Research Article |
Corresponding author: Karl J. Wittmann ( karl.wittmann@meduniwien.ac.at ) Academic editor: Tammy Horton
© 2017 Karl J. Wittmann, Charles L. Griffiths.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Wittmann KJ, Griffiths CL (2017) Three new species of Heteromysis (Mysida, Mysidae, Heteromysini) from the Cape Peninsula, South Africa, with first documentation of a mysid-cephalopod association. ZooKeys 685: 15-47. https://doi.org/10.3897/zookeys.685.13890
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Faunistic studies in sublittoral and littoral marine habitats on the Cape Peninsula, South Africa, have yielded three new species belonging to the genus Heteromysis, subgenus Heteromysis: H. cancelli sp. n. associated with the diogenid hermit crab Cancellus macrothrix Stebbing, 1924, and H. fosteri sp. n. extracted from ‘empty’ urchin and gastropod shells. The first documented mysid-cephalopod association is reported for H. octopodis sp. n. which was found in dens occupied by Octopus vulgaris Cuvier, 1797, but was also captured from tide pools. The three new species differ from previously known E. Atlantic species, among other characters, by a single spine on the endopods of uropods in combination with large cornea and absence of median sternal processes on thoracic somites. They are also characterized by a white stripe along the dorso-lateral terminal margin of the eyestalks in living specimens. The new species appear quite similar to each other, but are distinguished by different depths of the telson cleft, different distributions of spines on the lateral margins of the telson, different numbers of segments on thoracic endopod 4, and by differently modified setae on the carpus of the third thoracic endopod, as well as on the carpopropodus of the fourth endopod. An updated key to the species of Heteromysis known from the E. Atlantic is given.
Crustacea , hermit crab association, octopus association, ectocommensals, taxonomy, key to species, SE. Atlantic
Ongoing taxonomic surveys of littoral and sublittoral habitats along the coasts of the Cape Peninsula (South Africa) have yielded a number of previously unreported Mysidae species, of which one, Mysidopsis zsilaveczi, has already been described as new by
The distributions and habitats occupied by species belonging to this genus were reviewed by
The three species described below were collected at four stations in 0-20 m depth within 5.5 km of the False Bay coastline (34°11'S 18°27'E to 34°14'S 18°28'E), Cape Peninsula, South Africa, using different methods, as detailed below:
The first species was extracted from a gastropod shell occupied by a hermit crab, as part of a separate taxonomic study on the regional hermit crab fauna. Although numerous shells, occupied by a variety of hermit crab species, were collected individually by SCUBA diving or by hand-collecting on the shore at this and many other sites, mysids were only found associated with a single individual of the rarely-recorded hermit Cancellus macrothrix Stebbing, 1924.
The second, shell-occupying species was discovered during a separate and mysid-directed sampling operation, in which roughly 1 kilo of dead urchin and gastropod shells, without hermit crabs, were sampled from sublittoral habitats near Miller’s Point, False Bay, then put into a bucket of seawater, into which a small amount of formalin was added, just enough to expel any infauna from the recesses, but not to kill them. The sample was then rinsed with seawater and each shell shaken out back into the bucket. The seawater was then poured through a 1 mm mesh net. Only the single mysid species described below was obtained in this way (although along with numerous amphipods, isopods and other small crustaceans).
The third species described here was visually sighted and photographed in sublittoral dens occupied by octopus and in intertidal rock pools by a local underwater photographer, who then captured specimens with a small hand net, or by coaxing them into an open jar, and submitted them to us for identification.
Fixation, preservation, preparation, measurements, and examination of materials was carried out as described in
Holotype, adult male with 6.9 mm body length, in vial at
Carapace produced into well projecting, broadly-subtriangular rostrum with rounded apex. Eyes well developed; cornea occupies 40–55% of eye surface; eyestalks with small, distally directed, blunt extension of (obliquely anterior facing) inner margin. Antennular trunk with a number of smooth and barbed setae, but no particularly modified setae; inner distal corner of its terminal segment with anteriorly directed apophysis carrying two large, smooth setae. Antennal scale moderately stout and short, extending shortly beyond distal half of terminal segment of antennular trunk; outer margin feebly convex. First thoracic sternite with anteriorly projecting, terminally rounded median lobe; sternites 2–8 without lobes in both sexes. Carpopropodus of thoracic endopods 1–8 with 2, 2, 2, 3-4, 5, 6, 6, or 5-6 segments, respectively. Third thoracic endopod not dimorphic, without any spines or spine-like setae; carpus not swollen (with respect to merus). Carpus of third thoracic endopod with series of 2–3 subbasally spiny (i.e. with modified barbs) and medially to subterminally pectinate setae near outer margin. Carpopropodus of fourth thoracic endopod with series of 2–4 subbasally more strongly spiny setae near outer margin, these ‘spines’ thick but not tooth-like; no such modified setae in endopods 5–8. Penes long and slender, twice length of merus of eighth thoracic endopod; tip with three rounded lobes, each wider than long. Pleopods reduced to small, setose, bilobate plates, without any spines in both sexes. Exopods of uropods extend distinctly beyond endopods. Endopods with only one spine on inner margin, in subbasal position near statocyst. Telson subtriangular, though terminally transversely truncate; lateral margins weakly sigmoid, along their distal 56–60% furnished with continuous series of 18–21 spines each. Telson with apical cleft that forms a narrow, proximally rounded ‘V’, cleft four times deeper than wide, its depth 27–36% telson length. Cleft densely furnished with total of 29–33 acute laminae (= laminar processes) along basal 81–84% of its margins. Two latero-apical lobes of telson show transverse apical margins, each carrying 2–3 large spines of subequal size.
General appearance is that of mysids with intermediate proportions. Cephalothorax comprises 39–42% of body length without telson, pleon 58–61%, and carapace 33–37%, when measured along dorsal median line (Fig.
Carapace (Fig.
Eyes (Figs
Antennulae (Fig.
Antennae (Fig.
Mouth parts (Figs
Thoracopods in general (Figs
Maxillipeds (first and second thoracic endopods; Fig.
Gnathopods (third thoracic endopod; Fig.
Pereiopods (fourth to eighth thoracic endopods; Figs
Marsupium. Females with large marsupial plates on seventh and eighth thoracopods. Sixth thoracopod with rudimentary oostegite representing a small lobe, on its inner margin with three proximally weakly-barbed setae.
Penes (Fig.
Pleopods (Fig.
Uropods (Fig.
Telson (Fig.
Colour (Fig.
Nauplioid stage (Fig.
The species name is a noun in genitive singular, adopted from the hermit crab host Cancellus.
Sublittoral marine coastal waters at Roman Rock, off Simonstown, on the False Bay coastline of the Cape Peninsula, South Africa, 34°10.95'S, 18°27.50'E, 20 m depth. H. cancelli sp. n. was only found in a single gastropod shell inhabited by the hermit Cancellus macrothrix Stebbing, 1924, although four other Cancellus specimens and numerous other hermit crabs, mainly Paguristes gamianus (H. Milne-Edwards, 1836), were collected and examined from this and nearby sites.
Heteromysis cancelli sp. n., paratype male with 6.9 mm body length (A, E–H), paratype female 6.4 mm (B–D, J). A, B cephalic region plus carapace in male (A) versus female (B), dorsal view, details show pore groups (C, D) on carapace E male antennula, dorsal F labrum, obliquely ventral G mandibles with right palpus, caudal H labium, ventral J maxillula, caudal.
Heteromysis cancelli sp. n., paratype female with 6.4 mm body length (A, C, D, H, J, L, M) with one of its larvae (N), paratype male 6.9 mm (B, E–G, K). A maxilla, caudal B first thoracopod, caudal aspect, with thoracic sternites 1-8, ventral C second maxilliped, ventral, detail (D) shows modified seta E–M series of dactylus in thoracic endopods 1-8 with claw (if present), caudal N nauplioid larva at late substage 2, lateral.
Heteromysis cancelli sp. n., paratype male with 6.9 mm body length (A, F–J), paratypes female 6.1 mm (B, C) and 6.4 mm (D, E). A male third thoracopod, caudal aspect B tarsus of female thoracic endopod 3, rostral, detail (C) shows modified seta D fourth thoracopod, rostral, detail (E) shows modified seta F tarsus of sixth thoracic endopod, rostral G–J series of male pleopods 1, 4, 5, rostral.
Heteromysis cancelli sp. n., paratype male with 6.9 mm body length (A, C–E), paratype female 6.4 mm (B, F) A eighth thoracopod with penis, caudal aspect B tarsus of female eighth thoracic endopod, caudal C uropods, dorsal D telson, dorsal E, F terminal margin of sixth pleonite, lateral, in male (E) versus female (F).
Holotype, adult male with 6.7 mm body length, in vial at
Carapace produced into well-projecting, triangular rostrum with narrow rounded apex. Eyes well developed; cornea occupies 35–50% of eye surface; eyestalks with inconspicuous, distally-directed, blunt extension of (obliquely anterior facing) inner margin. Antennular trunk with a number of smooth and barbed setae, but no particularly modified setae; inner distal corner of its terminal segment with anteriorly directed apophysis carrying two large, smooth setae. Antennal scale stout, extending to 0-10% below tip of antennular trunk; outer margin convex. First thoracic sternite with anteriorly-projecting, terminally-rounded median lobe; sternites 2–8 without lobes in both sexes. Carpopropodus of thoracic endopods 1–8 with 2, 2, 2, 3, 6, 6, 6, or 5-6 segments, respectively. Third thoracic endopod weakly dimorphic, without any spines or spine-like setae; carpus not swollen in female, slightly swollen in male (with respect to merus). Carpus of third thoracic endopod with series of three subbasally toothed setae (i.e. with modified barbs) near outer margin. Carpopropodus of fourth thoracic endopod with series of 2–3 subbasally toothed setae near outer margin; no such modified setae in endopods 5–8. Penes long and slender, twice length of merus of eighth thoracic endopod; tip with three rounded lobes, each wider than long. Pleopods reduced to small setose, bilobate plates, without any spines in both sexes. Exopods of uropods extend distinctly beyond endopods. Endopods with only one spine on inner margin, in subbasal position near statocyst. Telson subtriangular, terminally truncate; lateral margins weakly-sigmoid, along their distal 83–93% furnished with slightly discontinuous series of 17–20 spines each. Telson with apical cleft forming proximally poorly rounded ‘V’. This cleft slightly deeper than wide, its depth 14–18% telson length. Cleft densely furnished with 16–24 acute laminae all along its margins. Two latero-apical lobes of telson show narrow, transverse apical margins, each bearing a large latero-apical spine plus much smaller medio-apical spine.
As described above for H. cancelli sp. n. unless stated otherwise in the following. Cephalothorax comprises 41–44% of body length without telson, pleon 56–59%, and carapace 30–38%, when measured along dorsal median line. First thoracic sternite with median lobe showing a smooth, rounded apex. Terminal margin of sixth pleonite with lateral shields more evenly rounded in females (Fig.
Carapace (Figs
Eyes (Figs
Antennulae (Fig.
Antennae (Fig.
Mouth parts (not figured). Pars incisivus of mandibles with 3–4 large teeth, and digitus mobilis with 3–4 large plus 1–3 small teeth. Pars centralis with 4–5 spiny teeth. Distal segment of maxillula terminally with 8–10 strong, inconspicuously serrated spines, subterminally with a transverse row of 5–6 barbed setae. Endite of maxillula with three large, distally-spinose setae, and a total of 15–20 smaller, smooth or barbed setae.
Thoracopods in general (Figs
Maxillipeds (first and second thoracic endopods; Fig.
Gnathopods (Figs
Pereiopods (Figs
Penes (Fig.
Pleopods (Fig.
Uropods (not figured). The exopods reach with 21–30% of their length beyond endopods and 17–25% beyond telson, the endopods 6–11% of their length beyond telson. Exopod length 4.3–4.4 times maximum width. Statoliths composed of fluorite; diameter 145–181 µm (n = 4); statolith formula is 2 + 3 + 1 + (8–13) + (16–19) = 31–38.
Telson (Fig.
Colour (Fig.
Nauplioid stage (Fig.
The species name is a noun in genitive singular, named after well-know underwater-photographer and diver Craig Foster, who has accompanied and assisted the second author in many collecting expeditions and who made all in situ photographs and sampled all specimens of both this species and the one following.
Sublittoral marine coastal waters at Miller’s Point, on the False Bay coastline of the Cape Peninsula, South Africa, 34°13.78'S, 18°28.47'E. This is only 5.5 km to the SSE of the type locality of H. cancelli sp. n. (above). Materials were extracted from mixed collection of dead shells mainly belonging to the whelk Argobuccinum pustulosum (Lightfood, 1786), the winkle Turbo cidaris Gmelin, 1791, and the urchin Parechinus angulosus (Leske, 1778).
Microphotographs of adult female of Heteromysis fosteri sp. n. with 7 mm body length (A) and of adult male of Heteromysis octopodis sp. n. with 9 mm (B), each from Miller’s Point, Cape Peninsula, South Africa. A laboratory photo by C.L. Griffiths B in situ image by Craig Foster, this last with background cleaned with electronic tools.
Heteromysis fosteri sp. n., paratype females with 7.0 mm (A) and 8.0 mm (C–H, L) body length, paratype male 6.0 mm (B, J, K). A cephalic region plus anterior part of carapace in female, dorsal view B male antennula, dorsal C epipod of first thoracopod, caudal D–H series of dactylus with claw in thoracic endopods 1, 3-5, 8 of female, caudal J tip of claw of third thoracic endopod in male K, L terminal margin of sixth pleonite, lateral, in male (K) versus female (L) M nauplioid larva at substage 3, lateral.
Heteromysis fosteri sp. n., paratype male (A, F–H) with 6.0 mm body length and paratype female 8.0 mm (B–E). A male tarsus with part of merus pertaining to third thoracic endopod, caudal aspect B the same for female, detail (C) shows subbasally toothed seta D tarsus of fourth thoracic endopod, caudal, detail (E) shows subbasally toothed seta F eighth thoracopod with penis, caudal G third male pleopod, rostral H telson, dorsal.
All materials from Miller’s Point, on the False Bay coastline of the Cape Peninsula, South Africa, leg. Craig Foster. Holotype, adult male with 7.0 mm body length, in vial at
Based only on adult males and subadult females. Carapace produced into well-projecting, (sub)triangular rostrum with rounded apex. Eyes well-developed; cornea occupies 60–70% of eye surface; eyestalks with inconspicuous, distally-directed, blunt extension of (obliquely anterior facing) inner margin. Antennular trunk with a number of smooth and barbed setae, but no particularly modified setae; inner distal corner of its terminal segment with apophysis carrying two medium-sized, smooth setae. Antennal scale stout, extending to 0–20% below tip of antennular trunk; outer margin convex. First thoracic sternite with anteriorly-projecting, terminally-rounded median lobe; sternites 2-8 without lobes. Carpopropodus of thoracic endopods 1-8 with 2, 2, 2-3, 4-6, 5-7, 5-8, 6-8, or 6-8 segments, respectively. Third thoracic endopod without any spines or spine-like setae; carpus not swollen with respect to merus. Carpus with series of three weakly-modified setae near outer margin; these setae subbasally furnished with bristles. Merus (sub)terminally with two subbasally toothed setae. Fourth thoracic endopod with series of 2–3 such toothed setae near outer margin of carpopropodus; no such modified setae in endopods 5–8. Penes long and slender, 1.6–1.7 times length of merus of eighth thoracic endopod; tip with three rounded lobes, each wider than long. Pleopods reduced to small setose, bilobate plates, without any spines. Exopods of uropods extend distinctly beyond endopods. Endopods with only one spine on inner margin, in subbasal position near statocyst. Telson subtriangular, terminally truncate; lateral margins weakly sigmoid, along their distal 46–53% furnished with almost continuous series of 13–17 spines each. Telson with apical cleft forming a proximally rounded ‘V’. Cleft slightly deeper than wide, its depth 17–23% telson length. Cleft densely furnished with a total of 26–37 acute laminae all along its margins. Two latero-apical lobes of telson show narrow transverse apical margins, each bearing a large latero-apical spine, plus much smaller medio-apical spine.
As described above for H. cancelli sp. n. unless stated otherwise in the following. Cephalothorax comprises 37–44% of body length without telson, pleon 54–63%, and carapace 32–38%, when measured along dorsal median line. First thoracic sternite with median lobe showing smooth rounded apex. Each of first to fifth abdominal somites measure 0.8–1.1 times length of sixth somite. Terminal margin of sixth pleonite with lateral shields triangular, with tip more rounded in subadult females (Fig.
Carapace (Figs
Eyes (Figs
Antennulae (Fig.
Antennae (Fig.
Mouth parts (not figured). Pars incisivus of mandible with 3–4 large teeth, and digitus mobilis with 3–4 large plus 2–3 small teeth. Pars centralis with 3–4 spiny teeth. Distal segment of maxillula terminally with 9–12 weakly serrated spines, subterminally with a transverse row of 5–6 barbed setae. Endite of maxillula with three large, distally spinose setae, and 18–28 smaller, smooth or barbed setae.
Thoracopods in general (Figs
Maxillipeds (Fig.
Gnathopods (Figs
Pereiopods (Figs
Penes (Fig.
Oostegites. The subadult females already have eggs in the ovaries, visible in Fig.
Pleopods (Fig.
Uropods. The exopods reach with 15–38% of their length beyond endopods and 33–43% beyond telson, endopods 6–17% of their length beyond telson. Exopod length 3.8–4.2 times maximum width. Statoliths composed of fluorite; diameter 120–196 µm (n = 12); statolith formula 2 + 3 + (0–1) + (8–16) + (12–19) = 27–39.
Telson (Fig.
Colour (Figs
The species name octopodis is a noun in genitive singular, derived from the substantive octopus by using the third declension of New Latin.
Octopus den (Fig.
Schools of this mysid were encountered during daytime in shallow sublittoral waters inside dens occupied by Octopus vulgaris (in case of Fig.
A subadult female of Heteromysis octopodis sp. n. with 11 mm body length from tide pool B multi-species association inside den in 3 m depth, occupied by Octopus vulgaris, to the right with the crab Guinusia chabrus; upper arrow points to a mysid school of what we assume to be H. octopodis sp. n., lower arrow to a different but undetermined mysid species. A, B from Miller’s Point, Cape Peninsula, South Africa; in situ images by Craig Foster B image is taken of the same octopus den from which the samples were collected, but on a different date.
Heteromysis octopodis sp. n., paratype adult male with 8.8 mm body length (A, D–K), paratype subadult females with 9.0 mm (B, L) and 8.8 mm (C). A cephalic region plus anterior part of carapace in male, dorsal view B anterior margin of antennular trunk in subadult female, dorsal C epipod of first thoracopod, caudal D–H series of dactylus with claw in thoracic endopods 1, 3-5, 8, caudal J fourth male pleopod, rostral K, L terminal margin of sixth pleonite, lateral, in male (K) versus subadult female (L).
Heteromysis octopodis sp. n., paratype adult male with 8.8 mm body length. A tarsus with part of merus pertaining to third thoracic endopod, caudal aspect, details show subbasally toothed seta on merus (B) versus subbasally barbed seta on carpus (C) D tarsus with part of merus pertaining to fourth thoracic endopod, caudal, detail (E) shows subbasally toothed seta F eighth thoracopod with penis, caudal G telson, dorsal.
There is a close morphological relationship between the three new Heteromysis species from the Cape Peninsula, which share most details described above for the eyes, antennula, mouth parts, carapace, and uropods. This regards also colour as the new species are essentially red, but share a white stripe along the dorso-lateral terminal margin of the eyestalks. As major differences from H. cancelli sp. n., H. fosteri sp. n. shows relatively shorter telson cleft, different distribution of laminae within the telson cleft, shorter spine-free basal portion of the lateral margins of the telson, as well as differently modified setae on merus and carpus of thoracic endopod 3 and on carpopropodus of endopod 4. H. octopodis sp. n. is most similar to H. fosteri, but is distinguished mainly by a longer spine-free basal portion of the lateral margins of the telson, by more segments at the carpopropodus of thoracic endopod 4, and by differently modified setae on carpus of endopod 3. It differs from H. cancelli by relatively shorter telson cleft, different distribution of laminae within the telson cleft, and by more segments together with differently modified setae on carpopropodus of endopod 4. Both, H. forsteri and H. octopodis, differ from H. cancelli by endopod 4 with shorter and less slender claw, and by endopods 5–8 with claws serrated on only their inner margin, while the outer margin is smooth.
The three new species described here are concordant with the original definition of the subgenus Heteromysis S.I. Smith, 1873, by non-dimorphic, rudimentary pleopods without spines or spine-setae. Among the eleven species of the genus Heteromysis listed for the E. Atlantic in the key below, six belong to this subgenus. Three species show dimorphic pleopods together with a subapically flagellate, modified seta near the inner distal corner of the antennular trunk, typical of the subgenus Olivemysis Băcescu, 1968, according to the diagnosis of
Among the three previously described E. Atlantic species of the subgenus Heteromysis, only H. (Heteromysis) microps (G.O. Sars, 1877) shares a single spine on the endopods of uropods with the three additional, new species described here for this subgenus. However, H. microps differs clearly from each new species by eyes with smaller cornea, by median sternal processes present on the last five thoracic somites, and by a single spine on basal third of each lateral margin of the telson. Single spines on the endopods of uropods are also found outside the E. Atlantic (two species without subgeneric assignment): in H. nouveli Brattegard, 1969, and H. (Heteromysis) spottei Price & Heard, 2000, from W. Atlantic; H. (Heteromysis) australica Băcescu & Bruce, 1980, H. (Olivemysis) kushimotensis Murano & Fukuoka, 2003, H. (Olivemysis) meenakshiae Bamber, 2000, and H. (Olivemysis) panamaensis O.S. Tattersall, 1967, from Pacific; and H. proxima W.M. Tattersall, 1922, from Indian Ocean. One to four spines are found in H. (Olivemysis) mayana Brattegard, 1970, from W. Atlantic. The three new species differ from members of the subgenus Olivemysis by absence of flagellate, modified setae on antennular trunk and by male pleopods without spines (spine-setae); and from the remaining five species listed above, including H. microps, by absence of spines or spine-like setae on carpopropodus of third thoracic endopod.
The nauplioids of Heteromysis cancelli sp. n. and H. fosteri sp. n. share setae at the tip of antennulae and antennae, so far known, with certain other species of Heteromysini, for example with H. wirtzi Wittmann, 2008, H. ekamako Wittmann & Chevaldonne, 2016, and Ischiomysis peterwirtzi Wittmann, 2013. Among these five species, H. cancelli and H. fosteri are the only ones showing cercopods close to the tip of the nauplioid abdomen. Including the new findings for Heteromysis (Figs
As in most species of Heteromysis, the three new species show a strictly benthic mode of live. The occurrence of H. fosteri in empty shells is in line with other five Heteromysis species reported by
As for H. cancelli and H. octopodis, benthic invertebrates may serve for many species as cryptic habitats in a broader sense, such as sponges, stony corals, gorgonians, sea anemones, brittle stars, tubes of annelids, and shells inhabited by hermit crabs (see list in
The facultative ectocommensal association reported here of Heteromysis octopodis with Octopus vulgaris represents the first documented regular association between mysids and cephalopods. On the first glance it sounds surprising that a commensal of sublittoral invertebrates may be also found in tide pools. However, there is a comparable case already known from Heteromysis: the E. Atlantic and Mediterranean H. microps G.O. Sars, 1877, is usually found on sublittoral mud flats, pebble bottoms, and in seagrass stands (
H. cancelli sp. n. follows H. dardani Wittmann, 2008, as the second association between mysids and hermit crabs documented from the E. Atlantic Ocean. The new species was found only in a large gastropod shell inhabited by Cancellus macrothrix, and not in any other type of microhabitat, although a variety of sampling methods was used. In order to test whether this commensalism may be obligate, a number of dead gastropod and sea urchin shells were collected 5.5 km from the type locality and then brought to the lab where the mysids were extracted and photographed still alive. Surprisingly, the shells yielded no H. cancelli, but only a different species described above as H. fosteri sp. n. (i.e. finding mysids in these empty shells was not surprising, but the exclusive occurrence of a different congeneric species in such shells was surprising). This points to obligate commensalism of the former species with hermit crabs, but insufficient data are available at present to demonstrate this, in that all specimens so far known derive from a single hermit specimen (among only five of this rare hermit crab species examined). The species has not, however, been observed amongst hundreds of hermit crabs of other species examined both at this site and in the broader region. With this new species a total of eight Heteromysis species have been reported as commensals of hermit crabs at a world-wide scale (
Modified and updated from the key given by
Heteromysini with normal eyes and a well-developed cornea. Males without mediocaudal lobe on appendix masculina of the antennular trunk; both sexes without a pair of backwards-oriented modified setae on inner terminal angle of antennular trunk, only forwards-oriented setae are present, not modified or modified in different ways. Gnathopod moderately to strongly stout, propodus separated from carpus by an oblique or a transverse articulation or not separated (propodus not always stouter than merus as in the three species described above). Thoracic endopod 4 with entire, apically not bifid claw. Thoracic endopod 8 in both sexes without flagellate spine on ischium and without spiniform extension of praeischium. Penes terminally not or only weakly widened by lobes. Females without sternal plate transversely projecting behind marsupium. Pleopods rudimentary and dimorphic or non-dimorphic. Genus Heteromysis S.I. Smith, 1873 | 1 | |
1 | Eyestalks without spiniform extension, or distally with small blunt extension of inner margin. All pleopods of male (if known) without spines or spine-setae | 5 |
– | Eyestalks distally with small spiniform extension of the inner margin. At least one among third and fourth (usually both) pleopods of male with flagellate spines (spine-setae) distally on outer margin of endopodal portion | 2 |
2 | Apical cleft 22-23% telson length. Antennular trunk with two forwards-directed, smooth setae on inner, distal corner of terminal segment; no flagellate seta present. Endopod of uropods with 3-4 spines near statocyst. Only one damaged male known | H. tattersalli H. Nouvel, 1942 (Cape Verde Islands, 91 m) |
– | Apical cleft longer than 23% telson length. One flagellate, strong, modified seta on inner distal corner of terminal segment of antennular trunk | 3 |
3 | Second male pleopod without spines. Endopod of uropods with 2–3 spines on inner margin near statocyst | H. (Olivemysis) sabelliphila Wittmann & Wirtz, 2017 (Cape Verde Islands, 6–18 m, associated with sabellids, also on gravel bottom or in submarine cave) |
– | Second male pleopod with one or more flagellate spines. Endopod of uropods with 3–4 spines | 4 |
4 | Fifth to seventh thoracic endopods with (4-6)-segmented carpopropodus. Endopod of uropods with three spines on inner margin near statocyst | H. (Olivemysis) dardani Wittmann, 2008 (Madeira, 10–20 m, commensal of hermit crab) |
– | Fifth to seventh thoracic endopods with seven-segmented carpopropodus. Endopod of uropods with four spines on inner margin near statocyst | H. (Olivemysis) wirtzi Wittmann, 2008 (Madeira, 28 m, commensal of sea anemone) |
5 | Telson with spines along distal 80-100% of the lateral margins | 10 |
– | Telson with spines mainly on distal half; without spines, or at most one spine, on basal third of each lateral margin | 6 |
6 | Telson cleft wider than deep. Endopod of uropods with four spines on inner margin near statocyst. Powerful gnathopod with stout carpus. Only one female specimen known | H. atlantidea O.S. Tattersall, 1961 (Cape Verde Islands, 8 m) |
– | Telson cleft at least about as deep as wide, in most species deeper than wide | 7 |
7 | Telson with one spine on basal third of each lateral margin, followed by a naked portion and then 8-13 spines on distal half; medio-apical spines distinctly shorter than latero-apical spines. Endopod of uropods with only one spine, which is near statocyst | H. (Heteromysis) microps (G.O. Sars, 1877) (NE Atlantic and Mediterranean: N Adriatic, Gulf of Naples, Sardinia, Tunisia, 0–16 m, mud flats, gravel bottoms, seagrass stands, burrows of mud shrimp, meso- to metahaline) |
– | Telson without spines on basal third of lateral margins | 8 |
8 | Telson on each side with one medio-apical spine being distinctly shorter than latero-apical spine; cleft with a total of 26–37 laminae all along its margins. Endopod of uropods with only one spine below statocyst | H. (Heteromysis) octopodis sp. n. (South Africa: Cape Peninsula, 0-3 m, associated with octopus or in tide pools) |
– | Telson with the 1–2 medio-apical spines on each side longer or subequal compared to latero-apical spines | 9 |
9 | Endopod of uropods with only one spine below statocyst. Telson cleft densely furnished with a total of 29–33 laminae along basal 81–84% of its margins | H. (Heteromysis) cancelli sp. n. (South Africa: Cape Peninsula, 20 m, associated with hermit crab) |
– | Endopod of uropods with 17-30 spines along inner margin between statocyst and tip. Telson cleft densely furnished with a total of 11–21 laminae along basal 50–70% of its margins | H. (Heteromysis) norvegica G.O. Sars, 1882 (NE Atlantic and Mediterranean, west coast of Norway, British Isles, English Channel, north and west coasts of France, Portugal, Madeira, Atlantic coast of Morocco, Mediterranean: off Monaco, Malta, 0–400 m) |
10 | Endopod of uropods with only one spine below statocyst. Telson cleft with 16-24 laminae all along its margins | H. (Heteromysis) fosteri sp. n. (South Africa: Cape Peninsula, 4 m, in empty shells) |
– | Endopod of uropods with 20–24 spines in dense series along inner margin. Telson cleft with 10-12 laminae only on its proximal half | H. (Heteromysis) armoricana H. Nouvel, 1940 (coast of Brittany, Galicia, Mediterranean, shallow coastal waters, muddy sand bottom, brown algae) |
We are greatly indebted to diver and photographer Craig Foster for initially sampling two of the three new Heteromysis species described herein and for providing some of the photographs of these. Also to Jannes Landschoff of the Department of Biological Sciences, University of Cape Town, for collecting and providing us with specimens of H. cancelli sp. n. Financial support for the work undertaken in South Africa was provided via a National Research Foundation Incentive Grant to C.L. Griffiths.