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A new species of the genus Liropus Mayer, 1920 (Amphipoda, Caprellidae) is described from the Mexican Tropical Pacific coast. Liropus alarconi n. sp. is described on the basis of four specimens collected in association with the tropical marine sponge Trikentrion helium Dickinson, 1945, near to coralline patches, between 2330 m depth. Liropus alarconi n. sp. can be distinguished from its congeners for the following characters: pereonites 25 each with one dorsodistal projection and pereonite 3 with a mediolateral projection.

A new species of caprellid, Deutella mazatlanensis n. sp., is described from Mazatlán Bay, (east Pacific México). Deutella mazatlanensis was found associated with bryozoans, hydroids and sponges in shallow waters. The new species can be differentiated from the remaining species of the genus mainly by the dorsal, anteriorly directed projection on the head; the two dorsal projections and a lateral acute projection anteroventrally projected on pereonite 2 and gnathopod 2 in males. The presence of this species on the Mexican Pacific coast, constitutes the fourth report of Deutella genus for the Pacific Ocean and the first record from the tropical Eastern Pacific.

Axinella nayaritensis n. sp. is a typical species of the genus Axinella in spiculation (oxeas and styles), skeletal arrangement (axial condensation from which radiate an extra-axial plumoreticulated skeleton), and external form (arborescent). The new species is orange, branching, up to 25 cm in height, and which usually live in soft bottoms. One of the most conspicuous characteristic of the new species is its aquiferous system, which is formed by a system of superficial canals and meandering ridges which run around the entire length of the branches. The species is compared with Axinella polycapella from Gulf of Mexico, which is very close in morphology, and which it shares a high similarity in the 18S ribosomal RNA region. It was also compared with Axinella aruensis, a very different species from a morphological point of view, which is distributed throughout the northern Australia, Indonesia and Papua New Guinea as both species share a high similarity in the COI mitochondrial gene region. The new species was included in the clade named Axinella by Gazave et al. (2010) for 18S and COI, where also are included eight Axinella-species. Species in this clade are typically arborescent with a choanosomal skeleton differentiated between axial and extra-axial regions. Axinella nayaritensis n. sp. constitute the first record of an Axinella for the east Pacific coast.

Excavating sponges are one of the main groups of bioeroders in coral reefs. Their diversity has been thoroughly studied in some regions: in the Caribbean, the Mediterranean, and the Indo-Pacific, including the Mexican Pacific. However, there is a lack of information from the Pacific of Central America, with only a few records from Panama and Costa Rica. This study provides additional distributional records and taxonomic descriptions of species collected between 2011 and 2016 at nine localities along the Pacific coast of El Salvador, Nicaragua, Costa Rica and Panama. A total of fourteen species of excavating sponges from three orders, three families, and five genera are considered valid in this area. Nine are new records for Central America, six are new records for El Salvador, three are new records for Nicaragua and eleven are new records for Costa Rica. The species collected from Panama were already recorded before. The species here described are Cliona amplicavata, Cliona californiana, Cliona euryphylle, Cliona microstrongylata, Cliona aff. mucronata, Cliona pocillopora, Cliona tropicalis, Cliona vermifera, Cliothosa tylostrongylata, Pione cf. carpenteri, Pione mazatlanensis, Thoosa calpulli, Thoosa mismalolli and Siphonodictyon crypticum. We also reviewed the literature related to excavating sponges from Central America, and the taxonomic status of respective species was updated. We provide a faunistic record of 14 excavating sponge species for Central America. Our data are expected to be useful for management and conservation purposes.