Liropus isabelensis, 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 : 102-108

Liropus isabelensis sp. nov.

( Figures 15–18 )

Type material

Holotype male plus 1 slide ( MNCN 20.04 /9226) , Allotype female plus 1 slide ( MNCN 20.04 /9227) . Paratypes: 2 males ( MNCN 20.04 /9228-29) , 1 female ( MNCN 20.04 /9230) .

Additional material examined

St1: 1 male; St6: 3 males, 3 females; St8: 3 males, 1 female, 1 juvenile.

Type locality

Cerro Pelón (Isla Isabel), México, 25 m, on hydroids and bryozoans.

Etymology

Named isabelensis alluding to the National Park of Isla Isabel (Nayarit), México.

Diagnosis

Eyes present. Body dorsally smooth. Anterolateral acute and downward-directed projections on pereonite 2 and mediolateral on pereonite 3 in males and absent in females. Flagellum of antenna 1 five-articulate. Gnathopod 2 basis slightly longer than pereonite 2; ischium and propodus elongated. Pereopods 3, 4 and 5 one-articulate. Abdomen without appendages in males.

Description

Male holotype. Body length: 3.25 mm.

Lateral and dorsal view ( Figure 15 ): Body dorsally smooth. Head rounded, eyes present. Pereonite 1 fused with head, suture present. Pereonite 2 with a pair of anterolateral acute and directed downwards projections. Pereonite 3 with a pair of mediolateral projections. Pereonite 5 the longest. Pereonite 7 the shortest.

Gills ( Figure 15 ): Present on pereonites 3–4, oval. Gills on pereonite 3 about 2.5 times longer than those on pereonite 4.

Mouthparts ( Figure 16 ): Upper lip symmetrically bilobed with small setulae apically. Mandibles with molar process and three-articulate palp; distal article of palp the longest, with one seta apically (lost in the dissection); second article of palp with one distal plumose seta; incisor and lacinia mobilis five-toothed; left and right mandibles with three and two pectinated setae respectively. Lower lip with inner lobes well-demarcated, inner and outer lobes setose apically. Maxilla 1 outer lobe carrying five robust setae; distal article of the palp with five apical setae. Maxilla 2 inner lobe oval, carrying five distal setae, and outer lobe rectangular, with six apical setae. Maxilliped inner plate rectangular carrying from inner to outer margin a nodular seta, two plumose setae and one seta; outer plate with four setae and one plumose seta apically; palp four-articulate, scarcely setose, third article provided with a projection.

Antennae ( Figures 15 and 17 ): Antenna 1 about one-third of body length; peduncle scarcely setose; flagellum five-articulate. Antenna 2 about two-thirds of antenna 1; proximal peduncular article with a developed acute projection distally; swimming setae absent; flagellum two-articulate.

Gnathopods ( Figure 17 ): Gnathopod 1 basis longer than ischium, merus and carpus combined (length about 1.5 times); propodus palm with proximal grasping spine and setae along the palm present. Gnathopod 2 inserted on the anterior half of pereonite 2; basis slightly longer than pereonite 2, with tiny tubercles on the proximal half; ischium elongated, half as long as basis; merus rounded; carpus short and triangular; propodus elongated, longer than basis, and four times as long as wide; palm with proximal projection with one grasping spine, followed by another proximal acute projection, margin setose; dactylus with setulae and widened medially.

Pereopods ( Figure 18 ): Pereopod 3 and 4 small, one-articulate, with three or four setae apically, respectively. Pereopod 5 one-articulate, with five setae and one plumose seta apically. Pereopod 6–7 increasing in length, six-articulate and attached to the posterior end of the pereonite; propodus palm carrying a row of robust setae.

Penes ( Figure 18 ): Situated medially, rounded.

Abdomen ( Figure 18 ): A pair of lateral lobes, and a single dorsal lobe.

Allotype female. Body length: 2.6 mm. Similar to male except for the following characteristics ( Figures 15 and 17 ): oostegites present, being slightly setose on pereonite 3 and 4; pereonite 2 and 3 lacking anterolateral and lateral projections, respectively; gnathopod 2 ischium less elongated than in male (one-quarter as long as basis), propodus oval, as long as basis, with only one proximal projection, dactylus not setose. Abdomen with a pair of lateral lobes and single dorsal lobe ( Figure 18 ).

Remarks

Liropus isabelensis represents the 10th species from the genus Liropus Mayer, 1890 . The other species included in the genus are as follows: L. africanus Mayer, 1920 , L. azorensis Guerra-García, 2004 , L. cachuchoensis Guerra-García, 2008 , L. elongatus Mayer, 1890 , L. gracilis Chevreux, 1927 , L. japonicus Mori, 1995 , L. minimus Mayer, 1890 , L. minusculus Guerra-García and Hendrycks, 2013 and L. nelsonae Guerra-García, 2003 . Most of the species have an Atlantic or Mediterranean distribution except L. japonicus , from Japanese waters, and L. minusculus , from California, USA. Therefore, the new species is the second record of the genus Liropus from the East Pacific coast.

A morphological comparison among Liropus species is given in Table 3. Liropus isabelensis can be distinguished from all other species mainly by the following characteristics: anterolateral acute and downwards-directed projections on pereonite 2, presence of mediolateral projections on pereonites 3 and gnathopod 2 ischium elongated. Liropus minusculus is the geographically nearer species and shares some characteristics with L. isabelensis such as pereopod 5 one-articulate and the anterolateral projections in pereonite 2 although this is more acute and downwards directed in the latter. Both species have the smallest size, although L. africanus and L. japonicus are also characterized by a very small size.

Habitat

This species was found attached to species of Thecata and Athecata hydroids, gorgonian ( Muricea cf. californica ), a bryozoan ( Bugula sp.), the seaweed Zonaria cf. farlowii with epiphytic hydroids and several red seaweeds. They occur from 3 to 25 m deep, although always in low densities. Other caprellids, such as Paracaprella spp. and Aciconula acanthosoma , live on these substrates together with L. isabelensis .

Distribution

Liropus isabelensis has been found from the type locality, Isla Isabel , México ( St 6, Bahía Tiburón ; St 8, Cerro Pelón ), and Mazatlán ( St 1, Isla de los Pájaros) .

Figures

Figure 15. Liropus isabelensis sp. nov. Holotype male lateral and dorsal view. Allotype female lateral view. Scale bar x: 0.5 mm; y: 1 mm.

Figure 16. Liropus isabelensis sp. nov. Holotype male mouthparts. Scale bar: 0.1 mm.

Figure 17. Liropus isabelensis sp. nov. Holotype male antennae, gnathopod 1 and 2. Allotype female gnathopod 2. Scale bar x (A1, A2) and y (Gn1-2): 0.1 mm.

Figure 18. Liropus isabelensis sp. nov. Holotype male pereopods 3–7 and abdomen. Allotype female abdomen. Scale bar x (P3-7) and y (Ad): 0.1 mm.