Pablo Hernández-Alcántara

Bathymetric distribution and diversity of deep water polychaetous annelids in the Sigsbee Basin, northwestern Gulf of Mexico

The deep water polychaete fauna is analyzed in this study particularly regarding its composition and variations with depth in the Sigsbee Basin, northwestern region of the Gulf of Mexico. Samples were taken at 10 stations along a bathymetric gradient with depth ranges from 200 to 3760 m with a USNEL (0.25 m2) corer. A total of 287 individuals were identified, from 21 families and 65 species. The most important families, both in terms of abundance and species richness, were: Paraonidae (65.4 ind./0.25 m2, 9 spp.), Cirratulidae (28.93 ind./0.25 m2, 7 spp.) and Spionidae (18.07 ind./0.25 m2, 7 spp.). In general, density tended to decrease with depth with minima at around 2000 m, although two abundance peaks were detected at 3700 and 3760 m, making the pattern seem an inverted parabolic curve. The Shannon-Wiener diversity values varied from 0.54–0.92 at around 2000 m to 3.39 at 3620 m and 3.34 at 3760 m. These results contrast with what is already reported from the North Atlantic and the Tropical Pacific deep benthic communities, where highest diversities are found at 2000 m. Faunal changes evaluated through Beta Diversity (0.08–0.1) and the low similarity found between the stations, emphasized the high variability in the composition of the fauna in the Sigsee Basin, meaning that the faunal composition is practically different at all the sampling stations. Ten species are newly recorded for the Mexican fauna.

Parasitism among polychaetes : A rare case illustrated by a new species : Labrorostratus zaragozensis, n. sp. (Oenonidae) found in the Gulf of California, Mexico

We describe a new species of polychaetous annelid from the family Oenonidae, Labrorostratus zaragozensis, n. sp., which is parasitic on another polychaete from the family Trichobranchidae (Terebellides californica). It can be differentiated from the other 4 species of the genus (Labrorostratus parasiticus, Labrorostratus jonicus, Labrorostratus prolificus, Labrorostratus sp.), basically by the shape of the mandibles and in the case of L. luteus, by the presence of hooded acicular hooks. Along with the description, a review and discussion of all previous records of the parasites in the Oenonidae and their related interactions with their hosts is presented.

Geographical patterns in species richness of the benthic polychaetes in the continental shelf of the Gulf of California, Mexican Pacific

The present study is the first attempt to describe meso-scale patterns in the species richness of polychaetes along the Gulf of California, which stretches from about 23°N to 31°N. We examine herein the spatial changes in species distribution and explore the overlapping of species’ ranges towards the centre of the Gulf, to test whether the mid-domain effect (MDE) could explain an expected mid-domain peak in species richness. The faunal composition and the latitudinal range of 244 species of polychaetes recorded along the continental shelf of the Gulf of California were analysed in latitude bands of 1°. The species composition changes around the Gulf’s archipelago (~29°N), and the highest values of species richness are found at the 25° (197 species) and 26° (193 species) of latitude. Although the species richness pattern could be described by a parabolic shape, the regional trend was not strongly consistent with the peak of diversity at 27°N (176–191 species) predicted by the mid-domain effect: the random sorting of species’ ranges within spatial domain does not explain satisfactorily the geographical patterns of diversity. Nevertheless, a partial contribution of MDE to these natural patterns of diversity could be detected, and the increase in species richness towards middle latitudes was basically determined by species with distribution ranges larger than 6°. The low level of significance between the empirical species richness pattern and the mid-domain model prediction for polychaetes in the Gulf does not restrict their use as a model for exploring the randomness of the diversity patterns.

Description of two new species of Pisione (Polychaeta: Sigalionidae) and first record of Pisione galapagoensis Westheide in the Southern Mexican Pacific.

The genus Pisione Grube 1857 was composed up to now of 40 species and 4 subspecies. Although distributed worldwide, in the Mexican Pacific little is known about its taxonomy and distribution, and only two species of this genus have been recorded: Pisione longispinulata Aguado & San Martín, 2004 and Pisione remota (Southern, 1914), but the records of the latter remain questionable. For this study, 406 pisionids from soft sediments of Acapulco Bay, Southern Mexican Pacific, were examined. Two new species are described: Pisione hippocampus n. sp. characterized by having protruding notoaciculae in posterior chaetigers, the second dorsal cirrus elongated and copulatory organs resembling the body shape of a seahorse and Pisione sanmartini n. sp. characterized by having protruding notoaciculae from the first chaetiger, buccal aciculae with a distal crenulate plate resembling the edge of a shell, and prechaetal bifurcated lobes along the body. Pisione galapagoensis Westheide, 1974 is newly recorded for the Mexican Pacific, its known distribution being extended northward from the Galapagos Islands and Panama. A comparative table with the main diagnostic characters and the distribution of all the species so far described in the genus Pisione is included, as well as a key to the species of the Eastern Pacific.

Nereis alacranensis , a new species of polychaete (Annelida, Nereididae) from Alacranes Reef, southern Gulf of Mexico, with a key to Nereis from the Grand Caribbean

A new species of polychaete, Nereis alacranensis n. sp., was found in dead coral rocks in the intertidal zone of Alacranes reef, southern Gulf of Mexico. N. alacranensis n. sp. can be included in a group of nereidids characterized by the absence of paragnaths in areas I and V of the pharynx, the presence of cones in a single row or absent in areas VII-VIII, and short blades in notopodial homogomph falcigers. The new species can be separated from the other species of the group by the presence of 3-7 cones in area VI and 7 cones arranged in a row in areas VII-VIII, finely dentate blades in notopodial homogomph falcigers, but most of all, by the presence of an unusual brown coarse arc shaped plate on the external ventral region of the peristomium. This structure has not yet been reported, at least in this genus. A taxonomic key of the species of Nereis recorded from the Grand Caribbean region is included.

Trochochaeta mexicana, a new species from an unusual family of Polychaeta, with comments on the world distribution of Trochochaetidae

The small, monogeneric family of polychaetes known as Trochochaetidae has been exclusively collected in the northern hemisphere, mainly in temperate–cold environments. Nine species have been described so far including Trochochaeta mexicana sp. nov. described herein, while one species remains unnamed. Only two species had previously been recorded in the eastern Pacific, so T. mexicana sp. nov. is the first record for the family in the tropical Mexican Biogeographic Province. The new species is characterized by having a pair of eyes, acicular neurochaetae on chaetigers 2 and 3, a small knob-like antenna and a nuchal crest projecting through chaetiger 1. Trochochaeta mexicana sp. nov., together with Trochochaeta kirkegaardi, Trochochaeta diverapoda and Trochochaeta cirrifera are the only trochochaetids that have been found exclusively in warm environments.

Nephtyidae (Polychaeta) from the Gulf of California (Mexican Pacific) with the description of two new species of Aglaophamus

The aim of this study is to analyse the Nephtyidae from the Gulf of California. Previous studies about the family Nephtyidae from the continental shelf of the Gulf include 21 species of which seven have been synonymized by several authors, so that at present only 14 species are recognized. In this study, 1763 specimens of Nephtyidae from the continental shelf of the Gulf of California were examined. Eight species were identified, from which Aglaophamus longicirrata sp. nov. and Aglaophamus foliosa sp. nov. are newly described. Aglaophamus longicirrata sp. nov. is characterized by the presence of very long dorsal cirri in median parapodia and by having 16 rows of subterminal papillae with 3–7 papillae per row, and a pair of middorsal papillae on the proboscis. Aglaophamus foliosa sp. nov. is characterized by foliaceous long dorsal cirri; the proboscis bears 16 rows of subterminal papillae and an irregular number of papillae per row, from 5 to 15. A taxonomic key is presented for the species of Nephtyidae recorded from the continental shelf of the Gulf of California, including the two new species of Aglaophamus .

Description, morphometric characterization and distribution pattern of Paradiopatra multibranchiata, a new onuphid (Annelida: Polychaeta) from the tropical eastern Pacific

ABSTRACT Paradiopatra multibranchiata, an onuphid found commonly in shelf sediments of the tropical eastern Pacific, is described here. It belongs to the group of Paradiopatra species characterized by the presence of branchiae on the most anterior parapodia (chaetigers 2–3), with at least seven filaments when fully developed. The new species closely resembles P. parva, also distributed in the eastern Pacific but in temperate habitats. It can be distinguished from the latter by the presence rather than the absence of eyes, and because it bears the highest number of branchial filaments (up to 37) observed in any Paradiopatra species known so far (14–18 filaments at most). The taxonomic status of the new species is supported by comparative morphometric and multivariate analyses, which also allowed us to verify its differences with P. parva. The branchial development was the most useful character to determine the relationships between the specimens of P. multibranchiata sp. nov., while its separation from P. parva (Wilks’ lambda = 0.060, P < 0.0001) was weighted most heavily by the number of filaments at chaetigers 2 and 10, and the length of the median antenna. An anatomical examination with methylene blue stain and with scanning electron microscopy was carried out to illustrate the ventral glandular pad staining pattern and the features of their cuticular pores. http://zoobank.org/urn:lsid:zoobank.org:pub:194636C6-A032-4B1F-B0B8-1D494C344623

Labrorostratus caribensis , a new oenonid polychaete from the Grand Caribbean living in the body cavity of a nereidid, with emendation of the genus

Endoparasitic relationships among polychaetes are uncommon and mostly restricted to about 20 species of the family Oenonidae. We herein describe Labrorostratus caribensis, a new oenonid species living in the body cavity of a nereidid polychaete in Chinchorro Bank (Mexican Caribbean). This is the first report of a parasitic relationship between oenonids and nereidids in the Grand Caribbean region. The new species is diagnosed by the jaw apparatus reduced to only maxillary carriers fused, one simple modified ventral chaeta from midbody and lack of acicular spines. The generic diagnosis is emended to include species without maxillary plates. A synopsis of parasitism among polychaetes worldwide is presented.

First record and distribution of Pisione longispinulata Aguado & San Martín (Annelida: Polychaeta: Pisionidae) in the Mexican Pacific coasts

Abstract Pisione longispinulata is newly recorded from the Mexican Pacific and is the first record outside its type locality, Coiba Island, Panamá, Pacific. Six specimens of the species were collected in the sandy soft bottoms of the intertidal zone of the Oaxaca coasts. The individuals found were three males and three specimens in which the sexual characters could not be distinguished. The holotype and two paratypes from the type locality of the species were also examined, and a short taxonomic note about their diagnostic characters is presented.