The Life Cycle of Huffmanela Huffmani Moravec, 1987 (Nematoda: Trichosomoididae), an Endemic Marine-Relict Parasite of Centrarchidae from a Central Texas Spring

Research Article

The life cycle of Huffmanela huffmani Moravec, 1987 (Nematoda: Trichosomoididae), an endemic marine-relict parasite of Centrarchidae from a Central Texas spring

McLean L. D. Worsham1, David G. Huffman1, František Moravec2 and J. Randy Gibson3

1 Freeman Aquatic Biology, Texas State University, San Marcos, TX, USA; 2!"#$%& 3'**+<"=#>?G'

Abstract: The life cycle of the swim bladder nematode Huffmanela huffmani Moravec, 1987 (Trichinelloidea: Trichosomoididae), $[$$$>#"J?K'NK$- mentally completed. The amphipods Hyalella cf. azteca (Saussure), Hyalella sp. and Gammarus sp. were successfully infected with larvated eggs of Huffmanela huffmani. After ingestion of eggs of H. huffmani%K$$$[Q" from their eggshells and penetrate through the digestive tract to the hemocoel of the amphipod. Within about 5 days in the hemocoel of the experimental amphipods at 22 °C, the larvae presumably attained the second larval stage and were infective for the experimen- ["Lepomis spp. The minimum incubation period before adult nematodes began laying eggs in the swim %["N%%R*VYY *?[K$$N J* Keywords: swim bladder nematode, Trichinelloidea, development, intermediate host, Amphipoda, Hyalella, Gammarus['

Adult trichinelloid nematodes occur in a wide range has been studied in detail (e.g. Löwenstein 1910, Thomas "% * ? " ! $ [\Y]<$[\^RJN epithelial surfaces, although a few species infect spleen 1980). The eggs of this nematode were directly infective to or liver tissues, or are found in other tissues (Anderson ["*?"%$ 2000, Anderson et al. 2009). Although the development about the life cycles of representatives of the trichosomoi- and transmission of some species with medical importance did genus Trichuroides # [\]\ _T. chiropteri # $ [ $ 1949 from the urinary bladder of bats), or of the numerous animal hosts have been extensively studied (for reviews species of Huffmanela>"[\`R$[* see Moravec et al. 1987, Anderson 2000, Moravec 2001), Huffmanela huffmani Moravec, 1987 (Trichinelloidea: the biology of trichinelloids as a whole still remains little ?j J{ $ - known. Aside from well-studied trichinelloid taxa, little tode known only from the swim bladders of centrarchid else is known about the morphogenesis of larvae during [$$$>#" "$$"! _>#{J?K_Y\ V|}|^}}~&\R VV}VY}}<{* of trichinelloid species. This is particularly true regarding ?[$H. huffmani was in 1979, whether or not an intermediate host is required (Moravec when Underwood and Dronen (1984) reported eggs from 2001). N%"># Most of the data available on the life cycles of [$[$ trichinelloids pertains to representatives of the species-rich of Capillaria Zeder, 1800. The species was later formal- $ # [\[V N ly described as Huffmanela huffmani based on eggs alone on the life cycles of representative of other trichinelloid (Moravec 1987) and the new genus Huffmanela was erect- families is rather scarce or absent (Anderson 2000). Within ed to accommodate it. Adults of the species were subse- the Trichosomoididae (apparently closely related to Cap- =%%J>"_[\``{*? illariidae), only the life cycle of Trichosomoides crassi- description of H. huffmani preceded the reassignment of cauda (Bellingham, 1840) from the urinary tract of rats several species from Capillaria into the genus Huffmanela,

Address for correspondence: M.L.D. Worsham, Freeman Aquatic Biology, Texas State University – San Marcos, San Marcos, TX 78666-4616, USA. Phone: (406) 600-5515; Fax:(512) 245-7919; E-mail: [email protected]

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani

Table 1. [ Q $ > $%%"%"*?[\"[% expected to encouter and consume benthic, spring-related, detritivorous invertebrates.

[ [ Example taxon 0 ~Q Herichthys cyanoguttatus Baird et Girard 1 Limnetic/zooplanktivorous Lepomis macrochirus#[= 2 Littoral/invertivorous Lepomis miniatus 3 Benthic/invertivorous Lepomis microlophus Günther 4 Spring-dominant benthic/invertivorous Lepomis auritus Linnaeus

NJ>"Y[% so, to identify that host and use it to experimentally com- Moravec (2001). plete the life cycle. Presented herein is the experimentally Some twenty other species of Huffmanela are now doc- completed life cycle of H. huffmani; the [% N[ %YN$J* coastal and blue-water habitats of diverse geographic re- NR_#*Y[| MATERIALS AND METHODS and Iwaki 2014). Since all species of Huffmanela other than H. huffmani are marine, it is likely that H. huffmani is a marine relict. This assertion is consistent with the presence of intermediate hosts numerous other marine-relict invertebrates unique to the Initially, centrarchids foraging around spring openings in >$_>{_J[\`{* $_$$>#{N$- Furthermore, even though many invertebrate taxa that are riodically observed, photographed and videographed by divers !$Q- %>Y[Y \'$$>#># inclusively. After determining the preferred feeding habitats of %$Q[- the centrarchid species known to be susceptible to H. huffmani %_%*Y`{*>>#- (Moravec et al. 1987, O’Docharty 2007), each species was as- "%K[$ signed to one of four feeding-niche categories. Because the pre- previous surveys have indicated that H. huffmani is also sumptive intermediate host was suspected of being a benthic, !$Q\'$$>#_> spring-dependent, detritivorous invertebrate, we were able to [\`]K*Y]RYR{*?[ use these category assignments to rank the centrarchid species are consistent with the hypothesis that H. huffmani is a ma- by how frequently they would be expected to encounter and con- rine relict with a spring-associated distribution. sume such invertebrates. These species are listed in Table 1 along ?!$Huffmanela are described with their feeding-niche categories and respective contrast coef- from eggs alone, with adults having been described thus far [* from only six species (Bullard et al. 2012). Each species Following the feeding preferendum analysis, centrarchids of Huffmanela$$Q$[ were collected from Spring Lake and necropsied in order to de- ["*JN" termine if the actual levels of parasitism for each species corre- egg deposition, little else is known about any of the life cy- sponded to the expectations that emerged from the feeding pref- cles of Huffmanela spp. The location of egg deposition by *?"[N% H. huffmani (and many other Huffmanela spp. that are his- N[$%% ["{- least 10 l of spring water. Because it was not known if eggs of %%%"[- H. huffmani are environmentally sensitive, and one of the goals tive host to infect the next host. Previous research has been [N%"% $[% unable to get ingested eggs of H. huffmani to hatch inside to the laboratory was expedited in order to ensure that dissolved ["_K[\\`>"Y[K* oxygen and temperature did not deviate substantially from op- Y]RYR{&[" timal conditions potentially required by H. huffmani. Fish were host laden with eggs of H. huffmani must be decomposed $$N\N- or digested in order for the eggs to become available to the sian well water physicochemically similar to SMS water in most presumptive intermediate host. %$*?[NYY Eggs of H. huffmani are appreciably denser than water, [Y[Y!%$* and once liberated from the host, they ultimately come to Fish were killed by pithing and the swim bladder was excised. rest on the benthic sediments. Because eggs cannot infect A small portion of the epithelium of the ventral wall of the swim [% bladder was separated from the remainder of the swim bladder %["%- and was used to roughly estimate the intensity of infection used that a benthic detritivore must be serving as the interme- $ $ ]& Y& [* diate host (Cox et al. 2004, O’Docharty 2007). Therefore, Because a single swim bladder might contain a million or more [$"H. huffmani was to eggs (Cox 1998), intensity was not determined by counts, but was determine if there is, in fact, an intermediate host, and if %$$K$"[N

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Table 2. Descriptions of infection-intensity categories used to es- at least 16 species of oligochaetes, 2 aphanoneurans and 3 leeches timate the intensity of infection with eggs of Huffmanela huffm- (Worsham et al. 2016). ani Moravec, 1987 in the ventral wall of the swim bladders of Benthic invertebrates were collected from near spring open- wild-caught centrarchids. ings using a Ponar grab sampler. Individual collections were Infection- transported back to the laboratory in separate containers of 22 °C intensity Description spring water and maintained alive until sorted. The organisms category were examined under a dissecting microscope and sorted into 0 no eggs detected containers representing the lowest discernable taxon. From these 1 trace infection; only a few eggs observed collections, live cultures of candidate intermediate hosts were es- 2 up to 25% of swim bladder infected with eggs 3 greater than 25% and up to 50% of swim bladder infected tablished and maintained in the laboratory in labelled 1200 ml 4 greater than 50% of swim bladder infected plastic food containers with windows cut in the sides and cov- NY3*?N\ \NQN$- eggs had been deposited. These intensity estimates were broken icochemical conditions similar to the SMS. ["Q[?%Y* Selection of candidate intermediate hosts was based on the The remaining tissue of each swim bladder was placed indi- notion that the intermediate host must be abundant enough to "R$[N account for the high prevalence of infection we observed, and artesian water. These containers were maintained in a water bath also the assumption that the intermediate host is a benthic species. \NN$ Since the hypothetical intermediate host was also presumed to be 22 °C (similar to the SMS water) while microbial decay was al- a detritivore, only benthic species that could be maintained on lowed to break down swim bladder tissues and free the eggs. Wa- a diet of detritus were used in experimental infection attempts. ter in these containers was refreshed twice monthly. Using the infection-intensity data derived from the wild- Testing of candidate intermediate hosts for susceptibility [_{N Candidate invertebrate species were tested for susceptibility performed to determine the factors that best predicted the ob- to infection with H. huffmani by placing them in a container with "NQ[*? an aliquot of larvated and viable eggs. Controls were maintained QN~_$*[{$ in the same way, but without exposure to eggs of H. huffmani. All [%"_?%[{ invertebrate exposures were run for two weeks, or until all treat- species as predictors of the intensity ratings observed for these $N"[* [*?QRN$ population decline in the treatment containers began to exceed NNN[ the rate of decline in the corresponding controls by a noticeable be expected to be positive for eggs of H. huffmani. If so, it could margin, all individuals in both groups were examined immedi- $"[- ately for larvae of H. huffmani. At the end of the two weeks, all "%[* K$%!NK"*< This, in turn, could have potentially provided useful hints about nematode larvae were discovered among the treatment replicates *?Q$RN$ of a species, the associated controls were also examined to assure to assess whether or not species-related differences in the sus- that they were negative. A list of the taxa tested for susceptibility ceptibility to H. huffmani could explain differences in the infec- to H. huffmani is provided in Table 3. Q*?Q[RN Of all the invertebrate taxa we attempted to infect, only the as a predictor to assess if observed differences in the prevalence talitroid amphipods of the genus Hyalella Smith and freshwater and intensity rating could best be explained by feeding niche of gammarideans of the genus Gammarus Linnaeus became infect- ["* ed. All Hyalella spp. tested for susceptibility showed evidence of larvae outside the gut lumen (no lumenal or extralumenal nema- Selection of candidate intermediate hosts tode larvae were found in the control Hyalella). At the time of this writing, approximately 200 species of mac- Subsequent methods pertaining to the intermediate hosts of "%"%$>>#_- H. huffmani employed amphipods belonging to two presumptive wards and Arnold 1961, Bowles et al. 2007, Gibson et al. 2008, species of Hyalella. One species is a common and widely dis- Diaz and Alexander 2010), most of which are benthic. To nar- tributed species in the Hyalella cf. azteca (Saussure) eco-morph row down the most promising candidate species from this list, complex, while the other is an undescribed species endemic to [ the SMS. All amphipods used in the experiments that follow were the Trichinelloidea was reviewed (Moravec et al. 1998, Køie and F1 or later generations raised in artesian water in the laboratory. ~ Y[{* "N H. huffmani was suspected of being either an annelid or an amphi- Graded exposure of candidate intermediate hosts and expo- pod. This conclusion complicated our life-cycle investigations, as there are at least 13 species of amphipods known to occur locally _J[\`%*Y`{ Titration of amphipod exposure intensity >#NQK* In an attempt to determine effective dosage regimens of eggs Therefore, it became necessary to survey the annelids of SMS, that would most likely produce detectable infections in amphipods which was found to contain at least 20 benthic species, including N$$N%!"

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Table 3. List of invertebrate taxa exposed to eggs of Huffmanela huffmani Moravec, 1987.

JK Taxon n Annelida: Aphanoneura Aeolosoma$$*_>#{ 10 Annelida: Clitellata Chaetogaster diastrophus _>#{ 10 Annelida: Clitellata Dero furcatus>_>#{ 5 Annelida: Clitellata Dero obtusaR'_>#{ 10 Annelida: Clitellata Haplotaxis$*_>#{ 2 Annelida: Clitellata %*$*[_>#{ 5 Annelida: Clitellata %*$*Y_>#{ 5 Annelida: Clitellata Pristina$*_>#{ 10 Crustacea: Amphipoda Crangonyctidae Crangonyx cf. pseudogracilis[_>#{ 6 Crustacea: Amphipoda Dogielinotidae Hyalella cf. azteca _{_$~N?GY\ ]Y}V]}}~&\` `}V}}<{ 10 Crustacea: Amphipoda Dogielinotidae Hyalella cf. azteca _+$"#"Y\ V|}^}}~&[ V\}V|}}<{ 10 Crustacea: Amphipoda Dogielinotidae Hyalella cf. azteca_>#{ 10 Crustacea: Amphipoda Dogielinotidae Hyalella sp. (SMS endemic) 10 Crustacea: Amphipoda Dogielinotidae Hyalella texana Stevenson et Peden _$%#">?G 10 | V]}YV}}~&\\ VR}|\}}<{ Crustacea: Amphipoda Gammaridae Gammarus$*_$#"[?G| Y`}\}}~&[[ ]`}[Y}}<{ 3 Crustacea: Amphipoda Crangonyctidae Stygobromus$$*_>#{ 6 Crustacea: Copepoda $_>#{ 10 Crustacea: Isopoda Cirolanides texensis_>#{ 5 Crustacea: Ostracoda Cypria$*_>#{ 10 Crustacea: Ostracoda Stenocypris$*_>#{ 10 Platyhelminthes: Macrostomida >*$*_>#{ 10 Platyhelminthes: Tricladida Dugesia$*_>#{ 10 Platyhelminthes: Turbellaria Schmidtea$*_>#{ 10 >#M>#"* of H. huffmani at various combinations of exposure intensity and quential differences in egg concentration across the design. The incubation duration. Amphipods from each species were divided N[N*? ["$K$$N$ container was then stirred gently to suspend the eggs, and the representing four levels of egg-exposure intensity (four durations suspension was promptly divided among three intermediate di- of exposure to the same density of eggs of H. huffmani), and the lution containers. Each of these was then stirred and its contents [$"_K$${* $$"[Q Each exposure-intensity group consisted of three replicates, with of 12 intermediate containers of relatively equal volume. These each replicate housed in a 1 200 ml plastic food container. 12 containers were then randomly assigned in sets of three to Prior to distributing amphipods to replicate containers, the one of four exposure-intensity levels (12, 24, 48 and 96 h of egg 15 marked containers were assigned random numbers, and then exposure), with the three containers on each level representing arranged in order of increasing random number. Each of the 15 treatment replicates. replicate containers received 27 lab-reared amphipods at the be- Following the habituation period, amphipods assigned to the ginning of a titration run, for a total of 405 amphipods for one en- four exposure-intensity levels were simultaneously exposed to tire run of the titration experiment. Disposable one-piece plastic eggs of H. huffmani$"[Q* transfer pipettes with 5 ml capacity (similar to Fisher S30467-1) The amphipods in exposure-intensity level 1 were examined for were used to transfer amphipods individually from container to larvae of Huffmanela after 12 h, exposure-intensity level 2 after container. Tips of pipettes were trimmed back along the taper to 24 h; exposure-intensity level 3 after 48 h, and exposure-intensity a larger bore size to allow for easy passage of amphipods. "]\^*?$$[$_{N The process of distributing amphipods from the main culture not exposed to eggs. The controls were used to determine if any container to the replicate containers started with selecting one population declines among the corresponding treatment replicates amphipod from the main culture with a transfer pipette and trans- were due to infection with H. huffmani (in which case the controls ferring it to the replicate container with the lowest random num- were expected to show a slower decline), or to causes unrelated to ber. A second amphipod was then transferred to the replicate con- egg exposure (with approximately equal decline rates expected). tainer with the next lowest random number, and so on, until all replicate containers had been supplied with 27 amphipods. This Titration of minimum prepatent incubation duration randomisation procedure was executed in order to ensure that any After the prescribed durations for each level of exposure-in- sequential bias introduced by the amphipod-selection procedure tensity had elapsed, amphipods were separated from eggs of was randomised across treatments. The amphipods were then al- Huffmanela and then incubated for varying durations. This was lowed to habituate to the replicate containers for two days prior done to estimate the minimum prepatent time after the exposure to exposure to eggs. of an amphipod to eggs before it can become infective to a cen- Prior to distribution of eggs of H. huffmani into the amphipod ["* N["=NQ ?$$N[$$"K- randomised serial dilution protocol so as to randomise any se- posure containers and rinsed thoroughly in fresh artesian water

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Table 4. Larval intensity ratings for amphipods exposed to eggs dan), L. megalotis _#[={ and L. macrochirus #[= of Huffmanela huffmani Moravec, 1987. N!%L. auritus and L. miniatus. K$[N># Larval intensity [$|Y]V=$[* rating of exposed amphipods Estimated number of larvae ="\NQN= 0 no larvae observed NN[N"- 1 up to 3 larvae %[_?++{%% 2 3 or more larvae, but less than 25 after exposure to infected amphipods. 3 25 or more larvae, but less than approximately 100 4 approximately 100 or more larvae +Q$$$|YK$[ was randomly assigned a treatment number representing a unique to ensure removal of eggs of H. huffmani. The replicate exposure combination of (1) the number of infected amphipods it had been N*#$$N _Y{%["_|{ then placed back into their respective containers for the incuba- exposure intensity and incubation duration of the amphipods it tion phase. received. Each amphipod was expected to have several viable All replicate containers at the four exposure-intensity levels larvae in some stage of development at the time it was fed out showed noticeable population declines, even before rinsing in [_$%%YV{*"$$N some cases, whereas the three control replicates showed no de- pipetted individually into the aquaria containing the experimental N""\^%*JN" [N$[N%"$ appeared to be no appreciable difference in amphipod survival amphipods. among the four exposure-intensity levels, indicating that the max- imum exposure-intensity had probably not been exceeded, even at 96 h of exposure. It was therefore decided to run all subsequent The survey of the literature on other trichosomoidid and cap- experiments using amphipods exposed to eggs for 96 h. illariid life cycles indicated that the prepatent period before eggs of H. huffmani could be expected to appear in the swim bladders Examination and feeding-out of exposed amphipods K$[N$%%%Y*? At the end of each prescribed incubation duration (following 1, [K$[NK| 4, 7, 14, 21, 28, 35, 42 and 49 days of incubation post-exposure), %NK$[ 3 to 21 amphipods were sampled from each exposure-intensity be examined each month thereafter. group, sampling evenly from the three replicate exposure-intensi- [%%$% ty containers. Each time amphipods were sampled, one of the am- were pithed and the swim bladder was removed for examination. phipods was necropsied and closely examined for infection with The entire ventral wall of the swim bladder was cut into small larvae of H. huffmani. The remaining amphipods in each sample pieces and each piece was mounted under a coverslip in physio- NK$[* logical saline. Each piece was then examined for later larval stag- After incubation of amphipods for 49 days post-exposure, all es, adults or eggs of H. huffmani under a compound microscope infected amphipods from all exposure intensities and incubation ]&[&[* %$K$[ *~$$]\ Completion of life cycle indicating that the treatment amphipods that died had probably F1 eggs of H. huffmani from the swim bladder tissues of ex- died from infection with larvae of H. huffmani. $[N%"%

In most cases, exposed amphipods were so heavily infected described above. Liberated F1 eggs were then fed out to laborato- that exact larval counts were not feasible; therefore, all amphi- ry-reared amphipods to verify that the eggs were infective, thus $ " N %!"* ? completing the life cycle. $ $ %!" $$ infection intensity are described in Table 4. organ of egg deposition for all reported species of Huffmanela ?$[""- K$[N" ious Huffmanela spp., as well as information regarding the diet #"NH. huffmani currently and habitat preference of the host species, were gathered from the does not occur [0% prevalence for 120 centrarchids examined by available literature. Each of the species of Huffmanela was then United States Fish and Wildlife Service (USFWS), and all cen- assigned to one of four cells in a 2 × 2 table (Table 5). The cells trarchids examined during three previous studies (Michel 1984, [%N"%NNj Cox et al. 2004, O’Docharty 2007) were negative], or from cap- of the organ in which eggs are deposited (internal vs epithelial) tive stock of a leucistic strain of Lepomis cyanellus #[= %["_%vs pelagic). [N>=#- ?"N!$Huffmanela were clas- _>#{$%'**+< [%*? Service. Species represented by wild-caught specimens from the relationship was then evaluated by comparing the proportion of #"NLepomis auritus (Linnaeus), L. miniatus _- Huffmanela spp. in only two of the four cells of the table: the

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Table 5. Two-by-two table for assigning known species of Huff- Table 6. Prevalence of infection and mean of intensity rating manela$[%%vs loca- categories of eggs of Huffmanela huffmani Moravec, 1987 in tion of egg deposition. swim bladders of wild-caught centrarchids from the San Marcos Springs. Location of egg deposition: Mean of in- Prevalence Internal Epithelial Species tensity rating (%) n categories1

11 Micropterus salmoides 3.00 90 10 Lepomis auritus2 2.64 89 56 Pelagic Lepomis miniatus 1.83 67 6 Lepomis microlophus 1.71 57 7 12 8 Lepomis macrochirus 0.17 8 12 J%j Benthic

1[>>& 2 calculated from 53 |!"* proportion of all species of Huffmanela that deposit eggs in an %["&$$- Table 7. Akaike information criterion (AIC) weights of compet- $J$$ ing models used to predict infection intensity ratings of Huff- $["* manela huffmani Moravec, 1987 in wild-caught centrarchids. RESULTS Model F ratio p AIC weight SL 8.23 0.00581 0.0 Species 9.33 6.65-07 0.057 intermediate hosts ~ 48.33 4.15-09 0.943 The centrarchid Lepomis auritus ># (TISI 2015) and wild-caught individuals exhibit a high prevalence and high intensity of infection with Huffmane- individuals were exposed to eggs of H. huffmani; one died, la huffmani (Table 6). Behavioural observations indicated one was lightly infected and the third was uninfected. All that individual L. auritus$N$[ subsequent attempts to experimentally infect centrarchids ward off other centrarchid species from their preferred employed the SMS Hyalella and Hyalella cf. azteca as the source of food – the benthic invertebrates around spring experimental intermediate hosts. openings. This spring-dominating behaviour was only dis- played by adult L. auritus, which also excluded smaller Exposure of susceptible hosts L. auritus from the spring openings. The adults of L. auri- If no amphipods had died during the exposure phase, tus had a prevalence of 96% and a mean rating of intensity a total of 36 exposed amphipods would have been available _[%"{Y*`_ V|{*Micropterus for necropsy on the three examination days (0, 3 and 7 days salmoides _$ {$"$ K${*JN"%$$% being top predators, proved to be opportunistic generalists, dying in some of the replicate containers after the examina- and were also frequently observed feeding on small ben- tions had been started; only 30 amphipods were necropsied thic spring invertebrates (they were apparently too large for infection-intensity rating. The regression slope of in- to be excluded by L. auritus). Micropterus salmoides was K$N[* also heavily infected (Table 6). After larvae had spent 1 week in experimental amphi- To evaluate our assumption that the intermediate host pods, internal development was observed in the larvae of H. huffmani is a benthic detritivore, three factors were (Fig. 1). Although no increase in the length of larvae was used to predict infection intensity rating and prevalence. observed (larvae were always 270–350 μm long) and no ?N[$[ moults were observed (even after 9 weeks of incubation (SL) and assigned feeding-niche category. The niche mod- in an amphipod), it can be assumed that they were sec- el was shown to be superior to the other models (Table 7), ond-stage larvae. The internal development was not ac- which is consistent with the intermediate host being a ben- companied by a change in the activity level of the larvae. thic detritivore. [%$$" only those that had been fed amphipods incubated for at Selection of candidate intermediate hosts least 5 days post exposure became infected, suggesting the Of all the invertebrate taxa exposed to eggs of Huff- prepatent period in the intermediate host is 5 days and is manela huffmani, only amphipods of the genera Hyalella likely associated with the aforementioned internal devel- and Gammarus became infected. All of the Hyalella that opment. After this initial duration of incubation in the in- were exposed to eggs of H. huffmani became infected with termediate host, no difference in infectivity was observed larvae of H. huffmani, including the Hyalella spp. that do for longer incubation durations. not co-occur with H. huffmani>#_?%|{* Dead larvae of H. huffmani (Fig. 2) were often observed one of the tested species of Hyalella is known to be endem- in some of the experimental amphipods exposed to eggs of ic to the SMS (MLDW – unpubl. data) and therefore prob- H. huffmani. Surprisingly, dead larvae were only observed ably coevolved with H. huffmani. Only three Gammarus in individuals of the presumably co-evolved endemic SMS

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A B

50 μm 50 μm

Fig. 1. ~"Huffmanela huffmani Moravec, 1987 after being consumed by Hyalella spp. A – a freshly hatched larva containing loose refractile bodies (reserve granules); B – 30 days after hatching, with none of the loose refractile bodies of freshly hatched larvae apparent, but instead, a single condensed central structure is visible throughout the posterior end of the worms.

100 μm 100 μm

Fig. 2.$$[" Fig. 3. Photomicrograph of numerous presumably fertilised, Huffmanela huffmani Moravec, 1987 from San Marcos Springs freshly deposited eggs of Huffmanela huffmani Moravec, 1987 Hyalella sp. about 5 days post exposure. recovered from an experimentally infected centrarchid incubated R*V $Q* ~ $$ and polar plugs, and with the contents of eggs enclosed by the the Hyalella sp. and never in any of the other exposed am- spinose membrane alone. phipods. In some cases, dead larvae had begun showing [>Hyalella sp. after as little as 4–6 days post exposure. Aside from this presumed immune were still infective to Hyalella, at which point the eggs response by SMS Hyalella sp., the life span of the larva of still showed no sign of decreased infectivity to amphipods. H. huffmani in the amphipod host seems to be limited by This suggests that eggs released naturally into the environ- the life span of the intermediate host, since numerous lar- ment could remain viable for well over two years and still vae were found alive and active 50 days after last exposing be infective to amphipods. their amphipod host to eggs. Individuals of Hyalella spp. ~ K$ [ % were shown to be capable of living for up to 7 months in 4.5 months post exposure showed any signs of infection. our laboratory cultures, but it is unlikely that they live past Y[%%]*V ]N_Y[{*~" after being fed experimentally infected amphipods (that of H. huffmani were incubated in Hyalella for the duration had incubated for 5+ days post exposure), 70% showed of the life span of the Hyalella, and there was no evidence "*>[N of progressive decline in number of live larvae at 9 weeks infected, with increasing evidence of infection as the incu- post exposure in H. cf. azteca. %["$*?[ Eggs of H. huffmani stored for more than 21 months [$$$N $ [" until after 7.5 months of incubation post exposure (Fig. 3).

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A B

50 μm 400 μm

Fig. 4. Eggs of Huffmanela huffmani Moravec, 1987 at various stages of development recovered from experimentally infected centrarchids incubated for 11.5 months post-infection. A – eggs showing evidence of larvation and having fully formed shells and visible polar plugs; B – lower resolution photomicrographs of swim bladder tissue contrasting darker larvated eggs with lighter, more recently deposited eggs.

A B C

100 μm 100 μm 100 μm

Fig. 5. Huffmanela huffmani>"[\`R"N%[K$K$H. huffmani 6.5 months ago. A – gross view entire worm; B – view of stichosome showing alternation of dark and light stichocytes typical of Huff- manela spp.; C – view of stichosome showing visible stichocyte nuclei and alternating dark (black arrows) and light (white arrows) stichocytes.

JN"N\% fect Hyalella amphipods, thus experimentally completing the intensity of infection with eggs in experimentally in- the life cycle and overlapping one full generation with the [$$%"%" next in captivity. Interestingly, numerous adults (Fig. 5) in the wild; however, none of these eggs were larvated at N%"[%$\ \*"N[%"- %%[K ter 10.5 months of incubation. Fully larvated eggs (Fig. 4) 10.5 months post exposure. This suggests that all the adults were not observed until 11.5 months post-exposure of the had naturally expired at about 10 months of age, since no ["*K$[%- $$%[- ed for at least 11.5 months post infection were able to inter the initial exposure. Infection results are presented in

Folia Parasitologica 2016, 63: 020 Page 8 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani

Table 8.#$$K$N"Huffmanela huffmani Moravec, 1987 to centrarchids.

Amphipod taxon Amphipods Duration of incubation Infected Comments fed out (n) [_{ _~[{ SMS Hyalella sp. 3 4.5 1 2 mm piece of posterior of 1 subadult female

SMS Hyalella sp. 4 5 1 3 worms 500 × 12 μm; probably L3 or L4 SMS Hyalella sp. 3 6.5 1 3 adult worms 600 × 25 μm SMS Hyalella sp. 3 7.5 1 Early stage eggs lacking eggs shells found in swim bladder tissue SMS Hyalella sp. 6 7.5 1 One unembryonated egg SMS Hyalella sp. 8 7.5 1 Anterior section of one adult (based on morphometry) SMS Hyalella sp. 5 7.5 1 One young adult male SMS Hyalella sp. 9 7.5 1 10 000 of freshly laid unembryonated eggs; numerous adults Hyalella cf. azteca 7 8.75 1 10 000 of freshly laid eggs (unshelled);10 of active adults; < 1% eggs partially larvated Hyalella cf. azteca 9 10.5 1 10 000 of partially larvated eggs, eggs had shells indicating they were more advanced in development SMS Hyalella sp. 5 12 1 10 000 of eggs; many fully larvated SMS Hyalella sp. 21 12 1 10 000 of eggs; many fully larvated Hyalella cf. azteca 21 12 1 100 000 of eggs, many fully larvated; intensity approaching that of wild- [ SMS – San Marcos Springs.

Fig. 6. Diagram showing steps in the life cycle of Huffmanela huffmani Moravec, 1987 (not to scale). AM[" host; at least 7.5 months must pass between ingestion of viable larva and the appearance of fertilised eggs in the host swim bladder, but eggs do not become fully larvated and infective to amphipods until 11.5 months post infection (p.i.): 1M["& 2 – photomicrograph of swim bladder tissue showing eggs in various stages of development; B M["j 3M["$&4M["%$"["%N[- ciently developed shells pass out in faeces; C – eggs free in sediments: 5a – young eggs (< 10 months p.i.) with inadequately developed shells will not survive in environment or passage through piscivore gastrointestinal (GI) tract; 5b – unlarvated eggs old enough to ""$_[$**{"""$"%" amphipods until they become fully larvated while in sediments; 5cM"_1[[*V$**{" to amphipods and are still infective to amphipods after 36+ months in sediments; D – fully larvated eggs ingested by amphipod: 6 – lar- "NV$**%%"["&7 – larva in hemocoel of amphipod and infective to centrarchid. Life cycle can be completed in a theoretical minimum of 12 months, but can probably take longer than 36 months.

Folia Parasitologica 2016, 63: 020 Page 9 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani Moravec et al. 1998 >"[\`RJ and Moravec 1988, Cox et al. 2004, present study Moravec et al. 2005 Bullard et al. 2012 Moravec et al. 1998 Moravec 1987 Moravec and Campbell 1991, Moravec and Gari- baldi 2003 Esteves et al. 2009 Moravec 2001 2000 Carballo et al. 2011 >"+!Q" 2000 Shikoku Island $J USA Texas, Columbia, Canada off Shikoku Island off and Congo and Ligurian Sea, Italy Portugal Zealand, South Island Argentinean Sea Argentinean Mexico Benthic/external ~~N YV Benthic/internal ~~N Y[[ Pelagic/internal Caribbean Sea, Curaçao, Benthic/internal ~N YR Benthic/external Gulf of Mexico Benthic/internal Mazatlán, Sinaloa State, #Y[| Moravec, 1987. Mesentery, outer swim Mesentery, bladder wall, body walls Outer skin between two gill openings Inner swim bladder wall Benthic/internal >#"- Skin, gill mucosa Benthic/external JN~ MacLean et al. 2006, swim bladder bladder wall Musculature Ocean, Benthic/internal Atlantic Outer skin, underlying [ bladder wall Huffmanela bathyal Littoral, reefs, sublittoral centrarchids Littoral Musculature Benthic/internal $ NY[] Littoral, sublittoral, bathyal # Mucosa of mouth and gills Benthic/external ~~N Y] Epipelagic Serosa of intestine, Pelagic# Skin Mesentery near swim Pelagic/external Ligurian Sea, Italy Moravec and Garibaldi bathyal Littoral, sublittoral Musculature Benthic/internal [~N Littoral, sublittoral Skin Benthic/external Gulf of Mexico #*Y[| Littoral Gill mucosa, skin Benthic/external ~" Littoral, reefs, sublittoral Invertebrates Littoral, sublittoral, Invertebrates and [ Invertebrates Littoral, reefs Musculature Benthic/internal $ Invertebrates Spring-inhabiting Fishes and some benthic invertebrates Invertebrates and [ Invertebrates Littoral, neritic, reefs Gill mucosa Benthic/external ~~N Y] Invertebrates Sublittoral, bathyal Skin Benthic/external Clayoquot Sound, British Invertebrates and zooplankton Invertebrates Littoral, neritic Gill mucosa Benthic/external ~~N Y] Invertebrates # Musculature Benthic/internal $ Invertebrates Littoral Musculature Benthic/internal Atlantic Ocean, Senegal Zooplankton and [ Fishes and invertebrates Invertebrates and [ Invertebrates Littoral, reefs Outer swim bladder wall Benthic/internal ~N YR Invertebrates Littoral, sublittoral, Invertebrates and [ Invertebrates Littoral, reefs Most bones, gill arch bones Benthic/internal ~~N Y]YR Invertebrates and [ Invertebrates and [ Invertebrates Littoral, reefs Inner layer of swim Invertebrates and [ ) (Günther), terraenovae

(Lethrinidae) _~${

(Balistidae)

(Carcharhinidae

spp. (Exocoetidae) spp. (Mullidae)

(Muraenesocidae)

(Carcharhinidae) spp.

(Ophidiidae) (Tetraodontidae)

spp. (Carcharhinidae)

Gymnocranius grandoculis (Lethrinidae) Carcharhinus amblyrhynchos amblyrhynchos Carcharhinus (Bleeker) Upeneus bensasi _J{ Centrarchidae Bleeker Muraenesox cinereus Muraenesox cinereus (Forsskål) Carcharhinus plumbeus Carcharhinus _~{ Gymnocranius grandoculis _{ Sebastes (Sebastidae) Pentapodus aureofasciatus Pentapodus aureofasciatus #_~${ Nemipterus furcosus Nemipterus furcosus _{ Stephanolepis cirrhifer Stephanolepis cirrhifer et Schlegel) (Temminck (Monacanthidae) Cynoglossus browni Cynoglossus browni (Chabanaud) (Cynoglossidae) Genypterus blacodes (Forster) Cheilopogon Xiphias gladius Linnaeus (Xiphiidae) leopardus Plectropomus (Serranidae) Abalistes stellatus (Anonymous) Trisopterus luscus Trisopterus (Linnaeus) (Gadidae) Bodianus (Labridae) Lutjanus campechanus _{_!{ Rhizoprionodon _#{ Odontesthes (Atherinopsidae) Sphoeroides annulatus Sphoeroides _{ Moravec, ##

Moravec,

sp. sp. sp. Comparison of diets, habitats, organs, and localities for reported populations of species Comparison of diets, habitats, organs, Huffmanela longa YR Huffmanela lata YV Huffmanela japonica N~N[\\` Huffmanela huffmani Moravec, 1987 Huffmanela hamo NY[] Huffmanela carcharhini Huffmanela carcharhini (MacCallum, 1925) Y] Moravec, Conboy et Speare, 2005 Huffmanela canadensis Huffmanela Huffmanela Huffmanela branchialis Y] Huffmanela shikokuensis N~N[\\` Huffmanela banningi Moravec, 1987 Huffmanela Huffmanela schouteni Moravec et Campbell, 1991 Huffmanela paronai Huffmanela paronai Moravec et Garibaldi, 2000 Huffmanela plectropomi Y[[ Table 9. Table SpeciesHuffmanela balista YR JK J J% infected Organ [ Locality # Huffmanela ossicola Y] Huffmanela oleumimica Cook, Grace et Bullard, 2013 Huffmanela marckgracei Huffmanela marckgracei #Y[| Huffmanela moraveci %~"Y[[ Huffmanela mexicana >"+!Q"Y

Folia Parasitologica 2016, 63: 020 Page 10 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani greater detail in Table 8 and Fig. 6 is a summary of what is Hyalella as its intermediate host, since this genus is one of now known of the life cycle of H. huffmani. %"%>#- springs; thus, this is a more evolutionarily stable strategy than requiring a rare organism. The undescribed spring-run of egg deposition for Huffmanela spp. endemic Hyalella species (referred to herein as SMS Hy- A survey of the literature revealed that Huffmanela spp. alella sp.) is restricted to the same geographic distribution "%$[`[ as H. huffmani, which initially led us to assume that some N[_?%\{*?$- $$[$Hyalella species osition for species of Huffmanela (Table 9) appeared to be was responsible for limiting the downstream distribution somewhat predictable by the habitat of the host (Table 5). of H. huffmani*JN"%>Hy- Y % [" $ $ alella sp. does not appear to be limiting the distribution of literature, 60% were parasitised by a Huffmanela species H. huffmani, since multiple other species of Hyalella were that lays eggs in an internal tissue, whereas, 50% of the two also experimentally demonstrated to be capable of serving reported pelagic host species were parasitised by a species as functional intermediate hosts. In fact, the only amphipod of Huffmanela which lays eggs in a surface tissue. species which showed any sign of being less suitable was the endemic SMS Hyalella sp., which, presumably, coev- DISSCUSSION olved with H. huffmani, but which often killed the larvae ~ $ N shortly after infection. Ultimately, both species of Hyalella observed to be susceptible to infection with Huffmanela >#K$"- huffmani _K[\\`{*JN"$" ["*JN"- and mean intensity rating was not evenly or randomly K$N%"[" distributed across naturally infected centrarchid species hosts that had been fed infected H. cf. azteca, suggesting (Michel 1984, Underwood and Dronen 1984, Cox et al. that the presumably coevolved SMS Hyalella sp. seems 2004, O’Docharty 2007, present study). This uneven dis- to have evolved immune responses to H. huffmani that tribution of infection with H. huffmani across wild-caught [$$%$$ centrarchid taxa was determined not to be a function of H. huffmani ["* $$[% Species of Hyalella are widespread in freshwaters, with feeding niches of the various centrarchid species. Indeed, a cosmopolitan distribution across the Americas, and with- it would seem that the internal environment of all centrar- out a single population reported from a marine environment chids is probably equally hospitable to H. huffmani, as is _! Y] < * Y^ <% demonstrated by the susceptibility1 of Ambloplites rupes- 2008). This observation presents an intriguing enigma, that tris #[= $ $ % is: “Why is it that H. huffmani cannot be found throughout related to Lepomis #[= and Micropterus $ all localities where Hyalella spp. and centrarchids coexist, N _~ * YV{* $ given that the former can be found co-occurring with cen- demonstrated susceptibility, wild-caught centrarchid spe- ~ N [ "" N - and H. huffmani seems to be able to infect numerous spe- most never infected in the wild-caught SMS collections, cies of Hyalella and centrarchids?” whereas wild-caught individuals of the more benthic cen- ?[K$K- trarchids that feed on interstitial invertebrates were almost ed geographic distribution of H. huffmani, which is obvi- N*?N! ously not due to the distributional limits of either its in- the intermediate host must be a benthic detritivorous inver- ["*?% tebrate, and is further consistent with the observation that has been thoroughly documented by a prior study on the $$%N*?! distribution of H. huffmani (Cox et al. 2004) and corrobo- was also well corroborated by the AIC contrast analysis in rated by the present study. Both studies determined that the which the niche model explained, by far, the most variance farthest downstream point where H. huffmani can be found _N*\]|?%R{* $K*>#" Therefore, when infection trials were initiated, only Park (ca R " & Y\ VY}\}}~& \R VV}]|}}<{ N benthic invertebrates thought to be detritivores were tested close to the downstream extent of the physicochemically for susceptibility to infection with eggs of H. huffmani. Af- stable spring-run waters (Groeger et al. 1997). Because the ter exposing several invertebrate taxa, only one taxonomic ># % Hyalella cf. azteca $>#$"%$%M$$ co-occurring with centrarchids, this leads us to the con- of the genus Hyalella. All specimens of amphipods belong- clusion that the distribution of H. huffmani is limited by ing to several species of Hyalella (including Hyalella spp. factors of water physicochemistry. taken from localities where H. huffmani does not occur) It is curious that the intermediate host in the life cycle of became infected with larvae of H. huffmani when exposed K"NK_! to eggs. It is not surprising that H. huffmani uses species of 2004), with all species of the genus Hyalella being found in

1 Based on unpublished accounts from several Ambloplites rupestris NQ>#"K$- tology laboratory exercises at Texas State University.

Folia Parasitologica 2016, 63: 020 Page 11 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani

N*JN"N Hyalella_!"{ $?#[=N is a highly diverse group of amphipods containing terrestri- QN$_! 2004). The nearest family to the Dogielinotidae appears to %J"N$$- ily that has numerous species with a circumpolar distribu- "_! 60 μm 2004). Therefore, it is possible that talitroids are serving as the intermediate hosts of at least some of the other species of Huffmanela* JN" [" Fig. 7. Eggs of Huffmanela huffmani Moravec, 1987 from a wild hosts of marine species of Huffmanela have a diet consist- caught centrarchid showing gradient of development early in em- %"%! bryogenesis. Left most egg has contents contained solely inside !%* spinose membrane and is therefore thought to have been laid re- The successful infection of Gammarus sp., though very cently. Egg second from left has developed egg shell and polar low in intensity, suggests that some marine Huffmanela plugs indicating it as laid some time ago. The two right most eggs may use species of Gammaridea as intermediate hosts. show evidence of darkening shells and embryogenesis indicating This suborder is extremely diverse and occurs in numerous they were earliest of the four eggs to be laid. %%N_#$ *Y[V{*JN"N$Huffmanela side of the host until they have formed a shell (examples of N$%QN["_>" developmental stages of eggs shown in Fig. 7). and Campbell 1991, Moravec and Garibaldi 2000) are Based on the observation that (1) eggs collected from $K%[ NQ [ % "" Y[ contact with any benthic invertebrates. With the eggs of without a noticeable drop in vitality and (2) eggs are not H. huffmani being appreciably denser than water (includ- larvated and infective until approximately 4 months after $QN]V$${[ being laid, it is likely that eggs of H. huffmani cannot infect how the eggs of these parasites of pelagic species, assum- an intermediate host and thus advance the life cycle for at ing their eggs are also denser than water, ever become con- [[%% sumed by a susceptible intermediate host that could then remain infective for several years after the eggs have been $%%%$[" * JN" " $*$["Q$Xiphias gla- cycle time would be realised in nature, i.e. an egg would be dius Linnaeus, is almost exclusively piscivorous on other available for consumption by an amphipod as soon as it is $[_*[\`[{N$- fully larvated, and that that amphipod would then be eaten sibility of a second intermediate or paratenic host in the life by a centrarchid 5 days post infection. cycle of Huffmanela paronai Moravec et Garibaldi, 2000. Therefore, the typical life cycle time would probably ? $$ [ K be much longer than the one year theoretical minimum $$%[ observed experimentally. Because it is not yet known Huffmanela, as they are never found in benthic waters and how long eggs can survive, it is impossible to estimate K"$_# a functional generation time; however, given our results 2008), thus eliminating the possibility of a second inter- it is almost certain that there is substantial overlap be- [$"Huffmanela tween putative generations. Therefore, the possibility for %["* Q\N- two species, it is highly likely that the intermediate hosts *[ in the life cycle of the other marine Huffmanela species are that the average generation time is several years, with the %"%*$[Huffmanela !"R$$* $$*"[" The prepatent period of H. huffmani in the intermediate then all Huffmanela spp. are probably using amphipods as $$%"N=[- intermediate hosts and most likely gammarideans. tive host. Amphipods that had been incubated with larvae of $$[""- H. huffmani for only 5 days successfully transferred infection of eggs of H. huffmani. Freshly laid F1 eggs that had ["""$N not yet formed a shell inside the spinose membrane were observed in the larvae until they had incubated in the inter- $[NN mediate host for at least 7 days. Despite the requirement were kept thermally stable in a water bath of artesian water of only modest developmental changes in the intermediate YY *~"% host before H. huffmani %"[" *JN"N"$ host, all evidence available at this time suggests that the successfully larvated while incubating in water. These ob- amphipod host is very likely an obligate intermediate host, servations suggest that eggs cannot survive or larvate out- and that the life cycle cannot be completed directly.

Folia Parasitologica 2016, 63: 020 Page 12 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani

?$$$["$$% The second moult of capillariid larvae in the earthworm relatively long for a trichinelloid nematode, as most trich- intermediate host was observed, e.g. by Shlikas (1967) inelloid species for which the life cycle is known usually in Aonchotheca bursata (Freitas et Almeida, 1934) and have a prepatent period around three months (Moravec et A. (Molin, 1858), both parasites of domestic *[\\`=~Y[{*Huffmanela huffmani is N % % #" _[\`{ remarkable in that it appears that the prepatent period is at A. erinacei_#$[`[\{$$ least 7.5 months at 22 °C as no eggs were observed until hedgehog Erinaceus europaeus Linnaeus. According to after 7.5 months of incubation and high intensities of eggs Shlikas (1967), in contrast to the L1 larvae, the L2 larvae were not observed until after nine months of incubation. have no stylet (although a stylet was reported by More-

$"$$%[" house 1942 in L2 of A. ) and their body is much ["N" less granulated. Taking this into account, the more fully K$ [ [" developed larvae of H. huffmani obtained from experimen- [$N%"* tally infected Hyalella spp. (Fig. 1B) apparently represent

[$Huffmanela to be understood, it second-stage L2 larvae, even though no evidence of larval is not known if a long prepatent period is a conserved trait moult was observed, and we detected no increase in larval across any of the other Huffmanela spp. dimensions while in the intermediate host. These L2 larvae According to Anderson (2000), trichinelloids always of H. huffmani have no stylet, and none of the loose refrac-

Q[R _ ["{ 1 stage even tile bodies (reserve granules) that are obvious in freshly

! _** N{ hatched L1 are apparent in the L2 larvae. " % "* JN" Unfortunately, very little information about larval mor- larval morphogenesis in trichinelloids remains practically phogenesis and the number of moults in the intermediate unknown, and data on the morphology of individual lar- host has been provided by the existing life cycle studies of "%*[Q trichinelloids with heteroxenous cycles. Mostly an increase stage larvae (L1) have a stylet, which may also be present in size of larvae during their development in the intermedi- in some other stages and adults (Anderson 2000), and their ate host has been reported. For example, the body length of posterior body end is widely rounded, with a subterminal larval Cystoopsis acipenseris Wagner, 1867 (Cystoopsidae * $ [Q " Skryabin, 1923) increases in gammarids from 170 μm to of H. huffmani expressed from the larvated egg (F.M. and %|`3_#[\|{&"Para- **J*M$%*>"Y[{$- capillaria philippinensis_N= tomicrograph provided by Cox et al. (2004) show clearly [\^`{[[|M[V3 $[Q"*$- to 250–300 μm (Cross 1992); larvae of Capillaria gracilis lariids, no moulting of larvae of H. huffmani was observed _[`]{[ inside the egg capsule. On the basis of experimental stud- | 3 R 3 _= ~ Y[{& ies and data from the literature, Shlikas (1978) concluded larvae of Schulmanela petruschewskii (Shulman, 1948) that it is a common feature of all aphasmid nematodes that in oligochaetes increase from 240–350 μm to 760–1 250 "N*JN" μm (Kutzer and Otte 1966). Because of the substantial mentioned by Moravec et al. (1987), van Banning (1980) growth reported for these larvae and considering the fact published a photomicrograph of the larva expressed from that these larvae can survive for at least several months QCapillaria spinosaR _ Huffmanela banningi in the intermediate host, Moravec et al. (1987) speculated >" [\`R{ $ [* ? that probably more than one moult is probably occurring in clearly indicates that the larva was undergoing its moult the intermediate host. In such a case, it could be expected and, therefore, it should be considered the second-stage that both L2 and L3"["* "*=~_Y[{ larvae of H. huffmani in amphipods become infective for it is the third-stage larva that hatches from the eggs of cap- [V$**N illariids. Obviously, more studies would be helpful in re- infective stage is L2, which is also indicated by the body solving this conundrum. size of these larvae (much the same as that of L1) much like Based on literature data, the life cycles of some capillar- $"N"[N% iid nematodes are direct (homoxenous), without participa- a week of hatching (see Kasparsone 1984). tion of an intermediate host,; whereas those of others are Crustaceans are rarely found to be the intermediate hosts obligately heteroxenous in which the intermediate host is of trichinelloids. Although Markevich (1951) incidentally required. In the homoxenous life cycles, all nematode stag- mentions gammarids (Amphipoda) to be the intermediate es (L1–L5{["$R hosts of the capillariid Piscicapillaria tuberculata (von development. Sometimes a paratenic host harbouring the Linstow, 1914), no relevant source for his report was found

L1 may be included, but this is not obligatory for complet- in the literature. Most data on capillariid life cycles are on ing the life cycle. On the other hand, in capillariids with species parasitising birds and mammals. Consequently, NK["- the most frequently recorded intermediate hosts have been curs in the intermediate host, so that only the second-stage ascertained to be various earthworms and less often other larvae (L2{"["_>" [*?- al. 1987). loid known to utilise crustaceans as intermediate host is

Folia Parasitologica 2016, 63: 020 Page 13 of 15 doi: 10.14411/fp.2016.020 Worsham et al.: Life cycle of Huffmanela huffmani the above-mentioned Cystoopsis acipenseris (Cystoopsi- and boat/diving support; and the U. S. Fish & Wildlife Service for dae), a parasite of the skin of sturgeons, whose interme- providing specimens and resources pertinent to this study through diate hosts were found to be three species of gammarids >=#*<$ _$${_#[\|{*Huff- K§J<$J$ "%[$N$- manela huffmani is another trichinelloid with a crustacean men collections. We would also like to thank Lindsay Stricklan for (amphipod) intermediate host. graciously providing access to SCUBA equipment making it pos- Acknowledgements. We are thankful to Texas State University for %$!N*?"N providing supplies, space and equipment; The Meadows Center for presented herein are those of the authors and do not necessarily Water and the Environment for providing access to Spring Lake represent those of the U.S. Fish and Wildlife Service.

REFERENCES

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Cite this article as: <>***J**>"+*%*#*Y[^j?Huffmanela huffmani >"[\`R_~j?{Q$?K$* Folia Parasitol. 63: 020.

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