Vol. 61, 2022
Host-parasite Interactions between a Copepod (Pharodes tortugensis) and Small Reef-associated Gobies (Coryphopterus) in the British Virgin Islands
Graham E. Forrester1,*,§ and Rachel J. Finley2,§
of Natural Resources Science, University of Rhode Island, Kingston,
Rhode Island 02881, USA. *Correspondence: E-mail: firstname.lastname@example.org
2Department of Natural Resources
Science, University of Rhode Island, Kingston, Rhode Island 02881, USA.
E-mail: email@example.com (Finley)
§GF and RF contributed equally to this work.
Received 21 February 2021 / Accepted 4 May 2022
Communicated by Benny K.K. Chan
The effects of parasitic copepods on free-living hosts are infrequently documented, and the copepod Pharodes tortugensis
has remained virtually unstudied since described. For the first time,
we document its host range in the British Virgin Islands (BVI), the
prevalence and intensity of infections on wild hosts, and its impacts
on host morphology and performance. Infections were observed on four
benthic gobies in the BVI (Coryphopterus glaucofraenum, C. venezuelae, C. dicrus and C. eidolon)
but not on other host species previously reported from other parts of
the western Atlantic. Infected gobies were widespread in the BVI
(detected at 33 of 52 sites, prevalence from 1–25%) but extremely rare
elsewhere in the Caribbean (detected at 2 of 16 sites, prevalence <
0.006%). As is typical of macroparasite infections, P. tortugensis
was over-dispersed in BVI host populations (mean intensity = 4.7, range
= 1–17). Infections were most common in juvenile and female hosts, and
rarely found in larger male hosts. The copepods attach in the branchial
chamber of the goby; female copepods show high attachment fidelity to
the ventral surface of the chamber, while male copepods attached most
often to the first two gill arches and in the branchial chamber
adjacent to the female. Infections caused substantial damage to the
host’s branchial chamber and gill filaments. Parasitized gobies also
had larger livers and smaller gonads than unparasitized individuals of
similar length. The changes in organ mass of infected gobies were not
sizeable enough to affect total body mass, and host condition (the
body-length vs. body-mass relationship) was similar for gobies with and
without infections. Parasitized gobies were, however, significantly
smaller in body mass at a given age, reflecting slower overall growth.
Effects of P. tortugensis on
individual hosts were broadly similar to those of other parasitic
copepods that infect fish gills and, for unknown reasons, the BVI
appears to be a persistent hotspot of infections on these goby hosts.
Key words: Coral
reef fish, Ectoparasite, Gill pathology, Host-range, Infection
intensity, Liver condition, Prevalence, Reproductive output.
Citation: Forrester GE, Finley RJ. 2022. Host-parasite interactions between a copepod (Pharodes tortugensis) and small reef-associated gobies (Coryphopterus) in the British Virgin Islands. Zool Stud 61:32.