From Microscale Interactions to Macroscale Patterns in Copepod-Crinoid Symbiosis

Abstract

Crinoids (Echinodermata) exhibit unique morphological and behavioral characteristics that facilitate a wide range of symbiotic relationships with diverse organisms. Our comprehension of their interactions with microscopic copepod crustaceans is, however, still in a nascent and fragmented state. Here, we review and discuss the 166 literature records to date in which a total of 39 copepod species in 6 families have been reported in association with 33 species of the crinoid order Comatulida. Many of these associations have been reported just once. The respective localities cover 5 of the World Ocean's 12 ecoregions, with a notable concentration of both host and symbiont diversity in the Central and Western Indo-Pacific. In contrast, the documentation of copepod-crinoid associations in the Atlantic appears markedly limited. Copepods have been found predominantly in ectosymbiotic relationships with crinoids, with a lower incidence of endosymbiosis. Copepods of the genera Collocheres Canu, 1893 and Pseudanthessius Claus, 1889 are particularly prominent in the list, and the comatulid family Comatulidae displays the most diverse assortment of copepod associations. The current scope of knowledge encompasses a mere 5% of the potential crinoid host diversity, underscoring the need for more extensive research in this area.

Keywords: Comatulida; copepod associations; crinoids; host-symbiont interactions; marine biodiversity; marine ecology; marine invertebrates; marine parasitology; symbiotic relationships.

Figure 1

Numbers of new species and cumulative percentage (green line) of known species of (A) crinoids and (B) symbiotic copepods associated with them and described in publications over time. Based on the WoRMS database [41].

Figure 2

Habitus of copepod crustaceans living on crinoids. (a) Enterognathus inabai, dorsal view, scale bar 1 mm; (b) Parenterognathus troglodytes, lateral view, scale bar 0.5 mm; (c) Critomolgus fishelsoni, dorsal view, scale bar 0.5 mm; (d) Doridicola patulus, dorsal view; (e) Kelleria gradata, ventral view, 0.2 mm; (f) Pseudanthessius comanthi, both sexes are shown, dorsal view, 0.5 mm; (g) Scambicornus pillaii, dorsal view, 0.1 mm; (h) Asterocheres crinoidicola, both sexes are shown, dorsal view, 0.3 mm; (i) Collocheres brevipes, both sexes are shown, dorsal view, 0.1 mm; ((a,b) Cyclopoida, (c–g) Poecilostomatoida, (h,i) Siphonostomatoida). After [65] (a), [64] (b), [73] (c,e), [77] (d), [53] (f), [75] (g), [10] (h), [66] (i).

Figure 3

Number of records per association of symbiotic copepod genera with crinoid families. The size of each oval mark denotes the number of records.

Figure 4

Distribution of the copepods associated with crinoids in the World Ocean. The marginal histogram illustrates the latitudinal and longitudinal distribution of the reports of copepods.

Figure 5

Distribution of symbiotic copepods associated with crinoids by depth. The horizontal line within each box represents the median of the dataset. The box defines an interquartile range from the 25th to the 75th percentile. Vertical lines extending from each box show the minimum and maximum data values. Data points appearing outside of these vertical lines are identified as outliers. Dashed lines demarcate depths not depicted, where no instances of copepod presence on crinoids were recorded.