REVIEW ARTICLE Caprellids (Crustacea: Amphipoda) from the Gulf of Mexico, with observations on Deutella mayeri, redescription of Metaprotella hummelincki, a taxonomic key and zoogeographical comments Author Paz-Ríos, Carlos E. Laboratorio de Bentos, Departamento de Recursos del Mar, Cinvestav, Merida, Mexico; Author Guerra-García, José M. Laboratorio de Biología Marina, Departamento de Zoología, Facultad de Biología, Universidad de Sevilla, Sevilla, España Author Ardisson, Pedro-Luis Laboratorio de Bentos, Departamento de Recursos del Mar, Cinvestav, Merida, Mexico; text Journal of Natural History 2014 2014-07-11 48 41 - 42 2517 2578 http://dx.doi.org/10.1080/00222933.2014.931481 journal article 10.1080/00222933.2014.931481 1464-5262 5194444 Phtisica marina Slabber, 1769 ( Figures 22 , 23 ) Phtisica marina Slabber, 1769: 77 , pl. 10. Chevreux and Fage, 1925: 434–436 , fig. 422. McCain, 1968: 91–97 , figs 46, 47. McCain and Steinberg, 1970: 65 . Arimoto, 1980: 96–101 , fig. 2. Krapp-Schickel, 1993: 806–808 , figs 549, 550. Guerra-García and Takeuchi, 2002: 705 . Ortiz et al., 2002 , fig. 40. Foster, Thomas, et al., 2004: 161– 163, fig. 2. Winfield, Escobar-Briones, et al., 2007: 56, fig. 20. Proto ventricosa Mayer, 1882: 22 , pl. 1, fig. 1, pl. 3, figs 16–29, pl. 4, figs 12, 13, pl. 5, figs 1–5. Mayer, 1890: 12 , pl. 3, figs 4–6; pl. 5, figs 3–6; pl. 6, fig. 1; pl. 7, fig. 1. Mayer, 1903: 20 , pl. 6, fig. 23. Figure 22. Phtisica marina Slabber, 1769 . Yucatan, Mexico; CYMX-78-CY. Scale bar: 1 mm. Material examined Station 8, one male , two females ( one male and one female from this station used for figures), CYMX-78-PY. Station 9, one male , CYMX-77-PY. Station 20, one male , 20 July 2010 , CYMX-37-PY; one male , 30 August 2010 , CYMX-43-PY. Station 23, three males , 21 July 2010 , CYMX-41-PY. Station 24, two juveniles , 18 June 2010 , CYMX-31-PY. Station 25, one male , 18 June 2010 , CYMX-32-PY; one male , 17 December 2010 , CYMX-46-PY. Station 27, one juvenile , CYMX-36-PY. Type locality Walcheren, province of Zeeland , the Netherlands . Distribution Atlantic Ocean; Pacific Ocean; Mediterranean ( McCain 1968 ; Krapp-Schickel 1993 ). Records in the Gulf of Mexico CUB: Cojímar Bay ( Ortiz 2001 ). MEX : Campeche Sound ( Winfield et al. 2006 ); Veracruz Coral Reef System (Winfield, Abarca-Arenas, et al. 2007); Northeastern Yucatan Shelf ( Paz-Ríos and Ardisson 2013 ); Celestun Offshore; Sisal Offshore (present study). USA : from Panama City to Dry Tortugas ( McCain 1968 ). Figure 23. Phtisica marina Slabber, 1769 . Yucatan, Mexico; CYMX-78-CY. Scale bar for Gn1, Gn1 of female, Gn2 of female, P3 and P4: 0.3 mm; scale bar for Gn2: 0.5 mm. Habitat This species has been found on green and brown algae, seagrasses, sponges, hydroids, bryozoans, echinoderms ( McCain 1968 ) and sandy and muddy bottoms ( Diaz et al. 2005 ; Winfield et al. 2006 ; Paz-Ríos and Ardisson 2013 ). The depth range reported is shallow water extending to 1470 m ( Winfield et al. 2006 ; Winfield and Escobar- Briones 2008 ; LeCroy et al. 2009 ). Remarks Phtisica marina is differentiated from Hemiproto wigleyi by the abdomen of both sexes, which has two pairs of well-developed bi-articulate appendages. The material examined is very similar to the Mediterranean species illustrated by Krapp-Schickel (1993) ; it includes a membranous sac on the male propodus palm of gnathopod 2 and a dactylus that is strongly curved. However, the material examined is different from the descriptions of McCain (1968) and Krapp-Schickel (1993) , as well as from the illustrations by Ortiz et al. (2002) and Diaz et al. (2005) , by possessing 4 instead of 3 spines on the propodus palm of pereopod 3 and 4. Key to species of caprellids in the Gulf of Mexico 1. Gills on pereonites 2–4. Pereopods 3–4 well-developed with 6 articles ..... 2 Gills on pereonites 3–4. Pereopods 3–4 reduced (1 or 2 articles) or absent … 3 2. Abdomen with 2 pairs of small 1-articulated appendages in males, 1 pair in females ............................................................................ Hemiproto wigleyi Abdomen with 2 pairs of well-developed 2-articulated appendages in males, 2 pairs in females ................................................................. Phtisica marina 3. Pereopod 5 reduced to 3 small articles ........................... Mayerella redunca Pereopod 5 with 6 articles ......................................................................... 4 4. Antenna 2 with dense row of long setae ventrally. Pereopods 3–4 absent .... 5 Antenna 2 with sparse, short, setae ventrally. Pereopods 3–4 reduced to 1 or 2 articles .................................................................................................... 9 5. Head with sharp, acutely tipped, anterodorsally directed spine ................... ............................................................................................. Caprella scaura Head smooth, without sharp anterodorsally directed spine ...................... 6 6. Head with blunt anterodorsally directed process. Male with gnathopod 2 inserted in middle of pereonite 2 ........................................................... 7 Head without blunt anterodorsally directed process. Male with gnathopod 2 inserted in posterior of pereonite 2 ........................................................... 8 7. Peduncle of antenna 1 inflated in males. Propodus of pereopods 5–7 convex with medial grasping spines .............................................. Caprella andreae Peduncle of antenna 1 not inflated in males. Propodus of pereopods 5–7 concave with proximal grasping spines ............................. Caprella penantis 8. Pereonite 2 with a ventral projection between gnathopod 2. Propodus of pereopods 5–7 with grasping spines ................................. Caprella equilibra Pereonite 2 smooth, without a ventral projection between gnathopod 2. Propodus of pereopods 5–7 without grasping spines .... Caprella danilevskii 9. Pereopods 3–4 with 1 article ................................................................... 10 Pereopods 3–4 with 2 articles .................................................................. 12 10. Body spinose. Head with single anterodorsally directed spine. Pereonite 1 with posterior dorsal projection ....................... Pseudaeginella biscaynensis Body dorsally smooth or with tubercles ................................................. 11 11. Body dorsally smooth. Pereonites hexagonal in dorsal view. Mandibular palp absent. Propodus of gnathopod 1 with a round projection proximally. Pereonite 2 with acute ventral projection between gnathopod 2. Pereonites 6–7 not fused ................................................................. Hemiaegina minuta Body with dorsal tubercles. Pereonites not hexagonal in dorsal view. Mandibular palp present (3-segmented). Propodus of gnathopod 1 without a round projection proximally. Pereonite 2 smooth, without acute ventral projection between gnathopod 2. Pereonites 6–7 fused ................................ ............................................................................ Metaprotella hummelincki 12. Body with dorsal projections on head and pereonite 2 ........................... 13 Body without dorsal projections on head. Pereonite 2 with dorsal tubercles or smooth ................................................................................................ 14 13. Head bearing a dorsal projection and pereonite 2 with 1 pair of dorsal tubercles. Propodus of gnathopod 2 widened distally, profusely setose ....... ....................................................................................... Deutella californica Head and pereonite 2 bearing a dorsal pair of projections. Propodus of gnathopod 2 not widened distally, scarcely setose ............. Deutella incerta 14. Pereonite 2 with 1 or 2 pairs of dorsal tubercles. Mandibular palp welldeveloped, 3-segmented. Propodus of gnathopod 2 with an elongate projection proximally in males ..................................................... Deutella mayeri Pereonite 2 dorsally smooth. Mandibular palp reduced (1–3 small segments) or absent. Propodus of gnathopod 2 with a trapezoidal projection proximally in males ......................................................................................... 15 15. Body dorsally setose. Gnathopod 2 with a distal very large robust tooth on proximal trapezoid projection of propodus, dactylus with inner margin serrate. Pereopods 5–7 with plumose setae ........ Paracaprella guerragarciai Body dorsally bare. Gnathopod 2 with a distal short robust tooth on proximal trapezoid projection of propodus, dactylus with inner margin smooth. Pereopods 5–7 without plumose setae ....................................... 16 16. Mandibular palp absent, represented by single seta. Anterolateral margin of pereonite 2 with large triangular projection in males, projection smaller in females. Basis of male gnathopod 2 with proximal knob on posterior margin ........................................................................... Paracaprella pusilla Mandibular palp absent, without single seta or composed of 1 to 3 minute segments with 1 terminal seta. Anterolateral margin of pereonite 2 with small triangular projection in males, absent in females. Basis of male gnathopod 2 without proximal knob on posterior margin .......................... ....................................................................................... Paracaprella tenuis Zoogeographical comments A summary of species distribution by depth and geographical region in the Gulf of Mexico is provided in Table 2 . From deeper zones there is a decrease in species number with increasing depth ( Figure 24A ). All species (17) are found on the shallow coast, 12 on the continental shelf, eight on the continental slope and three ( C. danilevskii , C. equilibra and C. penantis ) on the abyssal plain. Geographically, the southern regions hold a higher number of species (17) than the northern regions (11) ( Figure 24B ). The most widely distributed species in the Gulf basin are C. penantis , D. incerta , H . minuta , P. pusilla and P . tenuis , all of which have been reported from all four regions of the Gulf of Mexico . Table 2. Checklist and distribution of caprellid species by geographical region and depth in the Gulf of Mexico.

Species	NE	NW	SW	SE	Depth (m)
Caprella andreae ( Mayer, 1890 )	×	×	0–2
Caprella danilevskii ( Czerniavski 1868 )	×	×	0–2620
Caprella equilibra ( Say 1818 )	×	×	×	0–3700
Caprella penantis ( Leach, 1814 )	×	×	×	×	0–3700
Caprella scaura ( Templeton 1836 )	×	×	×	0–17
Deutella californica ( Mayer 1890 )	×	1–25
● Deutella incerta ( Mayer 1903 )	×	×	×	×	0–1470
● Deutella mayeri ( Stebbing 1895 )	×	×	1–18
● Hemiaegina minuta ( Mayer 1890 )	×	×	×	×	0–354
● Hemiproto wigleyi ( McCain 1968 )	×	×	25–76
● Mayerella redunca ( McCain 1968 )	×	×	0–320
● Metaprotella hummelinckii ( McCain 1968 )	×	×	1–29
Paracaprella guerragarciai ( Winfield and Ortiz 2013 )	×	16
● Paracaprella pusilla ( Mayer 1890 )	×	×	×	×	0–498
● Paracaprella tenuis ( Mayer 1903 )	×	×	×	×	0–11
● Phtisica marina ( Slabber 1769 )	×	×	×	0–1470
● Pseudaeginella biscaynensis ( McCain 1968 )	×	1–22

Notes: Recorded species found in the north coast of the Yucatan Peninsula, SE Gulf of Mexico, are indicated by a symbol ( ● ) preceding their name. NE, northeast; NW, northwest; SW, southwest; SE, southeast. From the faunal affinity among regions, two species assemblages are displayed at the 66% similarity level ( Figure 25 ). Geographically, one of them represents the southern sector fauna (SW and SE) at 69% similarity and the other represents the northern sector fauna (NW and NE) at 78% similarity.