Macvicaria shotteri, Aken'Ova & Cribb & Bray, 2008

Aken'Ova, Thelma, Cribb, Thomas & Bray, Rodney, 2008, Eight new species of Macvicaria Gibson and Bray, 1982 (Digenea: Opecoelidae) from temperate marine fishes of Australia, ZooKeys 1, pp. 23-58 : 27-32

Macvicaria shotteri n. sp.

Type-host: Apogon fasciatus (White) (Apogonidae) .

Other hosts: Sillaginodes punctatus (Cuvier) (Sillaginidae) , Sillago bassensis Cuvier (Sillaginidae) .

Type-locality: Moreton Bay, off Tangalooma, Queensland, 27°14'S, 153°19'E.

Other localities: Off Mandurah, 32°31'S, 115°41'E & off Point Peron, Western Australia, 32°18'S, 115°38'E., off American River, South Australia 35°48'S 137°46'E.

Site: Intestine/gut.

Material studied: Ex Apogon fasciatus: From Moreton Bay , Queensland: 8 Off Tangalooma, February & December, 1993 ; Ex Sillaginodes punctatus: From Western Australia: 8 Off Point Peron, 1 Off Mandurah Rockwall , December 1994. From South Australia: 12 Off American River , December 1995 ; Ex Sillago bassensis: From Western Australia: 3 Off North Mole , Fremantle , December 1994 .

Type-material: Holotype: QM G223130 , Paratypes: QM G 223131-223153 , G 230363 - G 230375 ; BMNH 2008.7.5.20-38.

urn:lsid:zoobank.org:act:EB4EA8A7-38FA-48F9-AE5B-6F0952DB7ECF

Description ( Figs 1-6 )

Based on 16 mature and 4 juvenile unflattened, whole-mount specimens and 1 set each of serial sagittal sections from Sillaginodes punctatus . Measurements of worms from Sillago bassensis and Apogon fasciatus are given in Table 1 .

Measurements are of 10 gravid, unflattened, dorso-ventrally mounted worms from Sillaginodes punctatus . Body elongate, oval, maximum width usually in area of gonads, sometimes in ventral sucker area, 1,345 -2,062 (1,786) × 366-546 (479); width to length ratio 1:3.1-4.2 (3.7). Oral sucker globular, ventrally subterminal, 124-178 (143) × 132-194 (157). Ventral sucker sub-spherical, in anterior third of body, 184- 267 (221) × 218-311 (256), sucker width ratio 1:1.5-1.7 (1.6). Forebody short, 371- 550 (449) long, 21.8-29.7 (25.3)% of body-length. Prepharynx distinct, short, dorsal to oral sucker. Pharynx subglobular, 65-97 (77) × 78-117 (98); pharynx to oral sucker width ratio 1:1.4-1.7 (1.6). Oesophagus distinct, short. Intestinal bifurcation 48-156 (107) anterior to ventral sucker. Caeca terminate blindly close to posterior extremity.

Testes 2, usually contiguous, rarely separate (n=1), tandem, with entire to incised anterior and posterior margins, anterior 137-282 (201) × 155-286 (239), posterior 184-338 (250) × 170-337 (244). Post-testicular region 312-498 (406) long, 19-27.4 (22.9)% body-length. Cirrus-sac clavate, thick walled, overlaps ventral sucker dorsally and extends posteriorly to point anterior to or slightly posterior to posterior margin of ventral sucker, 294-528 (403) × 64-142 (99). Internal seminal vesicle tubular, convoluted, fills most available space in posterior half of cirrus-sac. Pars prostatica distinct, small, surrounded by prostatic cells. Ejaculatory duct long, thick walled. Genital atrium small. Genital pore sinistral to and level with posterior end of oesophagus, anterior to intestinal bifurcation, 200-300 (251) from anterior end, 11.6-18.4 (14.2)% body-length.

Ovary entire, spherical, contiguous with and antero-dextral to anterior testis, 109- 208 (145) × 98-194 (144). Mehlis’ gland well developed, seen clearly in juvenile worms and sagittal sections, obscured by eggs in gravid whole-mounts, dorsally antero-sinistral and partly anterior to ovary. Canalicular seminal receptacle large, saccular, may be entirely dorsal or sinistral to ovary, overlapping left margin of ovary and anterior margin of anterior testis. Laurer’s canal present. Eggs oval, operculate, 54-79 (65) × 29-49 (37). Metraterm distinct, well developed, relatively long. Vitelline follicles extend from 176- 282 (229) from anterior extremity, 10.9-15.4 (12.9)% of body-length, to 10-55 (21) from posterior extremity; fields separate ventrally in forebody, confluent dorsally in forebody and post-testicular area; continuous follicle-free zone between ventral sucker and posterior margin of posterior testis, dorsally; follicles lie lateral, ventral and dorsal to caeca; anterior extent usually level with, or slightly anterior to or posterior to posterior margin of pharynx, rarely posterior to posterior limit of oesophagus (n=1).

Excretory pore dorsally subterminal. Excretory vesicle I-shaped, narrow posterior end surrounded by gland-cells, widens anteriorly and passes to point antero-dorsal to posterior margin of ovary.

3

Etymology: This species is named for Professor R. A. Shotter.

Comments: The specimens of Macvicaria shotteri from Sillago bassensis and Apogon fasciatus are similar to those from Sillaginodes punctatus except in a few morphological details which we do not consider to be of taxonomic importance, since most of the measurable features are comparable. The largest worms, the two from Sillago bassensis , had the largest eggs, whereas the eggs in the worms from Sillaginodes punctatus and Apogon fasciatus were similar in size. The worms from Sillaginodes punctatus had the longest forebody, 21.8-29.7 (25.3) % of the body-length compared with 20.9-25.8 (23.1)% and 18.6-21.6 (20.1)% of the body-length in the worms from Sillago bassensis and those from A. fasciatus respectively. The testes are usually contiguous in worms from all three hosts except in two worms, one each from Sillaginodes punctatus and A. fasciatus in which the testes are separate. Bray (1985) observed that larger specimens of M. taksengi had larger eggs than the smaller specimens. This may also be the case in M. shotteri , since the largest eggs were in the largest worms from Sillago bassensis . Although the sharing of this parasite between apogonid and sillaginid hosts is surprising, we can find no morphological basis to interpret these specimens as two different species.

Macvicaria shotteri n. sp. fits into the concept of Group B as outlined above. This species can be distinguished from the other worms in the group as follows:

M. aegyptensis , according to Shalaby & Hassanine (1997), is a less elongate worm with a width to length ratio of 1:2.2-2.8, a longer forebody, (33% of body-length), a larger ventral sucker with sucker-width ratio of (1:2), and a genital pore at about 21% of the body-length from the anterior end.

M. crassigula , according to Bartoli et al. (1989), is a less elongate worm with a width to length ratio of 1:2.1 [2.44], it has a longer forebody (32% [40%] of body-length), a longer post-testicular space (27% of body-length), a slightly larger oral sucker with a sucker-width ratio of 1:1.27-1.40 [1.28], and a genital pore which is more posteriorly situated than in M. shotteri n. sp., at 26% of body-length from the anterior extremity.

M. chrysophrys , according to Nagaty & Abdel-Aal (1969) and Hassanine & Gibson (2005), is a less elongate species with a width to length ratio of 1:2.3 [2.7-2.9]; it has a longer forebody (39 [31-43]% of the body-length); a shorter post-testicular area (17% of body-length) and larger eggs (80 × 50 [64–78 × 35–48 (71 × 42)].

M. cynoglossi , according to Madhavi (1975), is relatively narrower with a width to length ratio of 1:4.17-4.59, with a longer forebody at 32-33% of the body-length, a generally greater sucker ratio at 1:1.6-2.0, lobed, oblique testes and a subterminal excretory pore (at the level of the caecal ends in the illustration).

M. dactylopagri , according to Manter (1954), is clearly differentiated from M. shotteri n. sp. by the anterior extent of the vitellarium which reaches to the oral sucker or pharynx.

M. dubia , according to Bartoli et al. (1989), is a less elongate worm with a width to length ratio of 1:2.1, a longer forebody and a shorter post-testicular area of 40% and 14% of the body-length, respectively, it has larger eggs, 71-85 × 33-43 (79 × 39), and a genital pore which is more posteriorly situated, at 29% of the body-length from anterior extremity.

M. eleuthoronemae , according to Wang et al. (1992), differs from M. shotteri n. sp. in the intestinal bifurcation being in the middle of a long forebody (35% of bodylength), a short post-testicular region (14% of body-length) and all the gonads in the final third of the body.

M. hunghuaensis , according to Shen & Qiu (1995), is a squat worm (width to length ratio of 1:2.1-3.0 (1: 1.6 in illustration)). The cirrus-sac is confined to the forebody and the vitelline fields are widely separated.

M. longicauda , according to Hafeezullah (1971), is relatively narrower with a width to length ratio of 1:4.2-4.4, a slightly longer forebody at 29-30% of body-length, a long post-testicular region at 33% of body-length and the cirrus-sac does not reach the ventral sucker.

M. maillardi , according to Bartoli et al. (1989), has no distinct oesophagus, it has a smaller ventral sucker and a larger oral sucker shown by a sucker ratio of 1:1.06-1.48 (1.22), it has a longer forebody and shorter post-testicular area measuring 40% and 18% of the body-length, respectively, and a more posteriorly situated genital pore at 29% of the body-length from the anterior extremity.

M. mormyri , according to Bartoli et al. (1993), is a less elongate species, with a width to length ratio of 1:2.8, a smaller ventral sucker and larger oral sucker with a sucker width ratio of 1:1.16-1.54 (1.35); it has a longer forebody, 35% of the bodylength, and a genital pore which is more posteriorly situated at 19% of the body-length from anterior extremity.

M. obovata , according to Bartoli et al. (1989), is less elongate with a width to length ratio of 1:2.8, it has a longer forebody (37% of the body-length), and a genital pore which is more posteriorly situated at 23% of the body-length from the anterior extremity.

M. ophthalmolyci , according to Zdzitowiecki (1990, 1997), has a very large ventral sucker (width ratio 1:2.1-2.7), a very short forebody (about 13% of body-length) and the vitellarium reaches the pharynx.

M. taksengi , according to Bray (1985), is very close M. shotteri from which it can be distinguished by its smaller size (590-1,110 × 240-480), its less elongate form with a width to length ratio of 1:2.5, by its ovary which is situated dextrally or overlapping the anterior testis and by the distal expansion of the cirrus-sac.

M. sillagonis , according to Yamaguti (1938), is closest to M. shotteri from which it can be distinguished by its less elongate form, with a width to length ratio of 1:2.3, a slightly shorter post-testicular area of 20% of the body-length and a slightly smaller pharynx with a pharynx to oral sucker width ratio of 1:2.0.

The seminal vesicle in the new species is distinctive, in that it is thrown into two or more virtually parallel diagonal slings within the cirrus-sac, a feature not observed in M. sillagonis . Bray (1985) had commented that the holotype and two specimens of M. sillagonis which he examined were so extremely flattened that some of the features of the worms might have been altered; however, we do not think that the alteration will be so much as to unravel the slings of the seminal vesicle, if present in M. sillagonis .

Figures

Figs 1-3. Macvicaria shotteri n. sp. ex Apogon fasciatus. 1. Whole-mount ventral view. 2. Terminal genitalia. 3. Dorsal distribution of vitelline follicles. Scale bars: 1, 3, 250 µm; 2, 100 µm.

Figs 4-6. Macvicaria shotteri n. sp. ex Sillaginodes punctatus. 4. Whole-mount ventral view. 5. Terminal genitalia. 6. Dorsal distribution of vitelline follicles. Scale bars: 4, 6, 250 µm; 5, 100 µm.

Tables

Table 1. Measurements (in µm) of Macvicaria shotteri n. sp. from Sillago bassensis (n = 2) and Apogon fasciatus (n = 8).

Host species	S. bassensis			A. fasciatus
	Min.	Max	Mean	Min.	Max.	Mean
Total length	2,204	2,326	2,265	1,393	1,852	1,669
Maximum width	582	712	647	368	448	413
Length/width	3.1	4.0	3.5	3.4	4.3	4.0
Oral sucker length	159	188	174	122	149	132
Oral sucker width (OSW)	177	196	187	135	147	144
Pharynx length	87	101	94	64	83	71
Pharynx width	116	127	122	81	102	92
OSW/pharynx width	1.5	1.5	1.5	1.4	1.7	1.6
Ovary length	201	227	214	117	162	144
Ovary width	171	182	177	117	160	145
Anterior testis length	243	284	264	134	205	173
Anterior testis width	272	292	282	147	230	194
Posterior testis length	339	353	346	147	234	209
Posterior testis width	252	265	259	128	237	190
Forebody-length (FBL)	433	475	454	320	441	385
FBL as % of body-length	18.6	21.6	20.1	20.9	25.8	23.1
Ventral sucker length	251	270	261	203	224	214
Ventral sucker width (VSW)	284	331	308	225	262	244
VSW/OSW	1.6	1.7	1.6	1.6	1.8	1.7
Anterior extremity to genital pore (AEGP)	258	277	268	188	246	223
AEGP as % body-length	11.1	12.6	11.8	12.5	15.8	13.4
Cirrus-sac length	518	518	518	285	415	352
Cirrus-sac width	176	176	176	71	110	90
Intestinal bifurcation to ventral sucker	103	117	110	32	91	64
Post-testicular region (PTR)	501	632	567	333	525	426
PTR as % of body-length	22.7	27.2	25.0	20.4	28.3	25.5
Anterior extremity to vitellarium (AEV)	276	317	297	230	307	263
AEV as % of body-length	11.9	14.4	13.1	13.4	20.7	15.9
Posterior extremity to vitellarium	13	19	16	13	58	25
Eggs	62-76 (69) ×37-48			58-72 (64) × 32-45
	(42), n=11			(38), n=66

Table 1. Measurements (in µm) of Macvicaria shotteri n. sp. from Sillago bassensis (n = 2) and Apogon fasciatus (n = 8).