Paracaprella isabelae, Sánchez-Moyano & García-Asencio & Guerra-García, 2014

Sánchez-Moyano, J. E., García-Asencio, I. & Guerra-García, J. M., 2014, Littoral caprellids (Crustacea: Amphipoda) from the Mexican Central Pacific coast, with the description of four new species, Journal of Natural History 49 (1), pp. 77-127 : 115-124

Paracaprella isabelae sp. nov.

( Figures 23–26 )

Type material

Holotype male ( MNCN 20.04 /9239) , Allotype female ( MNCN 20.04 /9240) . Paratypes: 4 males ( MNCN 20.04 /9241-44) , 4 females ( MNCN 20.04 /9245-48) .

Additional material examined

St6: 12 males, 14 females, 34 juveniles; St7: 65 males, 56 females, 32 juveniles; St8: 12 males, 5 females, 3 juveniles.

Type locality

Las Monas (Isla Isabel), México, 6 m, on hydroids and bryozoans.

Etymology

The species is dedicated to Isabel Sánchez, daughter of the first and second authors. She was born just after the sample survey of this study.

Diagnosis

Head rounded and dorsally humped. Large bifid sharp-pointed anterolateral projection on anterior margin of pereonite 2 in males, simple and rounded in females. Pereonite 3 with a rounded anterolateral projection in males. Short ventral forwarddirected projection with ‘raspberry’-like surface between the gnathopods 2. Mandibles with molar process and without palp. Flagellum of antenna 1 10-articulate. Coxa of gnathopod 2 with a tubercle with ‘raspberry’-like surface in males. Propodus palm of gnathopod 2 with rectangular projection proximally, bearing one proximal grasping spine and a distal long robust tooth in males. Pereopod 3 and 4 two-articulate. Pereopod 5–7 without grasping spines. Abdomen with a pair of setose uni-articulate appendages in males.

Description

Male holotype. Body length: 5.4 mm.

Lateral and dorsal view ( Figure 23 ): Head rounded and dorsally humped, eyes present. Pereonite 1 fused with head, suture present. Body dorsally smooth, except blunt dorsal protuberance in the middle of pereonites 2–3. Large adult with other blunt dorsal posterior protuberance on pereonite 2. Large bifid sharp-pointed anterolateral projection on anterior margin of pereonite 2. It has a short ventral forwarddirected projection with ‘raspberry’-like surface between gnathopods 2. Pereonite 3 with a rounded anterolateral projection. Pereonite 3 the longest. Pereonite 7 the shortest.

Gills ( Figure 23 ): Present on pereonites 3–4, oval. Gills on pereonite 3 about twice as long as those on pereonite 4.

Mouthparts ( Figure 24 ): Upper lip symmetrically bilobed without setulae apically. Mandibles with molar process and without palp; incisor and lacinia mobilis five-toothed; left and right mandibles with three and two pectinated setae, respectively. Lower lip with inner lobes well-marked and with a medial suture, outer lobes setose apically. Maxilla 1 outer lobe carrying six robust-stout setae; distal article of the palp with three robust and two long apical setae. Maxilla 2 inner lobe oval, carrying four distal setae, and outer lobe elongated, with five apical setae. Maxilliped inner plate rectangular carrying three setae apically; outer plate with six submarginal setae; palp four-articulate, scarcely setose; third article provided with a large distal process and setose apically; terminal article with a row of setulae on grasping margin, and two setae subdistally.

Antennae ( Figures 23 and 25 ): Antenna 1 shorter than the combined lengths of head and pereonite 2–3. Peduncle setose; flagellum 10-articulate. Antenna 2 a little shorter than peduncle of antenna 1; proximal peduncular article with a short acute projection distally; swimming setae absent; flagellum two-articulate, proximal article 2 times the length of the distal one.

Gnathopods ( Figure 25 ): Gnathopod 1 basis as long as ischium, merus and carpus combined; propodus palm with a single proximal grasping spine; grasping margin of propodus with setae; ventral margin of dactylus with several teeth. Gnathopod 2 inserted on the anterior half of pereonite 2; coxa bearing anteriorly a tubercle with ‘raspberry’-like surface; basis elongated slightly shorter than pereonite 2, without proximal serrated knob on ventral margin; propodus length about twice width; propodus palm with rectangular projection proximally, carrying one proximal grasping spine and a distal long robust tooth; grasping margin setose; dactylus thickened medially and setose.

Pereopods ( Figures 23 and 26 ): Pereopod 3 and 4 two-articulate, with five and four setae apically, respectively, and one seta distally on basal article. Pereopod 5–7 increasing in length, six-articulate and attached to the posterior end of the pereonite, with several plumose setae. Palm of propodus of pereopod 5 with a proximal knob bearing a small spine; palm of pereopod 6–7 with several proximal knobs, each bearing a small spine. Grasping spines absent.

Penes ( Figure 26 ): Penes short, situated laterally.

Abdomen ( Figure 26 ): A pair of setose uni-articulate appendages, a pair of lateral lobes, and a single dorsal lobe.

Allotype female. Body length: 4.2 mm. Similar to male except for the following characteristics ( Figures 23 and 25 ): oostegites present, being slightly setose on pereonite 3; small and rounded anterolateral projection on pereonite 2, lacking anterolateral projection on pereonite 3; flagellum of antenna 1 six-articulate; propodus of gnathopod 2 oval, with a proximal knob bearing a grasping spine and a plumose seta, dactylus not setose. Abdomen with a pair of lateral lobes and single dorsal lobe carrying two plumose setae ( Figure 26 ).

Habitat

This species has been found on several substrates along the coast of Isla Isabel from 1 to 25 m depth. It was more abundant on hydroids and bryozoan ( Bugula sp.) at 6 m depth, although it was also recorded on gorgonians ( Pacifigorgia cf. agassizi), and several red seaweeds. Other caprellids such as Aciconula acanthosoma , Caprella pitu , C. equilibra or Liropus isabelensis live on these substrates together with P. isabelae .

Distribution

Paracaprella isabelae has been found from the type locality, Isla Isabel , México ( St 6, Bahía Tiburón ; St 7, Las Monas ; St 8, Cerro Pelón) .

Remarks on Paracaprella spp.

So far, the genus Paracaprella Mayer, 1890 is represented by eight species: P. alata Mayer, 1903; P. barnardi McCain, 1967 ; P. crassa Mayer, 1903 ; P. digitimanus Quitete, 1971 ; P. guerragarciai Winfield and Ortiz, 2013 ; P. insolita Arimoto, 1980 ; P. pusilla Mayer, 1890 ; and P. tenuis Mayer, 1903 . The main differences between Paracaprella spp. and the two new species, P. carballoi and P. isabelae , are summarized in Table 4. Paracaprella insolita has been excluded because only females have been described and it is the only Paracaprella with a characteristic projection dorsally on the head ( Arimoto 1980).

Paracaprella carballoi is morphologically close to P. barnardi and P. pusilla , but can be distinguished by the following characters: both P. carballoi and P. pusilla have a smooth body dorsally with an anterodorsal blunt protuberance on pereonite 2, whereas P. barnardi has a large tubercle in this position; the anterolateral projection of pereonite 2 is rounded and narrow as opposed to the sharp-pointed projection in the others; pereonite 4 and 5 are subequal in length whereas pereonite 3 is the longest;

Table 4. (Continued). Gnathopod 2 propodus Rectangular, one Rectangular, one Rectangular, two Rectangular, three Quadrate, one Quadrate, a Rectangular, one grasping Rectangular, one Rectangular palm, proximal grasping spine and grasping spine grasping teeth grasping grasping spine spine and long-robust grasping spine and large, projection short-robust tooth and short- spine and spine, short- and long-robust tooth and robust one small

robust tooth robust tooth robust tooth tooth tooth grasping

and a spine and

digitiform short-

projection robust

tooth Gnathopod 1 propodus 1 1 1? 1 2 1 1 1 palm, no. of proximal grasping spine Mandibular palp Absent A simple seta A simple seta? Absent A simple seta Absent A simple seta Variable, a

simple seta

to three-

articulated

basis of gnathopod 2 elongated without proximal serrated knob but with two distal short processes on lateral margin; gnathopod 2 propodus palm with rectangular proximal projection bearing two grasping spines, but only one in all other species of the genus (except P. crassa , without grasping spines and carrying three teeth); and mandibular palp as a simple seta (similar to P. barnardi , P. pusilla and P. guerragarciai ).

Paracaprella isabelae can be distinguished from all other species mainly by the following characteristics: head rounded and dorsally humped (similar to P. crassa , with which it also shares a blunt posterior protuberance on pereonite 2); large and bifid sharp-pointed anterolateral projection on pereonite 2 (in other species can be sharp-pointed but always single); rounded anterolateral projections on pereonite 3 (similar to P. alata although triangular on pereonite 3 and small and rounded on pereonite 4 in this case; triangular in P. digitimanus ; and absent in the other species of the genus); short ventral forward directed projection with ‘raspberry’-like surface between gnathopods 2; pereonite 4 and 5 subequal in length and pereonite 3 the longest, similar to P. carballoi ; and mandibular palp absent as is the case of P. alata and P. digitimanus .

According to Winfield and Ortiz (2013), the genus Paracaprella has a geographic distribution encompassing temperate, subtropical and tropical seas. However, only P. barnardi and P. pusilla have been recorded so far from the American Pacific coast. While P. barnardi has a more local distribution (it has only been recorded from the type locality in Culebra Island, Panama), P. pusilla is the species of the genus with a more worldwide distribution and it is the only species found in European waters, presumably introduced by ship fouling ( Ros and Guerra-García 2012; Ros et al. 2013), even though it has only been cited from the American coast in Chile (Guerra- García and Thiel 2001). Hence, both P. carballoi and P. isabelae represent the northernmost records of the genus on the East Pacific coast.

Figures

Figure 23. Paracaprella isabelae sp. nov. Holotype male lateral, ventral and dorsal view. Allotype female lateral view. Scale bar: 1 mm.

Figure 24. Paracaprella isabelae sp. nov. Holotype male mouthparts. Scale bar x (Mx1, Mx2, LMd, RMd, LL, UL) and y (Mxp): 0.05 mm.

Figure 25. Paracaprella isabelae sp. nov. Holotype male antennae, gnathopod 1 and 2. Allotype female gnathopod 2. Scale bar x (A1, A2) and y (Gn1-2): 0.2 mm.

Figure 26. Paracaprella isabelae sp. nov. Holotype male pereopods 3–7 and abdomen. Allotype female abdomen. Scale bar: x (P5-7): 0.3 mm; y (Ad): 0.1; z (P3-4): 0.05 mm.