Pseudalataspora vanderlingeni, Reed & Kalavati & Mackenzie & Collins & Hemmingsen, 2018

Reed, Cecile, Kalavati, Chaganti, Mackenzie, Ken, Collins, Catherine & Hemmingsen, Willy, 2018, Pseudalataspora vanderlingeni n. sp. (Myxosporea: Bivalvulida) from gall bladders of the Cape hakes Merluccius capensis Castelnau, and M. paradoxus Franca (Teleostei: Merlucciidae), Zootaxa 4497 (3), pp. 422-428 : 424-428

Pseudalataspora vanderlingeni n. sp.

Material studied. Type host: Merluccius capensis Castelnau, 1861

Other hosts: Merluccius paradoxus Franca, 1960

Site of infection: gall bladder

Localities and dates (where known): (1) Southern Benguela off West Coast of South Africa; (2) Southern Benguela south of South Africa, 36°62´S, 20°63´E, 16/04/2016.

Type locality: Southern Benguela, West Coast of South Africa.

Prevalence: (1) 100% (4 of 4 M. capensis, 8 of 8 M. paradoxus); (2) 61.5% (16 of 26 M. capensis).

Host length range: 270–743 mm

Accession number: SAMC-A 089049

Etymology: t he new parasite is named for Dr Carl van der Lingen, who provided the fish hosts in which it was found.

Morphological description. Sporoblast amoeboid, disporous and staining uniformly ( Fig. 1 ). Dimensions, based on 10 fixed specimens: 58.4–68.4 x 45.0–50.0. No vegetative stages from fresh material were available for measurements.

Spore ( Figs. 2-6 ) oval with rounded ends in side view, flat anteriorly and curved in apical view. Sutural line prominent and slightly bent. Sporoplasm deeply staining and binucleate. Valves drawn out into two delicate, broad, relatively small alate processes joined together at their proximal extremities. Polar capsules oval, widely separated. Polar filament with 5 to 6 coils. Dimensions, based on 17 fresh spores, as ranges with means ± SD in parentheses: spore length 12.2–15.3 (14.2 ± 1.0); spore width, excluding alate processes 18.2–23.4 (20.6 ± 1.8); polar capsule oval, length 4.4–5.5 (5.0 ± 0.3); width 4.2 –5.1 (4.8 ± 0.3); polar capsule length: spore length = 1: 2.3–2.9; spore length: spore width = 1: 1.2–1.7.

Further spore measurements were taken from formalin-fixed and frozen spores and found to be 30-70% greater than those given above for fresh spores.

Molecular Results. A product of approximately 1500 nucleotides was generated by PCR amplification from purified DNA from the gall bladder of a single specimen of M. capensis . Direct sequencing of 4 pools of purified PCR products (four PCR reactions per pool) gave identical sequences. Once primers and poor sequence at the 5’- and 3’ termini were removed, a sequence of 1447 nucleotides remained and was submitted to Genbank under Accession No. MF034897 .

Searches of the GenBank public sequence database found that the sequence was novel and represented a new myxozospoean species. Closest sequence identity was found with Ceratomyxa cretensis ( JX869942 ), Ceratomyxa filamentosi ( JX869943 / JX869944 ) and Ceratomyxa arcuata ( KJ419344 ), with an identity of 91% shared with all three species, over 99%, 98/96% and 93% respectively of the myxozoasporean sp. 18S rDNA sequence. Following alignment with other myxosporean species and removal of gaps and ambiguous nucleotides, a sequence of 1021 remained for phylogenetic analyses. ML and MP trees showed similar topologies, with the newly described myxosporean sp. from M. capensis being a sister group to a group containing C. arcuata , C. cretensis and C. filamentosi , with bootstrap support of 100/99 respectively ( Fig. 7 ).

Discussion. Myxosporeans have been reported on three previous occasions from the gall bladders of Cape hake. Fantham (1930) gave a brief description, without a figure, of Sphaerospora subelegans n. sp. from a single specimen of M. capensis caught in Table Bay. Fantham’s description suggests that it may well have been the same species as that described in this paper, but it is not possible to confirm this from Fantham’s description and we were unable to locate his original material for comparison. Aleshkina (1982) reported Ceratomyxa sp. and Leptotheca sp. from M. capensis caught off Namibia, while Reimer (1993) reported Leptotheca sp. from both M. capensis and M. paradoxus caught off Namibia. Neither Aleshkina (1982) or Reimer (1993) provided descriptions of the spores, although Reimer did provide some measurements, and the genus Pseudalataspora had not been described at the time of Aleshkina’s paper. The genus Leptotheca is no longer recognized and its former species have been reassigned to other genera, including Ceratomyxa and Sphaerospora (see Gunter and Adlard, 2010). Both authors reported very high prevalences similar to those found in the present study. It seems very likely that the species they reported was P. vanderlingeni .

Sixteen species of the genus Pseudalataspora have been described from the gall bladders of marine fishes (Table 1). Apart from P. vanderlingeni , the only one to have been characterised molecularly to date is P. kovalevae , which is also the only other species described from a member of the teleost family Merlucciidae (see Kalavati et al., 2013). Pseudalataspora vanderlingeni is the first to be described from a member of the genus Merluccius . Fig. 7 shows that the genetic sequences of these two species are more similar to species of Ceratomyxa than they are to one another.

We found that spore measurements taken from formalin-fixed and frozen spores were both significantly greater than those taken from fresh spores. Further evidence of the effects of freezing and fixation on spore dimensions can be found in Sarkar (2012). In his description of Pseudalataspora misrae, Sarkar reported marked differences between two sets of measurements – one from frozen unfixed spores and the other from fixed and stained spores, measurements from the frozen spores being 11-16% greater than those from the fixed and stained spores. The spores of members of the genus Pseudalataspora thus appear to be very susceptible to swelling and distortion when they are frozen and/or fixed. This makes comparisons of spore dimensions between species of Pseudalataspora of doubtful value for taxonomic purposes unless comparisons are based on fresh spores only. Those of P. vanderlingeni appear to be closest in size to P. beryxi Kovaleva & Gaevskaya, 1988 , described from the gall bladder of Beryx splendens caught in the Atlantic Ocean. In other respects, however, such as the spore shape and the dimensions of the polar capsules, the two species are quite different.

The difficulty of observing the fragile alate processes characteristic of species of Pseudalatospora and the close phylogenetic relationship between members of the genera Pseudalataspora and Ceratomyxa , based on rDNA sequences, prompted Kalavati et al. (2013) to suggest that some species of Pseudalataspora may previously have been assigned wrongly to the genus Ceratomyxa . Rocha et al. (2015) further suggested that sequencing of more species of Pseudalataspora and Alataspora would probably lead to the demise of the family Alatasporidae and the assignment of its species to the genus Ceratomyxa . While we agree about the possible demise of the family Alatasporidae , we feel that the clear and unambiguous morphological differences between Ceratomyxa , Alataspora and Pseudalataspora are currently sufficient to justify their status as separate genera, at least until genetic sequences are available for more species of the latter two genera.

Finally, a plea to authors of research papers and textbooks to use the correct spelling of Alatasporidae , Alataspora and Pseudalataspora , which are frequently misspelt as Alatosporidae , Alatospora and Pseudalatospora (or Pseudoalatospora ) respectively. The name Alatospora is preoccupied by a genus of fungus.

Figures

FIGURE 7. Maximum Likelihood consensus tree showing relationship of Pseudalataspora vanderlingeni (in bold), isolated from Merluccius capensis, to other Ceratomyza species, based on 18S rDNA sequence analysis. Bootstrap values indicating ≥ than 70% support for Maximum Likelihood and Maximum Parsimony analyses respectively are shown. Host species, geographical origin and accession numbers are listed after species names. 1 myxosporean species also isolated from Archamia fucata; 2 also isolated from Cheilodipterus quinquelineatus/ Nectamia fusca/ Ostorhinchus cookii/ Apogon doederleini/; 3 also isolated from Plectroglyphidodon leucozonus/ Chrysiptera cyanea/ Pomacentrus chrysurus/ Neoglyphidodon melas; 4 also isolated from Clupea harengus; 5 also isolated from Aulopus filamentosus; 6 also isolated from Aulopus filamentosus; 7 also isolated from Aulopus filamentosus; 8 myxosporean species isolated from monogenean Diplectanocotyla sp. on the gills of Megalops cyprinoides; 9 also isolated from Belone belone.

FIGURE 1–5. FIGURE 1. Pseudalataspora vanderlingeni: unstained disporic sporoblast. FIGURE 2. Pseudalataspora vanderlingeni: unstained spore in anterior/sutural view. FIGURE 3 & 4. Pseudalataspora vanderlingeni: unstained spores in valvular view. FIGURE 5. Pseudalataspora vanderlingeni: spore stained with Giemsa in valvular view. Scale bar = 10 µm.

FIGURE 6. Pseudalataspora vanderlingeni: fresh spore under phase contrast. Scale bar = 10 µm.