The Pinnotheridae of the northeastern Pacific (Alaska to Mexico): zoogeographical remarks and new bivalve hosts (Crustacea, Brachyura, Pinnotheridae)

Abstract

New bivalve host records for four pinnotherid crabs of the Mexican Pacific are reported: Fabia subquadrata Dana, 1851, in Modiolus capax (Conrad, 1837); Opisthopus transversus Rathbun, 1893, in Tivela stultorum (Mawe, 1823); Pinnaxodes gigas (Green, 1992), in Pinna rugosa (Sowerby, 1835), and Panopea generosa Gould, 1850; and Tumidotheres margarita (Smith, 1870), in Nodipecten subnodosus (Sowerby, 1835). The southernmost distribution of F. subquadrata is extended to about 600 km along the west coast of the Baja California Peninsula; the distribution of P. gigas is extended outside the Gulf of California more than 1000 km north to San Quintín, on the west coast of Baja California; and the range of T. margarita is restricted on the west coast of Baja California to Scammon´s Lagoon, Baja California Sur and Playa Kino Viejo, Sonora in the central region of the Gulf of California, Mexico to Panama. Based on the new material, new information on taxonomy, ecology, and life history is provided for each of these species. Pinnotheres nudus Holmes, 1895 is restored as a valid species and is removed from its synonymy with O. transversus. An updated checklist with remarks on zoogeography for the 60 pinnotherid species, included in 23 genera, of the northeastern Pacific region (Alaska to the Mexican tropical Pacific) is given.

A Review of the Ecomorphology of Pinnotherine Pea Crabs (Brachyura: Pinnotheridae), with an Updated List of Symbiont-Host Associations

“…The largest species of pinnotherine crab, Pinnaxodes gigas Green, 1992, has a carapace width of 36 mm as is reported from the siphon of a large geoduck, the mudburrowing bivalve Panopea sp. [30]. The smallest pea crab species, Nannotheres moorei Manning & Felder, 1996, can be found in narrow hammer oysters (Malleus candeanus (d'Orbigny, 1853)) barely reaching a carapace width of 1.5 mm [31].…”

Taxonomy of Pinnotheres bipunctatus Nicolet, 1849 with a distributional checklist of the Pinnotheridae of Chile and Peru, and a list of the Crustacea described by Hercule Nicolet in the Atlas of the Physical and Political History of Chile

“…This small crab was the only species of Pinnotheridae described by the Swiss naturalist Hercule Nicolet in the chapter of Crustacea (Zoology, section 3) of the "Physical and Political History of Chile" by Claudio Gay (1849). The morphology of P. bipunctatus was analyzed and compared with the type species of Pinnotheres Bosc, 1802, P. pisum (Linnaeus, 1767), as well as other genera of Pinnotheridae of the Eastern Pacific (Campos, 2009(Campos, , 2016. The long dactylus of the third maxilliped that overreaches the tip of the propodus and the subtriangular telson wider than the sixth abdominal somite are unique features that clearly support that P. bipunctatus does not belong to Pinnotheres.…”

On the pea crabs found in the chiton Tonicia chilensis (Frembly, 1827) (Mollusca, Polyplacophora: Chitonidae) identified as “Orthotheres sp.” by Melzer & Schwabe (2008), and its reassignment to Calyptraeotheres Campos, 1990 (Crustacea: Pinnotheridae)

“…It is noteworthy that these juveniles were collected within the geographic range of C. politus (see Campos 1999Campos , 2016. In both cases the ischium-merus widens distally, with the distoexternal angle obtuse and the distointernal angle produced and obliquely truncated; the carpus is robust, larger than the propodus, and the dactylus is tiny and inserted obliquely at the distal lower margin of the propodus, while the dorsal margin extends beyond the insertion point of the dactylus (Figs.…”

“…Crabs of the family Pinnotheridae have been considered a phylogenetically heterogeneous group and taxonomically problematic (Palacios-Theil 2009, 2016Tsang et al 2018). The lack of knowledge of sexual dimorphism and morphological variation throughout the life history for many species have complicated its taxonomy and has resulted in errors in its classification (Campos 1989(Campos , 1993(Campos , 2016.…”

“…The lack of knowledge of sexual dimorphism and morphological variation throughout the life history for many species have complicated its taxonomy and has resulted in errors in its classification (Campos 1989(Campos , 1993(Campos , 2016. Consequently, if the taxonomy of these symbiotic crabs had been based on juveniles and undeveloped character states, the problems get even more serious (Campos 1989(Campos , 1993.…”