Mating rendezvous in monogenean gill parasites of the humbug Dascyllus aruanus (Pisces: Pomacentridae)

The gills of the humbug, Dascyllus aruanus (Pomacentridae), were infected by a monogenean genus Haliotrema at a high prevalence (83%) but with a low mean intensity (5.6 worms/fish). All the gill arches of 365 fish, caught on the fringing reef of Moorea Island (French Polynesia), were examined for parasites. Each hemibranch was divided into 12 subequal sections. Monogeneans showing microhabitat overlap were defined as couples. Hosts with low intensity of infection (fewer than 5 monogeneans per gill) were selected and couples were recorded. Among the 37 hosts harboring 2 worms on their gills, 18 fish were infected with these 2 monogeneans on the same gill side of the body; 50% (n = 9) of these harbored monogeneans within the same gill arch and 55% (n = 5) of these last fish showed individual parasites within the same section of the gill. In the case of hosts with few monogeneans (3 and 4 individuals; n = 37) on the same arch, more than 40% (n = 16) harbored worms in couples. There may be some chemical communication that allowed these monogeneans to migrate toward each other and thus enhance mating success. Mating rendezvous appears to be a more important factor than site location for these gill monogeneans.     

Habitat use and behavioural ecology of the juveniles of two sympatric damselfishes (Actinopterygii: Pomacentridae) in the south-western Atlantic Ocean

Spatial distribution, microhabitat use and territorial and feeding behaviours were compared between the juveniles of two sympatric territorial damselfishes Stegastes variabilis and Stegastes fuscus on a small tropical reef in the south-western Atlantic Ocean. Juvenile S. variabilis were most abundant at sites subject to stronger hydrodynamics and with mixed benthic cover, whereas juvenile S. fuscus were most abundant at sheltered sites with dense turf algae cover. No differences regarding feeding habits were detected, with both species preferentially feeding on turf algae. Also, despite similarities in territory area and agonistic encounter rates, the identity and proportion of intruders involved in agonistic interactions differed significantly between species. These interdependent traits suggest strong asymmetric competition, with juvenile S. fuscus dominating high-quality sites and evicting juvenile S. variabilis to low quality, marginal areas of the reef.     

The microhabitat distribution of two Dactylogyrus species parasitizing the gills of the barbel, Barbus barbus

The microhabitat distribution of two congeneric species Dactylogyrus carpathicus and D. malleus (Monogenea) parasitizing the gills of the barbel (Barbus barbus L.) was investigated. We tested whether congeneric species exhibited microhabitat preference and whether interspecific interactions could be attributed to the microhabitat segregation of congeners. The outlying mean index method was used to evaluate species microhabitats. Gill variables (different microhabitats within gills) were used as environmental factors characterizing the gills. When abundances of both species were highest, and no significant difference was found between the abundance of the two species, the gill segments and gill areas were the most important factors segregating the Dactylogyrus species on the gills. Niche overlap was low within each of the four gill arches, and parasites were segregated in the same microhabitats within each gill arch. When abundances of both species were low, each monogenean species was segregated at the level of the gill arches. When abundances of both species increased, the niche and overlap between species increased. The distribution of both congeneric species confirmed microhabitat preference within the gills. The results suggest that microhabitat preference is dependent on species abundances, species being segregated in the case of low abundance, possibly to increasing mating opportunities. Both niche and overlap between species increased with species abundance. In the case of the high abundance of both species, microhabitat preference seems to be related to interspecific interactions between monogenean species, as previously found for endoparasitic species.     

Comparative trophic morphology in eight species of damselfishes (Pomacentridae)

Damselfishes show significant biodiversity in the coral reefs. To better understand such diversity, an ecomorphological approach was investigated in the trophic morphology of eight species of Pomacentridae (Chromis acares, C. margaritifer, Dascyllus aruanus, D. flavicaudus, Pomacentrus pavo, Plectroglyphidodon johnstonianus, Pl. lacrymatus and Stegastes nigricans) belonging to different trophic guilds (zooplankton, algal, coral polyp feeders and omnivores). Geometric morphometrics were used to quantify size and shape variations in four skeletal units: (1) neurocranium, (2) suspensorium and opercle, (3) mandible and (4) premaxilla. This method allowed us to reveal shape and size differences correlated to functional diversity both within and between trophic guilds. Among zooplanktivores, C. margaritifer, D. aruanus and D. flavicaudus have a high and long supraoccipital crest, short mandibles forming a small mouth and high suspensoria and opercles. These three species can be considered to be suction feeders. In the same guild, C. acares shows opposite characteristics (long and thin mandibles, lengthened neurocranium and suspensorium) and can be considered as a ram feeder. Among herbivores and corallivores, the two species of Plectroglyphidodon and S. nigricans can be considered as grazers. Differences in skeletal shape are mainly related to improving the robustness of some skeletal parts (broad hyomandibular, short and high mandibles). The shapes of P. pavo, which feeds largely on algae, strongly differ from that of the other three grazers exhibiting similar morphological characteristics to C. acares (e.g., long and shallow suspensorium, lengthened neurocranium). This highlights likely differences concerning cutting or scraping method. Finally, no strong correlations exist between size and shapes in the eight studied species. Size difference among species having a very similar shape could be viewed as a factor optimizing resource partitioning.     

Spatial distributions of two species of monogeneans on the gills of Siganus fuscescens (Houttuyn) and their seasonal dynamics in caged versus wild-caught hosts

Two monogeneans species, Polylabris mamaevi Ogawa & Egusa, 1980 and Tetrancistrum nebulosi Young, 1967, are sympatric on the gills of Siganus fuscescens (Houttugn, 1782) in the South China Sea. An investigation into their distribution on the host's gills based on monthly samples from both wild and caged populations revealed that these 2 species co-occurred on the same gill arches, but they were segregated. P. mamaevi attached to the distal half of the gill filaments, whereas T. nebulosi attached to the proximal half. This difference may partly be attributed to microhabitat specialization. Microhabitat distributions were intensity dependent for both species. As intensity increased, monogeneans were increasingly found on the second, third, and even fourth gill arches, and niche breadths increased. The changes in distribution and niche breadths at the host gill arch level in relation to differences in host size and sampling period were considered to represent a functional response to increased intensity. Differences in host resources, in either net-caged or wild populations, did not significantly influence the parasite distributions at the host gill arch level. Simultaneous infections of these 2 species were common, but there was no evidence of negative interspecific interactions.     

Microhabitats of gill parasites (Monogenea and copepoda) of teleosts (Scomberoides spp.)

Ramasamy P., Ramalingam K., Hanna R. E. B. and Halton D. W. 1985. Microhabitat of gill parasites (Monogenea and Copepoda) of teleosts (Scomberoides spp.). International Journal for Parasitology15: 385–397. The parasites Vallisia indica, Allodiscocotyla chorinemi, Heterapta chorinemi, and Dionchus remorae exhibited site specificity on the gills of Scomberoides commersonianus, S. tol, S. lysan and S. tala, whereas the copepod Caligus sp. did not. Observations on site preference revealed microhabitat differences along the length of gill filaments, along the anterio-posterior axis of the gill, between external and internal gill filaments and on different gill arches. Site preference varied with parasite density on each gill and host. An interspecific association test between pairs of species revealed, in some cases, a positive association, and in other cases a negative association. There were apparently no association? between certain pairs of species. A comparison of intensity within pairs of parasite species infecting the same host revealed either an inverse or a direct correlation. The numerical dominance and prevalence of parasites differed on each host species. This study indicates that intra- and interspecific competition may occur among the gill parasites. The direction and speed of ventilation water-currents and certain intrinsic factors of the parasite themselves may determine their microhabitat restriction on the gills.     

Species of Haliotrema Johnston & Tiegs, 1922 (Monogenea: Dactylogyridae) from Zanclus cornutus (L.) (Teleostei: Zanclidae) and Acanthurus nigrofuscus (Forssk?l) (Teleostei: Acanthuridae) in the South China Sea

Four species of Haliotrema Johnston & Tiegs, 1922, including three new taxa, are described from the gills of two species of coral reef fishes, Zanclus cornutus (Linnaeus) and Acanthurus nigrofuscus (Forssk?l), off the Dongsha Islands in the South China Sea. Haliotrema dongshaense n. sp., from Z. cornutus, is differentiated from other existing congeneric species by its peculiar male copulatory organ, comprising a harp-shaped copulatory tube and a cup-shaped base, and two groups of short longitudinal muscles lying on either side of the vaginal vestibule. Haliotrema zigmoidocirrus n. sp. from Z. cornutus and H. nigrofusci n. sp. from A. nigrofuscus are differentiated from other congeneric species by their male copulatory organ, which has a cup-shaped base, bell-shaped middle and Z-shaped distal part, and the latter can be readily differentiated from the former by its distinctively wider haptor and longer connecting bars. Haliotrema sicklocirrus Wang, 2007, from Z. cornutus, is redescribed with additional details, including the sinistral position of the accessory piece of the male copulatory organ, the absence of eyespots and the morphology of the connecting bars.     

红鳍原鱼白鳃部寄生单殖吸虫生态位分析

鱼类寄生单殖吸虫越来越多受到寄生虫学家和生态学家的关注 ,生态位分析也是生态学研究的一个重要方面 ,国外学者在这方面进行了较多的工作[5～ 8] 。近年来 ,我国单殖吸虫生态学的研究也吸引了不少科学家的兴趣[1～ 3 ,9] 。红鳍原鱼白 (Ｃｕｌｔｅｒｉｃｈｔｈｙｓｅｒｙｔｈｒｏｐｔｅｒｕｓ)是我国的一种自然经济鱼类 ,许多学者研究了不同水体红鳍原鱼白的寄生虫种类组成[4 ] 。作者现将红鳍原鱼白寄生单殖吸虫生态位分析作一报道 ,为研究寄生虫群落结构提供必要的背景参数。1　材料与方法1.1　材料来源洪湖系长江和汉江支流东荆河之间…     

The Hemiuroidea (Digenea) of pomacentrid fishes (Perciformes) from Heron Island,Queensland, Australia

The following species are described, figured and/or recorded from pomacentrid fishes from the vicinity of the southern Great Barrier Reef coral cay Heron Island, with some mention of comparative material from other host families and locations: Derogenes pearsoni n. sp. from Amblyglyphidodon curacao, Amphiprion akindynos, Plectroglyphidodon lacrymatus (type-host), Pomacentrus chrysurus, P. moluccensis, P. tripunctatus and Pomacentrus sp.; Derogenes pharyngicola n. sp. from Abudefduf whitleyi (type-host) and Plectroglyphidodon dickii; Lecithaster stellatus from Abudefduf sexfasciatus, A. whitleyi, Acanthochromis polyacanthus, Amblyglyphidodon curacao, Chrysiptera flavipinnis, Parma polylepis, Pomacentrus chrysurus, P. moluccensis, P. cf. nagasakiensis, P. cf. pavo, P. vaiuli, P. wardi, Seriola lalandi, Cheilinus diagrammus, Lethrinus miniatus and Choerodon cyanodus from Heron Island plus Acanthopagrus australis and Rhabdosargus sarba from Moreton Bay; Aponurus laguncula from Pomacentrus moluccensis plus Callionymus limiceps, Platycephalus endrachtensis and P. fuscus from Moreton Bay; Hysterolecitha nahaensis from Abudefduf bengalensis, A. sexfasciatus, A. whitleyi, Acanthochromis polyacanthus, Amblyglyphidodon curacao, A. leucogaster, Amphiprion akindynos, A. perideraion, Chromis atripectoralis, C. nitida, C. viridis, Chrysiptera flavipinnis, C. cf. rollandi, Dascyllus aruanus, D. reticulatus, Parma polylepis, Pomacentrus chrysurus, P. moluccensis, P. cf. nagasakiensis, P. nigromarginatus, P. cf. pavo, P. tripunctatus, P. wardi and Pomacentrus sp.; Hysterolecitha heronensis n. sp. from Pomacentrus philippinus (type-host), P. amboinensis, P. moluccensis, P. nigromarginatus and Pomacentrus sp.; Hysterolecitha sp. innom. from Parma polylepis; Thulinia microrchis n. comb. (new syns Hysterolecitha microrchis, H. xesuri, H. tinkeri, Thulinia tinkeri, H. sigani) from Abudefduf bengalensis, A. sexfasciatus, A. whitleyi, Acanthochromis polyacanthus, Amphiprion perideraion, Dascyllus aruanus, D. reticulatus, Dischistodus melanotus, Parma polylepis, Plectroglyphidodon dickii, Pomacentrus amboinensis, P. moluccensis, P. philippinus, P. taeniometopon, Pomacentrus sp. and Stegastes apicalis, plus Chaetodon citrinellus, C. kleinii, Chaetodontoplus meredithi, Lethrinus miniatus, Plectropomus leopardus, Siganus doliatus, S. lineatus and S. vulpinus; Leclthocladium sp. juv from Abudefduf whitleyi, Lecithochirium sp. (? ghanense-group) from Dascyllus aruanus; Lecithochirium sp. juv. from Abudefduf whitleyi; unidentified non-ecsomate hemiuroids from Chrysiptera cf. rollandi, Parma polylepis, Pomacentrus chrysurus, P. wardi and Stegastes apicalis.     

Parasite biodiversity in a coral reef fish: twelve species of monogeneans on the gills of the grouper Epinephelus maculatus (Perciformes: Serranidae) off New Caledonia, with a description of eight new species of Pseudorhabdosynochus (Monogenea: Diplectanidae)

Coral reefs are known for their high level of biodiversity, but parasite biodiversity has not been evaluated. Cases such as Epinephelus maculatus, described here, show that the numerical estimation of parasite biodiversity in coral reefs could reach more than ten times the number of fish species; consequently, the extinction of certain fish species from endangered coral reefs would result in the co-extinction of at least ten times the number of parasite species. E. maculatus is a grouper of intermediate size (1-2 kg) and common in the coral reefs of New Caledonia, South Pacific. Based on the examination of more than 800 monogenean specimens, 12 species of monogeneans (ten diplectanids and two ancyrocephalids) were differentiated on the gills. These species of diplectanids have not been found in other epinephelines in the same area and thus are considered as specific to this host. In addition, three species of copepods, and isopod larvae, are present on the gills; E. maculatus thus has a total of 16 species of gill ectoparasites, which can be found together on a single individual fish. Diplectanids include Laticola dae Journo & Justine, 2006, which is the most abundant species representing about 50% of the specimens, and nine species which are rare, each representing 2-7% of the specimens: Diplectanum uitoe n. sp. and eight species of Pseudorhabdosynochus Yamaguti, 1958. D. uitoe, provisionally attributed to Diplectanum Diesing, 1858, is characterised by a small conical penis with internal walls. Pseudorhabdosynochus auitoe n. sp., P. buitoe n. sp., P. cuitoe n. sp., P. duitoe n. sp., P. euitoe n. sp. and P. fuitoe n. sp. are differentiated on the basis of the morphology of the sclerotised vagina, but are very similar in other characteristics; P. guitoe n. sp. is characterised by a quadriloculate organ with very thick walls and a very small sclerotised vagina; and P. huitoe n. sp. is characterised by its sclerotised vagina and by very long ventral and dorsal haptoral bars. Two rare (2-3% of specimens) ancyrocephalids, Haliotrema epinepheli Young, 1969 and Haliotrema sp., are briefly described in relation to the male copulatory organs and haptoral bars; H. epinepheli is apparently a generalist species found in various epinephelines and other fish species. A table of the 50 species of diplectanids (Pseudorhabdosynochus, Laticola Yang et al., 2006, Echinoplectanum Justine & Euzet, 2006 and Diplectanum) from serranids is provided.     

Relationship between roving behaviour and the diet and client composition of the cleaner fish Labroides bicolor

Diet analyses and observations of cleaning behaviour of two cleaner fishes revealed that Labroides bicolor fed more on client mucus, but Labroides dimidiatus fed more on ectoparasites, and that L. bicolor interacted with fewer species (36 species) compared with L. dimidiatus (44 species). The client species which contributed most to the dissimilarity between cleaner species were the dusky farmerfish Stegastes nigricans and bicolor chromis Chromis margaritifer damselfishes, which L. dimidiatus interacted with more often than L. bicolor, and the striated Ctenochaetus striatus and brown Acanthurus nigrofuscus surgeonfishes, which L. bicolor interacted with more; L. bicolor interacted with all parrotfishes (Scaridae) more. These results confirm the importance of repeated interactions and partner choice in determining the nature of interactions in mutualisms.     

Co-existence of nine gill ectoparasites (Dactylogyrus: monogenea) parasitising the roach (Rutilus rutilus l.): history and present ecology

Co-existence among potentially competing species can be favoured by niche specialisation and/or by reducing the overall intensity of competition via aggregated utilisation of fragmented resources. We investigated the respective roles of niche specialisation and aggregation in the case of nine congeneric monogenean parasites on the gills of Roach (Rutilus rutilus L.) belonging to the genus Dactylogyrus. The position of each individual parasite of the nine Dactylogyrus species was recorded. Niche breadth and niche overlap of parasite species were estimated. Comparative methods, which take into account phylogenetic information of the analysed species, were used. We reconstructed a phylogeny of the nine Dactylogyrus species based on morphological characters. We used the 'aggregation model of co-existence' in the model to test if species co-existence is facilitated when intraspecific aggregation exceeds interspecific aggregation. We observed a lack of negative correlation in abundance between pairs of parasites, and a negative correlation between niche size and parasite aggregation, for both intraspecific and interspecific aggregation. Our comparative analysis showed that parasite abundance is positively correlated with niche breadth. Then parasite abundance, and not interactions between Dactylogyrus species, seems to be the most important factor determining niche size This result gives some support to niche segregation by specialisation. Niche size was negatively correlated with both intraspecific and interspecific aggregation. No relationship was found between an increase of interspecific aggregation with an increase of niche overlapping, which suggests that competition may play little role. A lack of competition could be also confirmed by the lack of negative correlation in abundance between species pairs. A parsimony analysis of the evolution of gill distribution indicates a change in one parameter of the niche (arch, segment and/or area) at each branching event.     

A novel obligate cultivation mutualism between damselfish and Polysiphonia algae

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant-herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant-herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.     

Kuhnia sprostonae Price, 1961 and K. scombercolias Nasir & Fuentes Zambrano, 1983 (Monogenea: Mazocraeidae) and their microhabitats on the gills of Scomber australasicus (Teleostei: Scombridae), and the geographical distribution of seven species of gill Monogenea of Scomber spp.

As a result of an extensive survey of monogeneans on the gills of scombrid fishes of the genus Scomber, especially S. australasicus in Australia, it has been shown that Kuhnia sprostonae as previously defined by Rohde & Watson is, in fact, two distinct species, namely K. sprostonae Price, 1961 and K. scombercolias Nasir & Fuentes Zambrano, 1983. K. sprostonae inhabits the pseudobranchs of Scomber scombrus in the North Sea, S. japonicus off Madeira and S. australasicus in Australian waters, and shows considerable variability in the lengths of the hamuli and the genital hooks. K. scombercolias occurs on the main gills of S. japonicus and S. australasicus in many regions of the Atlantic and Indo-Pacific. Other species of gill monogeneans on Scomber spp. are Kuhnia scombri, Pseudokuhnia minor, Grubea cochlear and G. australis. A damaged juvenile monogenean of unknown status was recovered only once in the Mediterranean. The geographical distribution of gill monogeneans of Scomber spp. is discussed.     

Haliotrema abaddon n. sp. (Monogenoidea: Dactylogyridae) from the gills of wild and maricultured West Australian dhufish Glaucosoma hebraicum (teleostei: Glaucosomatidae), in Australia

Haliotrema abaddon n. sp. (Dactylogyridae) is described from the gills of West Australian dhufish Glaucosoma hebraicum (Teleostei: Glaucosomatidae), from the Indian Ocean near Fremantle, Western Australia. The parasite is recorded from cultured dhufish and from a major portion of the known geographic distribution of its host. In cultured dhufish, H. abaddon causes branchitis and hyperplasia and metaplasia of the lamellar epithelial cells and may be a limiting factor in the development of an economically feasible mariculture industry. Comparable prevalences and densities of the parasite on wild and cultured dhufish were observed. In heavily infested captive fish, clusters of eggs (egg strands) appear to restrict blood flow to localized regions of the gills as a result of entanglement of egg filaments with secondary gill lamellae. Hatching of oncomiracidia occurs in 7-10 days at 20-25 C.     

Monoculture and mixed-species algal farms on a coral reef are maintained through intensive and extensive management by damselfishes

Algal farms maintained by different species of territorial herbivorous damselfishes vary in size, algal biomass, and species composition. To determine the factors that affect the structure of these farms, we compared farming behavior and intensity between two sympatric damselfish species, Stegastes nigricans (Lacepède) and S. obreptus (Whitley), which maintain two different types of farms in the Okinawa Islands, southern Japan. By weeding of indigestible algae and prompt exclusion of herbivorous fishes and grazing sea urchins, S. nigricans manage relatively small farms largely dominated by one algal crop species, Polysiphonia sp. In contrast, by delayed exclusion of herbivores, S. obreptus maintain larger farms invaded by diverse indigestible algae, such as Chondria sp. and Padina sp. As a result of intensive management, S. nigricans attains a higher algal biomass per area than does S. obreptus. This study provides a new perspective, as it suggests that damselfishes practise both intensive and extensive farming. The former results in small and highly productive monoculture farms of one palatable alga, while the latter leads to large, species-rich, mixed-culture farms.     

对鲇鱼鳃部寄生的固着鳋的生态研究

作者研究了江西江口水库鲇鳃部寄生固着鳋的种群生态学及其对寄生部位的选择性。固着鳋的感染率和丰盛度表现出明显的季节变化,以夏初最高;其繁殖也具有季节性,怀卵个体的比例同样有夏初最高。固着鳋对寄生部位的选择性似乎与种群的数量有关,当种群数量高时更多的固着鳋分布于中间的鳃片上,对多种寄生虫同时寄生条件下固着鳋寄生部位选择性的研究,将有助于进一步了解固着鳋和寄生鲇鳃部其它种类的寄生虫之间的关系。     

Microhabitat characteristics of <Emphasis Type="Italic">Stegastes planifrons</Emphasis> and <Emphasis Type="Italic">S. adustus</Emphasis> territories

Stegastes adustus and Stegastes planifrons are two species of damselfishes commonly found in the Caribbean. These territorial fishes have been widely studied due to their major ecological role on coral reef in controlling the growth of macroalgae that compete with corals for space and, inversely, on their deleterious role in destroying coral tissues to impulse the development of algae. However, few studies were conducted on the biotic and abiotic components of their territories. In the present study, territory size and surfaces of benthic components (macroalgae, algal turf, massive corals, branching corals, Milleporidae, sponges, sand and rubbles) were estimated for the two species at two contrasted sites. At Ilet Pigeon site (IP), the two damselfishes were found at different depth and exhibited different territory sizes. S. adustus defended a larger territory characterized by massive corals, sand and Milleporidae, while S. planifrons territories were smaller, deeper and characterized by branching corals, sponges and rubble. At Passe-à-Colas site (PC), the two fish species coexisted in the same depth range and defended territories of similar size. Their territories presented higher proportions of macroalgae, but smaller surfaces of Milleporidae than at IP. At PC, the main difference between the two species was a higher surface of massive corals inside S. planifrons territories than S. adustus territories. Differences in microhabitat characteristics between the two Stegastes seemed mostly site related. This resulted from the high plasticity of two species, allowing them to persist on Caribbean coral reefs after the decline of most branching acroporids, their former favorite habitats.     

Two new species of Haliotrema (Monogenoidea: Dactylogyridae) from Cirrhitus rivulatus (Perciformes: Cirrhitidae) from the Pacific coast of Mexico

During surveys of helminth parasites of marine fishes from the Pacific coast of the Guerrero State in Mexico, 2 undescribed species of Haliotrema Johnston and Tiegs, 1922 (sensu Young, 1968) (Dactylogyridae) were found infecting the gills of the giant hawkfish Cirrhitus rivulatus Valenciennes, 1846 (Perciformes, Cirrhitidae), i.e., Haliotrema cirrhitusi n. sp. and Haliotrema pollexinus n. sp. The new species are similar with respect to the morphology of the anchors with base-shaft junction crazed, hinged, or both; dorsal anchors with an elongate superficial root; a tubular male copulatory organ (MCO) with a cylinder-shaped base diagonally opening; and a membranous accessory piece, shaped like a vane, encircling MCO to form 2 complete spirals from the anterior margin of base to the terminal portion of the MCO. While H. cirrhitusi and H. pollexinus differ from all other species of the genus in the general morphology of the copulatory complex, only H. pollexinus notably differs from all these species in having a superficial, blade-like projection from the inner surface on the distal shaft of anchors. Haliotrema cirrhitusi and H. pollexinus are the only members of the genus recorded in the Mexican Pacific and from a cirrhitid host.