suction (yabby) pump, depth: 0.5 m, leg. A. Anker, 24.09.2022 [fcn AA-22-177] GoogleMaps .

Description. Small-sized palaemonid shrimp. Body moderately slender, subcylindrical, not particularly compressed laterally, not flattened dorsoventrally.Carapace ( Fig. 1A–C View FIGURE 1 ) smooth, slightly raised near middle of dorsal surface; orbit shallow; inferior orbital angle slightly produced anteriorly; postorbital area with distinct semicircular ridge; antennal tooth long, slender, sharp, submarginal, not reaching distal margin of antennal basicerite; hepatic tooth well developed, as long as antennal tooth, located slightly below it; anterolateral angle rounded, not produced. Rostrum ( Fig. 1A–D View FIGURE 1 ) well developed, straight, almost horizontal, about 0.7 of remaining carapace length, with somewhat truncate tip, latter not reaching distal margin of antennal scaphocerite; dorsal margin of rostrum and postrostral carina with eight or nine large, anteriorly directed, acute teeth, four or five of them anterior to posterior orbital margin, one above posterior orbital margin and three posterior to posterior orbital margin, posterior-most tooth with small notch and somewhat separated from remaining teeth, anterior-most tooth smaller than remaining teeth (very small in holotype, located near rostral tip, more widely separated from following tooth); ventral margin of rostrum with single tooth at about 0.6 of rostral length and row of setae on proximal margin half.

Pleon ( Figs. 1E View FIGURE 1 , 3B View FIGURE 3 , 4B View FIGURE 4 ) typical for genus; third pleonite not humped or posteriorly produced; pleura of first to fourth pleonites rounded; fifth pleonite acutely produced posteroventrally; sixth pleonite almost twice as long as fifth pleonite (along mid-dorsal line), with sharply produced posterolateral angle and blunter posteroventral angle.

Telson ( Fig. 1F View FIGURE 1 ) 1.2 times as long as sixth pleonite, 2.3 times as long as anterior margin width, smoothly tapering posteriorly; dorsal surface with two pairs of long, stout, submarginal spiniform setae situated at about 0.4 and 0.7 of telson length, respectively; posterior margin 0.3 of anterior margin width, rounded, with three pairs of spiniform setae, lateral spiniform setae noticeably smaller than dorsal spiniform setae, intermediate spiniform setae robust, four times or so as long as lateral ones, submedian spiniform setae slenderest, about 0.6 length of intermediate ones, setulose.

Eyestalks ( Fig. 1A, B View FIGURE 1 ) with anteromesial margin convex, about as long as wide (exclusive of cornea); cornea noticeably reduced, narrower than eyestalk, hemispherical, with distinct accessory pigment spot dorsally; feebly pigmented.

Antennule ( Fig. 1A, B View FIGURE 1 ) robust; first article of antennular peduncle by far longest and widest, 1.7 times as long as wide, with stout, acute distolateral tooth; statocyst visible, rounded; stylocerite slender, with acute tip overreaching mid-length of first article; ventromesial tooth small, acute; second and third articles subequal in length, together about 0.6 length of dorsally visible portion of first article; flagella long, slender; dorsal (= lateral) flagellum biramous, proximal fused portion with seven or so subdivisions, shorter free ramus slender, with at least three almost indistinct subdivisions and several groups of aesthetascs.

Antenna ( Fig. 1A, B, G View FIGURE 1 ) typical for genus; basicerite moderately stout, with acute distolateral tooth; carpocerite subcylindrical, reaching to about 0.3 of scaphocerite length; flagellum moderately slender; scaphocerite extending well beyond antennular peduncle, 3.7 times as long as maximal width; blade relatively narrow, its distal margin rather short, broadly rounded; lateral margin almost straight, distolateral tooth significantly exceeding distal margin of blade.

Epistome and labrum without specific features. Fourth thoracic sternite typical for genus, with strong, subacute, median process. Fifth thoracic sternite with two lateral lobes adjacent to second pereiopods, each lobe with acute triangular submedian process. Sixth to eight thoracic sternites unarmed.

Mouthparts typical for genus, as illustrated ( Fig. 1H–O View FIGURE 1 ). Mandible ( Fig. 1H, I View FIGURE 1 ) with small, biarticulated palp; molar process stout, with several large angular teeth and small fields of minute setae; incisor process stout, with three large acute distal teeth. Maxillule ( Fig. 1J View FIGURE 1 ) with coxal endite (proximal lacina) densely setose distally, some setae thicker, spiniform; basal endite (distal lacinia) slender, curved, furnished with row of simple and serrulate spiniform setae distally; endopod (palp) bilobed, ventral lobe descending, somewhat hook-shaped, both lobes apparently without setae (or setae broken). Maxilla ( Fig. 1K View FIGURE 1 ) with coxal endite reduced, its distal margin straight, without setae; basal endite well developed, bilobed, both lobes distally fringed with long setae; endopod (palp) well developed, curved, tapering distally, entire; scaphognathite broadly rounded on both anterior and posterior margins. First maxilliped ( Fig. 1L View FIGURE 1 ) with coxal endite broad, notched, moderately setose; basal endite broad, distally with rows of slender simple and serrulate setae; endopod (palp) simple, subdistally with one moderately long, plumose seta; exopod with long flagellum and well-developed, broad caridean lobe; epipod large, subtly bilobed, with truncate posterior margin. Second maxilliped ( Fig. 1M, N View FIGURE 1 ) with endopod typical for genus; dactylus narrow, transversely widening; exopodal flagellum long; epipod with small podobranch consisting of two elongate lamellae. Third maxilliped ( Fig. 1O View FIGURE 1 ) slender, pediform; coxa with large rounded epipod laterally; basis distinctly separated from endopod; antepenultimate article about five times as long as maximal width, somewhat twisted and flattened laterally, with setose ventral margin; penultimate article elongate, about 0.8 length of antepenultimate article, about six times as long as wide, setose ventrally; ultimate article 0.6 times as long as penultimate article, smoothly tapering distally, densely setose ventrally and less so dorsally; arthrobranch moderately developed, multilamellate.

First pereiopods ( Fig. 2A–C View FIGURE 2 ) slender, equal in size and similar in shape between left and right; ischium with deep constriction proximally, about four times as long as wide, with some long setae on ventral margin; merus about 1.5 times as long as ischium, slightly more than six times as long as wide; carpus 1.2 times as long as merus, widening distally; carpo-propodal grooming apparatus well developed; chela slender, somewhat more than half-length of carpus, with fingers subequal in length, 1.2 times as long as palm, with spaced tufts of short setae; fingertips curved, crossing; finger cutting edges straight, unarmed.

Second pereiopods ( Figs. 2D–G View FIGURE 2 , 3 View FIGURE 3 , 4 View FIGURE 4 , following description based mainly on paratype) equal in size and similar in shape between left and right, slender, elongate; ischium slightly convex distodorsally, shallowly concave proximodorsally, about 4.5 times as long as wide; merus about 1.6 times as long as ischium, 6.5 times as long as wide, distomesial margin unarmed; carpus 1.5 times (paratype) to 1.2 times (holotype) as long as merus, distally widening, except for shallow subdistal constriction, distal margin with two bluntly rounded or angular lobes; chela 0.8 times as long as carpus (paratype) to subequal to carpus (holotype), palm feebly swollen, smooth; fingers subequal in length, 0.8 length of palm, smooth; fingertips curved and crossing distally; cutting margins of pollex and dactylus each with two low, subtriangular teeth proximally, each tooth fitting into space between teeth on opposed margin.

Third pereiopod ( Fig. 2H–J View FIGURE 2 ) slender, elongate; ischium slightly curved dorsally, about five times as long as wide; merus about 1.8 times as long as ischium, nine times as long as wide, unarmed; carpus 0.7 length of merus, unarmed; propodus 1.4 times as long as carpus, subequal to merus in length, ventral margin with four widely spaced, short, appressed, spiniform setae, in addition to distal pair of longer spiniform setae adjacent to dactylar base, mesial ones reaching 0.3 length of dactylus; dactylus about 0.3 length of propodus, gently curved, simple, smoothly concave ventrally. Fourth pereiopod ( Fig. 2K View FIGURE 2 ) generally similar to third pereiopod, with somewhat longer propodus, latter armed with three spiniform setae on ventral margin and distal pair of spiniform setae adjacent to dactylar base; dactylus about 0.2 length of propodus, similar to that of third pereiopod. Fifth pereiopod ( Fig. 2L–N View FIGURE 2 ) longer than third and fourth pereiopods, particularly in relative lengths of ischium and propodus; propodus without spiniform setae along ventral margin, however, with distal pair of spiniform setae adjacent to dactylar base, grooming brush composed of two rows of serrulate setae on ventrolateral-distal surface; dactylus about 0.2 length of propodus.

Pleopods without specific features; male second pleopod with well-developed, slender appendix masculina bearing dense cluster of slender spiniform setae on apex and row of spiniform setae along lateral margin; appendix interna of about same size as appendix masculina, neither of them reaching distal margin of endopod. Uropod ( Fig. 1P View FIGURE 1 ) extending well beyond telson; protopod robust, with its lateral lobe ending in subacute process; exopod with lateral margin straight, terminating in subacute distolateral tooth; adjacent distolateral spiniform seta well developed, reaching far beyond distolateral tooth, but not reaching distal margin of exopod; endopod slightly shorter than exopod, ovate.

Ovigerous female (paratype) with about 30 eggs (with developing embryos), latter about same size as cornea, diameter about 0.45–0.50 mm.

Colour pattern. Body largely translucent with pale yellow tinge; carapace and pleon with scattered, small, dull reddish spots; eyestalks with pale reddish spots and reddish longitudinal line dorsally, cornea pale goldengreen; antennules with some pale red-orange spots; first pereiopods with merus tinged with red distally and with small white distal spot; carpus mostly reddish, distally with broad, transverse, white band; chela with red tinge; red and white pattern of second pereiopods generally similar to that of first pereiopods, but with colours brighter and red- and white-coloured areas larger and more conspicuous; chela reddish with whitish patch proximally, connecting with white distal band on carpus; remaining appendages, i.e., antennae, third maxilliped, third to fifth pereiopods, pleopods and uropods, as well as telson, largely translucent with occasional reddish spots; ovigerous female (paratype) with pale greenish eggs ( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ).

Etymology. The name of the new species is the Arabic word jamila meaning beautiful, pretty, elegant (also used as a female given name, Jamila), and alluding to the shrimp’s beauty and elegant appearance ( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ); used as a noun in apposition.

Distribution. Presently known only from the type locality on the Saudi Arabian coast of the Red Sea.

Ecology. The type locality of P. jamila sp. nov. is a shallow, relatively narrow sandflat (width about 50 m) located between some mangrove trees and deeper (4–5 m) channel, with bottom consisting of fine sand or sand mixed with small fragments of coral rubble, larger coral rocks, patches of seagrass and some algae. Both specimens were collected from burrows of goby-associated snapping shrimps, Alpheus spp. , judging from the relatively large (about 2–4 cm wide), slightly oblique burrow entrance, typically fortified by smaller rocks or pieces of coral rubble. Although neither of the specimens of P. jamila sp. nov. was collected together with its host(s), the presence of at least four species of goby-associated snapping shrimps at the type locality was confirmed, either visually or by collected material, on other occasions (Anker, in prep.). These species are Alpheus rapax Fabricius, 1798 , A. djeddensis Coutière, 1897 , A. aff. djeddensis , and A. karplusi Anker, 2002 (cf. Anker 2022b). However, A. karplusi was observed only twice in somewhat deeper water (> 2 m), near the channel drop-off and large fossilised corals, whereas P. jamila sp. nov. was collected from burrows in fine sand adjacent to patches of seagrass, between 0.5 and 1 m. The two most common snapping shrimps at the type locality are A. rapax and A. djeddensis , and any or both of them could be hosts of P. jamila sp. nov.

Remarks. Palaemonella jamila sp. nov. is one of four species of the genus characterised by the presence of a short, semicircular, postorbital ridge extending from the mesial margin of the orbit to the base of the antennal tooth, on each side of the carapace. The other species of Palaemonella displaying this feature are P. okunoi Komai & Yamada, 2015 from Japan, P. hachijo Okuno, 1999 from Japan and New Caledonia, and P. shirakawai Okuno, 2017 from Japan and South-East Asia, although in the last species, the postorbital ridge was described as “obsolete” ( Okuno 1999, 2017; Komai & Yamada 2015). In the original description of P. aliska, Marin (2008) did not clearly illustrate nor mention the postorbital ridge in the type specimens of this species. However, the presence of a postorbital ridge was confirmed in the Saudi Arabian specimen of P. aliska reported below, suggesting a possible small inaccuracy in Marin’s (2008: fig. 2a–c) illustrations of the rostro-orbital region of the carapace.

In the recent DNA-based phylogenetic analysis of Palaemonella and several related genera, Frolová et al. (2022) recovered both P. hachijo and P. okunoi within the same larger clade (Clade 3 in their fig. 2); however, these two species were not found to be particularly closely related. Therefore, the presence or absence of a postorbital ridge in Palaemonella may not necessarily be a phylogenetically informative character. On the other hand, P. jamila sp. nov. and P. aliska , which is also associated with burrows of Alpheus spp. (see below), do share the presence of a postorbital ridge, and may be indeed closely related. However, it must be noted that a less demarcated postorbital ridge may be observed in several other species of Palaemonella , including the common and widespread P. rotumana ( Borradaile, 1898) . Interestingly, the two burrow-associated palaemonid shrimps included in the phylogenetic analysis of Frolová et al. (2022), viz. P. aliska and Eupontonia nudirostris Marin, 2014 , clustered together forming a small lineage within Clade 3. In their study, both Palaemonella and Eupontonia Bruce, 1971 were recovered as non-monophyletic, with four species of Vir Holthuis, 1952 and two species of Eupontonia nested within Palaemonella sensu lato. The necessary generic rearrangements and redefinitions in Clade 3 of Frolová et al. (2022) are obviously beyond the scope of the present study and herein Palaemonella is treated sensu Komai & Yamada (2015) and Fransen et al. (2022).

Palaemonella jamila sp. nov. can be separated from P. hachijo and P. okunoi by the significantly smaller cornea, its diameter being smaller than that of the eyestalk, compared to the cornea being wider than and as wide as the eyestalk in P. hachijo and P. okunoi , respectively (cf. Fig. 1A, B View FIGURE 1 ; Okuno 1999: fig. 1A, B; Komai & Yamada 2015: fig. 2B, C). The new species also differs from P. hachijo in the distally unarmed merus of the second pereiopod (vs. armed with a sharp subdistal tooth in P. hachijo ), and the much longer and stouter spiniform setae on the dorsal surface of the telson (cf. Figs. 1F View FIGURE 1 , 2D, E View FIGURE 2 ; Okuno 1999: figs. 1E, 3C); and from P. okunoi in the presence of spiniform setae only in the distal part of the ventral margin of the fifth pereiopod propodus, adjacent to the dactylo-propodal articulation (vs. their presence along the entire ventral margin of the fifth pereiopod propodus in P. okunoi ) (cf. Fig. 2L View FIGURE 2 ; Komai & Yamada 2015: fig. 4I). Palaemonella jamila sp. nov. can be easily distinguished from the presumably closely related P. aliska by the third pereiopod propodus ventrally armed with fewer spiniform setae (which are also smaller and more appressed); the noticeably slenderer dactylus of the third pereiopod; and the slenderer third maxilliped, especially its penultimate article (cf. Figs. 1A, B, O View FIGURE 1 , 2H, I View FIGURE 2 ; Marin 2008: figs. 2a, c, 3h, 5a, b). The new species also differs from P. shirakawai in many aspects, for instance, in the proportions of the first article of the antennular peduncle; the shape of the scaphocerite; the shape and armature of the rostrum; the relative size of the cornea (compared to the eyestalk); the shorter and stouter first and second pereiopods; and the third pereiopod propodus with fewer, smaller and more appressed spiniform setae (cf. Figs. 1A, B View FIGURE 1 , 2A, D, E, H, I View FIGURE 2 ; Okuno 2017: figs. 1A, B, 2C, 4A, C, F, G). In life, P. jamila sp. nov. can be easily separated from the four aforementioned species by its diagnostic colour pattern (cf. Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ; Okuno 1999: p. 743; Marin 2008: fig. 9a; Kuiter & Debelius 2009: p. 101 [colour photographs of P. shirakawai , as P. aliska ]; Minemizu 2013: p. 42 [colour photograph of P. shirakawai , as P. aff. aliska ]; Komai & Yamada 2015: fig. 1; Anker & De Grave 2019: fig. 4A, B; see also Fig. 5 View FIGURE 5 in the present study).

None of the remaining species of Palaemonella , i.e., all other species listed in the key of Komai & Yamada (2015) and the recently described P. rubrolineata Fransen, Van Der Veer & Frolová, 2022 , seem to be closely related to P. jamila sp. nov. Some are deep-water species with little information available on their biology, whereas others are obligate associates of hard corals and crinoids, or are free-living, typically found within coral rock crevices or under coral rubble (e.g., Kemp 1922; Bruce 1991, 2002, 2008; Chace & Bruce 1993; Ďuriš 2017; Frolová et al. 2022; Fransen et al. 2022).

Palaemonella jamila sp. nov. is the fourth species within the family Palaemonidae associated with burrows of larger hosts from three very different animal groups: (1) snapping shrimps ( Alpheus sp. )— P. jamila sp. nov. and P. aliska ; (2) jaw fishes ( Opisthognathus sp. )— P. shirakawai ; and (3) echiurans (e.g., Listriolobus sp. )— E. nudirostris ( Marin 2008; Kuiter & Debelius 2009; Okuno 2017; Anker & De Grave 2019). It remains to be determined whether the reduction of the eye cornea in P. jamila sp. nov. ( Fig. 1A, B View FIGURE 1 ) and P. aliska ( Marin 2008: fig. 2a, c, d) has a common origin, i.e., whether these two taxa are phylogenetically close, or whether it shows an evolutionary convergence resulting from adaptation to similar, burrow-dwelling lifestyle.