Caribboecetes progreso, Paz-Ríos, Carlos E. & Ardisson, Pedro-Luis, 2013

Paz-Ríos, Carlos E. & Ardisson, Pedro-Luis, 2013, Caribboecetes progreso, a new species of sand-dwelling amphipod (Amphipoda: Corophiidea: Ischyroceridae) from the Gulf of Mexico, with a key for the genus, Zootaxa 3652 (3), pp. 370-380 : 371-377

Caribboecetes progreso sp. nov.

Figures 1–3

Caribboecetes sp. Paz-Ríos & Ardisson, 2013: 152.

Holotype. Male (dissected and drawn), 4.4 mm, Yucalpeten beach, Progreso , Yucatan State, Mexico, 21°16’36’’N, 89°42’49’’W (approx. to 80 m from the shoreline), 1 May 2002, sandy bottom, 1.2 m depth, col. A. Vega, E. Campos, M.T. Herrera-Dorantes and P.-L. Ardisson, CYMX-1-CP.

Paratypes. 7 males and 1 gravid female, data as for holotype, ECOSUR0150. 3 males and 4 females, Chuburna beach, Progreso , Yucatan State, Mexico, 21°14’30’’N, 89°51’54’’W (approx. to 120 m from the shoreline), 18 September 2002, sandy bottom, 1.8 m depth, col. A. Vega, E. Campos, M.T. Herrera-Dorantes and P.-L. Ardisson, CYMX-2-CP. 1 male, Uaymitun beach, Progreso , Yucatan State, Mexico, 21°19’08’’N, 89°28’30’’W (approx. to 160 m from the shoreline), 3 May 2003, sandy bottom, 2 m depth, col. A. Vega, E. Campos, M.T. Herrera-Dorantes and P.-L. Ardisson, CYMX-3-CP. 1 male, northeastern continental shelf of Yucatan, Mexico, 21°47’44.4’’N, 89°30’1.5’’W, 9 April 2004, sandy bottom, 19.6 m depth, col. C.E. Paz-Ríos, CYMX-61-PY. 1 male, 1 female, northeastern continental shelf of Yucatan, Mexico, 21°42’42.3’’N, 88°00’39.9’’W, 9 April 2004, sandy bottom, 19.3 m depth, col. C.E. Paz-Ríos, CYMX-62-PY. 1 male (dissected), Xtul beach, Progreso , Yucatan State, Mexico, 21°15’17’’N, 89°49’39’’W, 9 January 2008, sandy bottom, 2 m depth, col. C.E. Paz-Ríos and M.T. Herrera-Dorantes, CYMX-4-CP. 2 male (dissected), Xtul beach, Progreso , Yucatan State, Mexico, 21°15’17’’N, 89°49’39’’W, 10 April 2008, sandy bottom, 2 m depth, col. C.E. Paz-Ríos and M.T. Herrera-Dorantes, CYMX-5-CP.

Type locality. Progreso , Yucatan State, Mexico.

Etymology. The species name is derived from the type locality of the species.

Diagnosis. Antenna 2 as long as cephalon and pereon combined; setae on peduncular articles 5 in a single row. Eyelobes with short apical projection. Basis of gnathopod 2 with inflated triangular anterolateral flange. Anterior quarter of lateral surface on coxa plate 7 and basis of pereopod 7 densely setose.

Description. Based on male holotype (CYMX-1-CP) and three male paratypes (CYMX-4-CP; CYMX-5-CP). Rostrum acute, triangular, not reaching beyond eyelobes, straight though slightly depressed in lateral view. Base of rostrum microsetulose. Eyelobes slightly pedunculate, longer than broad, apex with pointed projection and a few setae (3–4). Cephalon and first 4–5 pereonites dorsally with 2–3 transverse rows of densely set polyflagellate setules.

Antennae 1 slightly shorter than antenna 2, article 1–2 extremely densely setose in male, less densely setose in female; sensory organs (aesthetascs) on last 8 articles. Antennae 2, ventral process of article 2 with 2–3 robust setae on rounded apex and lateral row of a few setae (5); peduncular article 3 medially with 1 distal, 1 midmedial, and 2– 3 proximal straight robust setae; article 4 with dorsal setae in 10–12 short, transverse rows; article 5 with dorsolateral setae in dense longitudinal row contiguous with row of setae on flagellar articles 1–2; flagellar article 2 with 1 ventroapical robust seta and 2 on flagellar article 3.

Lower lip with simple and rounded inner lobes; rounded outer lobes with 4 medial robust setae. Upper lip with small apical notch. Mandible with triturative molar, well developed incisor, 5-toothed lacinia mobilis and 3 raker setae; palp bi-articulate with article 1 plumose (omitted setules in the drawing) and article 2 tiny. Maxilla 1 with inner plate reduced; outer plate with 7 apical bifurcate robust setae; palp with 4–5 apical robust setae and 1–2 setae. Maxilla 2 with subequal, rounded plates. Maxilliped with outer plate bearing 7 slender, oval, medial robust setae (middle ones with a few small coarse denticles) and 2–3 long plumose setae; inner plate with 3 oval, undentated medial robust setae and short plumose setae.

Coxal plate 1 triangular, longer than broad; plate 2 nearly square; plate 3–4 tapering, rounded apex, apical margin and most of anterior margin dentate, distolateral surface densely covered by acute cuticular scales; plates 5– 6 with rounded, slightly upward turned posteroproximal lobe; plate 7 densely setose on anterolateral surface.

Gnathopod 1 simple; carpus with 1 posterodistal robust seta; propodus with 1 distal and 1 medial robust seta on posterior margin, medial surface with 2–3 transverse rows of short, stiff setae; dactylus with 4–5 posterior teeth. Gnathopod 2 simple; basis with inflated triangular anterolateral flange; propodus with posteroapical tooth, 5 medial robust setae along posterior margin (4 small and 1 large), and 1 distal robust seta on posterior margin; dactylus with 3–5 posterior teeth. Pereopod 3 and 4 pairwise similar; basis of pereopod 3 slightly wider and with much denser anterior and posterior setation than in pereopod 4; merus produced anterodorsally, anterodorsal lobe reaching midway along propodus anterior margin; robust setae row (5–7) on posterior margin of carpus; dactylus almost as long as combined length of carpus and propodus. Pereopod 5 and 6 pairwise identical; both pereopods geniculate at carpus; carpus with dense robust setae row (8–10) on posterior margin and apical and lateral surfaces covered by cuticular scales; dactylus short, curved and without accessory tooth. Pereopod 7 longest; basis oval with anterior and posterior margins densely fringed with long, heavily plumose setae and one quarter of anterolateral surface densely setose.

Pleopods 1–3 identical; peduncle broadly expanded medially with 2 serrated coupling spines.

Uropod 1 biramous; peduncle with 4–7 dorsolateral setae and 4–6 distal robust setae; inner ramus 1/3 the length of outer ramus with 5–7 lateral and apical robust setae; outer ramus 3 times as long as broad, with 14–17 robust setae along lateral and apical margin, medioapical robust seta notably longer than other robust setae. Uropod 2 absent. Uropod 3 without rami; peduncle apically rounded with numerous lateral seta of varying length and one apical robust seta.

Telson with oval field of spines covering ca. 1/2 of lateral margin, dorsal surface with a few setae proximal to normal setation.

Variation. There is some slight sexual dimorphism; female is similar to male, but with smaller size, antennae shorter and less setose and pereopods with fewer robust setae.

Remarks. A morphological comparison among the Caribboecetes species is presented in Table 1. Caribboecetes progreso sp. nov. is more similar to C. barbadensis , C. justi and especially to C. jenikarpae . The new species differs from C. barbadensis by the 2–3 transverse rows of setules dorsally on cephalon and first 4–5 pereonites, dorsolateral setae on peduncular and flagellar articles of antenna 2 in a single row, eyelobes slightly pedunculate, outer plate of maxilliped with oval medial robust setae, inflated triangular anterolateral flange on basis of gnathopod 2, coxal plate 3–4 with distal lateral surface covered with cuticular scales, and anterior lateral surface of coxal plate 7 and basis of pereopod 7 setose. It differs from C. justi by the rostrum not reaching eyelobes, 2–3 transverse rows of setules dorsally on cephalon and first 4–5 pereonites, dorsolateral setae on peduncular and flagellar articles of antenna 2 in a single row, eyelobes slightly pedunculate, outer lobes of lower lip with 4 medial robust setae, mandibular palp bi-articulate, outer plate of maxilliped with a few small coarse denticles on medial robust setae, coxal plate 3–4 with distal lateral surface covered with cuticular scales, and anterior lateral surface of coxal plate 7 and basis of pereopod 7 setose. It differs from C. jenikarpae by the outer lobes of lower lip with 4 medial robust setae, inflated triangular anterolateral flange on basis of gnathopod 2, and anterior lateral surface of coxal plate 7 and basis of pereopod 7 setose, which covers a half in C. jenikarpae and one quarter in C. progreso sp. nov.

Distribution. Central coast of the Yucatan State, Mexico; northeastern continental shelf of the Yucatan Peninsula.

Ecological notes. Caribboecetes progreso sp. nov. has only been collected on sandy bottoms and it has been found in empty gastropods shell, mainly of the genus Olivella . It has a depth range from the intertidal zone to shallow continental shelf (19.6 m).

The new species has been collected since the year 2002 on the central coast of the Yucatan State, Mexico, where it has achieved great abundance (Ardisson & Castillo-Fernández 2004). The spatial and temporal variation of abundance is displayed here for the first time ( Figure 4 ); the total number of specimens in the first study was 49,992. Of this study it is observed the higher average abundance among transects was recorded during the sampling of April-May 2002, before the hurricane Isidore struck on September 2002 ( Figure 4 A); it is also observed the higher average abundance was recorded at 60 m from shoreline, before the same hurricane. After the hurricane Isidore the abundance gradually increased among transects from the intertidal zone to shallow subtidal, with the higher value at 140–160 m from shoreline ( Figure 4 B). In the third study, the influence of the regional weather seasonality on population of C. progreso sp. nov. is observed; the total number of specimens in this study was 8,771. The higher average monthly abundance was recorded in April, a month characterized by a water column warmest and stable (proper to dry season); the lowest average abundance was recorded from August to February, a months characterized by a water column coolest and turbulent (proper to cold fronts season).

Figures

FIGURE 1. Caribboecetes progreso sp. nov., holotype. Scale for Ha represent 1 mm, scales for Fa and Pe represent 0.1 mm, remainder represent 0.2 mm.

FIGURE 2. Caribboecetes progreso sp. nov., holotype. Scale represents 0.2 mm.

FIGURE 3. Caribboecetes progreso sp. nov., holotype, except for Us’: paratype (CYMX- 4 - CP). Scale for Cx 3 represent 0.1 mm, remainder represent 0.2 mm.

FIGURE 4. Abundance of Caribboecetes progreso sp. nov. in the type locality. A: First study, abundance by transect and sampling campaign; B: first study, abundance by distance from the shoreline and sampling campaign; C: third study, abundance by month.