Procambarus montebelloensis, Villalobos, 2024

Villalobos, Fernando Álvarez Fernando Vera José Luis, 2024, A new species of crayfish (Decapoda: Cambaridae) from Montebello Lakes, Chiapas, Mexico, Nauplius (e 20240518) 32, pp. 1-10 : 3-6

Procambarus montebelloensis sp. nov.

( Figs. 2–5 )

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Diagnosis. Eyes pigmented, well developed, fitting under rostrum. Rostrum short, wide at base, devoid of lateral spines; acumen short, acute, reaching proximal portion of third antennular segment, ranging from 19.2% to 28.3% of RL (x= 24.7%). Areola 3.5 to 4.6 times as long as wide (x= 3.9), 27 to 36.6% of TCL (x= 31.8%), 34 to 45% of postorbital length (x=39.6%), with3–4 punctuations across narrowest part.Carapace postorbital ridges with anterior small spine, 1 minute cervical spine and 1 branchiostegal spine on each side. Antennal scale from to 2.09 to 2.33 (x= 2.22) times as long as wide, maximum width at midlength.Chelipeds subequal in length, elongate, longer than total body length in adult form I males; surface covered with blunt tubercles; chela not pubescent, elongate, fingers varying from subequal in size to shorter than palm; opposable margin of movable finger finely serrate distally, midportion with 8–10 teeth of similar size, proximally with 2–3 larger teeth; fixed finger with 2–3 large teeth proximally, remaining margin with few irregularly sized teeth. First pair of pereopods, or chelipeds, with all articles covered with blunt tubercles. Third pair of pereopods of form I males with acute hook on ischium, tip slightly overreaching basioischial articulation. Cephalic lobe of epistome approximately hexagonal, margins thickened, apex as distinct triangular tooth separated from lateral margins.

First pleopods of form I male asymmetrical, subequal in length, reaching posterior third of coxae of third pereopods, mesial surface densely covered with long plumose setae. In caudal view, mesial process straight, slender, digitiform, directed distally, reaching beyond all other apical elements; lateral shoulder rounded, surface smooth; central projection triangular, laterodistally directed ( Fig. 3A ). In cephalic view, lateral shoulder rounded, continued by straight apical margin to form central projection, mesial process straight slightly tapering distally, cephalic surface of gonopod smooth devoid of setae ( Fig. 3B ). In mesial view, central projection with inferior narrow opening forming slit, separating centrocaudal and centrocephalic processes, mesial process straight slightly tapering distally, mesial surface oval-shaped, setose, cephalic shoulder incipient ( Fig. 3C ). In lateral view, lateral shoulder becoming wider distally, apex rounded; central projection subtriangular, cephalically oriented; cephalic shoulder slightly perceptible, mesial process straight ( Fig. 3D ).

Annulus ventralis with preannular plate of constant thickness, bearing shallow incomplete median groove, slightly rounded to receive annulus. Preannular plate and annulus in contact ( Fig.4B ). Annulus subcircular; anterior margin slightly bilobed, forming shallow groove; sinus on right side, curved, S-shaped, extending from anterior third to posterior margin ( Fig. 4B ). Postannular plate triangular, anterior tip touching annulus, margins almost straight.

Description. Form I male — Body and eyes pigmented. Cephalothorax 95.4 length of pleon, posterior half wider. Areola5.05 times as long as wide, 32.1% of TCL, with 5–6 punctations across narrowest part, suprabranchial grooves well marked. Surface of carapace finely punctate ( Fig. 2A, B ). Rostrum concave, lateral margins thick, raised, converging anteriorly, devoid of lateral spines, anterior width 2.8 mm, width at base 4.8 mm. Acumen reaching middle portion of third antennular segment, 19.2% of rostrum length.Postorbital ridge as straight thick keel, anterior end with minute spine, not reaching orbital margin; fading posteriorly ( Fig. 2A, B ). Suborbital margin with superior portion straight, in lateral view forming acute angle with rostrum; inferior portion curving posteriorly to cervical groove. One acute branchiostegal spine, inferior portion of cervical groove widely rounded, appears as divided at level of single cervical spine ( Fig. 2A ). Pleon slightly longer than cephalothorax. Uropods with protopodite and endopodite bearing 1 distolateral spine; telson with 2 distolateral spines; distal margins setose.

Epistome as described in diagnosis. Chelipeds 1.07 times total length, 2.2 times length of carapace. Chela long, merus ventral surface with ventral row of teeth, carpus 0.54 length of merus, 0.52 length of dactyl; palm 3.2 times longer than wide, slightly longer than dactyl; surface covered with blunt tubercles. Opposable margin of fixed finger with 3 large proximal teeth, followed by 4 small teeth and 1 medium-sized tooth in middle. Opposable margin of movable finger with 2 large teeth proximally, 9 small teeth in central portion ( Fig. 2C ). Ischium of this pereopod with thick hook, tip slightly surpassing basioischial articulation ( Fig. 2E ).

First pleopods as decribed in Diagnosis.

Allotypic female — Similar to holotypic form I male, differing in the following characters. Areola 4.56 times as long as wide; cheliped 1.4 times length of carapace, 0.68 times total length (Fig. C). Uropods with protopodite bearing 3 distolateral spines, endopodite and telson with 2 distolateral spines. Annulus ventralis as described in Diagnosis.

Form II male — Differing from form I male in the following characters. Mesial process of first pleopod shorter, at same level as lateral shoulder. Ischium of third pereopod without hook, appearing as a rounded tubercle ( Fig. 5B ). Areola 3.7 times as long as wide, 33.3% of TCL. Chelipeds subequal in length, longest one right, 0.78 times total length, 1.57 times TCL. Cephalic lobe of epistome 1.2 times wider than long ( Fig. 5A ).

Figures

Figure 2. Procambarus montebelloensis, new species, holotypic male form I: A, carapace, lateral view; B, carapace, dorsal view; C, rightchela (lateral view); D, epistome,cephalic lobe; E, basal articles ofsecond,third(with developedhooks) andfourthpereopods.

Figure 3.Procambarus montebelloensis, new species, holotypic male form I, left gonopod: A, caudal view; B, cephalicview; C, mesial view; D, lateral view.

Figure 4. Procambarus montebelloensis, new species, allotypic female:A, epistome, cephalic lobe; B, annulus ventralis; C, right chela (lateral view).

Figure 5. Procambarus montebelloensis, new species, morphotypic male form II: A, epistome, cephalic lobe; B, ventral view of basal articles of pereopods and gonopods; C, right chela (lateral view).