Species richness and biogeographical affinities of the marine molluscs from Bahía de Chamela, Mexico.

For more than 10 years (2007-2018), the benthic macroinvertebrates of Bahía de Chamela (Mexican Pacific) were sampled at 31 sites (0-25 m depth). A total of 308 species of the five main classes of benthic molluscs were obtained (106 bivalves, 185 gastropods, 13 polyplacophorans, two scaphopods and two cephalopods). This is a significant increase in the number of species (246 new records) compared to the 62 species previously recorded more than 10 years ago. The distribution in the 31 localities of the bay is given for the first time for most of the species, together with information on its ecological rarity (incidence in the samples). Two families of bivalves (Veneridae and Mytilidae) and three families of gastropods (Calyptraeidae, Muricidae and Collumbellidae) comprised ~ 30% of all species. Ecological rarity was evident with 45 families (45.0%) with only one species and 178 species (57.8%) collected in one site and 67 (21.8%) in two sites. The molluscs of Bahía de Chamela represent 12.2% of all species recorded in the Mexican Pacific. Their biogeographic affinities are mostly related to the Tropical Eastern Pacific (TEP) including the oceanic islands and a few are restricted to the Tropical Mexican Pacific (TMP). Some have broader distributions to adjacent northern and southern temperate regions of the American Pacific, one to the western Atlantic, two pantropical (PAN) and two cosmopolitans (COS). The range distribution of each species was reviewed and updated, thus finding that seven species have extended their ranges of geographic distribution.

Description of a new species of Pagurus Fabricius, 1775 (Crustacea: Paguroidea: Paguridae) from the Pacific coast of Costa Rica, Central America, with notes on Pagurus albus (Benedict, 1892).

A redescription of Pagurus albus (Benedict, 1892) is presented together with a description of a new species of hermit crab, Pagurus pseudoalbus sp. n., from the Pacific coast of Costa Rica. Pagurus pseudoalbus sp. n. differs from P. albus and P. perlatus by the length of antennal acicles, which do not exceed the distal margin of the 4th antennal segment, whereas in the latter two species, the antennal acicles exceed the 4th antennal segment; the antennular peduncle is proportionally longer than the ocular peduncle in the new species compared to P. perlatus, but shorter than in P. albus; the palm of the right cheliped in P. pseudoalbus sp. n. is 1.3 times as long as broad, while in P. albus and P. perlatus it is 1.0 and 1.4 times as long as broad, respectively. Including the new species, the genus Pagurus in the Eastern Tropical Pacific currently includes 16 species.

New records and description of two new species of carideans shrimps from Bahía Santa María-La Reforma lagoon, Gulf of California, Mexico (Crustacea, Caridea, Alpheidae and Processidae).

Two new species of the family Alpheidae: Alpheus margaritaesp. n. and Leptalpheus melendezensissp. n. are described from Santa María-La Reforma, coastal lagoon, SE Gulf of California. Alpheus margaritaesp. n. is closely related to A. antepaenultimus and A. mazatlanicus from the Eastern Pacific and to A. chacei from the Western Atlantic, but can be differentiated from these by a combination of characters, especially the morphology of the scaphocerite and the first pereopods. Leptalpheus melendezensissp. n. resembles L. mexicanus but can be easily differentiated because L. melendezensissp. n. has the anterior margin of the carapace broadly rounded and has only one spine on the mesial margin of ischium in the major cheliped, versus an acute rostrum and an unarmed major cheliped. Additionally, a phylogenetic analysis was used to explore the relationships of these two new taxa. These results show that Alpheus margaritaesp. n. and Leptalpheus melendezensissp. n. are indeed related to the species against which we are comparing them, and demonstrate that they can be considered as different species. Additional specimens of Leptalpheus cf. mexicanus, Ambidexter panamensis and A. swifti are recorded for the first time in the Santa María-La Reforma coastal lagoon.

First zoeal stage of the hermit crab Enallopaguropsis guatemoci (Glassell, 1937) (Crustacea: Anomura: Paguroidea: Paguridea) obtained in the laboratory.

The first larval stage of Enallopaguropsis guatemoci is described in detail and illustrated. The larva is compared with larvae known for other genera of Paguridae except Pagurus. A synthesis of all characters provided herein indicates that first larvae of E. guatemoci can be separated from all known pagurid larvae (except Pagurus) by the combination of the following characters: carapace with long dorsal carina, posterolateral spines absent; abdominal somites 3-5 with pair of moderately long spines; telson narrowly triangular, not forked; spine at antennal protopod as long as endopod.

A new species of the hermit crab genus Areopaguristes Rahayu & McLaughlin (Crustacea, Decapoda, Anomura, Paguroidea, Diogenidae) from the Mexican Pacific.

A new species of hermit crab, Areopaguristes espetacioni, family Diogenidae, is described and illustrated in detail, including the color pattern in live/fresh specimens. This is the fifth species of Areopaguristes reported from the eastern Pacific. Given the morphological similarity between Areopaguristes espetacioni n. sp. and A. tudgei Lemaitre & Felder, 2012, these can be considered sister species. The presence of a long rostrum, the antennal flagella with short setae, chelipeds and ambulatories legs with dense plumose setae, and telson with calcareous teeth on the posterior margin allow to separate Areopaguristes espetacioni n. sp. from all other species in the genus previously described for the region. A key for Areopaguristes species from the eastern tropical Pacific is provided.

Caprella suprapiscis sp. nov. (Crustacea: Amphipoda: Caprellidae) from the Pacific coast of Mexico.

A new species of caprellid, Caprella suprapiscis sp. nov., is described based on several specimens collected from Bahía Chamela, Jalisco, Mexico. All specimens were found in association with the scorpionfish Scorpaena mystes. Caprellids are set on the dorsal surface of fishes. The species is distinguished by head with a short dorsal projection, eyes distinctive, body slender and smooth, peduncular articles of antenna 1 not setose, antenna 2 with swimming setae, gnathopod 2 with three ventral projections in males. The species is close to C. californica, C. mercedesae, and C. scaura for a sharp spine on the forehead but can be distinguished by gnathopod 2 finely setose, and basis of gnathopod 2 shorter.

A new species of the genus Typton Costa (Crustacea: Decapoda: Palaemonidae: Pontoniinae) from the eastern tropical Pacific.

A new species of commensal shrimp of the genus Typton from holothurians is described and illustrated. The specimens were collected from a single specimen of Holothuria (Halodeima) inornata Semper, 1868 at a depth of 7 m. This is the first record of an association between a shrimp of the genus Typton and echinoderms. With this record, five species of Typton are now known from the eastern Pacific region and four of them are found in the Mexican Pacific. In Typton granulosus sp. nov., the distal part of the outer margin of the uropodal exopod is serrated, a feature shared with T. fapespae Almeida et al., 2014, T. holthuisi De Grave, 2010, T. prionurus Holthuis, 1951, T. serratus Holthuis, 1951, and T. spongicola Costa, 1844. However, the new species can be separated from the other five species of the genus by several morphological characters.

Redescription and taxonomic status of Paguristes praedator Glassell, 1937 and P. oxyophthalmus Holthuis, 1959 (Anomura: Paguroidea: Diogenidae), with an emendation to the diagnosis of the genus Areopaguristes Rahayu & McLaughlin, 2010.

The taxonomic status of Paguristes praedator Glassell, 1937, and Paguristes oxyophthalmus Holthuis, 1959, is reevaluated, and the two species redescribed and illustrated in detail. Both species are transferred to the genus Areopaguristes Rahayu & McLaughlin, 2010, a genus previously defined to accommodate species of Paguristes sensu lato with 12 pairs of gills instead of 13. Two important characters in both species were found to differ or have not been mentioned in the current definition of Areopaguristes, i.e., the first maxilliped lacking epipod, and dactyls of second and third pereopods unarmed on the ventral margins. The presence of other diagnostically significant characters (e.g., lack of first pleopods in females) previously noted in other species of Areopaguristes, requires the generic emendation of this genus presented herein. With the transfer of A. praedator nov. comb. and A. oxyophthalmus nov. comb. to Areopaguristes, this genus now contains 27 species, of which nine occur in the Americas (four in the eastern tropical Pacific, and five in the western Atlantic). 

Calyptraeotheres sp. nov. (Crustacea: Decapoda: Pinnotheridae), symbiont of the slipper shell Crepidula striolata Menke, 1851 (Mollusca: Gastropoda: Calyptraeidae) from the Gulf of California, Mexico.

Calyptraeotheres camposi sp. nov. is described from the Gulf of California, Mexico. The new species is close to C. granti (Glassell, 1933) and C. pepeluisi Campos & Hernández-Ávila, 2010 from the Mexican Pacific and to C. hernandezi Hernández-Ávila & Campos 2006 from the Western Atlantic. These four species feature a third maxilliped with a 2-segmented endopod palp and the exopod with unsegmented flagellum. Calyptraeotheres camposi sp. nov. differs from C. granti and C. hernandezi by having the eyes visible in dorsal view, the carapace with arcuate anterolateral margins, the dorsal, longitudinal depressions connected with the transversal depression, and the propodus of pereiopod 2 equal or slightly longer than the carpus. From C. pepeluisi it is distinguished by the absence of a transversal depression on the carapace and the longitudinal depressions not connecting, the carpus and propodus of the third maxilliped being sub-trapezoidal and sub-conical, respectively, in lieu of subrectangular, and the inner surface of the fixed finger nude instead of bearing short setae near the cutting edge and ventral margin.

A new deep-water species of Odontozona (Decapoda: Stenopodidea: Stenopodidae) from the East Pacific, and new record of O. foresti Hendrickx, 2002.

A new species of the stenopodid shrimp Odontozona is described from deep-water off the west coast of Mexico. It is distinguished from the three other species of the genus known in the area, from O. rubra Wicksten, 1982, and O. foresti Hendrickx, 2002, by the absence of a series of spines on the posterior half of the carapace, behind the post-cervical groove, and from O. spongicola (Alcock & Anderson, 1899) by the presence of spines on the ventral margin of somites 1-5 (smooth in O. spongicola) and by the much slender third pair of pereiopods in the new species. A new record is provided for O. foresti, and the first male specimen, the third specimen on record, is compared with the female holotype.

A new species of Leptalpheus Williams, 1965 and new records of L. mexicanus Ríos & Carvacho, 1983 and L. hendrickxi Anker, 2011 (Crustacea: Decapoda: Alpheidae) from the Pacific coast of Mexico.

A new species of Leptalpheus is described from Estero Pérula, Jalisco, on the Pacific coast of Mexico. Leptalpheus corderoae sp. nov. is most similar to Leptalpheus azuero Anker, 2011 from Panama and Leptalpheus axianassae Dworschak & Coelho, 1999 from Brazil, differing from both of them by a combination of morphological characters, especially the presence of tubercles on the ventral surface of the major chela palm and pollex. The most common host of L. corderoae sp. nov. at the type locality is the callianassid ghost shrimp Lepidophthalmus bocourti (A. Milne Edwards, 1870). Additional specimens of Leptalpheus mexicanus Ríos & Carvacho, 1983, from Estero de Urías, Sinaloa, are reported and compared to the type material from Río Mulegé, as well as to Leptalpheus bicristatus Anker, 2011 from Panama. Finally, Leptalpheus hendrickxi Anker, 2011 is reported from Mexico for the first time, representing a significant northward range extension of the species. In Estero Pérula, L. hendrickxi lives in burrows of Lepidophthalmus bocourti, sometimes together with L. corderoae sp. nov. 

A new species of the caridean shrimp genus Ogyrides Stebbing, 1914 (Decapoda: Ogyrididae) from the eastern tropical Pacific.

The caridean shrimp Ogyrides wickstenae sp. nov. is described from Mazatlán, Pacific coast of Mexico. The new species is most closely related to O. tarazonai Wicksten & Méndez, 1988 and O. hayi Williams, 1981, sharing with them a single spine on the dorsal midline of the carapace. However, the new species can be distinguished from the two allied species by the presence of a single small spine on the second endopodal segment of the third maxilliped and the five-segmented carpus of the second pereopod. A key for the Eastern Pacific species of Ogyrides is provided.

Redescription and taxonomic status of Paguristes weddellii (H. Milne Edwards) (Crustacea: Anomura: Paguroidea: Diogenidae) from the eastern Pacific.

The type and additional material of Paguristes weddellii (H. Milne Edwards, 1848) were examined. The species is redescribed and illustrated in details. Comparison of P. weddellii with the monotypic genus Tetralobistes Ayón-Parente & Hendrickx, 2010b, shows many similarities, principally in the armature of the distal margin of the male first pleopod and the shape of the telson, which in both cases feature a tetralobular posterior margin, a character considered unique among the Diogenidae. Consequently, Pagurus weddellii is transfered to the genus Tetralobistes. Paguristes hirtus Dana, 1851, a subjective junior synonym of Pagurus weddellii is removed from the synonymy based on lack of direct evidences.